Many have advocated for tight houses with low-energy needs and highly efficient mechanical systems as one of the best ways to address climate change. California now requires all new houses to be zero-net-energy, although natural gas is still allowed. A new study by Chris Magwood, director of the Endeavour Sustainable Building School in Ontario, Canada, questions this singular focus on cutting building energy use. His research concludes that curbing the emissions resulting for the harvesting, manufacture, and transport of building materials — what he calls a building’s up-front embodied carbon emissions (UEC) — is significantly more important than the contribution from running a building on clean, renewable energy.
Zero-net-energy makes a big impact on carbon emissions, but most of that impact is in future years as a result of ongoing zero-energy consumption in the building’s operation. On the other hand, if UEC is zero or even provides net carbon storage, the impact on climate is immediate and powerful. Emissions that are avoided today do more to slow climate change than emissions that are averted in the future.
What materials make the difference between a high UEC structure and one that stores carbon? A high-carbon house would use such common construction materials as standard concrete, extruded polystyrene insulation, brick cladding, steel-frame vinyl windows, tile and carpet flooring, and concrete or clay tile roofing.