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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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Without the endangerment finding on greenhouse gases, the state could have a case for re-imposing its own greenhouse limits on auto emissions.
Trump’s Environmental Protection Agency has moved to abdicate the federal government’s responsibility to regulate greenhouse gas emissions for vehicles. At this point it’s only a proposal, and legal challenges to the shift could take years to resolve even after the change gets finalized.
But if the law eventually closes the door on national standards, it might open a new one for states.
The Clean Air Act prohibits states from enacting their own pollution regulations for mobile sources, such as cars and trucks. California, however, is allowed to request a waiver from the EPA to create its own, stricter rules, since the state was already regulating vehicle pollution prior to the law’s passage. Once EPA approves one of California’s waivers, other states can subsequently adopt the stricter rules without requesting the same federal dispensation.
At first California’s air quality regulations were focused on more traditional health-harming pollutants such as ozone and particulate matter. But in 2005, California created the world’s first greenhouse gas emissions standards for cars, beginning with model year 2009, and requested a waiver from the EPA to enforce them.
At the time the EPA did not have any national standards for greenhouse gas emissions, but a seminal court case would soon force it to create them. In 2007, the Supreme Court ruled in Massachusetts vs. EPA that greenhouse gases are pollutants, as defined by the Clean Air Act, and that the agency has a duty to regulate them if it finds that they endanger public health or welfare. In 2009, the EPA under President Obama issued its “endangerment finding,” determining under a mountain of evidence that yes, greenhouse gases threaten public health, and prompting the development of the first federal climate standards for vehicles.
Now the Trump administration is trying to reverse that finding and put an end to federal climate regulations for vehicles once and for all.
At the same time, Trump has approved a move by Congress to rescind California’s latest waivers — although the move was legally dubious and the state is challenging it in court. Congress revoked the waivers under the Congressional Review Act, a law that allows the legislative branch to undo recently-finalized agency rules with a simple majority, despite previous rulings from the Government Accountability Office and the Senate parliamentarian that the waivers are not “rules” as defined by the Congressional Review Act.
But if the EPA says the Clean Air Act does not require the agency to regulate greenhouse gas emissions, does California even need those waivers?
“If I were the state of California and the endangerment finding gets rescinded, I would argue that there are no federal standards,” Ann Carlson, a professor of environmental law at the University of California, Los Angeles, and a former Biden administration official, told me. “There is, in the view of EPA, no need to regulate, and therefore states shouldn’t be preempted. I don’t know if that’s a winner, but I think it’s worth a try.”
Eliminating the endangerment finding would give states a solid argument for being able to regulate greenhouse emissions themselves, Carlson told me. But what would make the argument a “slam dunk,” she said, was if the Supreme Court ultimately overturned Massachusetts vs. EPA, and ruled that greenhouse gases are not air pollutants under the Clean Air Act after all.
The road to that outcome would be long and could veer in a different direction if Democrats retake the White House in 2028. First, the EPA has to put out its proposal for public comments and issue a final decision. That process alone could take a year. Then states or environmental groups would challenge the decision in the D.C. Circuit Court of Appeals, which would likely take another year to reach a ruling, putting us into mid-2027 or so.
While we won’t know what EPA’s exact argument will be until it issues the final decision, the justifications it has put forward so far are weak, according to experts. The agency’s main claim in the proposal is that it can only regulate pollutants that endanger health through local or regional exposures — the global problem of climate change doesn’t count. “This is hard to square with the Supreme Court’s decision in Massachusetts vs. EPA,” Harvard Law School’s Jody Freeman told me, “but EPA claims that doesn’t settle it.”
Carlson said she thinks there’s a pretty good chance the D.C. court would strike down the EPA’s attempt to reverse the endangerment finding. But the Trump administration would presumably appeal that ruling to the Supreme Court, which would present an opportunity for the conservative majority to overturn Massachusetts vs. EPA. Chief Justice Roberts, along with Justices Alito and Thomas, dissented in the original 2007 decision, while Justice Brett Kavanaugh, who was confirmed in 2018, “has made clear his disdain for using the Clean Air Act to regulate greenhouse gasses,” Carlson said.
There are a lot of open questions about what would happen next. If the case is still ongoing by 2029, the next administration could decide to withdraw it, or simply to reinstate the endangerment finding.
Another wrinkle: The Inflation Reduction Act amended the Clean Air Act to explicitly define greenhouse gases as pollutants under new sections of the law. That could make it harder for the Supreme Court to overturn Massachusetts vs. EPA, although the court has previously held that different sections of the law may define “air pollutant” differently.
