In civil engineering practice, the issue of heat transfer usually tapers to the conduction problems. The heat transfer caused by convenction or radiation is often being neglected. Considering radiation the reflective sheetings are trying to assert themselves on the market by by multiplying the number of reflective layers. We have examined the influence of these reflective layers on the equivalent heat transfer coefficient depending on the thickness of insulation used on mineral fibers and the number of reflective sheetings.