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As heat waves get worse, these fixes will help keep your home cool and energy efficient.
July 2023 will almost certainly be declared the hottest month ever recorded, but it is unlikely to hold that record for long. Climate change is making heat waves more frequent, intense, and longer-lasting across the U.S.
Adapting to this hotter future is often discussed at the scale of a city; measured in early warning systems, green spaces, and cooling centers. But there’s also a lot that individual homeowners can do to help their communities and protect themselves.
While the vast majority of American households — some 88% — use air conditioning for relief, homeowners would be wise to consider a variety of additional, “passive” cooling techniques. These are strategies that can keep your home at a safe temperature during a heat wave if the power goes out, an increasingly likely scenario. They will also save you a bit of money on energy bills. In a sense, adapting your home to extreme heat is just another way of thinking about how to make it more energy efficient.
These retrofits also have wider benefits. Since air conditioners work by transferring heat from inside your house outdoors, these fixes can cool down your neighborhood. They’ll cut carbon emissions and air pollution by lowering demand for electricity. If widely adopted, they’ll also help prevent blackouts and could shrink the amount of renewable energy projects that need to be built to replace fossil fuels, alleviating pressure on conservation.
I spoke with Steve Easley, a building science consultant who specializes in energy efficiency, and Shawn Maurer, technical director of the Smart Energy Design Assistance Center at the University of Illinois, about how homeowners should prioritize their options when it comes to passive cooling.
“I always recommend that people do a home energy audit from a certified HERS rater,” Easley told me, referring to the Home Energy Rating System, a nationally recognized system for inspecting and calculating a home’s energy performance. The auditor will tell you how leaky your house is, and how well your roof insulation, windows, and other parts of your house are working to keep out heat, and help you figure out what to attack first. (Easley also recommends getting at least three quotes for any of these solutions, because different contractors bid this work out very differently.)
Below are five things you can do to improve your home’s resilience to heat. Depending on a number of factors — such as where you live, how your house is constructed, and the condition it's in — the mileage you can get out of each of these measures will vary. The good news is that the federal government and many state governments offer tax credits and rebates for most of these solutions. The Inflation Reduction Act created the Energy Efficient Home Improvement tax credit, which offers homeowners up to $1,200 per year to spend on energy efficiency improvements. As part of that, you can claim $150 simply for getting an energy audit.
Maurer said the very first thing he would do to improve the efficiency of a home is to seal up any cracks where air can get in — for example, along the edges of the floors, around the windows, and in the ceiling around light fixtures. “That carries in moisture, heat, and everything from outdoors into the house. It's going to offset any air conditioned air you got inside the house. So air leakage is usually the place we recommend to start,” he said. “And then from there, it's what your budget can handle as far as adding more insulation to your house.”
Insulation comes in a wide range of materials, such as fiberglass and rock wool, blown cellulose, and rigid foam boards. It can be blown into your walls, installed on the floor of the attic, or underneath your roof deck. It’s a jack-of-all-trades when it comes to energy efficiency, since it keeps heat inside in the winter and blocks it from entering in the summer. That means it’s a great option for those in colder climates that also want to prepare their homes for hotter summers.
A 2021 study by a group of researchers at Lawrence Berkeley National Lab modeled the efficacy of a wide array of passive cooling measures in low-income homes in Fresno, California. It found that roof insulation, along with solar-control window films, which we’ll get to in a moment, were the two most effective ways to keep heat from entering the buildings. However, the authors note that roof insulation is an expensive major retrofit, and recommend that it only be done when the roof needs replacement.
A good first step might be finding out what kind of insulation you already have. The most important metric when it comes to insulation is called “R-value,” and the higher the number, the more effective it is. Older homes may have attic insulation as low as R-13, whereas modern building codes typically require insulation between R-38 and R-60.
The new federal tax credit offers up to 30% of the total cost of a project for air sealing and insulation, maxing out at $1,200 total. (Labor costs are not covered by the credit.)
