Improve Windows & Glass

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Summary

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.

Description for Social and Search
Improve Windows & Glass is a Highly Recommended climate solution. Upgrading single-glazed windows to double-glazing saves money, improves comfort, and cuts GHG emissions.
Overview

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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A description of different glazing types.

Sources: Aguilar-Santana, J. L., Jarimi, H., Velasco-Carrasco, M., & Riffat, S. (2020). Review on window-glazing technologies and future prospects. International Journal of Low-Carbon Technologies, 15(1), 112–120; Moghaddam, S. A., Serra, C., Gameiro da Silva, M., & Simões, N. (2023). Comprehensive review and analysis of glazing systems towards nearly zero-energy buildings: Energy performance, thermal comfort, cost-effectiveness, and environmental impact perspectives. Energies, 16(17), Article 6283.

References

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Credits

Lead Fellow

  • Henry Igugu, Ph.D.

Contributors

  • Ruthie Burrows, Ph.D.

  • James Gerber, Ph.D.

  • Daniel Jasper

  • Alex Sweeney

Internal Reviewers

  • Sarah Gleeson, Ph.D.

  • Heather McDiarmid, Ph.D.

  • Amanda D. Smith, Ph.D.

Effectiveness

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
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Cost

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
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Methods and Supporting Data

Learning Curve

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

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.

Caveats

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). 

Current Adoption

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 mand 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
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Adoption Trend

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
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Adoption Ceiling

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
Left Text Column Width
Achievable Adoption

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
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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
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Additional Benefits

Income and Work

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). 

Health

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). 

Air Quality

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).

Risks

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.

Interactions with Other Solutions

Reinforcing

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. 

Competing

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.

Dashboard

Solution Basics

m2 windows minimum double-glazed

t CO₂-eq (100-yr)/unit/yr
00.040.065median
units
Current 1.99×10¹⁰ 03.29×10¹⁰4.0×10¹⁰
Achievable (Low to High)

Climate Impact

Gt CO₂-eq (100-yr)/yr
Current 1.3 2.12.6
US$ per t CO₂-eq
-123
Gradual

CO₂ , CH₄, N₂O

Trade-offs

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.

°C days
015,000

Space heating demand (18 °C basis)

Heating degree days are a measure 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

°C days
015,000

Space heating demand (18 °C basis)

Heating degree days are a measure 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

Maps Introduction

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.

Action Word
Improve
Solution Title
Windows & Glass
Classification
Highly Recommended

Lawmakers and Policymakers

  • Set clear and measurable targets for building efficiency, emissions reduction, and the deployment of improved windows.
  • Enact holistic policy plans and building codes to reduce GHG emissions from buildings through improved windows and framing systems.
  • Set public procurement standards for windows and glass, using double-glazed windows, at minimum, for public buildings.
  • Amend building codes to include minimum requirements based on window performance; gradually increase the standards over time if necessary.
  • Periodically update codes, policies, and public guidance to keep pace with research and development.
  • Make double-glazed windows the minimum standard option through a range of policy interventions, including regulations, subsidies, and educational programs where relevant; extend incentives to high performing secondary-, double- or triple-glazed windows, if relevant.
  • Offer financial incentives such as subsidies, tax credits, and grants for consumers, manufacturers, start-ups, and improved window installers.
  • Ensure financial incentives reach, and offer additional incentives for, low- and middle-income communities.
  • Ensure financial incentives cover both new installations and retrofits.
  • Create financial disincentives such as higher taxes and fines for lower performing windows.
  • Subsidize workforce or skills development and/or work with businesses to identify gaps and needs such as technical knowledge or the advantages of new technology.
  • Invest in research and development to improve window design, manufacturing, adoption, supply chain access, and circularity.
  • Create green building certification schemes and/or public-private partnerships that offer information, training, and general support for improved windows.
  • Offer educational resources, one-stop shops for windows, and demonstrations for installation and retrofits; offer tours of model builds that feature improved windows for commercial and private developers, highlighting the cost savings, and environmental benefits.

Further information:

Practitioners

  • Finance or develop only new construction and retrofits that use improved windows and other low-carbon practices.
  • Take advantage of financial incentives such as subsidies, tax credits, and grants for installing improved windows.
  • Seek or negotiate preferential loan agreements for developers using improved windows and other climate-friendly practices.
  • Use double-glazed windows as the most basic standard and offer a variety of better-performing options such as triple-glazed.
  • Work with designers and architects who integrate efficient windows and other efficient materials into their designs.
  • Integrate improved window designs into construction databases, including listing prices, thermal insulation properties, and environmental benefits.
  • Advocate for financial incentives, improved building codes, and educational programs advancing the use of improved windows.
  • Use educational resources, one-stop shops for retrofitting and weatherization, installation demonstrations, and tours of model builds.
  • Conduct research to improve the manufacturing, adoption, supply chain access, and circularity of windows.
  • Create or join green building certification schemes, green building councils, and/or public-private partnerships that offer information, training, and general support for improving windows.

Further information:

Business Leaders

  • Finance only new construction and retrofits that use improved windows and other low-carbon practices.
  • Expand product lines to include improved window designs.
  • Integrate improved window designs into construction databases, listing prices, thermal insulation properties, and environmental benefits.
  • Invest in research and development to improve window design, manufacturing, adoption, supply chain access, and circularity.
  • Advocate for financial incentives, improved building codes, and educational programs advancing the use of improved windows.
  • Join green building certification schemes and/or public-private partnerships that offer information, training, and general support for improved windows.
  • Create long-term purchasing agreements with improved window manufacturers to support stable demand and improve economies of scale.
  • Create or join green building certification schemes, green building councils, and/or public-private partnerships that offer information, training, and general support for improved windows.

