Building Science and Certification
Energy Star offers manufactured and modular home builders a certification that allows them to certify their products as Energy Star Qualified, pending on-site air-seal testing when multiple sections are assembled to create a single structure. The CertifiedGreen Modular Home Program is administered by the Systems Building Research Alliance (SBRA), certifying modular homes that comply with the off-site construction portion of the NGBS; full certification is dependent on site development compliance and final on-site testing. The NAHB Research Center will verify a factory’s claim of building green under its Green Approved listing.
Modular homes have an initial certification advantage of 4 points in the LEED for Homes rating system (under MR 1.5 Off-site Fabrication), due to inherent manufacturing efficiencies, with added points for advanced framing and other elements easily incorporated into the factory building process, and points for recycling. Under NGBS, 13 points are awarded under Section 601.5 (4) Modular Construction for the portion of the building prefabricated and located above grade.
Most of the manufacturers we spoke to will certify to any national standard in response to client demand. Epoch Homes of Pembroke, N.H., offers customers a certification menu; the company’s Eco Collection comes pre-engineered to the NGBS Silver level, and clients desiring higher-level certification can customize by choosing upgrades from a certification checklist. Some manufacturers, such as Seattle-based Method Homes, build only to LEED standards, “Since all of our homes are sustainable, this is not an upgrade,” says co-founder Brian Abramson. San Francisco’s ZETA does not always certify but builds only net-zero homes, focusing on net-zero community developers as primary clients.
Price and Predictability
The architects and developers we spoke with cite a 10% to 15% price benefit with modular construction when specifying green finishes and high levels of energy efficiency. They also emphasized that the fixed costs and scheduling offered by factory home builders have become increasingly important in the current economic environment, where clients may not have the resources to pay for unexpected change orders and delays. “The biggest difference between the site-built and modular approach comes with cost control and speed. Our clients fear the uncertainty of conventional construction,” says Kaplan, while admitting one tradeoff he has found in working with modular construction is the inability to make design changes on the fly.
Some manufacturers, such as Clayton Homes, have focused on serving the affordable market for high performance with moderately priced models one income step up from the traditional HUD-Code home. Clayton’s i-house, which features a photovoltaic system, a highly insulated and tight shell, and Energy Star windows, doors, lighting, and appliances, comes with an all-costs-in base price under $150,000, or about $93 a square foot. Despite the low price, O’Connor says the modern-styled, high-performance i-house “was meant to attract a buyer that would have never walked into our showrooms before. They came in Volvos and Audis, and they walked away with a whole new concept of what a factory home represents,” says O’Connor. This challenges the concept that high efficiency comes only with high prices, and, bucking the new normal, all of the green factory home builders we spoke to reported record profits during the housing bust from 2008 through 2011.
Fernando Pagés Ruiz is an EcoHome contributing editor.
