Focus on Energy: How Much Foundation Insulation Is Needed?

Insulated foundations have become the norm in recent years in the Northeast, but there are many ways to achieve the desired strength and insulation value. It’s important to decide what R-values you want before you select a system, since some methods lend themselves to achieving high Rvalues and some don’t. The criteria I use to determine appropriate R-values below grade include: Building code requirements. Increasingly, building codes are addressing foundation heat loss. In New York State the code requires R- 11 insulation. But there is a “flexible” component to the code that allows reduced R-values in one part of a house when another part exceeds code, and when the net effect on the building’s energy performance will be the same. Expected use of