Efforts are underway across North America to improve the energy performance of new building stock whether through building code or energy efficient building programs; however, it is also important to find ways to address energy performance in existing buildings. A research study was completed to identify and evaluate building enclosure retrofit strategies to use in near net zero retrofits for houses across all Canadian climate zones (ASHRAE/DOE Zones 4 through 8). This paper will present the key findings of this research study.

General thermal performance targets for net zero house enclosures in heating dominated climates were developed through energy simulations of four existing archetype houses constructed between the 1950s and 1980s. Retrofit strategies to achieve these targets were then identified and analyzed.

Retrofit measures are grouped into five categories: the attic or roof, above grade walls, windows and doors, below grade walls, and slab. Each retrofit was evaluated in terms of its thermal and hygrothermal performance. As improving the thermal performance of an assembly affects its hygrothermal performance, findings and retrofit design strategies for the control of air, vapour, and moisture in highly insulated enclosure assemblies were developed and are presented.

A cost analysis was completed for each retrofit strategy to determine the financial feasibility of near net zero enclosure retrofits. It was found that such retrofits are difficult to justify based on energy savings alone in most areas of North America; however, if retrofits are being completed for other reasons, such as to upgrade aesthetics or to repair water penetration issues, the incremental cost to complete a near net zero retrofit can have good financial return.

Presented at Thermal Performance of Exterior Envelopes of Whole Buildings XII, December 2013