Abstract

The design of a building for either new construction or a retrofit must consider the control of heat, air, and moisture flows. A large number of buildings were rehabilitated in the Lower Mainland of B.C. because of extensive deterioration due to rain leaks. Now buildings are being retrofitted for energy efficiency and to support electrification. Reduced air flow through the building envelope should be an outcome of any retrofit regardless of the objectives. Mechanical ventilation is essential for any retrofit that increases the building airtightness. Without adequate ventilation the humidity levels in the suites increases and, depending on the wall design, this can result in condensation on the windows or interior drywall, or within the wall assembly itself.

This paper draws on one rehabilitated wall assembly with high humidity levels to explore the assumptions and decisions faced by the design team when completing a retrofit project with respect to controlling heat, air, moisture. The case study building presented in this paper was rehabilitated over two decades ago, but the findings and discussion are still very much relevant today for deep energy retrofits.

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