A Methodological Approach to Predict and Estimate Air Leakage Through a Window-To-Wall Interface in Wood Frame Construction

Airtightness is an important phenomenon in building performance. Poor building airtightness can impact the IAQ, indoor comfort conditions, building envelope’s structural integrity, occupant’s health, and building energy performance. It is well documented that window-to-wall interfaces are an area of reoccurring air leakage location, contributing 15% to 35% to whole building air leakage. Therefore, there is a demand for adequate prediction methods to estimate air leakage through the window-to-wall joint to assist builders and designers in making cost-effective design decisions prior to construction. The objective of this study was to further an approach to model preconstruction relative airtightness of differing window-to-wall joint detail designs and variation in field construction. This research was done to further the work already conducted in determining if an experimentally based methodology can be used to alter predictions of whole building airtightness in new construction at the pre-construction phases of development (Khemet & Richman, 2020). An empirically-based design of experiments was created using a 23x3 factorial design to quantify the impact of air leakage through the window-to-wall joint. The four main effects that were selected for analysis were pressure, shim type, sealant technique, and detail length. The multiple linear regression model explained up to 38.7% of the air leakage through the joint (R=0.6387, p<0.001). The results of the experiment established an approach to predicting relative air leakage of varying window-to-wall joints.