Many new home builders are already incorporating foundation insulation on their basement walls. According to the US Department of Energy, an R-20 insulation applied to basement walls on a 1,500 square foot house will save a homeowner up to $390 per year. That is over $30 dollars per month.
Not only does this save the homeowner money, it also creates a better environment in the basement. Properly insulated basement walls generally stay dryer and smell better. Not all types of insulation work in a basement. No matter how water tight the foundation walls are, there will be moisture to control.
Basement wall insulation can be applied to the interior or exterior. There are advantages and disadvantages to both methods. Adding it to the interior does not require protection from the exterior elements and is typically easier to integrate into the construction schedule. The disadvantage on interior applications is making sure a process and product is used to avoid moisture that can lead to mold and mildew. Exterior insulation allows for continuous application, but the part that is exposed to ambient air will need to be protected from the sun.
I am a huge fan of Superior Walls. This company has developed a system that incorporates continuous insulation at the time the walls are poured. It also incorporates a studding system that eliminates thermal bridging. These walls can have a continuous R-Value up to R-21. If you compare the initial cost to a typical foundation price, the cost is higher, but once you factor in the additional costs of the typical insulation and studding, the cost is very comparable. I have been in many homes with this foundation wall system and you can feel the comfort difference. You don’t feel like you are in a basement.
Insulation for interior application:
Mineral wool blankets work really well and adhere to concrete easily. Ecocell blankets are a product we see a lot here in West Michigan. If you have a studded wall, closed cell spray foam is a very good product to use. Make sure the studs are kept off the concrete at least 1-2 inches. XPS or EPS work well, but make sure the perimeter of each piece is sealed. (The main blog picture at the top is Ecocell blanket insulation)
It is NOT recommended to use fiberglass batt insulation on a concrete wall. Fiberglass batts are like a sponge when introduced to water and they don’t dry out well.
Insulation for exterior application:
Polystyrene such as XPS, is a good product for exterior application. Closed cell spray foam can be used, but is rarely seen in the construction industry for this type of application.
The bottom line is basement insulation on all new construction should be done, period. Don’t let your builder talk you out of this. It’s much easier and cheaper to do it at the construction phase. Adding it to existing construction can be done. Make sure you use the right product and procedure to avoid future problems. If you are a builder who utilizes the HERS Index Rating, basement insulation will help bring your numbers down and increase the marketability to your customers.