Chapter 6:                      Floors and Foundations

The importance of defining the thermal boundary at the build­ing’s lower reaches depends on how much of the building’s heat loss is moving through the foundation or floor. The building’s thermal boundary may not be obvious because of the lack of insulation at both the floor and the foundation. The building owner and energy auditor must choose where to insulate and air seal if these ECMs are cost-effective.

Either the first floor or the foundation wall is the thermal boundary. After choosing, air seal and insulate the chosen ther­mal boundary.