Deploying district cooling is the process of connecting multiple buildings in a dense area to a single, highly efficient source of cooling. The increased energy efficiency and reduction in use of high global warming potential refrigerants can translate into substantial emissions reductions and lower operating expenses (International Energy Agency [IEA], 2018; Energy Sector Management Assistance Program, 2020). District cooling systems that integrate cool thermal storage have the potential to significantly reduce electricity demand during peaks when demand for cooling can strain electricity grids (Al-Nini et al.,2023; Voswinkel, 2025). However, the high upfront cost, long-term planning, and large number of stakeholders involved make this a challenging solution, especially in low- and middle-income countries where new demand for cooling is growing (Eveloy & Ayou, 2019). Lack of publicly available data also makes this potential solution difficult to explore in greater depth. Based on our assessment, we will “Keep Watching” this potential solution.
Based on our analysis, deploying district cooling is a potentially impactful option for reducing emissions from buildings as demand for cooling continues to grow. However, upfront cost and project complexity are major barriers to deployment, and a lack of data is a barrier to deeper analysis. This potential solution is therefore classified as “Keep Watching.”
| Plausible | Could it work? | Yes |
|---|---|---|
| Ready | Is it ready? | Yes |
| Evidence | Are there data to evaluate it? | No |
| Effective | Does it consistently work? | Yes |
| Impact | Is it big enough to matter? | Yes |
| Risk | Is it risky or harmful? | No |
| Cost | Is it cheap? | No |
District cooling consists of a centralized cooling system that distributes chilled water to multiple buildings through a network of insulated underground pipes (International District Energy Association [IDEA], 2008). The cooled water absorbs heat from the buildings, replacing the need for air conditioners or chillers in each building (IDEA, 2008). District cooling can produce cooled water from a variety of renewable sources, such as renewable electricity, solar cooling, and natural cooling sources, including seawater, lakewater, rivers, and groundwater. It can even use waste heat from industry to generate cooling (Al-Nini, 2023; Eveloy & Ayou, 2019; IEA District Heating and Cooling [IEA DHC], 2019). Many systems include thermal energy storage facilities where frozen water, cold water, or phase change materials are cooled when electricity prices are low for use during peak hours to save costs and reduce strain on the electricity grid (Al-Nini et al.,2023; Voswinkel, 2025). District cooling is best applied to high-density areas and can be combined with district heating to provide year-round conditioning (Eveloy & Ayou, 2019; Werner, 2017).
When district cooling replaces conventional standalone systems in residential and commercial buildings, it can reduce emissions through two main mechanisms. First, many district cooling systems exchange heat with natural sources of cooling such as oceans, deep lakes, and rivers, a process that can be many times more energy efficient than conventional cooling systems. This results in reduced energy use and reduced emissions from the electricity used to operate the system (Eveloy & Ayou, 2019; IEA DHC, 2019). Second, district cooling systems can reduce the use of refrigerants with high global warming potentials, which can leak at all stages of a cooling system’s lifespan. When replacing standalone systems, district cooling can significantly reduce the total volume of refrigerants used (IEA, 2018; IEA DHC, 2019). In addition, some district cooling systems do not use any refrigerants at all (e.g., exchanging heat with ocean or deep lake water), and many are able to use refrigerants with low global warming potential (Eveloy & Ayou, 2019; IEA DHC, 2019). For instance, the Zuidas International Business Hub in the Netherlands adopted a district cooling system that uses lake cooling combined with chillers, reducing emissions by 75% compared to conventional cooling systems (IEA DHC, 2019).
According to the IEA (2023), global carbon emissions from cooling buildings reached 1.02 Gt CO₂‑eq in 2022. The majority of emissions associated with cooling are from standalone systems such as window air conditioners and chillers that serve a single building. District cooling systems are relatively rare at this time, with most capacity found in the United States and the Gulf Arab States (Eveloy & Ayou, 2019). While existing district cooling systems can be made less emitting, there may be greater potential for new systems because demand for cooling is increasing by ~4%/yr as global temperatures rise and as standards of living improve in regions that experience high temperatures (Voswinkel, 2025). This is raising concerns about the new electricity generating capacity needed when demand peaks on very hot days. District cooling systems can reduce overall energy use for cooling relative to standalone systems, and when paired with cool thermal storage, can significantly reduce demand during peak hours and on hot days (Al-Nini et al.,2023; Voswinkel, 2025). Building owners can enjoy less maintenance costs, more reliable cooling, and increased floor space when district cooling systems replace bulkier standalone cooling systems (IDEA, 2008; IEA DHC, 2019; Lienard, 2025). In dense areas with good access to natural or low-cost cooling sources, district cooling systems can cost less to operate and offer lifetime savings despite the higher upfront costs (Eveloy & Ayou, 2019).
Deploying district cooling systems has high upfront costs and requires extensive planning and coordination among a wide range of stakeholders (Eveloy & Ayou, 2019; IEA DHC, 2019). These projects can face challenges in getting financing due to a lack of confidence for both investors and customers, uncertainty about future loads, and regulatory barriers (Eveloy & Ayou, 2019). These can be especially challenging in low- and middle-income countries where demand for cooling is growing rapidly (ESMAP, 2020). Many buildings are likely to invest in standalone systems in the near term, locking them into alternatives and weakening the business case for district systems in the area. Meanwhile, the full potential is difficult to assess due to a lack of data on district cooling systems globally.
Al-Nini, A., Ya, H. H., Al-Mahbashi, N., & Hussin, H. (2023). A Review on Green Cooling: Exploring the Benefits of Sustainable Energy-Powered District Cooling with Thermal Energy Storage. Sustainability, 15(6), 5433. Link to source: https://doi.org/10.3390/su15065433
Energy Sector Management Assistance Program. (2020). Primer for space cooling (Knowledge Series). World Bank. Link to source: https://documents1.worldbank.org/curated/en/131281601358070522/pdf/Primer-for-Space-Cooling.pdf
Eveloy, V., & Ayou, D. S. (2019). Sustainable District Cooling Systems: Status, Challenges, and Future Opportunities, with Emphasis on Cooling-Dominated Regions. Energies, 12(2), 235. Link to source: https://doi.org/10.3390/en12020235
IEA. (2018). The future of cooling: Opportunities for energy-efficient air conditioning. Link to source: https://iea.blob.core.windows.net/assets/0bb45525-277f-4c9c-8d0c-9c0cb5e7d525/The_Future_of_Cooling.pdf
IEA. (2023). Final energy consumption and carbon emissions for space cooling by region in the net zero scenario, 2000-2030. Link to source: https://www.iea.org/data-and-statistics/charts/final-energy-consumption-and-carbon-emissions-for-space-cooling-by-region-in-the-net-zero-scenario-2000-2030
IEA District Heating and Cooling. (2019). Sustainable district cooling guidelines. International Energy Agency. Link to source: https://iea.blob.core.windows.net/assets/a5da464f-8310-4e0d-8385-0d3647b46e30/2020_IEA_DHC_Sustainable_District_Cooling_Guidelines_new_design.pdf
International district energy association. (2008). District cooling best practice guide, first edition. Link to source: https://higherlogicdownload.s3.amazonaws.com/DISTRICTENERGY/998638d1-8c22-4b53-960c-286248642360/UploadedImages/Conferences/District_Cooling_Best_Practice_Guide.pdf
Lienard, V. (n.d.). How can we cool our cities? Euroheat and Power. Retrieved August 18, 2025, from Link to source: https://energy-cities.eu/wp-content/uploads/2025/03/District-cooling_Euro-Heat-and-Power.pdf
Voswinkel, F., Senat, D., Valle, N. D., D’Angiolini, G., & Callioni, F. (2025, July 28). Staying cool without overheating the energy system. IEA. Link to source: https://www.iea.org/commentaries/staying-cool-without-overheating-the-energy-system
Werner, S. (2017). International review of district heating and cooling. Energy, 137, 617–631. Link to source: https://doi.org/10.1016/j.energy.2017.04.045
Cool roofs cut GHG emissions from electricity generation by lowering the amount of cooling required to condition indoor spaces, thereby decreasing the use of air conditioners. Using cool roofs in building design lowers electricity use, improves thermal comfort for building occupants, and is relatively cheap to deploy. However, its potential climate impact is relatively small, and its relevance is largely limited to hot climates where buildings need more cooling than heating to be thermally comfortable. Its application has mostly been in pilot projects, but we conclude that this solution is “Worthwhile” with potential for large-scale deployment.
Our analysis concludes that the projected climate impact of using cool roofs on buildings is not large enough to be globally significant (>0.1 Gt CO₂‑eq/yr ). However, we consider it “Worthwhile” because it helps reduce electricity consumption in buildings, makes indoor spaces more thermally comfortable, and lessens the urban heat island effect.
| Plausible | Could it work? | Yes |
|---|---|---|
| Ready | Is it ready? | Yes |
| Evidence | Are there data to evaluate it? | Limited |
| Effective | Does it consistently work? | Yes |
| Impact | Is it big enough to matter? | No |
| Risk | Is it risky or harmful? | No |
| Cost | Is it cheap? | Yes |
Using cool roofs reduces the amount of electricity needed to cool indoor spaces, thereby cutting GHG emissions from electricity generation. Cool roofs are generally defined as light-colored roofs designed to reflect more sunlight and transfer less solar energy into the interior compared to traditional roofs, thereby reducing cooling loads. Cool roofs can be achieved by applying coatings or using roofing materials with a high solar reflectance index (SRI), which results from high solar reflectance and thermal emittance. These properties ensure that surface temperatures on cool roofs remain substantially cooler than conventional roofs.
Using cool roofs can effectively reduce the amount of air conditioning needed to cool indoor spaces, though their potential to cut annual electricity use in buildings and resulting GHG emissions is minimal. Nonetheless, evidence from real-world applications demonstrates that the surface temperatures of cool roofs can be as much as 28–30°C cooler than conventional roofs on extremely hot afternoons. Other studies have shown that cool roofs can decrease indoor air temperatures by 2–3°C while simultaneously reducing surrounding outdoor air temperatures by about 10°C, thereby minimizing the urban heat island effect.
Several organizations are deploying initiatives to drive cool roof adoption as a passive cooling strategy in the building sector. For example, C40 Cities previously launched a cool roofs program across New York City. Over a six-year period (2009–2015), the initiative resulted in nearly 530,000 m2 of building roof tops being retrofitted as cool roofs. As of 2023, the United States is estimated to have over 232 million m2 of installed cool roofs. Recently, the Million Cool Roofs Challenge organized by the Global Cool Cities Alliance resulted in 1.1 million m2 of additional cool roofs in 2022 across 10 countries, including Indonesia, Mexico, and Rwanda.
Some studies estimate that about 229 billion m2 of roof space existed as of 2022. Given the existing building stock – and the fact that the bulk of projected new construction by 2050 is expected in regions with hot climates – the impact of this potential solution could grow.
