Side-by-side evaluation of a stressed-skin insulated-core panel house and a conventional stud-frame house. Final report

Side-by-side energy testing and monitoring was conducted on two houses in Louisville, KY between 12 January 1993 and 5 March 1993. Both houses were identical except that one house was constructed with conventional U.S. 2x4 studs and a truss roof while the other house was constructed with stress-skin insulated core panels for the walls and second floor ceiling. Airtightness testing included fan pressurization by blower door, hour long tracer tests using sulphur hexafluoride, and two-week long time-averaged testb using perfluorocarbon tracers. While both houses were considered to be more air-tight than average houses in the Louisville area, an average of allthe air-tightness test results showed the SSIC panel house to have 30 percent less air infiltration than the frame house. Air-tightness testing resulted in a recommendation that both houses have a fresh air ventilation system installed to provide 0.35 air changes per hour continuously. Thermal insulation quali ty testing was by infrared imaging. Only two notable defects were found; both were in the frame house. Approximately 6 ft2 of ceiling insulation was missing over the stairwell and air leakage was observed where a bathroom exhaust duct penetrated the band joist. Pressure differentialtesting resulted in recommendations to use sealed combustion appliances, and to al low for more return air f low from closed rooms. This can be accomplished by separate return ducts or transfer ducts which simply connect closed rooms to the main body with a short duct. By calculation, the conductive building load coefficient (UA) was within 2 percent for each house. When blower door results for inf i l trat ion were included, the total UA was within 7 percent. The SSIC house UA was lower in both cases. By measurement, coheating tests showed the SSIC panel house total UA to be 12 percent lower than the frame house. Short-term energy monitoring was also conducted for the two houses. A 17 day period of electric heating and a 14 day period of gas furnace heating was evaluated. Monitoring results showed energy savings for the panel house to be 12 percent during electr ic heating and 15 percent during gas heating. A comparison of the two monitoring periods showed that the lumped efficiency of the gas furnace and air distribution system for both houses was close to 80 percent, which was the same as the manufacturers listed Annual Fuel Utilization Efficiency. Simple regression models using Typical Meteorological Year weather data gave a preliminary prediction of seasonal energy savings between 14 and 20 percent. More accurate seasonal predictions will require addit ional effort. In addit ion to the SSIC panel house having less building air leakage, there seem to be other factors, which remain unaccounted for, which cause the panel house to use less heating energy. These factors require further investigation.