Prepared for: Nevada Power Company
and Electric Power Research Institute
Report Dated: November 11, 1996
By: Proctor Engineering Group, San Rafael, CA., Boston, MA
Contributors: John Proctor, P.E., Tom Downey, Michael Blasnik, George Peterson
The primary difference between homes in the 1995 and 1996 cohorts was the reduction in duct leakage. The supply duct leakage to outside was reduced from 7% of air handler flow in 1995 to 3% in 1996. Similarly, the return duct leakage from outside was reduced from 6.7% of air handler flow in 1995 to 1.3% of air handler flow in 1996. Duct insulation was also increased from R-4 to R-6 between the two cohorts. Using a comprenensive duct and AC model, the projected savings for duct leakage reduction and duct insulation was 10% .
Proctor Engineering Group employed a number of statistical approaches for analyzing the electricity usage data to develop impact estimates. While all of the analysis methods focused on estimating the differences in hourly electricity usage rates between the 1996 and 1995 houses, the methods varied in how they accounted for other factors influencing usage rates. To minimize the risk of misleading results, PEG chose to pursue several alternative statistical modeling techniques in order to "triangulate" an estimate of program impacts. These techniques ranged from simple comparisons of mean usage levels to cross-section time series regression analysis and analysis of covariance models. The energy savings estimates from the metered data ranged from 6% to 14% which were comparable to the projections from the comprehensive model. Peak reductions ranged from .36 kW in the 4-5 pm hour to over 1 kW in the 8-9 pm hour.
This study tested the energy consumption and peak reduction effects of a pilot program that reduced duct leakage, increased duct insulation, and changed AC installation practice on new residential construction in Las Vegas. Potential savings and peak reductions were projected using a comprehensive duct and AC model. This model projected a 10% energy savings from reduced duct leakage and increased duct insulation . The model also projected 0.33 kW reduction in load at 4-5 pm. The study consisted of two cohorts, the 1995 cohort built to standard practice and the 1996 cohort built to improved standards.
The duct systems in the 1995 cohort were factory built. The 1996 cohort systems were built on site to specific prescriptive and performance criteria. The program was successful in substantially reducing duct leakage and producing a moderate increase in duct insulation. The air conditioner installation practice changes were less than totally effective. The air flow across the indoor coil did not increase to the desired levels, and the on site efficiency tests often showed efficiencies below the expected values for the test conditions.
The energy savings estimates were triangulated through a variety of analytical techniques. The savings estimates from the metered data ranged from 6% to 14%. These are comperable to the projections from the comprehensive model. Peak reductions ranged from 0.36 kW in the 4-5 pm hour to over 1 kW in the 8-9 pm hour.
Bound copies of this entire report are available for $40 each.
For details about obtaining a copy see How To Order Project Reports