There are several advantages to using cool roofs in buildings. First, it is cheap to implement, and the incremental cost of applying new coatings or selecting light-colored roofing materials during construction is often minimal compared to conventional roofs. Second, it is expedient as a cooling strategy when buildings are not mechanically air-conditioned or designed to be naturally ventilated. This is important because many countries in hot climates (where cooling is generally required for indoor thermal comfort more than heating) also lack access to reliable electricity, thereby necessitating the use of passive measures in building design.
In addition, a recent analysis of 77 low- and middle-income countries determined that cooling systems are not readily available, sustainable, or affordable, especially for building applications, placing nearly 4 billion people at risk. Deploying scalable strategies such as cool roofs in buildings helps reduce exposure to these risks, which could lead to greater adoption and climate impact. Several studies have also shown that using cool roofs can help reduce indoor heat stress, especially in hot and humid environments. Others are exploring the concept of cool-colored roofs, where non-white roof materials can provide similar cooling effects while preserving aesthetic choice for building owners and developers.
Despite the advantages of using cool roofs as a potential climate solution, a few challenges exist. Some studies have shown that cool roofs can slightly increase heating loads during winter, especially in cold climates. However, other studies conclude that the increase is marginal and often inconsequential. Another concern is that cool roofs can produce glare as the incident sunlight is reflected. This could adversely impact building users if the buildings with cool roofs are surrounded by taller structures with daytime occupancy, such as offices, which is an increasing reality in urban spaces. Lastly, we found examples of pilot projects and resources for cool roofs, but could not find reliable datasets for a comprehensive assessment of their current impact. Addressing such data gaps could help drive cool roofs research, integration into industry practices and building codes, and, ultimately, greater adoption.
Bamdad, K. (2023). Cool roofs: A climate change mitigation and adaptation strategy for residential buildings. Building and Environment, 236, Article 110271. Link to source: https://doi.org/10.1016/j.buildenv.2023.110271
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Henry Igugu, Ph.D.
Christina Swanson, Ph.D.
Heat pumps use electricity to efficiently move heat from one place to another. This solution focuses on the replacement of fossil fuel–based heating systems with electric heat pumps. Heat pumps are remarkably efficient because they collect heat from the outside air, ground, or water using a refrigerant and use a pump to move the heat into buildings to keep them warm in colder months. Heat pumps typically replace heating systems such as boilers, furnaces, and electric resistance heaters. Many will also replace air conditioners, because the same pump can move heat out of a building in warmer months (see Five ways heat pumps are more awesome than you think).
Heat pumps use a refrigerant cycle to move heat. When the liquid refrigerant enters a low pressure environment, it absorbs heat from the surrounding air (air-source heat pumps), water, or ground (ground-source heat pumps) as it evaporates. When the refrigerant vapor is compressed, it condenses back into a liquid, releasing the stored heat into the building. By passing the refrigerant through this cycle, a heat pump can move heat from outside to inside a building.
Absorbing heat from the outside gets more difficult as temperatures drop. However, modern cold-climate heat pumps are designed to work effectively at temperatures approaching –30 °C (–22 °F) (Gibb et al., 2023). The freezer in your home uses the same technology, moving heat out of the cold box into the warm room to keep your food frozen. In most systems, the refrigerant cycle in a heat pump can be reversed in warmer months, moving heat out of a building to ensure its occupants are comfortable year-round.
Heat pumps are very efficient at using electricity for heating. This is because they move heat rather than generating heat (e.g., by combustion). For example, a heat pump may have a seasonal coefficient of performance (SCOP) of 3, meaning it can move an average of three units of heat energy for every unit of electrical energy that it consumes. Conventional combustion and electric resistance heaters cannot produce more than one unit of heat energy for every unit of fuel energy or electrical energy provided.
Heat pump systems may be all-electric or hybrid, where a secondary fossil fuel-based heating system takes over in colder weather.
A heat pump’s potential to reduce GHG emissions depends on the heating source it replaces and the emissions intensity of the electricity used to run it. When heat pumps replace fossil fuel-based heating, they displace the GHG emissions – primarily CO₂ – generated when the fuel is burned. When replacing electric resistance heaters, heat pumps reduce the GHG emissions from the electricity to power the system because heat pumps are much more energy efficient. As electrical grids decarbonize, the GHG emissions from operating heat pumps will decrease.
All-electric heat pumps provide the most climate benefit because they can be powered with clean energy, but hybrid heat pumps also play an important emissions-reduction role. Hybrids consist of a smaller electric heat pump system that switches to fuel-based heating systems in colder weather. They may be attractive due to lower up-front costs and because they have lower peak power demand on cold days, but hybrids also have a smaller emissions impact. Our cost and emissions analyses assumed all-electric air-source heat pumps, while the data used in the adoption analysis included all types of heat pumps with the expectation that all-electric versions will dominate in the longer term.
In this analysis, we calculated effectiveness and cost outcomes from specific countries with high heat-pump adoption (European countries, Canada, the United States, Japan, and China) to avoid comparing research studies that use different assumptions. The analysis used global assumptions for heating system efficiency: 90% for fueled systems (International Gas Union, 2019), 100% for electric resistance (U.S. Department of Energy [U.S. DOE], n.d.), and SCOP of 3 for heat pumps (Crownhart, 2023). We also assumed all existing fueled systems use natural gas, which is currently the dominant fossil fuel used for space heating globally (International Energy Agency [IEA], 2023b). The analysis did not include emissions or costs from cooling but did assume the heat pump is replacing both a heating and cooling system.
The cost and effectiveness analyses focused on residential heating systems due to availability of data and also because large variations in the cost and size of commercial systems make it more challenging to estimate their global impacts. Commercial heating systems are typically larger than residential systems, and their emissions impacts are expected to be proportionally greater per unit. Cost savings may be different due the greater complexity of heating and cooling systems (Tejani & Toshniwal, 2023). Available data on heat pump adoption, on the other hand, typically include both residential and commercial units. Our adoption analysis therefore included both residential and commercial buildings, with greater adoption assumed in the residential sector.
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Sovacool, B. K., Evensen, D., Kwan, T. A., & Petit, V. (2023). Building a green future: Examining the job creation potential of electricity, heating, and storage in low-carbon buildings. The Electricity Journal, 36(5), Article 107274. Link to source: https://doi.org/10.1016/j.tej.2023.107274
Tejani, A., & Toshniwal, V. (2023). Differential energy consumption patterns of HVAC systems in residential and commercial structures: A comparative study. International Journal of Advancements in Science & Technology, 1(3), 47–58.
U.S. Department of Energy. (2022). Residential cold-climate heat pump technology challenge. Link to source: https://www.energy.gov/eere/buildings/articles/residential-cold-climate-heat-pump-technology-challenge-fact-sheet
U.S. Department of Energy. (n.d.). Electric resistance heating. Retrieved September 2, 2025, from Link to source: https://www.energy.gov/energysaver/electric-resistance-heating
U.S. Energy Information Administration. (2023). Updated buildings sector appliance and equipment costs and efficiencies [Report]. Link to source: https://www.eia.gov/analysis/studies/buildings/equipcosts/pdf/full.pdf
Van Someren, C., Visser, M., & Slootweg, H. (2021). Impacts of electric heat pumps and rooftop solar panels on residential electricity distribution grids. 2021 IEEE PES Innovative Smart Grid Technologies Europe (ISGT Europe), 01–06. Link to source: https://doi.org/10.1109/ISGTEurope52324.2021.9640090
Wilson, E. J. H., Munankarmi, P., Less, B. D., Reyna, J. L., & Rothgeb, S. (2024). Heat pumps for all? Distributions of the costs and benefits of residential air-source heat pumps in the United States. Joule, 8(4), 1000–1035. Link to source: https://doi.org/10.1016/j.joule.2024.01.022
Zahiri, S., & Gupta, R. (2023). Examining the risk of summertime overheating in UK social housing dwellings retrofitted with heat pumps. Atmosphere, 14(11), Article 1617. Link to source: https://doi.org/10.3390/atmos14111617
Zhang, Q., Zhang, L., Nie, J., & Li, Y. (2017). Techno-economic analysis of air source heat pump applied for space heating in northern China. Applied Energy, 207, 533–542. Link to source: https://doi.org/10.1016/j.apenergy.2017.06.083
Zhou, M., Liu, H., Peng, L., Qin, Y., Chen, D., Zhang, L., & Mauzerall, D. L. (2022). Environmental benefits and household costs of clean heating options in northern China. Nature Sustainability, 5(4), 329–338. Link to source: https://doi.org/10.1038/s41893-021-00837-w
Heather McDiarmid, Ph.D.
Stephen Agyeman, Ph.D.
Ruthie Burrows, Ph.D.
James Gerber, Ph.D.
Sarah Gleeson, Ph.D.
Yusuf Jameel, Ph.D.
Daniel Jasper
Jason Lam
Cameron Roberts, Ph.D.
Alex Sweeney
Eric Wilczynski
Aiyana Bodi
Hannah Henkin
Jason Lam
Zoltan Nagy, Ph.D.
Ted Otte
Amanda D. Smith, Ph.D.
Our analysis showed that each all-electric residential heat pump for space heating reduces emissions by an average of 0.97 t CO₂‑eq /heat pump system/yr (20-yr and 100-yr basis, Table 1).
Heat pumps reduce emissions by reducing the amount of fossil fuels burned for space heating or by reducing the use of less efficient electric resistance heating. Operating a heat pump generates no on-site emissions except refrigerant leaks, which are addressed by the Improve Refrigerant Management solution. Our analysis included the emissions from the electricity used to power heat pumps. Thus, the emissions reduction from heat pump adoption is expected to improve as electricity generation incorporates more renewable energy (Knobloch et al., 2020).
There are significant regional differences in heat pump effectiveness due to the electricity mix, climate, and types of heating systems used today (Knobloch et al., 2020). The global average is weighted based on regional heating requirements and existing heating technologies.
We did not quantify the reduction in pollutants such as nitrogen oxides, sulfur oxides, and particulate matter, which are released when fossil fuels are burned for space heating. We also refrained from estimating the global warming impacts of refrigerant leaks associated with the use of heat pumps, which is addressed by our Improve Refrigerant Management solution, or natural gas leaks associated with the use of fossil fuels for heating.
Table 1. Effectiveness at reducing emissions from space heating.
Unit: t CO₂‑eq/heat pump system/yr, 100-yr basis
| Mean | 0.97 |
A residential air-source heat pump has a mean initial installed cost of US$6,800 and an estimated US$540/yr operational cost for heating. Over a 15-year lifespan, this results in a net cost of US$990/yr. A heat pump generally replaces both a heating and cooling system with a combined mean installed cost of US$5,300. Operating a baseline heating system costs US$830/yr (operational cooling cost was not included in this analysis). Over a 15-year lifespan, the baseline case has a net cost of US$1,180/yr. This results in a net US$190 savings for households that switch to a heat pump. This translates to US$200 savings/t CO₂‑eq reduced (Table 2).
