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Hughes Construction: Lexington, NC
Four 2,048-square-foot duplex buildings were constructed on crawlspace foundations. Each two-unit building had similar layout, orientation, roof systems, doors, windows, interior finishes, HVAC equipment, and ductwork construction and location. All homes had the same amount of glazing with slight variation in the orientation.
 Site plan
 House
Summary of Structural and Insulating Systems for the Four Buildings
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Building #1
| Building #2
| Building #3
| Building #4
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Walls |
Arxx Insulating Concrete Forms |
ThermaSteel Composite Panels |
Conventional 2x4 studs spaced 16" on-center |
Babb Int'l Autoclaved aerated concrete |
Floor System |
TradeReady Steel Floor System |
TradeReady Steel Floor System |
Conventional wood |
Wooden I-joists |
Crawlspace Walls |
ICF |
8" CMU plus 4" brick |
8" CMU |
8" AAC plus 4" brick |
Crawlspace ventilation |
North unit - unvented
South unit -vented |
North unit - unvented
South unit - vented |
Vented |
Vented |
Unique features |
ICF used for above-grade and crawlspace walls |
Add'l 224 s.f. of exterior wall due to floor and wall bearing on foundation |
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First two courses of AAC in crawlspace were 6" thick
Interior walls 3" taller than other buildings due to AAC height |
- Four homes were built as a side-by-side comparison of alternative structural wall systems. A wood-framed building served as the basis for comparison.
- Researchers observed the construction of each building to gather qualitative data regarding use of alternative materials and to record the labor time associated with each system.
- Construction costs were gathered from rendered invoices.
- During construction the homes were instrumented with sensors to record data needed to compare energy usage of each home.
- A blower door test was conducted to measure the air leakage for each unit and ductwork was also tested for air leakage.
- Homes were unoccupied during the monitoring period. No energy-consuming devices were operating during the monitoring periods other than the heating or cooling equipment.
- For the heating study period (February 12 through March 5, 2002), the heat pump was operated in resistance heating mode to remove efficiency differences between installed HVAC systems.
- Cooling energy use data was collected for a 30-day test period from May 25 through June 23, 2002. A heat pump of the same efficiency rating was used for cooling in each unit.
- Heating and cooling energy usage of each home was recorded during two study periods. Sensors recorded interior temperature, temperature stratification, humidity, moisture, and time-of-day utility demand for interior space conditioning. An on-site weather station recorded outdoor weather conditions.
- Wetness was measured in unvented and vented crawlspaces. In addition, dew points were calculated to measure the likelihood of moisture.
- Using energy simulation software, results were adjusted for indoor air, air infiltration, and duct leakage.
Additional Information
View evaluation results of these technologies
February and September 2001: Monitoring equipment installed
February 12 through March 5, 2002: Heating study period
May 25 through June 23, 2002: Cooling energy use data was collected for a 30-day test period
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