Adjusted Benchmark Source MBtu = (Msize
) × Source MBtu
× (2400/Floor Area)0.184
Table 31. Source Energy Factors for Energy Delivered to Buildings (Deru and Torcellini 2007)
Electricity Natural Gas Fuel Oil/Kerosene Gasoline LPG
Source Energy Factor 3.365
1.092 1.158 1.187 1.151
Table 32 reports energy savings for individual energy efficiency measures applied to the Prototype, in terms of source energy and energy cost. “Source Energy Savings %” is determined by comparing the source energy for each measure increment to the source energy for the Benchmark (i.e., the first row). In this column, the incremental savings for each measure are added to the savings for all the previous measures. The final row of the column is the overall energy savings achieved for the Prototype house.
When available, actual energy tariffs for the Prototype house shall be used to determine whole- building energy costs. Energy cost and measure savings are compared to the Builder Standard Practice (representing a real design or set of practices that is currently being used by the builder) rather than to the Benchmark. This provides an evaluation of the improvements in the performance of the Prototype compared with that of homes currently being sold by the builder partner.
Reporting of peak hourly energy consumption is also encouraged for every Prototype. Peak energy is based on the hour with the greatest gas or electric energy consumption during the course of one year, as determined by the hourly simulation.
Every Prototype house performance analysis shall include documentation of whether the house meets the cost neutrality definition established as a “Should Meet” criterion for Gate 2 and a “Must Meet” criterion for Gate 3 of the Building America Stage-Gate Process. The “Summary of Technical Reporting Requirements” (Anderson 2008) defines neutral cost as the following:
“The final incremental annual cost of energy improvements, when financed as part of a 30 year mortgage, should be less than or equal to the annual reduction in utility bill costs relative to the BA benchmark house.”
The “annual reduction in utility bill costs relative to the BA benchmark house” is simply the difference between the two yellow cells in Table 32. This represents the estimated energy cost savings of the Prototype house compared to the Benchmark house based on current local utility costs.