These values include the average annual cost to operate the equipment for heating and the annualized up-front cost of a heat pump relative to both a heating and cooling system that it replaces. There can be significant variability in the up-front cost of equipment based on the type of heat pump installed, the size of the building, and the climate in which it is designed to operate. We assumed the cost to operate the equipment for cooling to be the same with heat pumps and the air conditioners they replace.
There are significant regional differences in the operational cost of heating systems due to climate, utility rates, and the heating systems in use today. The global average outcomes described here are weighted averages from Europe, Canada, the United States, China, and Japan based on regional heating requirements and existing heating technologies.
Utility cost estimates are from June 2023 (Global Petrol Prices, 2024) and may vary substantially over time due to factors such as volatile fossil fuel prices, changing carbon prices, and heat pump incentives. Additional installation costs, such as upgrades to electrical systems, ductwork, or radiators, are not included.
Table 2. Cost per unit climate impact. Negative values reflect cost savings.
Unit: 2023 US$/t CO₂‑eq , 100-yr basis
| Mean | –200 |
Insufficient data exist to quantify the learning curve for heat pumps.
The cost of installing a heat pump includes both equipment costs and the labor cost of installation. According to the U.S. Energy Information Administration ([U.S. EIA] 2023), retail equipment costs are 60–80% of the total installed cost of residential air-source heat pumps (central and ductless).
Equipment costs can decrease with economies of scale and as local markets mature, but may be confounded by technological advances as well as equipment and/or refrigerant regulations that can also increase costs (IEA, 2022). European estimated learning rates for heat pump equipment costs range from 3.3% for ground-source heat pumps (Renaldi et al., 2021) to 18% for air-source heat pumps (Jakob et al., 2020). Ease and cost of installation is a research and development goal for manufacturers (IEA, 2022).
The installed cost is also affected by rising labor costs and projected labor shortages (IEA, 2022). Renaldi et al. (2021) showed negative learning rates for the total installed costs in the United Kingdom due to increasing installation costs: –2.3% and –0.8% for air-source and ground-source heat pumps, respectively.
Heat pump manufacturer efforts to improve the performance of the technology may impact learning curves as well. In North America, the Residential Heat Pump Technology Challenge has supported the development of heat pumps with improved cold-climate performance (U.S. DOE, 2022).
Speed of action refers to how quickly a climate solution physically affects the atmosphere after it is deployed. This is different from speed of deployment, which is the pace at which solutions are adopted.
At Project Drawdown, we define the speed of action for each climate solution as emergency brake, gradual, or delayed.
Use Heat Pumps is a GRADUAL climate solution. It has a steady, linear impact on the atmosphere. The cumulative effect over time builds as a straight line.
Heat pumps can increase demand for electricity and can therefore increase demand for fossil fuel-based power generation. In areas where power generation relies heavily on fossil fuels, heat pumps may generate more emissions than gas heating systems. As the electricity sector adopts more renewables and phases out fossil fuel-based generation, the emissions impact of heat pumps will decrease. Once a building has been designed or retrofitted to accommodate a heat pump it is likely that new heat pumps will be installed at the end of equipment life, perpetuating the benefit.
Efforts are underway to retrofit buildings by improving insulation, air-sealing, and upgrading windows. When done alongside heat pump adoption, retrofits can reduce the size of heat pump needed and increase total energy, emissions, and cost savings.
As heat pump adoption grows, so too will the manufacture of refrigerants, some of which have high global warming potentials when they escape to the atmosphere. See Deploy Alternative Refrigerants and Improve Refrigerant Management solutions for more on accelerating change in this sector.
Our analysis suggests that 130 million heat pumps for heating are currently in operation primarily based on data in Europe, Canada, the United States, China, and Japan (Table 3). These include both all-electric heat pumps and hybrid heat pumps. The IEA (2023a) estimated that 12% of global space heating demand was met by heat pumps in 2022.
This value is based on market reports and national data sources plus IEA (2022) estimates of total GW of installed capacity. To convert installed capacity to the number of heat pumps, we used the median from the range of suggested average capacities (7.5 kW for Europe and North America, 4 kW in Japan and China, 5 kW global average). In Japan, where heat pump units typically heat only one room, we assumed 2.4 units per heat pump (International Renewable Energy Agency [IRENA], 2022).
Table 3. Current heat pump adoption level (2020–2022).
Unit: Heat pump systems in operation
| Mean | 130,000,000 |
Our estimates put the median adoption trend at 17 million new all-electric and hybrid heat pumps in operation per year (Table 4). This analysis is based on product shipment data (used as a proxy for installed heat pumps), market reports, national statistics, and IEA data for growth in installed capacity. For the IEA data (2010–2023), we assumed a global average of 5 kW of heat capacity per heat pump unit (IEA, 2024).
Shipment and market analysis reports consistently show growing markets for heat pumps in much of the world (Asahi, 2023; European Heat Pump Association, 2024; IEA, 2024). In the United States, shipments of heat pumps have outnumbered gas furnaces since at least 2022 (Air-Conditioning, Heating, and Refrigeration Institute, 2025).
Table 4. Heat pump adoption trend (2010–2023).
Unit: Heat pump systems in operation/yr
| 25th percentile | 12,000,000 |
| Mean | 15,000,000 |
| Median (50th percentile) | 17,000,000 |
| 75th percentile | 18,000,000 |
Our adoption ceiling is set at 1.200 billion heat pumps for space heating by 2050 (Table 5), most of which are expected to be in residential buildings. This is based on the IEA’s Net Zero Roadmap projection that heat pumps will represent 6,500 GW of heating capacity globally by 2050, covering 55% of space heating demand (IEA, 2023a). Our adoption ceiling assumes all-electric heat pumps cover all space heating demand.
We assumed that average heat pump sizes (capacities) will increase over time as heat pumps cover a greater portion of a building’s heating load and as more commercial buildings with larger heating loads install heat pumps. Using a global average of 10 kW per heat pump, the IEA projections imply 650 million heat pumps will be in operation by 2050 with the technical adoption ceiling for 1,200 million heat pumps if all heating demand were met by heat pumps.
Table 5. Heat pump adoption ceiling: upper limit for adoption level.
Unit: Heat pump systems in operation by 2050
| Mean | 1,200,000,000 |
We estimate the achievable range for heat pump adoption to be 600–960 million heat pumps in operation by 2050 (Table 6).
Most existing space heating systems will be replaced at least once between now and 2050 because this equipment typically has lifetimes of 15–30 years (U.S. EIA, 2023). Policies that encourage high efficiency heat pumps alongside insulation upgrades have the potential to provide lifetime savings, greater comfort, and energy efficiency benefits (Wilson et al., 2024). Given the available timelines and potential benefits, near full adoption is technically feasible.
We have set the Achievable – High heat pump adoption at 80% of the adoption ceiling to account for systems that are difficult to electrify due to very cold climates, policy, economic barriers, and grid constraints. This high achievable value assumes that some systems may be replaced before their end of life to meet climate and/or financial goals.
We have set the Achievable – Low heat pump adoption at 50% of the adoption ceiling. This is roughly consistent with the current adoption trend continuing out to 2050.
Our heat pump units adopted include both all-electric and hybrid heat pumps. This analysis assumes that hybrid heat pumps will become less common as fuels are phased out and that all-electric heat pumps will dominate by 2050.
Table 6. Range of achievable adoption levels.
Unit: Heat pump systems installed
| Current adoption | 130,000,000 |
| Achievable – low | 600,000,000 |
| Achievable – high | 960,000,000 |
| Adoption ceiling | 1,200,000,000 |
Our estimates show the global impact of existing heat pumps for space heating to be a reduction of 0.13 Gt CO₂‑eq/yr (100- and 20-yr basis) based on current adoption and today’s electricity grid emissions (Table 7). Because electricity grid emissions are decreasing for each kWh of electricity generated (IEA, 2025), the actual impact will be greater than our estimates when future electricity generation emissions are lower.
For the adoption ceiling, assuming heat pumps supply all of the IEA’s projected global heating demand in 2050 (IEA, 2023a), 1.2 Gt CO₂‑eq/yr (100- and 20-yr basis) could be avoided per year with today’s electricity grid emissions.
A high-end achievable target is 80% of the adoption ceiling, accounting for systems that might continue to use fossil fuels for heating due to factors such as cold climates, economic barriers, and grid constraints. This would result in avoiding 0.93 Gt CO₂‑eq/yr (100- and 20-yr basis) with today’s electricity grid emissions.
A low-end achievable target is 50% of the adoption ceiling, roughly equivalent to heat pump adoption continuing at today’s rate. This would result in avoiding 0.58 Gt CO₂‑eq/yr (100- and 20-yr basis) with today’s electricity grid emissions.
Table 7. Climate impact at different levels of heat pump systems adoption.
Unit: Gt CO₂‑eq/yr, 100-yr basis
| Current adoption | 0.13 |
| Achievable – low | 0.58 |
| Achievable – high | 0.93 |
| Adoption ceiling | 1.2 |
Heat waves and extreme heat are becoming increasingly significant factors of morbidity and mortality worldwide (Romanello et al., 2024). Some buildings that replace heating systems with heat pumps will gain access to cooling (Congedo et al., 2023; Wilson et al., 2024; Zhang et al., 2017; also see Let’s turbo-boost heat pump sales by making heat pumps the default for cooling). This can provide protection from heat stress in regions experiencing increasingly hotter summers (where air conditioning was not previously necessary) and for populations that are vulnerable to heat stress, such as the elderly (Malmquist et al., 2022). Some jurisdictions incentivize heat pumps for this reason. For example, the United Kingdom plans to install 600,000 heat pumps by 2028 (Zahiri & Gupta, 2023), and local climate adaptation plans in Canada recommend the installation of heat pumps to provide space cooling that can reduce morbidity and mortality during heat waves (Canadian Climate Institute, 2023; City of Vancouver, n.d.). Because exposure to extreme heat is disproportionately higher for minority communities – particularly in urban environments – access to cooling has important implications for environmental justice (Benz & Burney, 2021).
Installing heat pumps can lead to greater household savings on electricity. Research has shown that across the United States, heat pumps can reduce electricity bills for 49 million homes with an average savings of US$350–600 per year, depending on the efficiency of the heat pump (Wilson et al., 2024). Wilson et al. (2024) found that higher efficiency heat pumps could be cost-effective for about 65 million households in the United States. Heat pumps also create jobs (Sovacool et al., 2023). In its post-COVID-19 recovery plan, the IEA (2020) estimated that every US$1 million investment in heat pumps could generate 9.1 new jobs and reduce 0.8 jobs in the fossil fuel industry. About half of the new jobs will be in manufacturing, with the remaining distributed between installation and maintenance.
