Prefabricating Green: Building Environmentally Friendly Houses Off Site
by Allyson Wendt
In August 2007, a home appeared in Walpole, New Hampshire, over the course of eight days. Sponsored by Habitat for Humanity, the house was designed by design-build company Bensonwood, also of Walpole, and constructed by volunteer labor. This house was different from most Habitat houses, however, which are typically built on site using conventional wood-framing methods. For the Walpole home, Habitat chose to build a prefabricated home with precision-cut timbers and panels constructed at the Bensonwood factory by volunteers; the panels were later assembled on site, also with volunteer labor.
The resulting house produced less waste material than a site-built house, thanks to cutting equipment programmed to maximize the use of each piece of wood. It was also built faster than a site-built house, including the time spent assembling panels at the factory, and it featured a well-insulated building envelope with strong attention to construction details. The house included Bensonwood’s unique measures designed to “disentangle” the electrical, plumbing, and mechanical systems from the structure, making them easier to install and modify.
Not all prefabricated homes incorporate as many advanced features as the one in Walpole, but Bensonwood is not alone in exploring ways to bring environmental sensitivity and smart design to prefabricated housing. On paper, prefabricated housing has the potential to offer significant environmental benefits: stronger, better-insulated structures; less waste from construction; reduced transportation impacts; and, in some cases, easier disassembly for reuse. Prefabricated construction also has the potential, given the efficiency of factory production, to deliver these benefits at a lower cost than site-built housing.
The prefabricated housing industry has been slow to accept high-performance building practices, however, failing to realize the full environmental potential of prefabrication. Changes to assembly-line procedures to add high-performance features—super-insulation of the house, for example—can be prohibitively expensive, making prefabrication less attractive for environmentally friendly building projects. If the changes are adopted throughout the industry, however, the costs of changing procedures would be spread among thousands of houses, making green design affordable.
This article examines both mainstream and more advanced green prefabricated housing, looking at the potential environmental benefits of this form of building and the potential for making green housing more affordable.