The objective of this study is to examine the reduction in heating and cooling loads that may be attributed to the use of attic radiant barrier and to identify environmental parameters that influence this reduction. To this end, an experimental study was conducted in Zachary, Louisiana for 8 months on two houses built in the same manner and instrumented with thermocouples to measure the temperature in each hour and each layer of the roof. Results showed that an attic radiant barrier can reduce energy loads from 8% to 25% depending on the climatic conditions. Among the evaluated climatic parameters, ambient air temperature had the greatest effect on the ceiling heat flux.