Burning fossil fuels for heating directly emits health-harming particulates and can generate carbon monoxide. Replacing fossil gas heating with heat pumps can reduce air pollution (Carella & D’Orazio, 2021) and contribute to improving health outcomes (Zhou et al., 2022). A study in China showed that as the power grid moves to incorporate renewable energy, the air quality and health benefits of heat pumps will increasingly outweigh the benefits of gas heaters (Zhou et al., 2022). The risk of carbon monoxide poisoning also decreases in buildings that switch from fuel-burning space heating to heat pumps. In buildings that burn fuels for applications such as space heating, carbon monoxide can pose serious health risks, including poisoning and death (Mattiuzzi & Lippi, 2020).
Heat pumps contain refrigerants that often have high global warming potentials. Refrigerant leaks can occur during installation, operation, and end of life (McDiarmid & Parker, 2024). As more heat pumps are adopted, there is a risk of increased emissions from refrigerant leaks during operation as well as refrigerant release at the end of equipment life. Alternate refrigerants with lower global warming potentials are being phased in due to an international agreement to reduce hydrofluorocarbons, including many refrigerants (Kigali Amendment).
Higher rates of heat pump installation will require upscaling heat pump manufacturing and training, plus certification of skilled labor to install them. Skilled labor shortages are already creating bottlenecks for heat pump adoption in some countries, some of which can be met by reskilling other heating technicians (IEA, 2022).
Advancements in heat pump technology will support the development and adoption of heat pump technology for industrial applications.
The increased adoption of heat pumps will increase the market for alternative refrigerants and refrigerant management.
Heat pumps reduce the emissions from heating and cooling buildings. This reduces the effectiveness of technologies that reduce heating and/or cooling demands.
Adoption of heat pumps for space heating is likely to generate seasonal peaks in power demand during cold days that may require building out extra generating capacity that decrease grid efficiency (Bloess et al., 2018). Heat pumps can compete with electric cars for power during peak times (Van Someren et al., 2021).
heat pump systems
CO₂ , CH₄, N₂O
Enhanced grid infrastructure will be required to support widespread building electrification and the greater demand for electricity, especially on cold days when heat pumps are less efficient at moving heat (Cooper et al., 2016). Demand-side management, thermal storage, home batteries, bidirectional chargers, and greater adoption of ground-source heat pumps can all help to reduce this increased demand (Cooper et al., 2016; McDiarmid, 2023).
In general, heat pumps have higher up-front costs than do fueled alternatives but will save a building owner money over the lifetime of the system. This can create economic barriers to accessing the benefits of heat pumps, with low-income homeowners and renters who pay for their utilities being particularly vulnerable to being left behind in the transition (Sandoval et al., 2024). Equity advocates are also concerned that the cost of maintaining gas and other fossil fuel infrastructure may increasingly fall on lower-income building owners who struggle to afford the upfront cost of electrifying with heat pumps (Davis & Hausman, 2022).
Heating degree days are an indicator of total space-heating demand to maintain an indoor temperature above 18 °C. Here we show annual average heating degree days for the decade ending in 2025.
Copernicus Climate Change Service. (2023). ERA5 hourly data on single levels from 1940 to present [Data set]. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). Retrieved January 13, 2026 from Link to source: https://doi.org/10.24381/cds.adbb2d47
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz‐Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmins, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., … Thépaut, J. N. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049. Link to source: https://doi.org/10.1002/qj.3803
Heating degree days are an indicator of total space-heating demand to maintain an indoor temperature above 18 °C. Here we show annual average heating degree days for the decade ending in 2025.
Copernicus Climate Change Service. (2023). ERA5 hourly data on single levels from 1940 to present [Data set]. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). Retrieved January 13, 2026 from Link to source: https://doi.org/10.24381/cds.adbb2d47
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz‐Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmins, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., … Thépaut, J. N. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049. Link to source: https://doi.org/10.1002/qj.3803
In this solution, heat pumps replace space-heating options that rely on fossil fuels. This primarily applies to North America, Asia, and Europe. Limited data are available for some regions, so this analysis focuses on European countries, Canada, the United States, Japan and China.
The effectiveness of heat pumps at reducing GHG emissions is influenced by the heating needs of the region and the generation mix of the electricity grid. Areas with higher heating needs will generally show greater emissions reduction because more energy is needed to keep buildings warm. However, this is partially offset because heat pumps are less energy efficient on colder days. The local electricity grid mix matters because heat pumps are powered by electricity. Given the same outside temperature, regions with a largely emissions-free grid (e.g., France or Canada) will have higher emissions impacts from heat pump adoption than areas where electricity is largely generated from fossil fuels (e.g., China). The type of heat pumps (all-electric vs. hybrid) best suited to each region depends on technological and economic factors.
Let’s turbo-boost heat pump sales by making heat pumps the default for cooling. McDiarmid (2026)
Electric heat pumps are generally viewed as the primary strategy for reducing GHG emissions from buildings. The Intergovernmental Panel on Climate Change ([IPCC] 2023) noted that heat pumps drive electrification in buildings and help decrease emissions. The European Commission (2022) claimed that heat pumps are an essential way of decreasing reliance on gas in heating while increasing the use of renewable energy in the heating sector. The IEA (2022) reported that heat pumps powered by electricity generated with renewable energy “are the central technology in the global transition to secure and sustainable heating.” IRENA (2024) claimed heat pumps in buildings “will play a crucial role in reducing reliance on fossil fuels.”
In one of the largest scientific reviews on the topic, Gaur et al. (2021) concluded that heat pumps “have the potential to play a substantial role in the transition to low carbon heating,” and noted that emissions impacts of heat pumps are dependent on the type of heat pump technology, their location, and the electricity grid mix. Knobloch et al. (2020) studied 59 world regions and found that electrification of the heating sector via heat pumps will reduce emissions in most world regions where they are adopted.
The results presented in this document summarize findings from 46 reports, reviews and meta-analyses and 13 original studies reflecting current evidence from 30 countries, primarily European countries, Canada, the United States, Japan, and China. We recognize this limited geographic and technology scope creates bias, and hope this work inspires research and data sharing on this topic in underrepresented regions and in the commercial sector.
We define Deploy Building Automation Systems (BASs) as reducing commercial (i.e., nonresidential or industrial) building energy use and associated GHG emissions by using sensors to monitor a building in operation and control systems such as heating, cooling, ventilation, plug loads, and lighting for the purpose of saving energy. This solution does not include automated building systems that control security, safety, and other functions, and applies to existing buildings only.
BASs (also referred to as building energy management systems, building management systems, or building automation control systems) use automation to optimize system performance and reduce the energy needed to operate commercial buildings. This cuts emissions generated by the energy sources, including emissions from fuels burned to provide heating as well as emissions from generating the electricity used to power air conditioners, plug loads, and lighting. Together, these contribute to an estimated 3.7 Gt of energy-related emissions associated with operating nonresidential buildings per year (International Energy Agency [IEA], 2023b). This solution reduces critical climate pollutants, primarily CO₂, but also methane and nitrous oxides.
The energy savings from BASs are the outcome of processes such as scheduled and occupancy-based control of heating, cooling, ventilation and lighting; optimization of set-point temperatures; predictive maintenance; and fault detection and diagnostics (Akbulut et al., 2025). Some BAS include smart controls that learn from occupant behaviors to optimize performance and energy savings (O’Grady et al., 2021).
BASs can reduce commercial energy use by an estimated 5–40% (IEA, 2025). Local climate conditions, the type of BAS and how it is operated, building type and condition, and user behaviors can affect this outcome (Fernandez et al., 2017; Morkunaite et al., 2022). For example, modeling of U.S. buildings showed an average potential 23.3% energy savings with a BAS in supermarkets but a 48.8% energy savings for secondary schools and 29% savings for commercial buildings overall (Fernandez et al., 2017). These outcomes also included measures to correct for operational faults such as miscalibrated sensors and problems with seals.
BASs typically consist of three architectural layers (Domingues et al., 2016) (Figure 1). At the field layer, sensors monitor conditions such as temperature, air flow, humidity, and lighting levels within a space and actuators adjust equipment in response to control signals. The control layer receives and processes incoming sensor data and sends control signals to the actuators according to programmed control logic and set parameters. The management layer is where data are logged, monitored, and analyzed to track and optimize performance, identify trends, and adjust automation settings.
Figure 1. A typical BAS has three layers: a field layer, which senses the environment and adjusts equipment as needed; a control layer, which handles communication between the sensors and actuators; and a management layer, which logs and analyzes data to optimize performance. Modified from dos Santos et al. (2021) and Fluke (2009).
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Zarco-Soto, F. J., Zarco-Soto, I. M., Ali, S. S. S., & Zarco-Periñán, P. J. (2025). Energy consumption in buildings: A compilation of current studies. Energy Reports, 13, 1293–1307. Link to source: https://doi.org/10.1016/j.egyr.2024.12.069
Heather McDiarmid Ph.D
Ruthie Burrows, Ph.D.
James Gerber, Ph.D.
Daniel Jasper
Alex Sweeney
Henry Igugu, Ph.D.
Amanda D. Smith, Ph.D.
Christina Swanson, Ph. D.
We estimate that BASs reduce GHG emissions by 0.011 t CO₂‑eq/yr (20- and 100-yr basis) for every m2 of building space (Table 1) by reducing fuels and electricity used for heating, cooling and lighting.
BASs reduce more emissions when installed in buildings that are energy intensive (e.g., hotels) or that use highly polluting fuels (e.g., heating oil) than in buildings that have low energy intensity (e.g., educational facilities) or that use renewable energy (Zarco-Soto et al., 2025).
We assumed 21% energy savings with BASs, which represents the median from 11 estimates, models, or measurements of whole-building energy savings from installed BASs. The effectiveness value is an average that was weighted for annual energy use per m2 by commercial building type and by the mix of fuels used for energy in buildings (IEA, 2023a). The analysis assumes that the relative proportion of commercial building space by type in the U.S. (U.S. Energy Information Administration [U.S. EIA], 2022b, 2022c) is representative of the proportions globally.
Table 1. Effectiveness at reducing emissions.
Unit: t CO₂‑eq (100-year basis)/m2 using BAS/yr
| Mean | 0.011 |
We determined that a BAS will cost US$0 per t CO₂‑eq reduced (Table 2) because the up-front cost is recovered through operational savings over the system’s lifetime. Buildings where energy savings are higher than average will show net savings because of higher operational savings, while more energy-efficient buildings may see a net cost.
The median up-front cost of the system is US$46/m2 building space but once installed, the system will save a building owner US$3.00/m2/yr in energy costs. Assuming a 15-year lifespan for the system, this results in a net cost of US$0/m2/yr. In other words, the system pays for itself in 15 years through operational savings.
