Net Zero Energy Housing - Lessons Learned
A review was carried out of a select group of Net Zero Energy Houses (NZEH) constructed in Canada and the United States to identify best practices and lessons which could be learned. Half a dozen NZE houses were studied in detail using published information supplemented with detailed discussions with their designers and builders. From this emerged general trends, observations and conclusions which have direct relevance for future Net Zero Energy Houses.
Perhaps most significantly, mechanical system complexity was identified as a major issue faced by almost all NZE house designers. Most systems were too complex, too unreliable and too difficult to maintain in a residential environment.
The analysis also questioned the economic viability of passive solar energy given that a unit area of window costs roughly 2 to 10 times as much as an equivalent area of exterior wall yet provides only a marginal energy benefit. Likewise, the economics of using thermal mass as an energy saving measure was questioned. Overheating was also identified as a concern although this was sometimes an issue in a single room or zone within the house as opposed to the overall structure. Reduced output from photovoltaic and solar thermal systems due to snow cover and adjacent shading was also noted by some of the designers. Likewise, some houses experienced problems finding adequate roof area to mount these systems, particularly in an urban environment.