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Having a light-colored roof and exterior will most certainly keep your home cooler than darker options, but not all light colors are created equal. “Cool” roofs and walls are made with special materials that reflect solar energy back into space, preventing it from being absorbed by the building. They also have high “thermal emittance,” meaning they release a lot of the heat that they do absorb, rather than sending it indoors.
All kinds of materials have been developed with these properties. For roofs, there are tiles, shingles, membranes, liquid coatings, and products made of slate, wood, and metal.
Cool roofs don’t necessarily have to be white, although the color does work very well. According to a database maintained by the Cool Roof Ratings Council, the most effective products tend to be bright white coatings, but there are also gray, green, blue, brown, and tan products that are rated highly.
For reflective walls, the most effective products similarly come in white and other light-colored paints, which can reflect 60 to 90 percent of sunlight when new. An extensive 2019 study of reflective wall paints by the same group at Lawrence Berkeley National Lab found that cool walls can reduce annual energy use in single-family homes in warmer U.S. climates by 2% to 8.5%.
Easley said it’s worth considering a cool roof if you have a central air conditioning system in your attic. Otherwise, attics in places like Arizona can get upwards of 130 degrees, taxing the equipment and forcing it to work harder. If your attic isn’t home to your AC, it may only make financial sense to do this kind of retrofit if your house is already in need of a new paint job or your roof needs work.
But it’s probably not worth considering a cool roof if you live in a colder climate, like the Northeast and upper Midwest, since cool roofs can actually make it colder inside in the winter.
There’s no federal incentives for cool roofs, but several states and utilities offer rebates.
This is a big category, and it’s easy to get overwhelmed by the options. Starting with those that will likely cost the most to the least, you can:
• Replace your windows altogether.
• Add storm windows to the interior or exterior of your existing glass.
• Purchase films that can be applied to the existing glass to increase its reflectivity.
• Install external shutters or awnings that block the sun.
• Install interior blinds and curtains that block the sun.
Here’s a rundown of each option.
New windows: Replacing your windows can cost tens of thousands of dollars, so unless they are already in need of repair, you may want to hold off on that option. But when the day does come around, you’ll want to look for “Low-E” windows, which stands for low emissivity. The inside of the glass is coated with microscopic layers of silver that reflect heat while still allowing light to pass through.
Within that category, you’ll also want to look for windows that have what’s called a low “solar heat gain coefficient.” This measures how much heat is absorbed by the glass and transferred inside. It’s rated on a scale of 0 to 1. If you live somewhere that’s sunny year round like Arizona, you ideally want one rated 0.25 or lower.
Through 2032, homeowners can claim up to $600 in federal tax credits for purchasing Energy Star rated windows.
Storm windows: Rather than replacing your windows entirely, it’s far cheaper to install storm windows with Low-E glass, which basically involves bolting another window to the outside of your house. Storm windows have an added benefit of improving air sealing, eliminating drafts.
Film: An even lower-cost option is to look into films with low solar heat gain coefficients that can be applied to existing windows. However, Easeley warned that many manufacturers will void your warranty if you add films to your windows.
Shutters, awnings, blinds, and curtains: Exterior shutters and overhangs that block the sun from ever reaching your windows will generally be more effective than interior shades or blinds, but all of these measures can help. “Window blinds and curtains are really dirt cheap ways to control energy,” said Maurer. “It’s not a very good buffer, but it’s something.”
The Berkeley study on passive cooling measures notes that blinds moderately improve how much heat from the sun enters your home, but they can feel more effective by reducing the sensation of sunlight streaming into your house.
If you still have any incandescent lights, they can also be a significant source of heat. They should be replaced with LED lights.
Planting trees, climbing ivy, and other vegetation can also passively cool your house by shading both your house and any surrounding pavement. However, if you have solar panels, or plan to get them in the future, do not plant trees on the south side of your home as it may reduce the solar system’s effectiveness.
Maurer cautioned that if you do a bunch of work in your home to reduce your cooling needs, you’ll want to keep that in mind if you ever have to replace your air conditioner. He advised having a contractor come in to re-measure what size system you need, since doing a like-for-like replacement will probably be overkill and could result in it malfunctioning.