The up-front cost includes the installed cost of the sensors, controllers, and networking infrastructure (Domingues et al., 2016). Operational costs consider only the cost savings from the 21% energy savings weighted by annual energy use per m2 by commercial building type, and relative building energy consumption by energy source (IEA, 2023a). The ongoing maintenance, software, and personnel costs are not included in this analysis. Additional savings may also be achieved through automated fault detection and diagnostics or other BAS features such as security.
Table 2. Cost per unit climate impact.
Unit: US$ (2023) per t CO₂‑eq (100-year basis)
| Median | 0 |
Insufficient data exists to assess the learning rate for BASs. However, market analyses suggest prices will decline due to competition and economies of scale, especially for midsize commercial buildings (Rai, 2026).
Speed of action refers to how quickly a climate solution physically affects the atmosphere after it is deployed. This is different from speed of deployment, which is the pace at which solutions are adopted.
At Project Drawdown, we define the speed of action for each climate solution as emergency brake, gradual, or delayed.
Deploy Building Automation Systems is a GRADUAL climate solution. It has a steady, linear impact on the atmosphere.
Energy savings outcomes can differ based on whether they are derived from real world measurements or models, with modeled values often overestimating energy savings (Van Thillo et al., 2022; Vandenbogaerde et al., 2023). Model assumptions and simplifications, occupant behavior, real world conditions, and other factors contribute to the discrepancy (Van Thillo et al., 2022). Due to a lack of observed data, this analysis relies heavily on modeled energy savings.
There can be very significant differences between building types in terms of total energy usage and energy savings potential. A U.S. study of BAS savings in commercial buildings modeled 4% energy savings in an efficient retail strip mall and 59% for an inefficient secondary school, with an aggregated average of 29% for all building types (Fernandez et al., 2017). Some building types, such as health-care facilities and technology centres, are underrepresented in studies of energy consumption in buildings (Zarco-Soto et al., 2025).
We estimated that 10 billion m2 of commercial building space use BASs (Table 3). We estimated this represents 18% of total commercial floor area based on collected data (ABI research, 2025; Global Growth Insights, 2026; IEA, 2023c; U.S. EIA, 2022a). This value is comparable to ABI research (2025) estimates that 15% of global commercial building stock use BASs, with highest adoption in North America and Western Europe.
These estimates were based on market reports from 2025 plus U.S. statistics from 2018 (ABI research, 2025; Global Growth Insights, 2026; U.S. EIA, 2022a). Market reports may overestimate BAS adoption as we defined it because they include BASs that focus on security and other applications. We expected most BASs to be ones that control the energy use of equipment. Adoption rates in the market reports are also expressed as a percentage of commercial buildings with BASs. We used this as a proxy for percentage of floor area, although this may be an underestimate because large buildings are more likely than small ones to use BASs (Trenbath et al., 2022).
Common barriers to BAS adoption are largely economic and technical ones such as high up-front costs, challenges with estimating savings, system complexity, and lack of interoperability (Trenbath et al., 2022). In low-income countries, there can be additional barriers such as power supply issues, limited access to technology, lack of awareness, and lack of trained workers (Ayorinde & Kekana, 2025).
Table 3. Current adoption level (2025).
Unit: m2 using BASs
| Mean | 10,000,000,000 |
We estimate that commercial building spaces add BASs at a rate of 730 million m2/yr (Table 4). This is based on a single market research report that estimated the percent of the global commercial buildings with BASs in 2024 and projected values for 2030 (ABI research, 2025).
This value may not be an accurate indicator of the actual adoption trend for three reasons. First, it is based on a market report used to project future adoption. Second, we assume the percentage of the number of commercial buildings with BASs is a proxy for the percentage of building space with BASs, although larger commercial buildings may be more likely to adopt BASs. Finally, the market analysis did not differentiate between BASs that focus on energy savings and those that serve other purposes such as security.
Market research groups are generally optimistic that BAS sales will see strong growth in the foreseeable future, especially in North America and Europe (Backman, 2021; Global Growth Insights, 2026).
Table 4. Adoption trend (2024–2030).
Unit: m2 BASs installed per year
| Estimate | 730,000,000 |
If all existing commercial building space used BASs, they would serve 55 billion m2 of floor space globally (Table 5). This is based on the IEA’s estimate of total floor area for nonresidential buildings in 2022 (IEA, 2023d).
Table 5. Adoption ceiling: upper limit for adoption level.
Unit: m2 using BASs
| Estimate | 55,000,000,000 |
We estimate that 17 to 34 billion m2 of existing commercial building space could be served by BASs (see Table 6).
For the low achievable value, we applied Global Growth Insights’ (2026) estimate that 66% of U.S. commercial building stock use BASs to all high-income countries and applied ABI Research’s (2025) estimate that 12% of Asia Pacific buildings use BASs to all low- and middle-income countries. We used the percent of buildings with BASs as a proxy for the percent of commercial building area with BASs. The estimated low achievable adoption for BASs is consistent with our adoption trend applied over 10 years.
For the high achievable value, we assumed all building space in high-income countries use BASs and applied the reported U.S. 2018 adoption rate of BASs for heating, cooling and ventilation to low- and middle-income countries (U.S. EIA, 2022a). The European Union’s Energy Performance of Buildings Directive requires all commercial buildings above a threshold output for heating and cooling to install BASs by the end of 2029 (European Parliament & Council of the European Union, 2024).
The high achievable adoption for BASs is consistent with an accelerated adoption trend, similar to that projected by market research (Backman, 2021; Global Growth Insights, 2026).
Table 6. Range of achievable adoption levels.
Unit: m2 using BASs
| Current adoption | 10,000,000,000 |
| Achievable – low | 17,000,000,000 |
| Achievable – high | 34,000,000,000 |
| Adoption ceiling | 55,000,000,000 |
Current use of BASs reduces emissions by an estimated 0.11 Gt CO₂‑eq/yr (100- and 20-year basis, Table 7). If all existing commercial building space were served by BASs, it would reduce emissions by 0.58 Gt CO₂‑eq/yr (100- and 20-year basis). The estimated achievable range for existing buildings is 0.18–0.36 Gt CO₂‑eq/yr (100- and 20-year basis).
Table 7. Climate impact at different levels of adoption.
Unit: Gt CO₂‑eq (100-year basis)/yr
| Current adoption | 0.11 |
| Achievable – low | 0.18 |
| Achievable – high | 0.36 |
| Adoption ceiling | 0.58 |
Reducing energy use may lower air pollution and limit exposure to pollutants such as lead and fine particulate matter generated by fossil fuels, thereby improving the health of nearby communities (Henneman et al., 2023; U.S. Environmental Protection Agency [U.S. EPA], 2026). There is limited evidence that building automation systems can improve visual and thermal comfort, leading to a better employee experience and increased productivity (Garzia et al., 2023; Trenbath et al., 2022).
Reducing energy use can reduce climate and air pollutants associated with burning fossil fuels, such as CO₂, nitrogen oxides, methane, lead, and fine particulate matter (U.S. EPA, 2026).
Installing a BAS is no guarantee that the system will be used optimally. The complexity of BASs means that facility managers may not have the skills to realize the potential of the system (Mulayim et al., 2025). Occupant behavior is also a well-documented reason for why BASs fail to achieve energy savings. Occupant overrides of thermostats, opening of windows and blinds, etc., can significantly increase energy use (Ebuy et al., 2023).
Interoperability is a major challenge for BASs. New subsystems and controls are not always able to interact with existing BASs due to lack of universal standards. This can leave building owners locked into a single vendor for projects and services and can increase system complexity (Taboada-Orozco et al., 2024; Van Roosmale et al., 2024).
Existing buildings risk seeing their BASs becoming obsolete as the technology advances and technical support for legacy equipment disappears (Van Roosmale et al., 2024). In addition, the reliance of BASs on data collection and communication leaves systems vulnerable to reliability and security issues (Van Roosmale et al., 2024).
Artificial Intelligence (AI) and big data analytic tools are increasingly being combined with BAS to improve performance. However, AI and associated data centers are energy intensive and, because emissions associated with AI computing are higher than emissions associated with rule-based automation tools, emissions savings at the building may not overcome the significant emissions from AI data centers (Oliveira et al., 2026).
BASs can be used to increase or decrease electricity demand during critical times to facilitate integration of renewable energy and minimize grid peak events (Fernandez et al., 2017).
There are diminishing returns when solutions that reduce building heating and cooling energy use are combined. Thus the climate impact of these solutions will be reduced when combined with BASs.
square meter (m2) of commercial building space in which operational systems are controlled by a building automation system for the purpose of saving energy
CO₂ , CH₄, N₂O
BASs add complexity and new costs to building management even while overall saving operational costs and emissions. Operating BASs effectively to maximize savings requires competencies in both the technical aspects of building operation and also data management and even programming, skill sets that often require ongoing training (Abuimara et al., 2021). Many BASs are internet connected which increases vulnerability to cyberattacks (Li et al., 2023). Depending on the priorities of the owners and operators and the characteristics of the building, investments in alternative energy efficiency measures such as building envelope upgrades and improved windows could provide a better return on investment.
Heating degree days are an indicator of total space-heating demand to maintain an indoor temperature above 18 °C. Here we show annual average heating degree days for the decade ending in 2025.
Copernicus Climate Change Service. (2023). ERA5 hourly data on single levels from 1940 to present [Data set]. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). Retrieved January 13, 2026, from Link to source: https://doi.org/10.24381/cds.adbb2d47
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz‐Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmins, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., … Thépaut, J. N. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049. Link to source: https://doi.org/10.1002/qj.3803
Heating degree days are an indicator of total space-heating demand to maintain an indoor temperature above 18 °C. Here we show annual average heating degree days for the decade ending in 2025.
Copernicus Climate Change Service. (2023). ERA5 hourly data on single levels from 1940 to present [Data set]. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). Retrieved January 13, 2026, from Link to source: https://doi.org/10.24381/cds.adbb2d47
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz‐Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmins, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., … Thépaut, J. N. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049. Link to source: https://doi.org/10.1002/qj.3803
BASs can save energy and GHG emissions in all geographies. We expect buildings in climates with high heating or cooling demand to show higher-than-average energy and emissions savings. Emissions savings will be lower in geographies that use cleaner heating fuels and low carbon electricity grids.
BAS adoption is currently focused in high-income countries, but we expect it to grow in all parts of the world. Adoption is projected to increase significantly in the Asia-Pacific region due to rapid urban development and high uptake in new construction (ABI research, 2025; Global Growth Insights, 2026). In the Middle East and Africa, BASs are becoming common in new commercial buildings, driven in part by regional government mandates (Global Growth Insights, 2026). Meanwhile, the EU is requiring BASs in all commercial buildings with high heating and cooling needs (European Union, 2024) and more than 67% of new commercial buildings in North America now contain BASs (Global Growth Insights, 2026).
Consensus of effectiveness in reducing GHG emissions: High.
The IEA (2025)’s report on energy efficiency highlighted the importance of digital optimization using automation to boost efficiency gains in commercial buildings worldwide.
