We’ve fielded quite a few questions on why would it make sense to insulate foundation walls and basement slabs since these areas are below grade, and below-grade soil is generally a consistent temperature all year.
Part of this statement is true – below-grade soil is generally a consistent temperature all year. However, this temperature is about 55 degrees, which isn’t a very comfortable temperature for most people, regardless of the time of year.
In this article, we’re going to share with you how and why insulating the exterior of a basement’s foundation and slab makes a difference in the comfort of your home.
Insulating Your Basement
So let’s dig in a bit more, shall we?
Let’s say it’s wintertime and you want your home to be a comfortable and consistent 70 degrees inside. If the foundation walls and slab are not insulated you will be experiencing a large surface area that will be radiating a pretty uncomfortable 55 degrees while you are trying to keep the area 15 degrees warmer.
Not only will the floor you’re walking on feeling cold (no thank you) but your furnace will also be working harder as it is battling the cold concrete to keep this space at 70 degrees. At this point, the case for why insulate these areas seems pretty clear. But wait – there’s more!
Nerd alert! Concrete is a material that has thermal mass, which means its density and conductivity help to keep the internal temperature of your home more stable since it provides the ability to absorb, store and release the heat or cold that it is coming in contact with it.
Having an insulation-wrapped foundation and slab also helps supercharge this function of the concrete. For example, in the winter as your furnace is pumping warm air into your home, the slab and foundation walls are absorbing it and then dissipate that heat back into the home to keep it warmer. The insulation helps hold on to the heat creating an even more efficient temperature regulator for your home.
The same concept applies to your basement during the sweltering summer season, but instead of retaining heat, the insulation retains the cold air your home’s AC is pumping throughout the space.
The first two feet of soil surrounding your foundation will be hotter than the inside of your home – which is why it’s important the insulation is still doing its job of preventing the heat from the soil from penetrating into your home.
You may notice your basement is particularly cooler during the summer, though. That’s because concrete acts as a natural bumper between extreme temperature swings. On 110 degree days, you have a room that can help temper the large swings in temperature caused by the summer heat.
Extruded polystyrene (XPS), which is the pink insulation you see wrapped around foundation walls and sits below the basement slab, serves as an additional layer of waterproofing for moisture to have to travel through creating a more durable and water-resistant basement floor and wall assembly.
A few extra inches might not sound like a huge deal but properly managing that underground hydrostatic pressure (or pesky moisture that is trying to intrude into your basement) is crucial in maintaining a dry basement. Anyone who has ever experienced flooding can attest how valuable a dry basement truly is!
Like all dedicated green home builders, we’re constantly seeking opportunities to improve the health and performance of our homes.
Having a basement that is properly insulated and protected from moisture as well as seasonal conditions gives you more flexibility in how you can use the entirety of your home. This also provides for a healthier, safer, more comfortable space for you and your family to relax.