Thermal and Economic Evaluation of Slab-on-Grade Insulation in Wood-Framed Buildings

Abstract

This paper presents a new one-equation model, and case studies utilizing it, for evaluating the thermal effectiveness of slab-on-grade perimeter insulation in common wood-framed buildings for any time period such as a month, a season, or an entire year. Many previous studies focused on heat losses in very cold climates, but this new model can be effective for both heating and cooling in potentially any climate that has coefficients available. Two case studies, of residential and commercial buildings, are presented in this paper for three levels of foundation insulation and for three different, somewhat-warm to somewhat-cold, climates. Economic analyses of their heating seasons, cooling seasons, and annual performance are then presented, and the overall worthiness of the insulation, from energy cost and other perspectives, is discussed. The hand calculation method presented differs from previous efforts because it uses a new, single transient analytical equation and site-specific coefficients. The model gives designers, builders, and code officials, for example, the specific, defensible information needed to make decisions on whether insulation is needed. For the residential and commercial building examples presented at least a minimal amount of perimeter insulation is justified, both thermally and economically, for at least two of the three locations studied.