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A list of terminated grants obtained by Heatmap contains a number of grants that will cost jobs and revenue in Republican-led states.
The Trump administration terminated billions in climate and clean energy grants on Wednesday, in what appears to be yet another act of retribution against Democrats over the government shutdown. White House budget director Russell Vought announced on X that “nearly $8 billion in Green New Scam funding to fuel the Left's climate agenda is being cancelled,” noting that the projects were in 16 states, all but two of which — Vermont and New Hampshire — have Democrats in their governor’s mansion. A Department of Energy release published late last night further clarified that it was terminating 321 awards supporting 223 projects, with a total closer to $7.5 billion.
But a list of the 321 canceled grants that the Department of Energy sent to Congress, obtained by Heatmap, tells a different story. While much of the funding was awarded to blue state-based companies, the intended projects would have benefitted communities elsewhere, including in Texas, Florida, and Louisiana.
The list identifies the grants by their award numbers, and includes information on the DOE office overseeing the grant, the recipient name, and state. The document does not specify the project names, the programs under which they were awarded, or the amounts awarded.
That leaves a lot of open questions about the true impact of the terminations. It’s unclear, for instance, whether the $7.5 billion price tag the Department of Energy assigned to the cancellations is an estimate of the total amount awarded or the unspent remainder still in the agency’s coffers. Five of the listed projects, worth nearly $900 million, were already announced as terminated in an earlier round of cuts back in May.
Many of the projects listed have signed contracts with the government, are already well underway, and have spent at least some of their award. For example, the Northeast Energy Efficiency Partnerships has already published copious educational materials related to its community-driven transportation plan for the Northeast, a project supported by one of the terminated grants.
The list does seem to confirm that blue state grants were the hardest hit, with 79 award cancellations in California, 41 in New York, 34 in Colorado (Secretary of Energy Chris Wright’s home state), 33 in Illinois, and 31 in Massachusetts.
But when I began looking up projects by their award number, I found that many would actually have benefitted Republican strongholds. Take, for example, Moment Energy, a Delaware-based company that was awarded $20 million by the Office of Manufacturing and Energy Supply Chains to build the first certified manufacturing facility in the United States producing battery energy storage systems from repurposed electric vehicle batteries. The plant was set to be built in Taylor, Texas, creating 50 construction jobs and 200 new permanent positions. After receiving the Energy Department’s stamp of approval, the company raised a $15 million Series A funding round in January to help finance the plant.
Also listed are a $10 million grant for Carbon Capture Inc, a California-based company, to conduct an engineering study for a direct air capture plant in Northwest Louisiana, and a $37 million grant to New York-based Urban Mining Industries to build one of its low-carbon concrete manufacturing plants in Florida. Linde, the global industrial gas company based in Connecticut, had $10 million to build hydrogen fueling stations for heavy duty trucks in La Porte, Texas, clawed back. BKV, a Colorado-based natural gas company set to study the transportation of captured CO2 by barge throughout the Gulf Coast region, also had its $2.5 million grant canceled.
In addition to hurting investments and jobs in Republican states, the Department of Energy’s cancellations also target some unlikely victims. The list names 16 grants for General Electric, including 11 for GE Vernova, the company’s manufacturing arm, which produces natural gas turbines and components for wind energy generation; many of those awards were for wind technology research projects. The agency also canceled 24 grants for the Institute for Gas Technology and the Electric Power Research Institute, the research arms of gas and electric companies’ two biggest trade groups, respectively. Several of these awards funded research projects into carbon capture and storage.
Also on the list was a more than $6.5 million grant for a controversial study to retrofit the Four Corners coal plant in New Mexico with carbon capture equipment. The plant is currently scheduled to close in 2031.
Back in May, Wright promised Congress his agency’s review of Biden-era climate funding would be over by the end of the summer. “Certainly in the next few months, by the end of this summer — hopefully before the end of this summer — we will have run through all of the four or 500 large projects that are currently in the pipeline at the DOE,” he said during a House Appropriations Committee hearing.
