Perhaps in its early years, prefabricated design looked to consumers like tacky boxes. No more. “Design-wise, modular systems don't hold you back any more than a sheet of plywood,” says Paul Irwin, of Landis Construction in Washington, D.C., who has worked with modular systems for many years. “Structural insulated panels, for instance, can be very liberating,” he says. “[Using these] sheet goods with specific sizes, thicknesses, and benefits, a designer is free to implement bays, bump-outs, and dormers that can be prefabricated, are structural and insulated — something that stick building cannot do nearly as effectively.”
According to Sheri Koones, author of Prefabulous (The Taunton Press, 2007) and Modular Mansions (Gibbs Smith, 2005), both about prefabricated construction, the benefits of prefab construction — mainly modular, timber frame, SIPs, and panelized (see below) — are legion. It is “beautiful, strong, and intrinsically green,” she says. Modular walls are built on a flat surface so they're even and straight; their tight-layered makeup means better insulation and, hence, improved energy use in the home; construction is faster; and there is less mess and disruption for clients living in the home during a remodel. SIPs, too, are easy to install and are extremely energy efficient. Projects may run more smoothly using these systems since you must plan ahead, but structural change orders are near impossible. And using prefab systems can help differentiate your company in the market.
There are caveats. For instance, shipping can be an issue because of costs associated with permits for oversize loads, and possible damage. Using in-state suppliers will minimize permit costs, since crossing state lines ups the ante. As for damage, materials do get jostled, but they are built to sustain the loads they face en route as well as loads in the home. Some prefab companies will ask that tile or other brittle materials be installed on site.
Also, there is a learning curve, says architect Doug Cutler, whose Wilton, Conn., practice does about 60% of its residential work with modular building systems. “It might take a builder a project or two to get enough experience under [his] belt to see the efficiencies,” Cutler says, “but once they do, they become real believers.” It's also imperative to have an architect on the project. “Because of liability, factories typically won't do [these] projects without a licensed architect involved.”
Pricing can be comparable to traditional stick building if you factor in lowered labor costs and, for the customer, future benefits such as reduced energy bills. Cutler says, “You have to understand the parts and what each one costs so you can design within budget. Plus, it may not be worth your while to do an addition under 1,000 square feet; the bigger the addition, the more economic benefits there are.” He points out, too, that if you're building in an expensive market such as New York and are able to get materials from a less-expensive market such as Pennsylvania, you'll be able to save money.
Definitions Modular: six-sided cubes. A house can be built with any number of modules, which are placed on a foundation and attached to one another with special clips. “You wouldn't know it was anything other than stick-frame construction,” Prefabulous author Sheri Koones says.
SIP: Structural insulated panels consist of an outer panel bound to an insulated foam core.
Timber frame: framing work for the structure. Used mostly for its aesthetic, to create an open, airy interior, possibly a soaring interior ceiling with exposed wood. It can be enclosed and is often enclosed with SIPs.
Panelized: similar to traditional construction but it's a whole piece of a house built in a factory and brought on site to be put together like a giant jigsaw puzzle. Some are delivered with doors and windows already installed.
Resources www.bensonwood.com: The Web site of Bensonwood Homes in Walpole, N.H., which is owned by Tedd Benson, an early devotee of timber frame who went on to help develop SIPs. Benson began the “Open Built” system based on the principle of bringing organization and structure to building systems to make it easier for tradespeople to work with the products and to ensure that homes using this system can be more easily maintained and remodeled.
www.openprototype.com: a cooperative effort between Bensonwood Homes and M.I.T.'s architecture department
www.insulspan.com; www.panelpros.com; www.winterpanel.com; www.pbspanels.com: makers of SIPs
www.apawood.org: Engineered Wood Association
www.tfguild.org: Timber Framers Guild
www.sips.org: Structural Insulated Panel Association
