| Abstract | Thermal mass plays an important part in the transient thermal performance of wall assemblies and buildings. It has been shown that if the thermal mass is used correctly, it can improve the thermal performance of wall assemblies and hence the energy efficiency of buildings. The position where a thermally massive layer is placed within a wall can affect the transient thermal behaviour of the wall assembly. In this study, we simplified a wall assembly into simply two thermally resistant components: that of insulation and a thermally massive layer. The transient thermal behaviour of the wall was then investigated concerning the different placement within the wall of the thermally massive and insulation layers. Two cases were studied: (i) a three-layer wall having one layer of insulation and two thermally massive layers, and (ii) a three-layer wall, one layer of which is thermally massive and the other two layers of insulation. For each of the two case studies, walls were shown to have identical values for overall thermal resistance and heat storage capacitance. The interior temperature was assumed to remain at 21 °C, and three climate conditions were considered for exterior, representative, respectively, of heating-dominated, temperate, and cooling-dominated weather conditions. The results showed that amongst the case studies for the set (i), the wall that had the optimum transient thermal performance was that for which the insulation layer was placed at the exterior and the thermally massive layers were placed at the interior side of the wall. Whereas the case for which one thermally massive layer was sandwiched between two insulation layers showed the minimum energy demand for the case study set (ii). Based on the cases considered and the corresponding results, it can be concluded that to improve the transient thermal performance of a wall with a given amount of heat storage capacitance and heat resistance, the thermally massive layer(s) should not be directly exposed to the fluctuations of the outdoor climate. |
|---|
