SF-98-06-3 -- Calculations for Reflective Roofs in Support of Standard 90.1 PDF

This paper summarizes the results of a simulation effort in support of ASHRAE SSPC 90.1 for the inclusion of reflective roofs in the proposed standard. Simulation results include the annual electricity and fuel use for two buildings types, residential and nonresidential. The residential model is intended to apply to hotel guest rooms, patient rooms in hospitals, and high-rise residential apartments. In order to be consistent with other requirements of the draft standard, we used the 90.1 Envelope Subcommittee DOE-2 prototype building and operating schedules, which were supplied to us. The parametric simulations were performed for 19 climate bins, as defined in the current 90.1 draft (a total of 26 climate bins are used in 90.1, while only 19 are considered in this study); a range of roof absorptivities from 0.25 to 0.95; and three roof U-factors (corresponding to roof insulation of R3, R11, and R38). The results are condensed into climate-dependent adjustment factors to reduce roof insulation for buildings with reflective roofs such that the net energy use of the building stays constant when compared with the energy use of a dark-colored roof.