Finally, even if the case goes all the way to the point of reversing Massachusetts vs. EPA, there would probably still need to be additional litigation to clarify what states can do, Atid Kimelman, a clean vehicles attorney for the National Resources Defense Council, told me.
He noted that the federal government might argue that regardless of the fact that the EPA isn’t regulating greenhouse gases, states are still preempted, as the whole point of the preemption in the Clean Air Act is to make sure that the country doesn’t have 50 different standards for motor vehicles. Another hurdle might be that the federal Energy Policy Conservation Act, which authorizes the Department of Transportation to set fuel economy standards, also preempts states from adopting their own vehicle regulations.
“This is somewhat novel territory that hasn’t really played out in courts,” he said. “These are arguments that have to be tested.”
Along with Senator John Curtis of Utah, the Iowa senator is aiming to preserve the definition of “begin construction” as it applies to tax credits.
Iowa Senator Chuck Grassley wants “begin construction” to mean what it means.
To that end, Grassley has placed a “hold” on three nominees to the Treasury Department, the agency tasked with writing the rules and guidance for implementing the tax provisions of the One Big Beautiful Bill Act, many of which depend on that all-important definition.
Grassley and other Republican senators had negotiated a “glidepath for the orderly phaseout” of tax credits for renewables, the senator in a statement announcing the hold, giving developers until July 2026 to start construction on projects (or complete the projects and have them operating by the end of 2027) to qualify for tax credits.
Days after signing the law, however, President Trump signed an executive order calling for new guidance on what exactly starting construction means. The title of that order, “Ending Market Distorting Subsidies for Unreliable, Foreign Controlled Energy Sources,” has generated understandable concern within the renewables industry that, as part of a deal to get conservative House members to support the bill, the Treasury Department will write new guidance making it much more difficult for wind and solar projects to qualify for tax credits.
“What it means for a project to ‘begin construction'’ has been well established by Treasury guidance for more than a decade,” Grassley said. Under these longstanding definitions, “beginning construction” can mean undertaking “physical work of a significant nature,” which can include or buying certain long-lead equipment or components like transformers. Another way to qualify for the credits is to spend 5% of the total cost of the project.
A more restrictive interpretation of “begin construction,” however, could turn the tax credit language into a dead letter, especially when combined with the rest of the administration’s full-spectrum legal assault on renewable energy.
Grassley said that new guidance is expected within two weeks, and that “until I can be certain that such rules and regulations adhere to the law and congressional intent, I intend to continue to object to the consideration of these Treasury nominees.”Grassley has a long history with production tax credits for wind energy, playing a pivotal role in their extension in 2015. “As the father of the first wind energy tax credit in 1992, I can say that the tax credit was never meant to be permanent,” Grassley said at the time. “The five-year extension for wind energy brings about the best possible long-term outcome that provides certainty, predictability and a responsible phase-down of a tax incentive for a renewable energy source.”
Almost 60% of Iowa’s electricity is generated by wind turbines, the highest proportion of any state, according to Energy Information Administration data.
Utah Senator John Curtis has joined Grassley in placing a hold on nominees, delaying their vote before the whole Senate, according to Politico’s Joshua Siegel. Grassley and Curtis, alongside Lisa Murkowski of Alaska and Thom Tillis of North Carolina, were unable to get a meeting with the Treasury Department to discuss the guidance, Siegel reported.
On Puerto Rico’s water crisis, LNG’s tax scam, a nuclear safety scandal
Current conditions: Wildfire smoke in Alberta, Canada, is so thick that the airport had a visibility of just about 650 feet, and the air quality index hit 2241, 10 times higher than “hazardous” levels • At least 10 Chinese provinces are on alert for heavy rainfall this week, with as much as 8 inches deluging Beijing • Prolonged heatwave conditions in southeastern Europe are raising the risk of fires.
A wildfire in Arizona’s Grand Canyon National Park that has burned for nearly a month has grown into the largest blaze in the continental U.S. so far this year, scorching more than 114,000 acres as of this weekend. The Dragon Bravo fire, near the park’s North Rim, is expected to increase in size in the coming days due to the exceptionally dry, hot weather, The New York Times reported.
It’s far from the only major fire burning out West. The Gifford fire in California grew to nearly 40,000 acres on Sunday within the Los Padres National Forest in south-central California. The fire was just 3% contained as of late Sunday evening, according to the federal wildfire tracker, InciWeb. Last month, my colleague Jeva Lange wrote that the “next big wave” of wildfires out West “could happen any day.” As she reported, “the components for a bad fire season are all there — the landscape just needs a spark.” Lightning has been a particular concern in the Pacific Northwest, where thunderstorms led to 72 fires in two Oregon counties during just one night in June. A lightning strike is the likely cause of the Dragon Bravo fire.
