The project will focus on the performance of different attic assemblies and their associated heating, ventilating and air conditioning (HVAC) systems. Field measurements of attic and HVAC system performance will be conducted in two new high performance homes in California with sealed and insulated attics. One home will be built to be about 30 percent better than Title 24 and the other will be a ZNE home. The attic insulation approach will be a new lower-cost approach using blown insulation that does not use expensive spray-foam. The results of the measurements will be used directly to provide technical support for potential changes to Title 24 and provide information to contractors and builders on sealed and insulated attic performance and alternative approaches.