As reported yesterday by Bloomberg, two regional Hydrogen Hubs in California and the Pacific Northwest — projects awarded funding from the Bipartisan Infrastructure Law to develop full hydrogen production and consumption ecosystems — are on the list. That leaves the agency’s intentions for the remaining five hubs scattered throughout the Midwest, Midatlantic, Appalachia, the Great Plains, and Texas unclear. And while the list includes a few smaller grants for early-stage Direct Air Capture Hubs, it is still a mystery whether the Department of Energy plans to support the two more advanced direct air capture projects in Louisiana and Texas that were selected for $1.2 billion under the Biden administration.
On a major energy acquisition, carbon cycle cash, and a cheaper EV
Current conditions: Hurricane Imelda hit Bermuda as a Category 2 storm • Storm Amy, the first named UK storm of the season, will bring heavy rains and wind to Scotland, England, and Wales on Friday • Sudan’s Ministry of Agriculture declared a state of emergency this week after the Nile River rose to record levels.
The Department of Energy said on Wednesday that it is terminating 321 grants supporting 223 projects, cutting a total of more than $7.5 billion in funding for clean energy projects. While the Department has not yet specified what the awards were, Office of Management and Budget Director Russ Vought posted to social media yesterday that the canceled projects were located across 16 Democrat-led states. An administration official told Bloomberg that at least two of the projects in question were hydrogen “hubs” under development in California and the Pacific Northwest. The cuts come on top of $13 billion in climate funds that had not yet been dedicated to specific projects that the Department of Energy said it would “return” in late September, as instructed by the reconciliation bill.
The Department of Energy has left the recipients of billions in obligated funds for climate projects in limbo since Trump took office. Secretary of Energy Chris Wright said the agency was “reviewing” the awards in May. He testified in Congress that his office would make a decision about many of them by the end of the summer, but this week’s terminations — amid the government shutdown — are the first announcement the agency has made since an initial batch of cuts at the end of May.
The Trump administration said Wednesday that it is putting $18 billion in funding for New York City transit projects on hold while it investigates violations of a rule barring diversity considerations in hiring that the Department of Transportation published on Tuesday. “The timing is, shall we say, noteworthy,” my colleague Matthew Zeitlin wrote on Wednesday, “not least because the Democrats’ two top congressional negotiators — Representative Hakeem Jeffries and Senator Chuck Schumer — are both from New York.” In a statement, Secretary of Transportation Sean Duffy blamed those two lawmakers for the shutdown, lamenting that thanks to them, “USDOT’s review of New York’s unconstitutional practices will take more time.”
Blackrock-owned Global Infrastructure Partners, an investment fund, is in talks to buy energy developer AES for more than $38 billion in “what would be one of the largest infrastructure takeovers of all time,” according to the Financial Times. AES owns utilities in Ohio and Indiana in addition to owning both conventional and renewable energy generation projects across the globe. The company is also the top supplier of renewable energy to corporate buyers in the world. AES stock jumped nearly 17% on Wednesday on the news.
A new report from the Union of Concerned Scientists found that residential customers in seven states that are part of the PJM Interconnection, an electricity market that covers the Mid-Atlantic and parts of the Midwest, are paying nearly $4.4 billion for transmission upgrades intended to deliver electricity to data centers. The finding is not a big surprise — PJM’s own Market Monitor has acknowledged that data center load growth is the primary factor driving up rates. But the report specifically analyzes the amount the whole ratebase is shelling out for transmission projects that only benefit a single customer. It recommends that the Federal Energy Regulatory Commission create a new customer class for such customers and require them to shoulder the cost alone.
