Like a lot of building-industry professionals who run their businesses solo, Tucson-based Michael Ginsburg has become a utility player in his market. La Mirada Homes, which he launched in 1976, offers design, construction, remodeling, and general contracting services. And now, Ginsburg is bringing his experience to bear on the design and construction of a near-net-zero-energy, modest-size house that, he says, could be offered for a comparably modest price.
Ginsburg calls it the S.E.E.D. Home (for its “super energy efficient design”) and will celebrate its inception with a ceremonial groundbreaking on Friday. The 1,935-sq.-ft. four-bedroom home’s performance is pegged tightly to the energy efficiency of the structural-insulated panels that will comprise its exterior walls and roof, Ginsburg told GBA. He said he chose SIPs filled with polyurethane foam over alternatives that feature polystyrene because the former offers better thermal resistance for a negligible difference in price.
The wall panels are rated R-24, which, with R-5 foam board under the exterior stucco and 2 inches of interior-side dead space for electrical wiring, would bring the composite R-value of the exterior wall to 34. The roof panels, supported by structural gluelam beams (no 2x wood), will provide R-41 insulation.
A slow-curing floor
The walls and roof will go up before the slab foundation is poured to shade and prevent cracking in the concrete, which will later be colored and polished. The slab will be insulated to R-8 underneath and at the edges, Ginsburg said.
The house is not, however, designed to take advantage of direct solar gain, a prospect the builder “completely rejected as a passive heating strategy because of the inherent overheating and management problems” it would have presented in a single-story house of this size and layout. Rather, the building will be equipped with a SEER 16 dual-stage heat pump, hydronic radiant floor heating, radiant floor cooling, and a whole-house fresh-air exchange.
In an e-mail to GBA, Ginsburg also pointed out that “there are no interior (weight-)bearing walls to interrupt the thermal integrity of the floor of the shell. Therefore, the concrete floor is, in effect, a thermal mass element for the entire square footage of the home. With no direct solar gain, I can now use, control, and manage the floor for heating and cooling. In essence, I’ve created a ‘living cave.’ Achieving and maintaining a constant interior temperature will be easy and cost-effective.”
The home’s renewable-energy equipment will include solar hot water collectors and a photovoltaic system capable of feeding electricity back into Tucson Electric Power’s grid.
The project design has received HERS ratings of 18 and 20 from two independent, accredited HERS raters, Ginsburg said, although he noted that getting financing was a bit more difficult. After several rejections from other lenders, the builder explained, the president of Bank of Tucson “gave me a hearing regarding the concept and nature of the project first, before even considering our financials,” and then proceeded with an appraisal, financial review, and loan approval.
We’ll post cost details, more specs, updates, and images as they become available.