Variations in Airtightness of Houses Constructed with Polyethylene and ADA Air Barrier Systems Over a Three-Year Period

Abstract

Periodic airtightness tests were carried out on twenty-four new houses over a three-year period to evaluate their air barrier systems and to search for evidence of air barrier degradation. Ten of the houses were constructed with polyeth ylene air barriers while the remaining fourteen used an early version of the Airtight Drywall Approach (ADA). The twenty-four project houses were architecturally sim ilar and of approximately equal size and general layout; stucco was the predominate exterior wall finish. All were exposed to similar terrain shielding. The study found that the airtightness of the polyethylene air barrier houses re mained stable over their respective monitoring periods. Two of the ten houses dem onstrated possible, albeit slight, evidence of airtightness degradation, however, the magnitude of these changes was small and judged to not be of practical significance. For example, all but one of the polyethylene houses met the airtightness requirements of the Canadian R-2000 Standard for energy efficient housing at the end of their monitoring periods. With respect to the critical issue of air barrier degradation, no evidence was found to indicate that polyethylene is unsuitable for use as an air barrier material in residential construction. The airtightness of the fourteen ADA houses also remained stable over the moni toring period. Six of the fourteen houses displayed possible, but once again slight, evidence of airtightness degradation, however, the magnitude of the changes was also small and not of practical significance. All fourteen ADA houses met the airtightness requirements of the R-2000 Program at the end of their respective monitoring periods. It was concluded that no evidence could be found to indicate that the ADA system is unsuitable for use in residential construction.