Trump has slashed millions in grants for climate science research and plans to cut the federal government’s climate science funding and staff dramatically in next year’s budget. Stepping in to replace some of that lost cash is Schmidt Sciences, a philanthropy founded by former Google CEO Eric Schmidt. Schmidt announced Thursday that it’s committing up to $45 million over five years for research to advance understanding of some of the least-studied parts of the global carbon cycle. For example, one project will measure how much carbon dioxide the Southern Ocean absorbs from the atmosphere with the help of robotic sailboats that can collect data year-round, including during times when it’s too dangerous for research ships to operate.
The 2026 Ioniq 5 Limited. Image courtesy of Hyundai
Hyundai is cutting the price tag on its 2026 Ioniq 5 by nearly $10,000, and will continue to offer $7,500 off the 2025 model — equivalent to the now-expired federal tax credit. The 2026 Ioniq 5 base model will start at just $35,000, making it one of the cheapest EVs available in the U.S.
Some of the industry’s biggest names are joining forces to keep the momentum moving forward.
Climate tech funding has slowed in the face of federal government pushback — but it has certainly not stopped. As the administration has cranked up its hostilities against everything from electric vehicles to wind turbines, companies and investors are responding by getting strategic, forming new coalitions to map, fund, and shape progress in the absence of public support.
Last month I covered the launch of the Climate Tech Atlas, an interdisciplinary effort that includes venture capitalists, nonprofits, and academics working to map out the most salient climate tech opportunities and help guide external research and funding in the sector. There’s also the All Aboard Coalition, which unites big name investors to help plug the missing middle finance gap. Sector-specific investment vehicles are popping up too, like the Oneworld BEV fund, a partnership between major airlines in the Oneworld Alliance and Breakthrough Energy Ventures to advance the commercialization of sustainable aviation fuels. All three of these new initiatives were announced in September alone.
“We are in a unique moment right now,” Carmichael Roberts, a managing partner at BEV told me via email. “Over the past decade, the climate tech ecosystem has made enormous progress driving innovation across every sector of the economy. That puts us in the position to step back and ask first, what areas are still crying out for urgent innovation?”
This year has also seen a number of climate tech companies struggle at key points in their attempts to scale. Sodium-ion battery company Natron Energy shut down in September, while direct air capture leader Climeworks laid off 22% of its staff in May, citing “current macroeconomic uncertainty” and “shifting policy priorities where climate tech is seeing reduced momentum.” Another direct air capture company, Noya, shuttered this August, while the battery recycling company Li-Cycle filed for bankruptcy in May.
Other startups pursuing emerging technologies — from carbon capture to long-duration battery storage, advanced geothermal, and next-generation nuclear — are looking to avoid the same fate. But while federal funding from places such as the Department of Energy’s Office of Clean Energy Demonstrations and the Loan Programs Office once provided an avenue for financing capital-intensive demonstration plants, the Trump administration is now retracting funding, going so far as to cancel contracts with projects previously approved under Biden.
The Oneworld fund, announced in mid-September, is BEV’s first to focus on a specific theme and its first to be backed by an industry coalition. Members of the Oneworld Alliance — which include Alaska Airlines, American Airlines, British Airways, and Cathay Pacific — had already committed to using SAF for 10% of their fuel by 2030, while also “playing an active role in the development of SAF at commercial scale.” Now, with alliance members serving as limited partners in the venture fund, they’ll benefit from the technical and commercial expertise of one of the sector’s most influential VC firms.
When I asked the BEV team to what degree the current political and economic uncertainties were making partnerships like this more valuable, Eric Toone, another BEV managing partner, responded with a refrain I’ve become familiar with — that the firm only backs technologies that “can ultimately compete on their own merits.” Yet it’s undeniable that the federal government tore up its decarbonization agenda at a moment when many climate tech firms’ investments are almost ready for deployment, a stage when government support can make all the difference.
“Many promising SAF technologies already exist, but they are stuck between lab success and commercial scale,” Roberts told me. “This is the moment when they most need capital, technical rigor, and committed offtake to bridge that gap.” While the Trump administration did maintain and extend the tax credit for clean fuels, it also reduced the maximum credit amount for SAF from $1.75 per gallon to $1, while private funding for SAF production and distribution infrastructure remains inadequate.
