The Efficiency Characteristics and Opportunities of New California Homes project examined 40 single‑family and 40 multifamily units that were built under the 2005 Building Energy Efficiency Standards for Residential Buildings. Data gathered in the field on lighting, heating, ventilation, and air conditioning (HVAC) and other characteristics showed that the homes often didn’t perform up to code. In a second phase of the project, HVAC upgrades were implemented in nine of the homes, and the improvements were measured.

The findings point to areas in the existing codes that are in need of improvement, and the project includes a list of recommendations for the 2013 version of the Energy Efficiency Standards for Residential and Nonresidential Buildings, Title 24.