One of many anti-corruption protests in San Juan, Puerto Rico. Jose Jimenez/Getty Images
Nearly eight years after Hurricane María decimated Puerto Rico’s power grid, the United States’ most populous territory still suffers electricity outages every week and faces rising utility bills. But the island of more than 3 million American citizens is reeling this week from yet another utility failure: Water outages. As many as 180,000 households in Puerto Rico lost access to running water last week, and thousands are still without service. The electricity and water issues are combined. Updates on the state-run water utility’s X page indicated that several water pumping stations are out of service due to a lack of electricity. Governor Jenniffer González Colón called in the National Guard to help distribute water.
It’s just the latest crisis afflicting the Caribbean territory’s basic infrastructure as the island enters the peak of hurricane season. The local government last month escalated its battle with New Fortress Energy, the financially troubled New York-based gas company that provides its fuel and operates its power plants. González Colón is considering ending the island’s contract with LUMA Energy, the private consortium that controls the power grid. Faced with ongoing blackouts, the government just scrapped Puerto Rico’s renewable energy targets and extended the life of a highly polluting coal plant, threatening devastating health consequences for the surrounding community, as I reported earlier this summer for the MIT Technology Review. And, despite González Colón’s chummy relationship with President Donald Trump, federal funding for Puerto Rico’s post-María reconstruction is still trickling out almost a decade after the storm.
The One Big Beautiful Bill Act is bringing tax credits for wind turbines, solar panels, and electric vehicles to a swift end on the grounds that the technologies are mature and therefore no longer worth subsidizing. Yet America’s largest exporter of liquified natural gas is seeking “alternative fuel” tax credits simply for running its vessels on the fuel they carry, exactly as they’re designed to do. The tax credit, originally signed into law by former President George W. Bush in 2005, was intended to incentivize the switch from gasoline and diesel to biofuels, LNG, and liquid fuels derived from coal. The tankers Cheniere Energy, the nation’s top overseas seller of American LNG, uses to ship its fuel around the world are built to boil off fuel from the tanks that hold its cargo. But the company is seeking federal rewards for using the LNG, according to an investigation by Inside Climate News. If the Internal Revenue Service approves the request, Cheniere could net more than $140 million.
The Trump administration has vowed to cut back and streamline nuclear regulations to make building new reactors easier, potentially compromising safety. The effort has stirred enough drama at the Nuclear Regulatory Commission that a Republican commissioner resigned last week. Now a scandal at the St. Lucie Nuclear Power Plant in Florida is providing a timely reminder of why strict oversight exists over atomic energy stations. An inspection report on the plant, owned by Florida Power & Light, revealed that workers feared reporting safety problems to upper management lest they face retaliation. And that comes right as a database shows safety violations soared over the past year, according to the Tampa Bay Times.
The investigation came as the Department of Energy discovered four radioactive wasp nests at the defunct Savannah River nuclear facility in South Carolina. The finding suggested that environmental contamination at the site, which previously developed weapons-grade material for the U.S. government, is more extensive than previously understood. While advocates of nuclear energy draw clear distinctions with the military-related sites, political upheaval at the federal agency that oversees radioactive materials could put the growing bipartisan consensus on building more reactors at risk.
Tesla’s board approved a $30 billion payout of shares to Elon Musk in a new compensation deal, according to a regulatory filing on Monday that followed the billionaire's threat to leave the electric automaker if he didn't receive more stock.
The move came days after a jury in Florida found flaws in Tesla’s self-driving software partly responsible for a crash that killed a 22-year-old woman in 2019 and severely injured her boyfriend, The New York Times reported. If Friday's verdict holds, Tesla will be on the hook for as much as $243 million in damages to the parents of the woman and her boyfriend. The jury decided that Tesla bore 33% of the blame for the crash. Tesla said it would appeal. It’s a setback for Musk’s driverless ambitions. As Tesla’s human-driven automotive offerings stalled out last year, Heatmap contributor Andrew Moseman wrote that, “sure, maybe it will be the one to crack full autonomous driving. But in practical terms, that tech is not close to reality, and Tesla’s version of it has encountered its fair share of bugs and been sued over crashes.”
New research from Stanford University has “upended conventional wisdom about electric vehicle battery management. Contrary to popular belief, a more dynamic driving style could significantly extend the lifespan of EV batteries,” including not charging the units to 100%.