Given this landscape and the urgency airlines face in meeting their clean fuel targets, Toone told me the firm is open to backing companies “that are further along than what a typical BEV fund might pursue.” And while sustainable fuels are the first technology to benefit from this type of thematic focus, Roberts said that BEV is already eyeing other sectors where it plans to apply this same funding model.
As of early September, the firm is also part of the All Aboard Coalition. This elite group of venture firms is aiming to raise a $300 million fund by the end of October that will match investments in later-stage venture rounds, filling a gap known in climate tech circles as the “missing middle.” Assembled by Chris Anderson, an entrepreneur and primary convener of the TED Talks conference — which has featured many inspiring climate visionaries — the group includes 14 members such as Khosla Ventures, Prelude Ventures, DCVC, Gigascale Capital, and Energy Impact Partners.
“One of the consequences of being in the front row seat at TED all these years is you get persuaded of certain things,” he told me. “And I definitely got persuaded that climate is the outstanding, major problem we really have to fix.”
The bulk of the capital for the coalition will come from outside investors, though some members will contribute as well, Anderson told me. The goal is to incentivize these hotshots to co-invest with each other, providing a one-to-one funding match if they do so.
“First-of-a-kind rounds seem out of reach for a lot of people in the chain,” Anderson explained, referring to the network of investors that must come together to help a company fund expensive new infrastructure. At this stage, its tech has progressed beyond the capital-light, early-stage rounds but is still considered too risky for traditional infrastructure investors to take on. Companies might be seeking $100 million or more from venture firms that are used to writing checks for orders of magnitude less. “Really the purpose of the fund is to create a collective belief that there is a pathway to getting these companies funded. If you have that collective belief, then it’s much easier for a lead investor to step forward and to pull a few other people in.”
Anderson acknowledged that a $300 million fund will not go “nearly far enough.”
“It’s a starter fund. It’s a proof of concept,” he told me. “The world needs to make a couple hundred of these bets at some point.”
Other coalitions, such as the Climate Tech Atlas, are working to steer the sector towards the best bets. This group — which also includes Breakthrough Energy Ventures, alongside others such as the nonprofit investment platform Elemental Impact, the consulting firm McKinsey, and Stanford University’s Doerr School of Sustainability — has mapped out the technological milestones it sees as the clearest pathways to decarbonization. The aim is to help investors, founders, policymakers and academics alike direct their energies towards the most relevant and investable opportunities, regardless of political headwinds.
“The scale at which the government participates in the development of these new technologies — or puts a thumb on the scale for technologies in particular — will vary,” Sonia Aggarwal, CEO of the policy firm Energy Innovation, which is also a member of the alliance, told me. “But certainly that has no real bearing on the fundamental fact that innovators are out there right now thinking about these grand challenges, and there are exciting new ideas for technologies that can get to that commercial scale in the coming years.”
And indeed, sometimes the most promising ideas can take shape in moments of deep uncertainty. Some of the biggest success stories of recent tech history — Uber, Airbnb, WhatsApp, and Square — all got their start during the 2008 financial crisis or its aftermath. “Some of the strongest companies and founders are building in uncertain times,” Dawn Lippert, founder and CEO of Elemental Impact, told me. “That’s very much what we see right now.”
These groups are far from the only private-sector actors coming together to help navigate industry headwinds. When the Environmental Protection Agency withdrew support for the most widely used U.S.-based carbon accounting model for estimating scope 3 emissions, leading emissions accounting platform Watershed partnered with Stanford University’s Sustainable Solutions Lab to launch an initiative that ensures continued access. And recognizing the difficulty that early stage climate tech startups face in securing insurance, the nonprofit GreenRE Coalition and the philanthropic funder Trellis Climate partnered to create a new type of bond tailored to the needs of climate tech startups.
Whether it will all be enough to accelerate or even sustain much-needed momentum in climate tech funding is impossible to predict. But at least the private sector seems to agree that, in this moment, good old teamwork is worth one heck of a try.