Opportunities for Energy Conservation and Improved Comfort From Wind Washing Retrofits in Two-Story Homes - Part I

Abstract

Wind washing is a general term referring to diminished thermal control caused by air movement over or through a thermal barrier. The primary focus of this paper is towards a specific type of wind washing where wind can push attic air into the floor cavity between first and second stories of the home through ineffective (or missing) air barriers separating attic space from the floor cavity. A second type of wind washing studied in this project involved insulation batts on knee walls where space between the batts and the wall board allowed air movement against the gypsum wall board. During hot weather, the first type of wind washing pushes hot air into the floor cavity (between the first and second stories) thereby heating ceiling, floor, and interior wall surfaces (see Figures 1 and 2). Condensation may occur on cold supply duct surfaces within the floor cavity resulting in ceiling moisture damage. In cold climates, cold air from wind washing can chill surfaces within the interior floor space and result in frozen water pipes. Through the summer of 2009, a field study tested thirty-two two-story homes and found significant wind washing potential in 40% of the homes. Part I of this paper will highlight the evaluation methods used and the extent of wind washing found in this study. Repairs and energy monitoring were completed in six of these homes to evaluate retrofit methods and cost effectiveness of retrofit solutions. These results are discussed in Part II of this paper.