Impact of the temperature dependency of fiberglass insulation R-value on cooling energy use in buildings

摘要: Building energy models usually employ a constant, room-temperature-measured value for the thermal resistance of fiberglass roof insulation. In summer, however, mean temperature insulation can rise significantly above room temperature, lowering insulation`s by 10% to 20%. Though dependence porous materials like has been extensively studied, it is difficult theoretically predict variation with particular blanket, from first principles. Heat transfer within complicated presence three significant mechanisms - conduction through air, glass matrix, and radiative exchange matrix complex, unknown internal geometry. Purely theoretical heat assume highly simplified structures require typically-unavailable information about fiberglass, such as its optical properties. There also dearth useful experimental data. While resistances many individual samples have measured, there only one practical published table vs. both density. Data this was incorporated in DOE-2 building model. used simulate surface flux, cooling consumption school bungalow whose use had monitored 1992. The predictions made without conductivity were compared measured values. Simulations run typical office building. Annual loads annual peak hourly powers calculated using fixed variable conductivities, five different climates. decrease R-value building`s led 2% 4% increase load.