A quasi-steady-state model of attic heat transfer with radiant barriers.

During the cooling season, heat transfer from the attic into the conditioned space of a residence can represent a significant portion of the total envelope heat transfer. Radiant barriers are one method used to reduce this heat transfer. A quasi-steady-state model was developed or predicting attic heat transfer in residences with radiant barrier systems. The model was used to estimate the reduction in cooling load that would occur with a radiant barrier and to identify important construction and environmental parameters that influence this cooling load reduction. The model's output consisted of hourly ceiling heat fluxes inside the house based on hourly weather data inputs. Model results were compared with detailed experimental results from two small test houses. The model predicted typical summer heat flux reductions of between 35 and 43% with different radiant barrier configurations and levels of insulation. These compared to measured heat flux reductions of between 29 and 37% in attics under the same conditions. Sensitivity studies were also conducted to show the effect of uncertainty in several of the important physical attic parameters on the final heat flow predictions of the model.