Towards A Methodological Approach to Builder Specific, Preconstruction Airtightness Estimates for LightFramed, Detached, Low-Rise Residential Buildings in Canada
Bomani Khemet, Doctor of Philosophy in Civil Engineering, Ryerson University, 2019
This research is an investigation into residential building airtightness. Its purpose is to establish a methodology to predict preconstruction airtightness in Canadian homes. The dissertation presented an analysis of a large, national blower door testing population, numbering over 900,000 low-rise detached homes.
The relationship between airtightness and various building factors, such as; insulation levels, building size, and year of construction, is explored. Regressionbased models were found to be highly significant (p<<0.01) and explained up to 48% (R = 0.69, p<<0.01) of whole building airtightness. The national models’ scope was confined to predicting airtightness in existing homes with heterogeneous wall construction.
In order to estimate preconstruction airtightness in conventionally constructed homes, a local blower door testing population of nearly 3000 homes was examined. Three builder-specific, geometricbased, temporally independent, multiple linear regression models were developed. Some of these builder-specific models were found to be strong, and explained over 58% (R = 0.79, p<<0.001) of whole building airtightness. A five variable, geometrically based model which controlled for handicraft was found to be very strong, explaining up to 73% (R = 0.87, p<<0.001) of the whole building airtightness. The regression-based analyses on the local population suggests that air leakage is prominent through two building details: the floor-to-wall details, and at the window-to-wall assemblies.
An empirically based design of experiments was devised to quantify the impact of air leakage through a floor-to-wall detail. A very strong laboratory-based model explained up to 88% of the air leakage through the floor-to-wall joint (R = 0.95, p<<0.001). A builder-specific, temporally-independent model was combined with the empirically-based, floor-to-wall model to illustrate the applicability of the approach residential building designers. The synthesis of the two models resulted in a novel, whole building, preconstruction airtightness forecasting model.
The dissertation demonstrated that airtightness in homes could be estimated with temporally independent, builder-specific, and geometrically-based preconstruction models. The estimation approach spurred models that were stronger in explanatory power, and industrial applicability as compared to previous airtightness models.
