Net zero buildings don’t exist – at least, not yet

A certified “net zero” building, “climate neutral” building, or even a “climate positive” building does not mean a building without negative consequences for the climate or the environment. There are many certification schemes for getting to zero, and most of them will result in a much better building than if the designer and builder had used typical practices. I’ve written before about why that’s worth celebrating, even though net zero isn’t a very useful concept for an individual building. But it’s equally important to be honest about what such designations do and don’t mean. 

Buildings (even the good ones!) drive emissions.

To claim “zero” for a building, even the most highly efficient one, you first need to reduce emissions as much as possible. That’s the good part of these certifications.

There are many ways our buildings cause emissions, all of which are detailed in a webinar I gave last year. They include burning fossil fuels; using electricity, refrigerants, and manufactured materials; transporting people and materials to and from the building; and producing waste. Look around at the building you're currently in. How many of these can you see right now? I’m confident it’s more than zero.

Offsetting doesn’t erase those emissions.

For the emissions remaining after you’ve cut as much as you can, “zero” claims rely on some combination of narrowing the scope of the emissions to be addressed or offsetting your actual emissions.

Narrowing the scope might mean you only address the on-site emissions, or that you only look at emissions due to the building’s energy consumption and ignore emissions from industry and transportation. Estimating all the emissions associated with a building throughout its lifetime is extremely tricky. It requires deep expertise and a lot of time to do a life cycle assessment that captures all the environmental impacts of a building. And even the best life cycle assessments will include a lot of uncertainty. It makes sense to focus on what you can meaningfully measure, given the available expertise, data, and budget for studying a building’s emissions. But your building isn’t zero emissions even if, for example, you’ve been able to cut all of your on-site emissions.

Offsetting emissions by paying for someone else to cut their emissions, produce more renewable energy, or support the Earth’s natural carbon sinks does not make your building’s emissions go away – it’s more like shuffling around the math than truly mitigating your impact.

For instance, let’s say you’re building a new house. You consider either building a house using standard practices in your location, which cause a lot of emissions, or building a house that’s much “greener.” Given the materials and construction expertise available in your area, your home builder tells you that the greenest house they can deliver will result in about half the life cycle emissions of a typical house.

Next door to where you’re building that new house, your neighbor is already living in an existing house that was built with standard practices.

You decide to go with the greenest house your builder can deliver. You’re proud that your house is better for the climate than the average house in your neighborhood, but you’re sad that your house still causes so many emissions. So you pay for your neighbor to retrofit their home to be just as green as your new house and “offset” the rest of your emissions.

Does this mean you’ve neutralized your climate impact? After all, you’ve built a new house and retrofitted your neighbor’s, so the emissions from both homes are now equal to the emissions your neighbor’s home was previously causing by itself. 

But who’s going to offset the emissions associated with your house? Because what’s left (in both houses) are the very hardest emissions to address, like the ones coming from producing the concrete, insulation, or windows in the home’s structure, or from using electrical power from a utility. And even if you have solar panels that produce more electricity than you use, you are still driving electricity sector emissions if you’re using any power from the grid – we’re getting better and better at incorporating renewable energy sources into the power grid, but we don’t yet have any utilities that can generate 100% zero-emissions electrical power around the clock.

There’s an even bigger problem, though, when you’re paying for someone else to reduce their emissions: It’s almost never your neighbor. Verifying that someone else cut emissions and guaranteeing that they will continue to do so is extremely difficult, and carbon markets are rarely trustworthy because they are prone to fraud and double-counting the emissions cuts that do occur. When researchers investigate, they most often find that carbon offsets purchased in offset markets don’t result in actual emissions cuts. While carbon offset trading has made money for lots of people, it hasn’t been a success for the climate.

If you’re paying for someone to protect or restore one of nature’s carbon sinks, that’s great! People who genuinely care about the climate use their social influence and market power to protect rainforests, not to hold climate summits that drive deforestation. But even if your action actually results in forest protection, it does not change your emissions. And if you agree that the goal is to stop the accumulation of greenhouse gases in the atmosphere, you should understand that market signals simply do not work in a net zero world, and cannot show us the pathway that’s best for society.

The real need is cutting emissions well beyond what current net zero standards can do.

Let's be clear: even if you built it from locally grown materials by hand and never used fuel or electricity from the grid, your building is still driving emissions. We have to acknowledge that each building has a climate impact, because we have to be honest about our starting point if we’re to reach our goal – a planet without increasing climate change.

We can vastly improve our buildings and, by doing so, help reduce emissions in industry, transportation, electricity, and agricultural sectors. But if we want the changes in our buildings sector to actually drive us toward a net zero world, we will need to build fewer, better buildings and more circular buildings. We need to provide safe, healthy housing for those who don’t have it now and for those who have yet to join us on the planet. We need radical change in how we plan for new buildings and how we operate them. And that change must grow from all of us, holding steady in the solid ground of truth about what’s happening to our climate and why – it’s radical in the biological sense, “from the root.”

In 2050, the electrical grid won’t look anything like it does today, but we do know what a climate-friendly grid will look like: mostly renewable energy sources, with more energy storage capacity, and perhaps some remaining nuclear power. 

In 2050, I hope most of our buildings look nothing like they do now. I don’t know what the most climate-friendly buildings will look like, but isn’t that exciting? We have big challenges in front of us, to be sure. Changing everything about how we build in just one generation is so dramatic that it might seem impossible. But Octavia Butler wrote that “predicting doom in difficult times may have more to do with the sorrow and depression of the moment than with any real insight into future possibilities.” These times are difficult. And the possibilities are many.

We have a long history of human architecture and urban development to draw from that is more appropriate to the surroundings and thus more long-lasting and sustainable than the “American Way of Building” that’s often disconnected from its surroundings, creating problems and then solving them with more technology and more energy use. We need to both learn from older and non-Western forms of architecture and create entirely new ways of designing and operating our buildings that are appropriate for this moment, buildings that are attuned to their surroundings and thus longer lasting and more sustainable. 

In a truly net zero world, I don’t know what materials will make up our buildings, or what systems will provide services like lighting, cooling, or hot water. We haven’t identified a perfect suite of solutions to address the many ways our buildings drive emissions. But I do expect that truly climate-friendly buildings will be more like plants than machines: providing beauty and comfort because they are uniquely suited to their environment, constructed with non-toxic, biologically based materials, and running on renewable energy. And it’s past time for us to do our part by planting and nurturing the seeds for the buildings of the future.

Amanda D. Smith, Ph.D., is a senior scientist at Project Drawdown with expertise in building science and distributed energy systems. 

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