CCHRC is evaluating a construction technique currently being practiced in Anchorage of using interior insulation on foundation walls and crawlspace floors as a way to improve energy efficiency. The primary concern is whether this approach adequately protects the foundation from potential heaving due to seasonally freezing ground. The dashed blue line shows the potential freezing front over the course of two years in Anchorage climate and soil conditions. Note how a foundation with no wall insulation keeps the frostline (the blue dotted line) away from the bottom of the foundation, avoiding problems like frost jacking. Foundations with a large degree of insulation along the foundation wall and crawlspace floor, on the other hand, prevent heat loss into the ground and could make the foundation more susceptible to freezing. Building Science See the effect of different amounts of insulation on the frostline. • No wing insulation (current video) • R-19 wing insulation • R-38 wing insulation