Measuring California ENERGY STAR® Homes: Inside and Out

Matt Brost and Bob Kasman, RLW Analytics
Dionne Green, Pacific Gas and Electric

Keywords

Abstract

The California ENERGY STAR® New Homes Program provides millions of dollars in rebates to production builders to construct more energy efficient housing. Program implementers use performance-based Title 24 software applications as a tool for estimating program-driven energy savings. A recent California new construction potential study (Itron 2006) used a similar performance-based approach to project energy savings potential. However, Title 24 performance-based programs were designed to demonstrate code compliance, not for estimating energy savings.

Title 24 (for low-rise residential buildings) only considers the energy use of end-uses that builders can affect during construction: hot water heating, space cooling and space heating.1 To meet the CA ENERGY STAR® New Homes Program guidelines, these combined end-uses must perform at least 15% better than a minimally compliant home (2001 Title 24 Package D). California Home Energy Rating System (C-HERS) protocols are followed to ensure that the construction characteristics match the design intent of the participating builders. This paper focuses on a number of issues that are at the heart of the evaluation. The paper will discuss how independent inspections of building characteristics at 110 ENERGY STAR® New Homes were used to verify how well C-HERS protocols perform as a checks and balances system for the Program. The paper discusses differences found between the proposed and asbuilt projects and how the inspection results are used to re-simulate building performance for calculating energy savings. The paper also provides some comparisons between participant construction practice and standard practice. The paper also explores challenges related to the impact evaluation and why different measurement approaches were used to understand the energy effects of the Program, including the installation of metering equipment, which continuously recorded hourly hot water, heating and cooling energy use for one year in 100 ENERGY STAR® Homes.