O’Grady et al. (2021)’s review showed consistent energy and peak power savings plus improved human comfort with BASs. Most studies relied on models and there was a noted lack of field case studies to understand discrepancies between measured and modeled values.
Fernandez et al. (2017) modeled the energy savings potential with advanced building control systems focussing on heating, cooling, and ventilation across 14 commercial building types and 16 U.S. climate regions. They reported an aggregated average of 29% annual energy savings with building control systems.
Taboada-Orozco et al. (2024)’s comprehensive review of BAS studies noted discrepancies between model predictions and real world measures due to occupant behaviors. They highlighted emerging applications of BASs such as health-care assistance, indoor navigation, and improving indoor air quality.
Poyyamozhi et al. (2024) profiled how the use of Internet of Things (IoT) technology in BASs has the potential to enhance its energy savings through machine learning and adjustments based on real-time data.
The results presented in this document summarize findings from two reviews and meta-analyses, five original studies, six technical reports, four market reports, eight product information webpages, and four databases reflecting current evidence from the U.S. and for the world as a whole. We recognize this limited geographic scope creates bias, and hope this work inspires research and data sharing on this topic in underrepresented regions.
We define Improve Windows & Glass as reducing the heat transferred through typical windows used in residential and nonresidential buildings by improving the thermal insulation capacity of the glass. Windows typically constitute a small portion of a building envelope but account for a substantial portion of the heat transferred (gained or lost) between the indoor space and the external environment. Using double-glazed rather than single-glazed windows cuts GHG emissions by reducing the energy required to heat or cool a building’s interior and improves the thermal comfort of its occupants.
Windows represent 15–40% of a building's total envelope surface area (Shah et al., 2024). A significant amount of the heat transmitted through the building envelope occurs via windows (Basok et al., 2022; Cuce & Riffat, 2015), and the uncontrolled flow of heat due to poor thermal insulation capabilities of windows and glass can generally increase the energy required for heating or cooling indoor spaces by 30–50% (Arasteh et al., 2006; Balali et al., 2023; Gustavsen et al., 2011). Improving windows and glass helps reduce heat gain in warm climates and heat loss in cold climates, thereby reducing the energy required to thermally condition indoor spaces and cutting energy-related emissions while improving occupant comfort.
Operating buildings accounts for approximately 30% of global energy consumption (Delmastro & Chen, 2023). The International Energy Agency (IEA, 2023e) stated that heating indoor spaces accounted for more than 41 EJ of energy in 2022 (an equivalent of about 11,400 TWh). This energy is mainly fossil fuel–based (oil, natural gas, and coal), but also includes electricity, modern bioenergy, and solar thermal (IEA, 2023b; 2023e) (Figure 1). Space cooling is largely achieved through air conditioners. In 2022, cooling buildings used approximately 2,111 TWh (an equivalent of about 8 EJ) (IEA, 2023d; Ritchie, 2024). According to the IEA (2018), annual space-cooling energy consumption in 2016 (2,020 TWh) was more than three times its levels in 1990. Considering the mix of energy sources (IEA, 2023b), this solution potentially cuts CO₂, methane, and nitrous oxide emissions and reduces black carbon and F-gas refrigerant emissions from operating heating and cooling systems (Richardson, 2024; Pistochini et al., 2022).
Figure 1. Energy used in buildings globally largely originates from fossil fuel–based sources.
Source: International Energy Agency. (2023b, June 15). Energy consumption in buildings by fuel in the net zero scenario, 2010-2030.
The properties of a window determine the rate of heat transfer (i.e., its thermal transmittance or U-value) and thus its efficacy at decreasing the flow of heat between the indoors and outdoors (Aguilar-Santana, 2020; Saint-Gobain, 2018). Window types such as double-glazed, double-glazed with low emissivity (low-e) coating, or triple-glazed (Figure 2) perform better than single-glazed windows due to their lower U-values (Aguilar-Santana et al., 2020; Li et al., 2023; Salazar et al., 2024). In more resourced countries or regions such as the United States, Canada, and the European Union, a minimum of double glazing is considered standard practice, accounting for a growing share of the number of windows installed or sold annually (Hermelink et al., 2017; Janssens, 2021). However, the minimum glazing U-value standards set by building energy regulations in most low- and middle-income countries, where the bulk of new construction occurs (IEA, 2023c), often do not mandate the use of better performing windows in buildings (Gaum, 2023).
Improve Windows and Glass assesses the impact of retrofitting single-glazed windows in the current (2022) global building stock, focusing on scaling up the use of double glazing as the minimum. Retrofitting extends the lifespan of building components and helps these buildings remain in use. The U-value of 2.7 W/m2K we used for double glazing during our analysis also includes other double pane window types with similar U-values such as secondary glazing where a second window is added to the outside of the existing one.
Figure 2. Multiple-glazed windows reduce heat transmission better than single glazed windows and so create less demand for GHG-producing fuels. Modified from Aguilar-Santana et al. (2020) and Moghaddam et al. (2023).
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Henry Igugu, Ph.D.
Ruthie Burrows, Ph.D.
James Gerber, Ph.D.
Daniel Jasper
Alex Sweeney
Sarah Gleeson, Ph.D.
Heather McDiarmid, Ph.D.
Amanda D. Smith, Ph.D.
Each 1 m2 of single-glazed window glass in buildings that is upgraded to double glazing has the potential to cut GHG emissions by approximately 0.07 t CO₂‑eq/yr (20-yr and 100-yr basis).
To determine the solution’s effectiveness (Table 1), we evaluated the emissions cut from reducing space heating and space cooling. Since studies often capture different U-value ratings for similar window glass, we weighted the energy saved (kWh/yr) from improving the glass using consistent U-values for the baseline and solution (see Figure 2). Thereafter, we weighted the energy impact by the total area of glass substituted (m2) to determine the savings intensity (kWh/m2/yr) and multiplied the estimate by emission intensities of heating and cooling fuels based on the IEA’s world energy balances data (IEA, 2024).
This solution cuts CO₂, methane, and nitrous oxide emissions by reducing the amount of fossil fuels used for heating and for producing electricity used for cooling. The analysis includes studies from countries representative of heating-dominated and cooling-dominated climates such as the United States (Calautit et al., 2025) and Malaysia (Balasbaneh et al., 2022), respectively. Notably, the solution is also effective in other climates (Magraoui et al., 2025).
Table 1. Effectiveness at reducing emissions.
Unit: t CO₂‑eq /m2/yr, 100-yr basis
| 25th percentile | 0.043 |
| Mean | 0.095 |
| Median (50th percentile) | 0.065 |
| 75th percentile | 0.13 |
Our estimate of the cost per unit climate impact (Table 2) indicates that replacing single-glazed windows with double-glazed windows in buildings globally results in considerable savings of approximately US$123/t CO₂‑eq.
We found that the solution’s initial cost varies considerably, from about US$31/m2 in Malaysia (Balasbaneh et al., 2022) to US$257–684/m2 in France (Harkouss et al., 2018), highlighting regional price differences that could affect adoption. Ultimately, we chose an initial cost of approximately US$144/m2 for double glazing. Using the cost of single glazing we found in studies from different regions (Aruta et al., 2025; Krarti & Ihm, 2016), our analysis determined a baseline initial cost of approximately US$35/m2. While the solution cost is more than four times the baseline, less energy is used for space heating or cooling, reducing the annual operating cost from US$23/m2 to approximately US$12/m2. After amortizing the initial cost over 30 years, the solution resulted in a net savings of US$8/m2/yr, compared with the baseline.
During our analysis, we normalized the initial cost by the baseline and solution U-value (see Figure 2) to ensure consistency. We assumed the initial cost includes the glass component alone, but some of our sources were ambiguous about the scope of the investment and may have also included frames and installation costs. To determine the cost per adoption unit, we weighted the amount of energy consumed for heating and cooling in each data source using the total area of windows upgraded in the respective case study buildings. The analysis does not include revenues because building owners typically do not generate any revenue from window glass installed.
Table 2. Cost per unit of climate impact.
Unit: 2023 US$/t CO₂‑eq , 100-yr basis
| Median | -123 |
We found no definitive data on the solution’s learning rate. While the adoption of double glazing grows, some studies have reported rising cost of glass in recent periods (MLI Building Products, 2023). In an assessment of regional float glass price trends, Procurement Resource (n.d.) argued that rising material, energy, and labor costs amid other economic pressures are driving up the cost of glass. Since modern windows are often made using float glass (Asahi India Glass Ltd., 2025), the initial cost could become more expensive.
Speed of action refers to how quickly a climate solution physically affects the atmosphere after it is deployed. This is different from speed of deployment, which is the pace at which solutions are adopted.
At Project Drawdown, we define the speed of action for each climate solution as emergency brake, gradual, or delayed.
Improve Windows and Glass is a GRADUAL climate solution. It has a steady, linear impact on the atmosphere.
Our analysis for this solution focused on the U-value of the glass component alone. It did not include other parameters such as the material type of the window frames or coatings on windows, though these also impact space heating and cooling energy use (Owolabi et al., 2023). We ensured that the data used in our analysis aligned with our approach (i.e., indicated the impact of solely substituting double-glazed or better glass for single-glazed). Due to limited data, we assumed that current adoption in LMICs is 5%. The adoption scenarios and climate impact may be influenced if the actual percentage is higher or lower.
A window’s orientation impacts the solar heat gain. Thus, the influence of upgrading to double-glazing on heating or cooling loads is affected by window placement. We found limited data that incorporates orientation and did not account for this difference.
Recently, some studies have indicated concerns about the payback period of upgrading to double glazing for building owners (Calautit et al., 2025), especially in LMICs, where higher initial costs could be a barrier. Creative initiatives such as incentive schemes can improve the payback period (Aruta et al., 2025).
To determine the current adoption of double-glazed windows, we first estimated the total amount of window glass installed in buildings by applying window-to-floor area ratios from studies to the currently existing 198.1 billion m2 residential and 54.6 billion m2 nonresidential building floor space (IEA, 2023f). This yielded approximately 23.3 billion m2 and 42.2 billion m2 of window glass installed in high-income countries (HICs) and low- and middle-income countries (LMICs), respectively (IEA, 2023c).
We found limited data for the proportion of minimum double-glazed windows in HICs. The U.S. Energy Information Administration (U.S. EIA, 2023) reported that 80 million housing units (65%) in the U.S. have double-glazed windows installed. Percentages reported for other countries include 88% of housing units in the United Kingdom (Department for Levelling Up, Housing and Communities, 2023), 90% in Canada (Natural Resources Canada, n.d.), and 15% in Australia (Paarhammer, n.d.). Using these percentages, we estimated a 76% (median) solution adoption rate in HICs.
Since we found no definitive data for the solution’s adoption in LMICs, and considering a few LMICs have building energy codes that either mandate or encourage the use of higher performing windows (Gaum, 2023; Gaum & Laubscher, 2022), we assumed that double-glazed windows represent a conservative underestimate of 5%.
