Only 52% of new homes complied with California's Title-24 energy code requirements in a field audit of 96 houses built in 1993. The Residential Field Data Project was conducted by the Berkeley Solar Group (BSG) for the California Energy Commission's (CEC) Residential Compliance Report.

BSG performed the project for the CEC and the California DSM Measurement Advisory Committee to determine conservation and occupancy characteristics of new single-family homes built to comply with the residential energy efficiency standards. The study was conducted in four warmer inland climate zones where new home construction activity is high.

One component of the study was the collection of 1,230 Compliance Form 1R forms (CF1s) for homes completed in 1993, from building departments. Data from these forms were analyzed to determine the reported conservation measures and characteristics of the new homes. Homes that had participated in utility conservation programs were removed from the study.

CF1 information showed that over 90% of the homes had slab-on-grade floors as compared to raised floors. More than 90% of the window area was double glazed, and almost 90% of the window area had metal frames. The CF1s also showed that Micropas4 was the favorite software (used with 65% of the CF1s) to determine compliance with the 1993 standards. Micropas3 and Calpas4, although not valid for the 1993 standards, were used for about 15% of the CF1s.

BSG then visited about 8% of the homes and performed an on-site audit. The goal was to compare the homes' characteristics and installed measures with the information on the CF1s.

Based on the CALRES energy analysis program for 1993 standards, 50 homes were in compliance and 46 were not. As a general observation about the audited homes, BSG's president Bruce Wilcox said, "Probably none of these homes had everything the forms say they had, and people completing the forms tended to understate almost as often as they overstated."

One common error was the calculation of conditioned floor area (CFA); it was misstated on the CF1 for 43 of the 96 houses. For some homes, the measured CFA differed by as much as 35% from the CF1 number. Indeed, the discrepancies were so great that BSG concluded that the CF1 was in some cases prepared for a different house or house plan. However, the average CFA for all of the homes was not that different--1,967 ft² measured, as compared with 1,903 ft² stated on the CF1s.

One discrepancy was in the direction of improved efficiency. This occurred with air conditioner Seasonal Energy Efficiency Ratio (SEER) and furnace Annual Fuel Utilization Efficiency (AFUE) ratings. BSG found that the installed equipment most often had higher efficiencies than those reported on the form. BSG explained that when a compliance analysis is done, the equipment rating may not be known, so minimum efficiencies are used on the form.

See Table 1 for a comparison of audit and CF1 information for five major measures.

A third component of the study measured duct leakage in 97 of the audited homes, to determine compliance with Title-24 and to assess duct leakage issues for consideration in future standards. Using a new simplified leakage measurement procedure (which will be discussed in more detail in a future Home Energy article), Modera Consulting Engineers found that the Title-24 energy standards apparently have not improved airtightness of duct systems in California. Almost one-third of the return systems and 40% of the supply systems had more than 100 cfm (cubic feet per minute) of leakage to outside at normal operating conditions.

Blower door tests indicated that the houses were fairly tight, so the impact of duct systems and exhaust fans on house depressurization was analyzed to determine the potential for combustion appliance spillage or backdrafting. Modera found that approximately 30% of the houses have the potential to be depressurized by more than 5 Pascals, and 6% of the homes have the possibility of being depressurized by more than 10 Pa. Although several events have to occur at the same time for it to happen, backdrafting becomes a possibility when the house is depressurized by about 3 Pa, is worthy of concern above 5 Pa, and is relatively likely above 10 Pa.

Modera had several suggestions for the CEC to help reduce duct leakage in California. These included revising the way that the Title-24 model calculates a delivery efficiency for duct systems (the assumed duct surface areas are much too low, return-system leakage and conduction losses are considered zero, and off-cycle losses due to the duct system are not accounted for). The best way to reduce duct leakage in new homes, said Modera, is to specify required leakage levels and verify them by measurement in all new houses, and also to put limitations on the materials and techniques used to achieve those leakage levels.