Development of Commercial Building Shell Heating and Cooling Load Factors
Release Date: February 13, 2018
Shell energy efficiency of a building envelope is an important determinant of the heating and cooling load. Improvements in the heating and cooling loads of buildings reduce the amount of energy these buildings need. The U.S. Energy Information Administration (EIA) contracted this report from ICF L.L.C., in order to inform modeling and analysis of domestic commercial building energy consumption. As part of its Annual Energy Outlook (AEO), EIA models the consumption of commercial building energy in the Commercial model. The efficiency of building envelopes influences building energy consumption by affecting heat and/or cooling losses by the heating and cooling equipment through the envelope such as walls, floors, roofs, and windows. Building shell efficiencies were calculated for existing building stock in 2012 and for new construction in 2012 and in the AEO projection years 2020, 2030, 2040, and 2050.
The U.S. Department of Energy’s (DOE’s) Commercial Reference Buildings and EIA’s 2012 Commercial Buildings Energy Consumption Survey data were used to develop the 2012 building stock models and estimates of building envelope values in the 2012 building stock by building, element, assembly, climate zone, and construction type. The research was paired with the prescriptive building envelope requirements of ASHRAE Standard 90.1 to project building envelope thermal performance values (U-factors and SHGCs) for new construction in 2012 and in AEO projection years 2020, 2030, 2040, and 2050. Specifically, projections were made for opaque (wall, floor, slab, and roof), fenestration (window and skylights), and whole-building infiltration rates.
The building envelope thermal performance values were used as inputs to dynamic building energy models. ICF simulated about 2,000 unique models to produce annual heating and cooling energy demand. The energy demand data were post-processed to develop commercial building shell heating and cooling load factors and represent the relative heating and cooling energy demand for new construction floorspace in the AEO projection year indexed to the heating and cooling energy demand of the 2012 building stock.
EIA’s National Energy Modeling System (NEMS) uses a building shell efficiency index in the assumptions for the commercial building sector. The commercial shell heating and cooling load factors are indexed to the average base-year values by building type and Census division. These load factors affect the amount of energy needed to heat and cool the floorspace as well as the purchasing decisions for new heating and cooling technologies.
Building shell efficiencies were indexed to the existing building stock in 2012. The average improvement for new construction in 2012 compared with the existing building stock was 0.9194 for heating loads and 0.9317 for cooling loads. In other words, in the commercial module of NEMS, on average, new construction in 2012 demands 91.94% of the amount of heating and 93.17% of the amount of cooling for the same amount of existing stock floorspace.
When referencing the contract report, it should be cited as a report by ICF International, L.L.C. prepared for the U.S. Energy Information Administration.