All told, we estimate that as of 2022, installed double-glazed windows in buildings cover roughly 19.9 billion m2 globally (Table 3).
Table 3. Current (2022) adoption level.
Unit: m2 windows minimum double-glazed
| 25th percentile | 14,300,000,000 |
| Mean | 17,100,000,000 |
| Median (50th percentile) | 19,900,000,000 |
| 75th percentile | 22,700,000,000 |
According to the Department for Levelling Up, Housing and Communities (2023), the percentage of UK homes that have double-glazed windows increased by 9% between 2012 and 2022. Similarly, adoption grew by about 6% in five years (2015–2020) in the United States (U.S. EIA, 2018). Using these countries as representatives, this growth translates to approximately 438–448 million m2 of double-glazed or better windows being added every year in HICs.
We found limited data for adoption trends in LMICs. Based on our assumption for the current adoption in LMICs, we assumed that the percentage adoption of double-glazed windows grew by 4% over 10 years (2012–2022). This assumption, which is likely a conservative underestimate, translates to an annual addition of about 178 million m2/yr of double glazing.
Based on these findings, we estimate that the adoption of double glazing or better windows has grown globally by nearly 622 million m2 annually (Table 4).
Historically, the bulk of the solution’s adoption has occurred in HICs. However, the Global Alliance for Buildings and Construction, IEA, and the United Nations Environment Programme (UNEP) emphasize that adopting double-glazed windows is a necessary sustainability strategy for the building sector, especially in Africa and LMICs (GlobalABC/IEA/UNEP, 2020). This indicates considerable potential for scaling the solution, with 76% of the global building sector’s growth in the past 12 years occurring in LMICs (IEA, 2023f), where there has been less adoption of double glazing or better windows.
Table 4. 2010–2022 adoption trend.
Unit: m2/yr
| 25th percentile | 620,000,000 |
| Mean | 622,000,000 |
| Median (50th percentile) | 622,000,000 |
| 75th percentile | 624,000,000 |
We estimated an adoption ceiling (Table 5) of approximately 46.7 billion m2 of double-glazed windows globally. For this adoption scenario, 90% and 61% of window glass that existed in 2022 will be retrofitted to double-glazed or better by 2050 in buildings in HICs and buildings in LMICs, respectively.
In our analysis, we used the current double-glazed windows ratio of 90% in Canada (Natural Resources Canada, n.d) as a benchmark for the building sector’s adoption ceiling in HICs. For buildings in LMICs, we used the IEA’s recommended 2%/yr retrofit rate (IEA, 2022b) over 28 years (2022–2050). This estimated 56% growth was added to the current adoption of 5% to determine the region’s adoption ceiling. The analysis results in about 21 billion m2 and 26 billion m2 of double-glazed windows installed in buildings in HICs and LMICs, respectively.
Table 5. Adoption ceiling.
Unit: m2 windows minimum double-glazed
| Estimate | 46,700,000,000 |
Our analysis estimated a low achievable adoption of approximately 32.9 billion m2 of double-glazed or better windows installed in buildings globally (Table 6). For this scenario, we estimate that the percentage of windows that were at minimum double-glazed as of 2022 in buildings in HICs (76%) and buildings in LMICs (5%) grows to 81% and 33%, respectively.
Under the high achievable scenario, 86% of window glass in buildings in HICs and 47% of window glass in buildings in LMICs is at minimum double-glazed. This translates to a total of nearly 40.0 billion m2 of double glazing or better installed by 2050.
The achievable adoption scenarios are largely driven by the growth that is possible in LMICs. We assumed a retrofit rate of 1%/yr for the Achievable – Low scenario, which is the current global retrofit rate in the building industry (IEA, 2022b); for Achievable – High, we used 1.5%/yr. We also assumed that the current (2022) building stock will still be in use by 2050.
Table 6. Range of achievable adoption levels.
Unit: m2 windows minimum double-glazed
| Current adoption | 19,900,000,000 |
| Achievable – low | 32,900,000,000 |
| Achievable – high | 40,000,000,000 |
| Adoption ceiling | 46,700,000,000 |
The current adoption of double-glazed windows in buildings reduces global GHG emissions by approximately 1.3 Gt CO₂‑eq/yr on a 100-yr and 20-yr basis (Table 7). If the low achievable adoption scenario is reached, this solution could potentially cut about 2.1 Gt CO₂‑eq/yr (100-yr and 20-yr basis). The high achievable scenario would decrease global emissions 2.6 Gt CO₂‑eq/yr year (100-yr and 20-yr basis). We estimated that the adoption ceiling could avoid up to 3.0 Gt CO₂‑eq/yr of emissions on a 100-yr basis (3.1 Gt CO₂‑eq/yr, 20-yr basis).
This solution only accounts for the impact of retrofitting the building stock that exists as of 2022. However, the current global built floor area (252.7 billion m2) is projected to grow by an additional 183 billion m2, by 2050 (IEA, 2022a; 2023b). This means a possible addition of 1.6 billion m2 of new window glass every year, indicating that the potential for scaling the climate impact exists.
Table 7. Climate impact at different levels of adoption.
Unit: Gt CO₂‑eq/yr, 100-yr basis
| Current adoption | 1.3 |
| Achievable – low | 2.1 |
| Achievable – high | 2.6 |
| Adoption ceiling | 3.0 |
While multi-glazed windows are often more of an initial investment than single-pane windows, improved performance of these windows is associated with more energy and cost savings (Menzies & Wherrett, 2005). Regional climates often affect the most appropriate window type and the amount of savings (Karabay & Arici, 2012). In residential buildings, double-glazed windows can add value to homes and increase property values (Aroul & Hansz, 2011).
Reductions in air pollution due to lower heating and cooling demand decrease exposures to pollutants such as mercury and fine particulate matter generated from fossil fuel–based power plants, improving the health of nearby communities (U.S. Environmental Protection Agency [EPA], 2025). These pollutants have been linked to increased morbidity from cardiovascular and respiratory disease, asthma, infections, and cancer (Gasparotto & Martinello, 2021) and to increased risk of mortality (Henneman et al., 2023).
Better-performing windows can benefit health through improved thermal comfort (Bulut et al., 2021). When combined with other measures to reduce cooling loads, double-glazed windows can help with the risk of indoor heat stress (Ren et al., 2014). Improved windows may also reduce condensation and mold growth in buildings (Lozinsky et al., 2025). Residents of households with double-glazed windows have reported improvements in noise insulation after retrofitting single-pane windows (Bulut et al., 2021).
Higher-performing glass can reduce air pollution by lowering gas and electricity demand for heating and cooling, which can decrease pollutants such as CO₂, nitrogen oxides, methane, mercury, and fine particulate matter generated from fossil fuel–based power plants (U.S. EPA, 2025).
Faulty installation could compromise the expected benefits of double glazing. It could also lead to condensation on the inner pane if the sealant deteriorates, affecting visibility, aesthetics, and performance and resulting in a potential shorter lifespan than single glazing (Duan et al., 2021; Likins-White, 2023). Additional costs may be incurred when attempting to secure adequate expertise and equipment to ensure proper handling and installation (DIY Double Glaze, n.d.). Depending on the extent of the retrofits, this may drive up construction costs, which is a concern for building developers. However, it also represents opportunities to improve available technical expertise in regions where these services are unavailable or underdeveloped.
Improve Windows and Glass reduces the amount of space heating and cooling required. This may reduce the required size and complexity of heating and cooling systems, making them more economically accessible.
Upgrading window glass can motivate building owners to improve other elements of the building envelope. This could improve the cost efficiency of the upgrades when approached holistically.
The potential climate impact of deploying these solutions could be lower due to the reduced amount of space heating and cooling required in buildings from improving window glass.
m2 windows minimum double-glazed
CO₂ , CH₄, N₂O
Manufacturing double-glazed or better windows generates more industrial sector emissions than does manufacturing single-glazed windows due to the additional materials used. However, life-cycle analysis studies such as Balasbaneh et al. (2022) compared different glazing options ranging from single to triple glazing and determined that the emissions reduced by using better windows outweighs the embodied emissions. Although it is outside the scope of this solution, window frames account for as much as 46–80% of a window's embodied emissions, especially when using conventional window frame materials such as polyvinyl chloride and aluminum (Saadatian et al., 2021). Despite the higher embodied emissions, the emissions reductions from implementing the solution are substantial.
Heating degree days are an indicator of total space-heating demand to maintain an indoor temperature above 18 °C. Here we show annual average heating degree days for the decade ending in 2025.
Copernicus Climate Change Service. (2023). ERA5 hourly data on single levels from 1940 to present [Data set]. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). Retrieved January 13, 2026 from Link to source: https://doi.org/10.24381/cds.adbb2d47
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz‐Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmins, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., … Thépaut, J. N. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049. Link to source: https://doi.org/10.1002/qj.3803
Heating degree days are an indicator of total space-heating demand to maintain an indoor temperature above 18 °C. Here we show annual average heating degree days for the decade ending in 2025.
Copernicus Climate Change Service. (2023). ERA5 hourly data on single levels from 1940 to present [Data set]. Copernicus Climate Change Service (C3S) Climate Data Store (CDS). Retrieved January 13, 2026 from Link to source: https://doi.org/10.24381/cds.adbb2d47
Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz‐Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmins, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., … Thépaut, J. N. (2020). The ERA5 global reanalysis. Quarterly Journal of the Royal Meteorological Society, 146(730), 1999–2049. Link to source: https://doi.org/10.1002/qj.3803
The effectiveness of replacing single-glazed windows in buildings to mitigate climate change varies depending on how buildings are heated and the emissions intensity of electricity used for cooling in each region. We used regional data for the share of heating fuel in buildings (IEA, 2023a). For the electricity used to provide cooling in buildings, we used a global estimate for emission intensity. While the need for heating has historically outweighed the need for cooling, global trends show a steady increase in cooling degree days and a decline in heating degree days, even in colder climates (Eurostat, 2024; U.S. Environmental Protection Agency (U.S. EPA), 2024). Nonetheless, studies such as Kennard et al. (2022) claim that population growth, especially in cooling-dominated climates, will drive rising cooling demand. This growth could potentially drive up the amount of electricity needed to air condition buildings (Waite et al. 2017).
Building energy efficiency codes, especially mandatory regulations, could help drive the adoption of the solution via higher U-value requirements for windows and glass, particularly in low- and middle-income countries (Gaum, 2023). Our analysis also shows that the cost of double-glazed windows varies by country and region.
Consensus of effectiveness in reducing GHG emissions: High
Improving windows and glass helps optimize the amount of heating required in buildings by reducing heat loss. Calautit et al. (2025) reported that energy used for heating in a United Kingdom residence dropped nearly 23% after reducing the glass U-value from 5.6 W/m2K to 2.8 W/m2K. Using the same building parameters, the study tested the impact of reducing the U-value by 1.35 W/m2K in the climatic conditions of Netherlands, Japan, United States, Sweden and Australia. The outcomes were similar, with about a 10–12% reduction in heating loads (Calautit et al., 2025). The results from Yuk et al. (2024), Magraoui et al. (2025), and Ahmed et al. (2025) further support these findings.
