Long Term Performance of Vacuum Insulated Panel Walls and Energy Use Assessments of a Net Zero Energy House
Please note: The attached file below contains a paper linked to a presentation in pdf format from the BEST5 conference. Open with Adobe Acrobat for best results.
In 2011, Canada's pioneering EQuilibrium Homes Initiative developed and sponsored by Canada Mortgage and Housing Corporation (CMHC) supported the construction of a number of net-zero energy demonstration homes across Canada. One of the most successful projects, Harmony Home located in Burnaby, British Columbia, demonstrated the use of vacuum insulated panels (VIPs) for above-grade walls, low u-factor windows, high performance mechanical systems and grid connected photovoltaics to achieve zero energy levels. The exterior VIP wall assemblies consisted of 15 mm thick VIPs in the center of the stud cavity, covered by a 50 mm foil-faced isocyanurate foam board on the exterior and open cell spray-foam on the interior. This provided an estimated effective insulation, averaged over the entire wall, of 38.5 ft2F/Btu R) or 6.8 m2K/W (RSI). This field study evaluated the long- term performance of this home after five years of operation with respect to heat transmission through the building envelope, moisture performance of VIP wall assemblies and annual energy consumption. The thermographic survey of wall assemblies and joints showed that vacuum insulation panels are intact and, overall, building envelope is in excellent condition. In-situ wall assembly moisture measurements, gathered in four wall sections in different orientations, within the framing and sheathing showed no appreciable moisture accumulation.
The energy-use data over a period of five years showed varying trends: (1) photovoltaic systems were performing as per the design intent; however, on year-to-year basis, there was a significant Â±20% variation in electricity generation mainly due to climate conditions; (2) occupant-driven load showed little changes; and (3) significant variations in space heating and space cooling requirements. Overall, the Harmony Home demonstrated comparatively close to net-zero energy performance over the years. This paper presents the results of the field study of building envelope components and also provides discussions on ways to mitigate challenges of year-to-year variations in energy use patterns to meet the "net zero" energy target.