Designing net-zero energy buildings for the future climate, not for the past

Net-zero energy buildings (NZEBs) are expected to play an important role in fighting climate change and reducing the energy use of the built environment. But even if the best design practices are widely adopted and implemented, this will only mitigate global warming. It is too late to prevent it. Yet buildings - including net-zero energy buildings - are often designed using historical data representing the average climate between 1961 and 1990, or between 1976 and 2005 at best. This paper investigates the use of the downscaling method known as morphing, proposed by Belcher et al. (2005), to generate weather data files. The impact of using these weather files on the energy performance of an actual NZEB is then assessed. Morphing is applied to typical horizon years representative of future climate and also on a month-by-month and year-by-year basis using raw data from a selected GCM. A 50-year series of hourly weather data is obtained and analyzed for two different locations, Montreal (QC) and Massena (NY). The data are then used to simulate the performance of a net-zero energy home as it was designed using historical data. The results show that the building misses the net-zero energy target for most years. The year-to-year variability of the total energy use is relatively small but the impact on the energy excess or shortage in relation to the net-zero target is significant. climate-sensitive buildings such as NZEBs should always be designed using multi-year simulations with weather data that take climate change into account. (C) 2011 Elsevier Ltd. All rights reserved.