The whole building, including hvac

These whole-building designs extend into more-efficient hvac systems.

Rod Siegfried, of Cooper Heating and Cooling, said, “Once people get used to the idea of energy-efficient homes, it will be well worth the work it is taking to get all the bugs out of designs and systems.”

The “Cottage Series,” which will be constructed in the greater Boulder, CO area, will include six different designs for single-family homes. The floor plans in the series, including two single-story and four two-story models, range in size from 1,166 to 1,813 sq ft. Up to 200 of these homes may be available for purchase later this year and the next, with the potential for adoption in three separate developments.

Christine Bruncati, SWA project manager, said the following specifications contribute to the higher performance of a Cottage Series home over its lifetime:

• High-performance, low-e windows, double paneled with 1/2-in. airspace;

• Wet-blown cellulose insulation with more than 90% recycled content (R-38 in ceilings, R-30 for vaulted areas, R-22 for exterior 2x6 walls) and R-11 foundation blanket (fiberglass);

• 90% AFUE sealed-combustion furnace;

• High-efficiency water heater;

• “Advanced” ventilation system (optional);

• Low-VOC mastic sealant for furnace ductwork;

• Polycel foam sealing package for vertical penetration in floor and plate areas due to plumbing, heating, and electrical, selective horizontal penetrations, electrical boxes on exterior walls, wall corners, and bottom plates;

• Shortened duct runs with wall stacks;

• Recycled-content decking materials;

• Structural-engineered lumber material;

• Panelized framing system;

• Non-solvent-based foundation damp proofing; and

• Fiberglass front entry door (R-5).

Building America aims to build 2,000 of these homes across the country by the end of this year. The program hopes its “system engineering approach” will enable it to design and construct in 70% of the country’s new housing markets within 10 years.

Hvac design: no fudging

Due to the fact that the project is relatively new, the hvac contractor said there were elevated costs that should go down with the familiarization of the housing designs.

“When home buyers understand that these options are available today, contribute to the health and well-being of their families, and are extremely attractive from the perspective of life cycle cost, broad-based acceptance is inevitable,” said Will Zachmann, SWA’s director of communications.

“The original hvac design was modified to work with the realities of the field,” added Bruncati. This means an area with a set specification is followed to exact measurements. Comfort systems are designed and installed to fit an area exactly, closing unwanted openings and enabling ventilation to work to its fullest potential.

McStain and SWA said a constant airflow regulator is installed in the duct to maintain appropriate airflow under varying pressure conditions. A manual damper is included so the duct can be closed during extremely cold weather.

Chuck Lambert, McStain’s construction superintendent, said, “The [hvac] cost is a little bit higher due to wall stacks.”

Fine-tuning needed

Cooper Heating and Cooling’s Siegfried said that there were other reasons for the elevated cost of building these homes. “The thing to remember is this was the first time anyone had built these homes,” he said. “Therefore, the labor costs did rise, because we had to take time to weed through problems that arise with new housing design. This was due to basically trial and error, and design flaws discovered between McStain, SWA, and us.”

Specifically, Siegfried said, difficulty arose between differences in building CARB homes and building standard homes.

“High wall registers instead of low, and a larger air return caused difficulties at first,” said Siegfried. “Another example of difficulties that had to be overcome was in the bath fan. Normally, the bath fan is individual of everything else, but in this case, all bathroom fans are combined and exit through the fan located in the attic.”

The fan located in the attic draws moisture from the air from all over the house, and adds to the “tight” nature of the building design.

Siegfried also said that the initial installation of the system was a bit of a rocky process, as it diverged from standard practices and caused some frustration for the installers.

“It was difficult at first because we [Cooper] and SWA got involved late,” he said. “Because the design of the homes came before any contractor got involved, implementation took longer than it would with a housing system not as new.”

Cost effective over time

McStain’s Lambert said that while the ventilation systems used did add costs not typically incurred with standard homes, they are needed because of the tightness of the structure.

“The configuration is different,” said Lambert, “but the end result is worthwhile. Overall, I think the system performs well in terms of both construction cost and energy-efficient operation over time.”

Bruncati said that although homes in McStain’s existing product line already qualify for a four-star rating from the Energy Rated Homes of Colorado program, CARB’s integrated whole-building approach to design and construction will further reduce energy consumption while improving indoor air quality.

“Upon completion, the Cottage Series homes are expected to achieve a 30% to 40% reduction in energy costs in comparison to a home built to current Model Energy Code standards,” said Bruncati.

Siegfried said contractors who have not worked with this kind of design before may have difficulty at the beginning, as would anyone working with a new design. However, he added that in the end, when all the bugs are worked out, it will cost less and be worth the effort.

“I would work with this design group again,” said Siegfried. “Down the road it will save money, and will work out. People just need to get used to it.”

Publication date: 08/21/2000