Evaluating ten years of energy performance of HERS-rated homes in Alachua County, Florida

Abstract

This paper evaluates the performance of 1,346 homes in Alachua County, Florida that were Home Energy Rating System (HERS)-rated between February 1998 and December 2009 for participation in various energy-efficiency programs for new residential construction. The primary analysis objective is to measure the energy-efficiency performance of these HERS-rated homes against conventionally built homes using metered energy consumption data for calendar years 2000–2010. A secondary objective is to assess performance of the four major builders of HERS-rated homes. In calendar year 2000, average energy savings for all HERS-rated homes was 18 %. However, over the following decade average savings degraded steadily, stabilizing around 7 % in the last 5 years of the analysis. We conclude that, while HERS-rated homes in the study area are performing better than similar conventionally built homes, the average HERS-rated home is not achieving the level of savings anticipated based on its HERS score and related energy-efficiency program participation. Differences in savings among builders of HERS-rated homes suggest that variations in program implementation and construction practices can yield significantly different energy performance results. Of the four builders tested, the least efficient averaged 3 % less energy consumed than conventionally built homes, while the most efficient averaged 21 % less. Overall, findings of this study indicate the need for re-examination of the HERS-rating process as a primary benchmark and for increased emphasis on direct measurement and verification of performance using historical energy consumption data.