Why is my house so hot with the AC on?

Hot summer weather can really take a toll on comfort inside your southern Vermont home— even with the air conditioner running! The reason may not lie in an underpowered AC but in an underinsulated home. We usually think of insulation as a winter heating problem, but inadequate insulation can also make your house hot in the summer. So why is my house so hot?

Start at the Source: Radiant Heat from the Sun

Radiant heat travels in one direction and heats whatever it comes in contact with. You can feel radiant heat when you step out of the shade and into the sunlight. Radiant heat because of its one-way direction can really heat up enclosed spaces, like your attic. Temperatures on a hot, sunny day can reach above 100 degrees in some attics, with all that hot air trying to get into your house! 

Reverse Stack Effect Draws Attic Heat Down

You may have heard of a phenomenon called the stack effect which is named after smoke stacks. Basically, the stack effect in a house during winter is caused by warm air rising to the highest part of the house. Upward warm flow can draw in cooler air from outside or the basement and make your home feel cold. In the summer the reverse stack effect has hot air drawing down toward cool air, as cool conditioned air escapes from small gaps. This hot reverse flow makes it difficult for your AC to keep up.

Poor Insulation is the Reason—Not Your AC!

Most homes in Western NH and Southern Vermont have less inadequate insulation, which means that their AC is strained to the max on hot summer days. Compounding poor insulation are the small — and sometimes large— gaps and cracks that allow the reverse stack effect to occur in summertime heat. Improving and upgrading old insufficient insulation is the key to keeping cool and lowering your energy bills.

Insulation Keeps Radiant Heat Out

Insulation prevents the transfer of radiant heat into your living areas in the summer. When your southern Vermont home has new insulation installed, it’ll be able to defend against the summer heat and the winter cold. Plus with an insulation upgrade,  your home’s air conditioning will work less hard and last longer! Ultimately, new insulation will mean your energy bills will decrease and you’ll spend less each month to be comfortable.

Pinpoint Gaps & Ineffective Insulation with an Energy Assessment

The best way to determine where your insulation and air sealing needs to be improved is with an energy audit set up by Vermont Foam Insulation. We’ll inspect your homes’ accessible areas like the attic to assess the depth and quality of your home’s insulation. We’ll also scan your walls and ceilings with an infrared camera that identifies different heat signatures. Each temperature has a different color, and referring to the readout, we can pinpoint areas of poor insulation and air leaks. These air leaks in particular can contribute to the reverse stack effect that makes your western New Hampshire home feel warm even when the AC is cranking.

Spray Foam Insulation Seals and Insulates 

At Vermont Foam Insulation, we’ve got three decades of experience in improving home insulation while saving energy and money. Our professional spray foam techs can apply the spray foam insulation to proper, even thickness to air seal your attic and keep excess radiant heat from seeping into your living areas. You’ll notice immediately how much cooler and more comfortable your house can be!

Rebates for Insulation Upgrades

There are some attractive rebates & incentives for improving your home’s efficiency and performance. Adding an insulation upgrade as part of a more comprehensive retrofit improvement could be worth up to $2000 to $4000 for qualifying homeowners depending on income. The efficiency pros at Vermont Foam Insulation is an ENERGY STAR® partner so you can count on the efficiency improvements to be installed and completed with the highest attention to detail.

Insulation upgrades can keep your AC from wearing out

Combat summer heat with insulation and air sealing.


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