Design Heat Loss Factors for Basement and Slab Floors

Abstract

The heat loss factors for selected types of earth contact surfaces, such as basement walls and floors and slab-on-grade floors, are presented to supplement data in the ASHRAE Handbook of Fundamentals for estimating the building design heat loss. The perimeter heat loss factors are derived from the procedure developed by Mitalas and from monthly normal temperature cycles of many localities in the United States. Except for those for cities in California, the heat loss factors are found to be a relatively well-defined function of degree-days and remain constant for degree-days beyond 3000 (engineering units). The heat loss factors show that the most effective way to reduce the earth contact surface heat loss is to insulate the inside corners of wall/floor joints. The insulation installed below the floor slab is found to be the least effective as long as the wall foundation is left uninsulated.