Virtually no architect or contractor would design or construct a building without insulation in the walls or roof. Savvy building professionals also insulate below-grade, including buried foundation walls and under floor slabs. However, how important is insulation in those areas?
The EPS Industry Alliance notes that a lack of insulation on below-grade foundations, crawlspaces and under-slabs accounts for up to 25 percent of a building’s total energy loss. The Green Building Advisor website explains, “If you live in Climate Zone 3 or anywhere colder, it’s cost-effective and wise to install basement wall insulation”—in other words, insulation below grade and under slab makes sense in most of the U.S.