BC Housing Owner Builder Exam 2026 – Complete Practice Test for Preparation

Most heat loss in a building primarily occurs through windows due to several key factors. Windows typically have a much lower insulation value compared to walls, roofs, and attics. This means that they facilitate greater heat transfer, especially if they are single-pane or not properly sealed. Additionally, the presence of gaps and cracks around windows can exacerbate heat loss through air infiltration.

Furthermore, windows allow for increased thermal bridging, where heat escapes more rapidly through the frames and sashes. This is particularly pronounced in colder climates, where temperature differences between the inside and outside create significant pressure that drives heat out.

While walls, roofs, and attics also contribute to heat loss, they generally have more effective insulation and can maintain more stable temperatures when properly constructed and insulated. Thus, addressing window quality and installation is critical for improving overall energy efficiency and reducing heat loss in a building.