Buildings, among the largest greenhouse gas emissions culprits, are getting easier to make sustainable

The places human beings spend the most time are among the largest producers of greenhouse gas emissions in the world.

Making buildings more sustainable will be key to mitigating climate change and keeping inhabitants safe amid the extreme temperature swings expected in the future, experts told ABC News.

Building construction and operation is responsible for about 40% of global greenhouse gas emissions, researchers say.

"It's not surprising when you think about where we spend our time," Ben Evans, federal legislative director at the U.S. Green Building Council, a nonprofit that promotes sustainability in building design, told ABC News. "Humans spend 90% of our time indoors, and we use a lot of energy when we do that."

Promoting better energy and water efficiency, choosing sustainable materials, and driving innovations in building design are among the actions needed to mitigate the carbon footprint of the buildings sector, Elizabeth Beardsley, senior policy counsel of the U.S. Green Building Council, told ABC News. Leaders in sustainable construction are incorporating technologies that have been around for decades but are just now seeing wider implementation as costs decrease.

How heating and cooling buildings is becoming more sustainable

While commercial heat pump technology has been in general use for more than five decades, that use has become more widespread in recent years, Srinivas Katipamula, energy and environment scientist at the Pacific Northwest National Laboratory, one of the U.S. Department of Energy's national laboratories, told ABC News.

Heat pumps are essentially air conditioners that can run in reverse. While air conditioners pull the heat from a room and dump it outdoors, a heat pump has the same functionality but can also run in reverse, giving the appliance the ability to provide significant heat in the winter, equivalent to what a traditional gas furnace can provide.

In the past, heat pumps were installed primarily in warmer climates, like the Southeast U.S., because once temperatures dipped below about 32 degrees Fahrenheit, a heat pump's ability to provide warmth decreased, necessitating a backup heating source.

But the electrification of heat pumps has transformed the technology into something that can be installed in regions where temperatures drop below 0 degrees Fahrenheit, Katipamula said.

"Heat pumps are a game-changer," said Simon Mugo, program manager of the New York City Accelerator, a city-backed program that provides building owners and tenants with the resources to improve efficiency and comply with local laws as well as explore different technologies. That's because heat pumps "are not creating heat – they're merely moving heat from one place to another," Mugo told ABC News.

Moving heat rather than creating it means heat pumps have the potential to go beyond 100% efficiency, Mugo said. Their installation is gaining traction in New York City, allowing residents to replace both their air conditioners and gas furnaces with one unit.

In other regions, geothermal energy is being installed into homes and businesses, Mugo said.

Geothermal energy, which taps into the groundwater temperature to extract energy, has been around for thousands of years, but retrofits of existing buildings to take advantage of it are becoming more commonplace.

Of equal importance is optimizing buildings to eliminate waste, which includes several low-cost options. Leaky walls and windows need air sealing. Solar panels could help offset energy needs. Insulation also must be considered – especially in attics, Evans said.

Buildings will soon need to be optimized for all weather types, regardless of region

Many buildings in the Northeast were built in the early 20th century, when the so-called Spanish Flu pandemic was active. Buildings were designed with oversized heating systems so that interior rooms could stay warm while windows remained open in order to allow fresh air circulation, in hopes of staving off virus infection.

"Most buildings in New York that are over 100 years [old] were really designed to operate on the coldest day with the windows open and still provide sufficient heat to ensure the occupants are comfortable," Mugo said. "So if you walked around in New York City in the winter, you'd still, to this day, you see windows open in the winter."

The good news is, best practices in building sustainability are now becoming the standard, Beardsley said: "The technology is just rapidly improving and becoming lower in costs as it becomes more widely used,"

Experts agree that a changing climate will necessitate that buildings in all locations are optimized for environmental sustainability.

In the historically temperate Pacific Northwest, where the vast majority of homes are not equipped with central air conditioning, summer heat waves have been intensifying and elongating. All-time high temperature records were broken there in the summer of 2023, which saw multiple consecutive days with highs of 100 degrees Fahrenheit. Similar heat waves have already occurred in the Pacific Northwest this year.

Conversely, in Texas, where temperatures are typically warm, the severe 2021 winter storms rendered millions there without power, killing hundreds of people. Had those homes been properly insulated, the interiors would have been able to retain warmth for much longer and may have prevented many of those deaths, Evans said.

"We need to be prepared to deal with both extreme cold weather as well as extremely hot weather," Chrissi Antonopoulos, senior analyst and residential building researcher at PNNL, told ABC News.

Of the estimated 170 million single-family homes in the U.S., about 60% of them were built before energy codes existed in the early 90s, Antonopoulos said.

"They are inefficient. They're not insulated. They have high-load mechanical systems and they're not made to weather the storm, so to speak," she said.

Technology is improving fast

Emerging technologies such as thermal storage, and expanding and improving power grid integration to make it more resilient, are currently being tested, the experts said.

Virtual power plants consisting of distributed renewable energy resources, such as solar panels and on-site batteries used to charge electric vehicles, is also an up-and-coming solution that would allow a campus or neighborhood to serve as its own power plant, Beardsley said. Additionally, heat pumps small enough to mount in windows like conventional window air conditioners, and which plug into conventional wall power outlets, are also becoming more available, Antonopoulos said.

The U.S. General Services Administration (GSA) Green Proving Ground focuses on testing new technologies for buildings, funded by the Inflation Reduction Act, Jetta Wong, deputy chief of staff and senior climate advisor for the GSA, told ABC News.

New heat pumps, ceiling tiles that can absorb and store heat energy, and window films that promote energy insulation are among the technologies the GSA is testing, Wong said.

Programs to finance improvements are available

Helping to make these energy optimization options more obtainable is the emergence of financing options that allows homeowners and business owners to use their monthly savings in energy costs to pay for the initial construction costs.

Many local governments offer weatherization assistance program for low-income families to makes sure enclosures are intact and insulation is up to par, Antonopoulos said.

"Typically, the utilities have a lot of different financing and grant programs that they provide to reduce the cost of making upgrades to the buildings," Mugo said.

New York City's NYC Accelerator Program, for example, provides free assessments to determine whether solar panels can be installed in a building. The program also locates installation contractors and calculates month-to-month energy cost savings.

Additionally, the Inflation Reduction Act, signed into law in 2022, includes a number of tax incentives and grant programs, as well as low-cost financing programs, aimed at making investments in optimizing buildings more affordable. Projects for solar storage or geothermal installation that meet the right criteria can be reimbursed up to 30% the cost, Evans said.

"There are also very lucrative incentives for home builders now where they can get up to $5,000 per unit for building new homes that are that are highly energy efficient – that either meet Energy Star or Zero Energy Ready criteria," Evans said.

Some federal agencies have begun programs to promote low-embodied carbon construction materials – meaning their manufacture has a low carbon footprint – especially for materials that have the greatest carbon emissions like concrete, glass and steel, Beardsley said.