Further information:

Nonprofit Leaders

  • Finance or develop only new construction and retrofits that use improved windows and other low-carbon practices.
  • Advocate for clear and measurable public targets for building efficiency, emissions reduction, and deployment of improved windows.
  • Advocate for holistic policy plans and building codes to reduce GHG emissions from buildings that include improved windows and framing systems.
  • Advocate for financial incentives, improved building codes, and educational programs advancing the use of improved windows.
  • Conduct research to improve window design, manufacturing, adoption, supply chain access, and circularity.
  • Work with businesses for workforce or skills development.
  • Offer educational resources, one-stop shops for windows, and demonstrations for installation and retrofits; offer tours of model builds that feature improved windows for commercial and private developers, highlighting the cost savings and environmental benefits.
  • Create, join, or administer green building certification schemes and/or public-private partnerships that offer information, training, and general support for improved windows.

Further information:

Investors

  • Finance only new construction and retrofits that use improved windows and other low-carbon practices.
  • Invest in research and development and start-ups to improve window design, manufacturing, adoption, supply chain access, and circularity.
  • Issue green bonds to invest in projects that use improved windows and integrate other climate-friendly construction practices.
  • Offer preferential loan agreements for developers using improved windows and other climate-friendly practices.
  • Join green building certification schemes and/or public-private partnerships that offer information, training, and general support for improved windows.

Further information:

Philanthropists and International Aid Agencies

  • Finance only new construction and retrofits that use improved windows and other low-carbon practices.
  • Offer grants for developers using improved windows and other climate-friendly practices.
  • Create financing programs for private construction in low-income or under-resourced communities requiring the use of improved windows.
  • Advocate for clear and measurable public targets for building efficiency, emissions reduction, and the deployment of improved windows.
  • Advocate for holistic policy plans and building codes to reduce GHG emissions from buildings that include improved windows and framing systems.
  • Advocate for financial incentives, improved building codes, and educational programs for improved windows.
  • Fund research to improve window design, manufacturing, adoption, supply chain access, and circularity.
  • Offer educational resources, one-stop shops for retrofitting and weatherization, installation demonstrations, and tours of model builds for commercial and private developers, highlighting the cost savings and environmental benefits.
  • Create, join, or administer green building certification schemes and/or public-private partnerships that offer information, training, and general support for improved windows.

Further information:

Thought Leaders

  • Advocate for clear and measurable public targets for building efficiency, emissions reduction, and the deployment of improved windows.
  • Advocate for holistic policy plans and building codes to reduce GHG emissions from buildings that include improved windows and framing systems.
  • Advocate for financial incentives, improved building codes, and educational programs for improved windows.
  • Conduct research to improve window design, manufacturing, adoption, supply chain access, and circularity.
  • Contract with businesses for workforce or skills development.
  • Offer or support educational resources, one-stop shops for retrofitting and weatherization, installation demonstrations, and tours of model builds for commercial and private developers, highlighting the cost savings and environmental benefits of improved windows.
  • Create, join, or administer green building certification schemes and/or public-private partnerships that offer information, training, and general support for improved windows.

Further information:

Technologists and Researchers

  • Research and develop high-performance window technologies such as vacuum glazing, aerogel applications, potential integration of solar photovoltaic glass, and the use of unconventional gases to fill multi-pane windows and improve performance.
  • Create improved alternatives to common practices for air and vapor sealing.
  • Find alternative materials for spacers with reduced thermal conductivity in double- and triple-glazed windows.
  • Research and develop alternative window frame designs to improve thermal performance, structural insulating materials, and improve ease of installation (e.g., out-of-the-box window installation kits).
  • Improve efficiency of the window manufacturing process, supply chain access, and the circular economy of glass.

Communities, Households, and Individuals

  • Finance or develop only new construction and retrofits that use improved windows and other low-carbon practices.
  • Take advantage of financial incentives such as subsidies, tax credits, and grants for installing improved windows.
  • Advocate for clear and measurable public targets for building efficiency, emissions reduction, and the deployment of improved windows.
  • Advocate for holistic policy plans and building codes to reduce GHG emissions from buildings that include improved windows and framing systems.
  • Advocate for financial incentives, improved building codes, and educational programs for improved windows.
  • Organize local “green home tours” and open houses to showcase climate-friendly builds, fostering demand by highlighting cost savings and environmental benefits of improved windows.
  • Capture community feedback and share it with local policymakers to address barriers such as permitting logistics or up-front costs, helping to shape policies that drive adoption.
  • Create, join, or administer green building certification schemes and/or public-private partnerships that offer information, training, and general support for improved windows.

Further information:

Evidence Base

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.

Updated Date
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Improve Building Envelopes

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Improve building envelopes
Coming Soon
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Methods and Supporting Data

Action Word
Improve
Solution Title
Building Envelopes
Classification
Highly Recommended
Updated Date
Coming Soon Label
Coming Soon

Improve District Heating: Buildings

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District heating facility
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Methods and Supporting Data

Action Word
Improve
Solution Title
District Heating: Buildings
Classification
Highly Recommended
Updated Date
Coming Soon Label
Coming Soon

What can memes tell us about the state of corporate sustainability?

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?

To get back on track, we need new climate leadership and approaches

This year marks a key milestone in the struggle to address climate change.

After decades of continued warming, the effects of climate change are becoming increasingly evident around the world – and are impossible to deny. Temperature records are being shattered year after year. And countless heat waves, severe storms, floods, droughts, and wildfires are affecting millions, often with dire consequences. All the while, greenhouse gas emissions have continued, fueling the unrelenting heating of our planet.

Image
A headshot of Lisa Laurente

Lisa Laurente

Administrative Manager
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