Similarly, the solution reduces heat gained from the outdoors into buildings, thereby cutting cooling loads. Gomaa et al. (2025) reported that energy use in a Saudi Arabian residence was reduced by 1,265 kWh/yr (49%) after improving the glass U-value from 5.6 to 0.9 W/m2K (84%). Es-sakali et al. (2022) recorded 36% less electricity consumed after reducing the U-value by 1.44 W/m2K in Morocco’s climate.
The results presented in this document summarize findings from 10 original studies reflecting current evidence from 13 countries. We recognize this limited geographic scope creates bias, and hope this work inspires research and data sharing on this topic in underrepresented regions. The studies we found used simulations to assess the impact of retrofitting windows due to the inherent difficulty of real-world experiments. However, we used studies that include field measurements and calibration of the building simulations to validate their models.
Improving building envelopes cuts GHG emissions by increasing thermal resistance, which reduces unwanted heat exchange through the envelope, thus lessening the heating and cooling energy and associated emissions required to keep indoor spaces thermally comfortable.
Improving building envelopes reduces heating and cooling costs, helps maintain indoor thermal comfort, reduces heat stress risk and air pollution, and aids climate mitigation and adaptation in new builds and retrofits.
Improving building envelopes likely has a globally significant climate impact, but the adoption data required for a thorough analysis is limited.
Improve Building Envelopes cuts GHG emissions by enhancing the thermal resistance of the building shell, reducing unwanted heat exchange between the external environment and indoor spaces. These thermal improvements help decrease the amount of energy required to heat and cool buildings and the associated emissions. The solution’s effectiveness is well documented but it varies depending on the climate, the envelope's design, and emissions intensity of local electricity generation. Where available, building energy codes that specify minimum thermal requirements for envelopes and their deployment could help scale the solution. However, adoption data are limited. The solution has a climate impact that is likely globally significant along with meaningful additional benefits, but due to the data gap we categorize it as “Worthwhile.”
We found strong evidence that improving the thermal performance of building envelopes reduces heating and cooling loads. However, effectiveness typically varies depending on the climate. While the solution’s potential climate impact is likely globally significant (>0.1 Gt CO₂‑eq/yr ), data are not available to confirm this. We consider the solution “Worthwhile” because it can reduce energy use in both retrofits and new construction, and helps provide thermally comfortable indoor spaces.
| Plausible | Could it work? | Yes |
|---|---|---|
| Ready | Is it ready? | Yes |
| Evidence | Are there data to evaluate it? | Limited |
| Effective | Does it consistently work? | Yes |
| Impact | Is it big enough to matter? | ? |
| Risk | Is it risky or harmful? | No |
| Cost | Is it cheap? | Yes |
Improve Building Envelopes cuts GHG emissions from burning fossil fuels for direct indoor heating, district heating, or to generate electricity to power cooling systems. Thermal performance upgrades to the envelope can be achieved through various design and material interventions. Our assessment focuses on thermal insulation added to the roofs, external walls, and floors of buildings (Conley et al., 2018; McDiarmid et al., 2024). Such upgrades give the envelope a higher thermal resistance, which means that the envelope reduces heat gain better in hot periods and minimizes heat loss in cold seasons (Brunoro, 2024; Gupta & Deb, 2023).
Improving the thermal resistance of building envelopes is widely used and has been strongly demonstrated to enhance indoor thermal comfort and reduce GHG emissions. Since the emission intensity of fuels (International Energy Agency (IEA), 2024), and heating and cooling demand vary, so does this solution’s potential effectiveness. Various studies provide evidence of substantial heating energy savings. For example, work in China, Australia, Denmark, and Canada demonstrated that energy use reduced 17–62% due to added insulation in external walls and roofs (Abuseif et al., 2023; Jradi et al., 2017; Khayrullaev et al., 2026; Luo et al., 2024). Evidence also substantiates that envelope improvements significantly reduce cooling loads in warmer regions (Abdeen et al., 2024; Shittu et al., 2020). Despite the benefits, thermal improvements to building envelopes tend to have diminishing returns (Luo et al., 2024). For example, adding insulation to a building that has none will have a greater influence on reducing energy use than it would if some insulation is already present in the building, and even less if the envelope has a lot of insulation.
Improve Building Envelopes and other climate solutions that enhance buildings’ thermal performance (see Improve Windows and Glass) can offer both climate mitigation and adaptation benefits. First, they are applicable to existing buildings and new construction, help save heating and cooling energy costs, and improve occupant comfort. Studies show that the lower energy costs often offset the price of the improvements, with relatively low payback periods depending on the scope of intervention and insulation materials. For example, work in Türkiye, Italy, Morocco, and Saudi Arabia determined payback periods fewer than two years, reaching up to five or seven years (Akyüz, 2025; Dlimi et al., 2019; Makawi et al., 2025; Scrucca & Palladino, 2023). Second, improving the thermal performance of building envelopes increases resilience to heat waves and power outages in cold climates, especially for vulnerable populations like the elderly (Howden-Chapman et al., 2007; Ham et al., 2024, Jain 2024). Third, it could help reduce energy poverty, as well as noise infiltration and mold growth, improving the quality of lived spaces (Evin & Ucar, 2019; Janssen et al., 2023; Kattenberg et al., 2026). Finally, it reduces air pollution by lowering the demand for energy generated using fossil fuels (Levy et al., 2016).
Analysis of building energy codes across 88 countries shows that some regions (largely in colder climates, which are often high-income countries) have stringent or mandatory thermal performance requirements for building envelopes (World Bank, 2024). Thus, the greatest opportunities may be in countries that lack codes or minimum thermal performance requirements for building envelopes, or where such requirements are poorly implemented and enforced (Gaum, 2023; Gaum et al., 2026; World Bank, 2024). This highlights the potential for greater future adoption and ample opportunity to scale the solution’s climate impact, where it is globally significant (>0.1 Gt CO₂ eq/yr).
Improve Building Envelopes carries a few challenges and tradeoffs. First, it typically requires using more building material (e.g., to achieve better insulated walls or roofs). This often leads to buildings with greater embodied emissions, depending on the materials (Füchsl et al., 2022). Other climate solutions have explored alternatives which could potentially alleviate this concern (see Deploy Alternative Insulation Materials and Improve Other Building Materials). Second, insulation may be easily added to a new building during construction but can require extensive renovations in existing buildings such as opening up walls, and could include losing living space in the process (Conley et al., 2018). If not done well, adding insulation can create new problems with moisture control (Craven & Garber-Slaght, 2014). This is particularly significant in regions (especially high-income countries in cold climates) where the rate of new construction has slowed compared to that of low- and middle-income countries (IEA, 2023) and building energy codes already specify high thermal resistance requirements. In such cases, greater heating and cooling energy efficiency improvements in buildings may be derived from implementing other solutions such as Use Heat Pumps. Third, building energy codes can either be mandatory or voluntary and are not always enforced effectively (Gaum et al., 2026). This means that buildings may not always be developed with the specified envelope requirements, which could limit the solution’s adoption. Despite these challenges, the solution likely has a climate impact that is globally significant. However, our analysis could not arrive at a conclusive climate impact estimate because the data required to determine current adoption and estimate future adoption scenarios are severely limited.
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Abuseif, M., Jamei, E., & Chau, H.-W. (2023). Simulation-based study on the role of green roof settings on energy demand reduction in seven Australian climate zones. Energy and Buildings, 286, Article 112938. Link to source: https://doi.org/10.1016/j.enbuild.2023.112938
Akyüz, M. K. (2025). Enviroeconomic optimization of insulation thickness for building exterior walls through thermoeconomic and life cycle assessment analysis. Case Studies in Thermal Engineering, 65, Article 105606. Link to source: https://doi.org/10.1016/j.csite.2024.105606
Brunoro, S. (2024). Passive envelope measures for improving energy efficiency in the energy retrofit of buildings in Italy. Buildings, 14(7), 1–17. Link to source: https://doi.org/10.3390/buildings14072128
Conley, B., Cruickshank, C. A., & Baldwin, C. (2018). 2.24 Insulation materials. In I. Dincer (Ed.), Comprehensive energy systems (pp. 760–795). Elsevier. Link to source: https://doi.org/10.1016/B978-0-12-809597-3.00252-2
Craven, C., & Garber-Slaght, R. (2014). Exterior insulation envelope retrofits in cold climates: Implications for moisture control. HVAC&R Research, 20(4), 384–394. Link to source: https://doi.org/10.1080/10789669.2014.887028
Dlimi, M., Iken, O., Agounoun, R., Kadiri, I., & Sbai, K. (2019). Dynamic assessment of the thermal performance of hemp wool insulated external building walls according to the Moroccan climatic zoning. Journal of Energy Storage, 26, Article 101007. Link to source: https://doi.org/10.1016/j.est.2019.101007
Evin, D., & Ucar, A. (2019). Energy impact and eco-efficiency of the envelope insulation in residential buildings in Turkey. Applied Thermal Engineering, 154, 573–584. Link to source: https://doi.org/10.1016/j.applthermaleng.2019.03.102
Füchsl, S., Rheude, F., & Röder, H. (2022). Life cycle assessment (LCA) of thermal insulation materials: A critical review. Cleaner Materials, 5, Article 100119. Link to source: https://doi.org/10.1016/j.clema.2022.100119
Gaum, T. (2023). Building energy codes in the global south: Comparing selected variables to develop a decision-making model to address climate-change guidelines [spreadsheet] Link to source: https://docs.google.com/spreadsheets/d/1aP4zaeDvfwSI-3Abuj8Z_VUUEHJzjMZS/edit?gid=988383392#gid=988383392
Gaum, T., Laubscher, J., & Igugu, H. O. (2026). The real-world use of building energy regulations as a mechanism to accelerate climate resilience in the Global South. Encyclopedia, 6(5), 1–32. Link to source: https://doi.org/10.3390/encyclopedia6050107
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Henry Igugu, Ph.D.
Nina-Francesca Farac, Ph.D.
Sarah Gleeson, Ph.D.
Megan Matthews, Ph.D.
Heather McDiarmid, Ph.D.
Amanda D. Smith, Ph.D.
Christina Swanson, Ph.D.
If you’re chronically online like me, you probably get a fair share of your daily laughs from internet memes.
If you also happen to work in climate or sustainability, you’ve probably been exposed to niche sustainability memes that flawlessly capture the struggles and anxieties of this work (with a healthy dose of levity). Beyond releasing some steam, these memes also serve as a great window into what it’s like to work in sustainability right now, particularly corporate sustainability. So, what do these memes reveal?
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