New materials raise efficiency; foregoing cost of certification
NORTH BAY -- Homebuilding in the North Bay has slowed to a trickle in the past few years, but a number of the custom homes are being built greener than even the newly increased state green-building standards.
Yet the impact of the economy is being reflected somewhat in whether owners of such home projects put out the additional cost of having them third-party certified under a green-building rating system.
[caption id="attachment_23766" align="alignright" width="324" caption="Leff Construction is building a structurally insulated panel home in Cazadero that won’t be LEED for Homes-certified. "][/caption]
In the western Sonoma County community of Cazadero, Leff Construction of Sebastopol is almost done with the exterior of a nearly 4,000-square-foot home, the builder’s first project with structurally insulated panels, or SIPs, according to President David Leff. Sebastopol architect Marilyn Standley recommended the home be built with SIPs, initial LEED certification-related energy modeling by AIM Associates of Petaluma.
“It was designed for LEED for Homes Gold or Platinum, and it will be built to meet standards for those specifications,” Mr. Leff said. “But the client decided they were not interested in spending the extra money for documentation and certification.”
Doing so would have added an estimated $6,000 to $10,000 to the cost of the project for documentation and a third-party certifier, he said. Still, he plans to do performance-related adjustments to the finished home, such as blower-door leak testing and systems commissioning.
Panelized construction involves wall and sometimes roof panels built in a factory out of wood or light-gauge steel framing, delivered to the job site on trucks and moved into position.
That can result in less waste that would need to be recycled and faster construction. The Cazadero house will have a framed exterior in two months, instead of four to frame walls on-site, partly enclose them and spray in closed-cell foam insulation to achieve the same air-tightness of SIP panels, Mr. Leff said.
SIPs for the Cazadero project were built in Colorado out of eight inches of polystyrene foam sandwiched between oriented strand board panels, providing insulation ratings of R-40 in the walls and R-60 in the roof.
Other “very green house-equivalent” features include a large photovoltaic array that will handle electrical demand and store the excess in batteries, hydronic forced-air heating via a recycled-wood pellet furnace and solar thermal rooftop panels.
However, outage-prone local utilities necessitate installation of a propane-fired backup generator, depriving the project of the net zero-energy design goal, Mr. Leff said.
Cotati-based custom home builder Hammond & Company has three home projects with highly green features under construction or finishing and a project pipeline of one and a half to two years, according to longtime green-building advocate Bruce Hammond.
The builder recently finished a 2,000-square-foot house between Cotati and Sebastopol and is under construction on a 6,000-square-foot home compound near Sonoma and a 4,000-square-foot dwelling and studio near the west Marin County community of Nicasio.
The newly completed home was registered under the LEED for Homes rating system but won’t be certified, he said. The project encountered construction financing challenges because of fluctuating valuations on the home the owners would be moving out of and how much could be applied to financing and capital reserves.