A new report from the Intergovernmental Panel on Climate Change (IPCC) states that global warming of 1.5°C (2.7 °F) is essentially inevitable in coming decades. The question now is whether the world can prevent further, more destructive warming of 2°C (3.6°F), or, even worse, 3°C (5.4°F), which is what current policies put us on a trajectory to experience. Our economies can only put another 420 gigatons of greenhouse gas emissions into the atmosphere if we want a good chance of keeping a temperature increase to 1.5°C instead of 2°C. At our current pace, the world’s carbon budget will be used up before 2030. We need to phase out fossil-fuel use, build thousands of new clean power plants -- and swiftly move to power our homes, offices, schools, and transportation systems with clean energy.
Globally, buildings account for nearly 40 percent of greenhouse gas emissions. To keep warming to 1.5°C, we need to retrofit existing buildings to be net-zero in terms of their energy use well before 2050 and build all new buildings to meet the new net-zero standard by 2030.
Today, in developed countries, far less than 1 percent of buildings are designed and constructed to the net-zero standard. However, this is changing. The State of California and the European Commission have mandated net-zero buildings moving forward, which is expected to add hundreds of thousands of these new and retrofitted buildings in coming years.
Furthermore, as of 2020, 28 major cities, including New York City and Washington, DC, in the US, Medellín in Colombia, and Cape Town and Johannesburg in South Africa, representing more than 125 million people, have committed to achieving net-zero building operations by 2050.
Still, many more governments at all levels need to join the effort and ratchet up their commitments. And architects, commercial and residential developers, home builders, and building product manufacturers must do much more to get us on a path to scaling up net-zero buildings more rapidly.
A key foundation of the net-zero transformation—the photovoltaic (PV) panel—is proliferating across roofs around the world. Yet the rooftop PV—or any other form of residential renewable energy generation—is really just one component in making a single-family house, apartment complex, or residential community net-zero or energy-positive, which refers to buildings that generate more energy than they use.
As I outline in my book, Good Energy: Renewable Power and the Design of Everyday Life, homes need to fully electrify, eliminating the use of coal, oil, and gas in boilers, furnaces, and stoves, which not only pollute but also contribute to unhealthy indoor air. This enables homes to transition to only relying on electricity from renewable energy sources. To further reduce energy use, buildings need to incorporate low-cost, low-energy appliances, insulation, and energy-efficient windows.
In temperate climates, passive house techniques can be used to also achieve deep energy savings from heating, cooling, and ventilation. The term “passive house” refers to a set of techniques that essentially turns a house, apartment building, or commercial building into an airtight ship that doesn’t leak heat in the winter or require much cooling in the summer. These buildings are designed with the seasonal path of the sun in mind, maximizing solar heat gain in the winter and reducing it in the summer. They can also be designed around the daily movements of the sun, inviting in light at certain times and blocking it when temperatures are warmest in the afternoon. Passive houses of all sizes can reduce energy use by up to 90 percent over conventional building practices and provide much healthier indoor air. These projects don’t have to cost more either.
In developing countries with tropical and sub-tropical climates, which will face increasingly dangerous heat in the coming decades, houses, apartment complexes, and other buildings can be designed to be cooler but without increasing energy use for air conditioning. A few proven strategies include deep verandas and overhangs that reduce the amount of sunlight warming interior spaces; thermally-massed structures, which helps draw out heat from interior spaces; and maximized airflow, which increases reliance on breezes. Multi-story buildings can use systems of solar chimneys and earth ducts that use convection to continuously draw in cool air and expel hot air. Residential communities can orient street grids to capture prevailing winds. These architectural strategies increase the flow of outside air, which improves air quality.
Innovation must also come to how net-zero buildings are constructed. Architects, major developers and home builders, and product manufacturers need to encourage greater standardization of building components and how these components integrate with PV panels and energy management systems. The local pre-fabrication of net-zero building components can speed up the construction process, thereby lowering labor costs. At the same time, pre-fabricating building components in local factories will create more good-paying green jobs and help revitalize manufacturing infrastructure. Producing components with local materials also reduces emissions from transporting materials.
The more net-zero and energy-positive buildings function like a standard kit of parts, the faster we can reduce the time and cost of constructing these buildings, making them easier to scale up in developed and developing countries.
While net-zero homes are necessary for reducing emissions from the building sector, policymakers, planners, developers, and architects need to imagine an even more sustainable built environment. Homes and residential communities can’t just generate energy for themselves.
Today, many homes and commercial buildings powered by their own PVs send energy to the central grid when they are producing more energy than they can use, and then tap the grid when their PV panels aren’t producing as much energy on cloudy days or during the winter. Net-zero energy use is achieved over the course of a year. While these buildings are becoming even more energy-efficient through the incorporation of in-home batteries and increasingly sophisticated energy management systems that enable homeowners to better track their own energy use, we can go further.
We can imagine highly energy-efficient buildings powered by clean energy that form the basis of new decentralized energy networks that further improve resilience to climate shocks. A few forward-thinking residential communities across the world, like Trent Basin in Nottingham, UK, have become virtual power plants that actively trade energy with neighboring communities, engaging in energy market arbitrage that can also help reduce any intermittency issues created by an all-renewable energy-based grid.
These communities could form the basis of future, more locally sourced energy systems that could even supplant central power plants, which are increasingly at risk from extreme weather events brought on by climate change. With net-zero homes, powered by clean energy, we can all become energy producers and even profit from the clean energy revolution.