Reflective multi-foil insulations for buildings: A review

Slightly more than a decade ago, reflective multi-foil insulations were introduced onto the building market as a highly promising new type of thermal insulation material. These materials consist of several layers of thin metallic foil or metallised polymer film with a low emission coefficient combined with spacer materials in-between. Because of the low emission coefficient of the foils, radiation through the insulation material is significantly reduced as a result of which these materials are claimed to have very high thermal resistance, even up to 5 or 6 m2 K/W. However, debate is still ongoing into whether these claims are correct. In contrast to some in situ measurements, hot box and hot plate measurements performed in laboratories result in much lower thermal resistance values. Based on a review of research reports and journal papers, this paper identifies the causes for the different results among different research institutes. From this analysis, conclusions are drawn about the thermal performance that can likely be expected from reflective multi-foil insulations.

► Very high thermal resistances of reflective multi-foil insulations are not likely. ► A thermal resistance of 1.5–2.5 m2 K/W is more likely for this type of material. ► Three factors were identified that explain differences between measurement results.