During a heat wave, some homes remain livable while others heat up fast. The homes that overheat during heat waves are often the ones whose design does not match the climate they face. From aging houses with little insulation to sleek condos with expansive windows, different properties overheat for different reasons and need different solutions.
Why Glass Towers Overheat
When a home heats up during a heat wave, the problem usually starts with how heat gets inside. There are three main ways this happens: heat moving through walls, warm air entering through gaps and vents, and sunlight coming through windows. Windows are often the biggest problem because they let solar energy in but do not easily allow that heat to escape.
One way experts measure this risk is through the Solar Heat Gain Coefficient (SHGC). This rating shows how much solar energy a window allows into a property. Homes with windows that have a higher SHGC can experience greater heat buildup and higher cooling costs during summer heat waves.
While newer homes are often more energy efficient, they are not automatically protected from overheating. For homeowners, the best cooling upgrades often depend on understanding how their specific property gains and holds heat.
Older Buildings
Many older homes and apartments face a cooling problem created by their original design. Pre-war buildings were designed to retain heat during harsh winters, but those same features can work against residents during extreme summer temperatures. Thick masonry walls absorb heat throughout the day and slowly release it at night, making it harder for apartments to cool down during extended heat waves.
Heating systems can also play a role. Many steam-heated buildings still use equipment designed when open windows were considered part of normal ventilation practices. These oversized systems often created excess heat, and a 2019 Urban Green Council survey found that 70% of tenants in New York steam-heated buildings reported chronic winter overheating.
Modern upgrades have improved energy efficiency, but they can create trade-offs. New windows and tighter building envelopes reduce drafts and energy loss, yet they can also trap heat when temperatures rise. For buyers considering older properties, cooling performance depends on more than just the building’s age.
Retrofit Owners are Trying–and Where HOAs Push Back
For condo owners living in glass towers, one of the easiest upgrades is adding window film that reduces how much solar heat enters the unit. Modern ceramic and low-E films can block much of the heat from sunlight while still keeping rooms bright.
Some luxury buildings are turning to smart glass technology, which can automatically adjust tint levels based on sunlight. While effective, this type of upgrade is typically too expensive for individual condo owners because it requires extensive installation and electrical work.
Before installing any window film, condo owners need to check their building rules. Boards often reject products that make one unit look different from the rest of the building. A clear or neutral film that blends with the existing glass is usually easier to get approved than a dark or reflective option.
The Regulatory Response and Where It’s Actually Stalled
For years, governments treated heat as a problem homeowners and tenants had to manage themselves. That is starting to change. As heat waves become more intense, some policymakers are looking at cooling as a basic housing need, similar to heating in colder climates.
New York City
New York City is moving toward a new standard for rental housing: access to cooling during extreme heat. In December 2025, the City Council passed Int. 994-A, known as “Cool Homes for All,” requiring landlords of market-rate and rent-stabilized buildings to provide and maintain cooling systems capable of keeping bedrooms at or below 78°F when requested by tenants.
This does not mean every apartment must already come with air conditioning. Instead, tenants gain the right to request cooling. Landlords have several years to prepare, since enforcement will not begin until summer 2030. Public housing follows different rules, with the New York City Housing Authority (NYCHA) required to create cooling plans rather than meet the same standard.
Oregon
Oregon has taken steps to make cooling more accessible for renters, but not every proposed change became law. After the deadly 2021 heat dome, the state passed Senate Bill 1536, which prevents landlords from banning portable or window air conditioners during the summer months in most situations. The law also requires certain new buildings to include cooling in at least one room.
A proposed expansion, Senate Bill 54, would have taken a bigger step by recognizing cooling as an essential service in larger rental buildings. However, the bill did not move forward during the 2025 legislative session.
Chicago
Instead of requiring every apartment to have air conditioning, Chicago’s Cooling Ordinance focuses on making sure residents have somewhere safe to cool down during extreme heat.
The rule, passed in 2022, applies to larger residential buildings and requires them to provide an air-conditioned common area when the heat index reaches 80°F or higher. For residents, it creates a cooling option during dangerous weather, but it does not guarantee that every apartment will have its own cooling system.
The Gap These Laws Don’t Close: Who Pays the Electric Bill
For many renters and homeowners, the bigger challenge is paying the electricity bill that comes with running it all summer.
New York’s energy assistance programs show the imbalance. The state’s Home Energy Assistance Program (HEAP), which supports heating and cooling costs, is expected to provide nearly $300 million for heating assistance this fiscal year but only about $15 million for cooling. That means cooling support accounts for 3% of total funding, despite rising summer temperatures.
The pressure is growing as heat waves arrive earlier and last longer. New York’s cooling assistance funding was depleted on July 19 in 2024, June 23 in 2025, and June 5 in 2026, leaving fewer households with assistance before the hottest part of the season.
Choosing the Right Fix for Your Building
The homes that overheat during heat waves are not always the oldest ones or the newest ones. The real problem is whether a building was designed for the climate it faces today.
That is why there is no single fix for every property. Window film might help a sunny condo with floor-to-ceiling glass, but it will not solve the problems of an older apartment building with hot steam pipes and limited cooling options.
Before investing in upgrades, owners need to understand how their building handles heat. As cities create new cooling rules, knowing the cause of overheating will help residents find solutions that actually work.
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