TechPractices are outstanding housing projects throughout the U.S. where innovative technologies are implemented. Builders and remodelers can use these examples as models for projects of their own.
|The Cornell Project Snapshot
||Energy tested, 1,200 sf prototype home for a large production builder
||Design funding by US DOE. Materials and labor supplied by builder and product manufacturers
||Systems engineering, Precast Concrete Foundation, Optimum Value Engineering, Residential Steel Framing, HVAC Equipment and Duct Installation Within Conditioned Space, Flexible Gas Piping, Wastewater Heat Recovery, Duct Blaster, Blower Door
Perceived first cost is a big deterrent to builders considering energy efficiency. So DOE funded a study to show that builders can both have their cake and eat it. The Cornell is an efficient but small two-story colonial (highly desirable in Rochester markets). It was built as a more energy-saving version of the Hathaway-an existing Ryan model noted for its efficiency. What's news here is that the Cornell is less expensive to build than the older
model. The home received an NAHB Gold Energy Value Housing Award for a cold region production home.
The Cornell's success is the result of the comprehensive approach of the Consortium for Advanced
Residential Buildings (CARB). The Cornell is a product of CARB, one of four consortia, co-funded by the US Department of Energy (DOE) through the National Renewable Energy Laboratory under the Building America program. This program applies a systems approach to residential construction that emphasizes the mutual benefits of innovations that reinforce each other.
The Cornell prototype home was built in upstate New York by
CARB team primary member Ryan
Homes and designed by Ryan Homes and Steven
Winter Associates (SWA). Materials and manufacturing support
came from such other team members as Kistner
Concrete Products (foundation), US
Steel (interior and garage framing), Owens
Corning (insulation, ice dam, roofing, siding), Andersen
(windows and doors), and York
(HVAC systems). The aim of the consortium was to produce a newer,
more efficient home by modifying Ryan's Hathaway model home at
little or no increase in first cost. SWA used sophisticated
DOE-2.1E computer energy simulations to determine the most cost-effective
methods. As a test home in the Building America Program, the Cornell
was monitored to evaluate the cost and performance benefits associated
with the new technologies it incorporates. Results show the Cornell
to perform even better than CARB's expectations.
Ryan's standard wood framing system was optimum value engineered
for increased thermal performance and economy. R-15 insulation
in exterior walls, R-38 fiberglass blown-in insulation in the
attic, and argon-filled vinyl/wood-frame windows with low-e glazing
increased energy savings. Precut vinyl siding with cost-saving
corner detailing further cut costs.
An integrated HVAC design with minimal duct runs within the conditioned space, dramatically reducing the effect of duct losses. This was first
confirmed by calculations and computational fluid dynamics studies. A central, simplified duct supplies air between the first (downflow) and second (upflow) floor. The 1,200 sf home is served by a gas furnace with only 37,000 btu/h output, with 92.4% annual fuel utilization efficiency. House ventilation is microprocessor controlled with a central exhaust fan connected to both the bath and powder rooms.
A flexible stainless steel gas piping system is used for easy installation and line turn-off. A waste water heat recovery device in the basement waste stack channels waste heat from all hot water-using devices (except the washing machine) and preheats incoming cold water,
reducing the load on the water heater.
An integrated systems approach blended architecture, structure and systems at the outset and throughout the design process. An
open plan with a Great Room reduced interior partitions 20% while increasing flexibility. Options include Great Room extension,
fireplace, powder room, second bath, and one- or two-car garages. The plan offers flexibility and can be expanded or modified easily
to meet buyer needs and first cost considerations.
Building year-round in northern climates is easier, faster and less costly. The Cornell explored cold-weather construction techniques. A fully insulated and waterproof precast concrete foundation with full basement was installed with partial R-11 rock wool insulation. No footings are necessary as the panels bear on crushed stone. Each panel has steel stud nailers for finish material and a cavity for insulation. The panels can
be erected in hours in any weather. The basement slab was cast after the house was closed in and had temporary heat. Sherwin Williams cold weather paint allowed for application in lower temperatures. The precast concrete stoop and steps allow for quick installation and reduced foundation costs.
The many incremental changes result in a tight, high quality, low-maintenance house that is ultra-value engineered to increase thermal performance and economy. The Cornell was tested side-by-side with the old Hathaway model. Although the Hathaway was already 21% more energy-efficient than N.Y. State Energy Code required, the Cornell proved to be an additional 31% more efficient than the Hathaway, 46% more efficient than the code required. Beyond the energy savings, thermal comfort was increased due to improved air distribution and better-performing windows. There were dramatic reductions in duct leakage confirmed by duct blaster results: 67% on the supply side and 82% on the return. And the whole package cost no more than the bargain home it was compared to.
The original design called for CPVC hot water piping and air admittance vents to further cut plumbing costs, but New York State does
not yet allow their use.
Ryan's management elected to include the Cornell in its standard
new product line. The project's success is attributed to the systems
approach of CARB, a comprehensive process beginning with potential-buyer
focus groups through construction management. The design charette
included architectural designers and systems engineers working
closely to eliminate nonessentials, then blending structure and
systems throughout the design process, minimizing mechanical equipment
and structural costs.
Do you have a specific question? Try the contacts listed below:
50 Washington Street, Norwalk, CT 06854
US Department of Energy
1000 Independence Ave., SW
National Renewable Energy Laboratory
1617 Cole Blvd.
Golden, CO 80401
210 Carroll St.
Thurmont, MC 21788
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