Page 20 - CodeWatcher Spring 2017 Issue

Aebi started the ICF walls below grade where they serve as the A self-adhered bitumen membrane was installed at the roof edges,
foundation stem walls, providing R-22 of slab-edge insulation for the and valleys, and the roof is covered with enhanced-performance
basement floor slab. The slab was poured over 4.3 inches (R-27) of shingles that have a 130-mph wind-speed rating.
closed-cell spray foam sprayed onto a gravel base.

Heating, Cooling, and Cleaning the Air home. The PV system was an additional $42,000 for a total
The home is so airtight that a blower door test of whole- of $87,000 in costs above a code-built home. Incentives offset
house air leakage showed the home had leakage of only 0.16 about $33,000 of this added cost, bringing the total upcharges
air changes per hour at 50 Pascals pressure difference. That to $54,000.
level of airtightness is far below the 3 ACH 50 required by
the 2015 International Energy Conservation Code and even Building on Success
well below the 0.60 ACH 50 required in the Passive House Aebi builds about five homes a year, ranging in size from
U.S. standard. 2,400 square feet to more than 4,000 square feet, with prices
Aebi installed an energy recovery ventilator (ERV) with a from the high $400s to $700s. “Most are spec houses, about
MERV 7 filter to provide fresh air for the homes. The ERV a 50 percent spec market,” he says. “When I first started
runs 24/7 at low speed to exhaust air from the bathrooms, building homes like this, I stuck my neck out to show people
kitchen, laundry, and attic. The bathroom exhaust registers what was possible; they had to see it, so I built spec houses.
are also equipped with occupant-controlled boost settings This was 2007, and the public had no concept of what zero-
and the kitchen range has a dedicated, occupant-controlled energy meant with the massive amount of greenwashing at
100-cfm range hood fan. the time and the confusing definitions of Zero back then.”
The home is heated and cooled with a highly efficient “The award is great validation,” Aebi continues. “But also,
ground source heat pump rated to have a coefficient of though, it’s a shock to see that there is not more competition
performance (COP) of 5.7 and an energy efficiency ratio (EER) [from other home builders]. It’s our standard product, and
of 44. The air handler is located inside the home in a utility we’ve won lots of awards for it—that’s very satisfying.” CW
room and all of the sealed metal ducts are located within the
conditioned space of the home. The heat pump draws heat
from the ground using a closed-loop system installed in a
500-ft-deep standing well column that is filled with ground
water, which increases efficiency by 15%.
Complementing this, a 13.4-kW solar electric system
provides power from the rooftop.
Deconstructing Costs
Aebi and his team developed strategies to reduce the
construction costs associated with building such a high-
performance home. He believes he could incorporate the
ICF and spray foam thermal and air-control strategies to
achieve the DOE Zero Energy Ready certification without The orange lines to the outlet boxes show the electric that goes in
any significant costs over a code-built home. the exterior walls is foamed back in after the wires are installed.
Adding the ground-source heat pump for space The ICF blocks that make up the home’s walls have a center core
conditioning, the air-source heat pump for hot water, the of steel-reinforced concrete with rigid foam layers on both the
inside and outside to form a very sturdy structure with a
triple-pane (rather than double-pane) windows, and the ERV continuous thermal blanket, comprehensive draft protection, and
increased the cost approximately $45,000 over a code-built a continuous wall water barrier.

20 CodeWatcher / Spring 2017 www.codewatcher.us