As temperatures climb into the 90s and heat index values push past 100 degrees across much of the country, millions of Americans are cranking up their air conditioners and wondering why their homes still can’t seem to cool down. The instinct is to blame the AC unit. You call for a repair, upgrade to a bigger system, or shell out thousands for a replacement. That instinct is almost always wrong. The real culprit is far more fundamental: a poorly insulated, inadequately sealed building envelope that is letting every degree of hard-earned cool air slip right out of the house.
The building envelope is the most critical factor in determining how well a home holds temperature. In the winter, a compromised envelope lets heated air escape. In the summer, it works against homeowners in the opposite direction, allowing scorching outdoor air to infiltrate while conditioned cool air leaks out. This isn’t a seasonal problem. It’s a year-round structural one. And as summer heatwaves grow more intense and prolonged, the consequences of an underperforming building envelope are becoming harder to ignore.
One of the most significant points of failure is the attic. On a hot summer day, attic temperatures can soar to between 130 and 150 degrees Fahrenheit. When insulation is insufficient or air sealing is incomplete, that superheated air doesn’t stay put. It radiates down into living spaces and infiltrates through gaps around attic hatches, recessed lights, and ductwork penetrations, forcing air conditioning systems to work overtime.
Mason Herlitzke, a building analyst technician at Ultimate Insulation, puts it plainly: “If the house isn’t air sealed properly or insulated properly, that AC has got to work really hard. And a lot of times, those ACs go down … Your attic is leaking between 30 and 40 percent of the air that you put in there. So, it leaves so fast, and you try to cool it down, but it never gets to temperature.”
Kyle Smrekar, general manager of Bridgeport Menards in West Virginia, has seen this firsthand as customers flock to his store during heatwaves looking for affordable solutions. His advice cuts straight to the point: fill gaps and cracks, keep cooling equipment clean and efficient, and don’t wait until conditions become unbearable. “Getting on it before it gets too hot,” Smrekar said. “It’s a lot easier to keep it cool than it is to cool it off.” He also noted that spray foam and draft stoppers, tools most commonly associated with winterizing a home, work just as effectively in summer to keep cool air in and hot air out.
When it comes to addressing the building envelope’s two most critical summer vulnerabilities, heat transfer and air leakage, no product does both as effectively as spray foam insulation. Unlike traditional insulation materials that only slow conductive heat transfer, spray foam expands on application to fill gaps, cracks, and hard-to-reach spaces, creating a continuous barrier that stops air movement entirely. An attic that is insulated but not air sealed will still bleed conditioned air through every unsealed penetration.
This summer’s heat is a reminder that a home’s ability to stay cool is determined by the quality of its building envelope. Homeowners who invest in proper insulation and air sealing now are better positioned to weather not just this summer, but every summer that follows.