A new design of metal-sheet cool roof using PCM

Heat flow through the roof contributes in the total heat gain of a building. The contribution becomes more severe for single story houses covered by metal sheet roofing. This paper presents a new design for metal sheet roofing structure in order to improve its total thermal resistance. Its main concept is to utilize phase change material properties to firstly absorb the downward heat flow made by incident solar radiation to the room and then release it back to the environment by means of the naturally favored external convection especially during the nocturnal cycle. Experimental and numerical analyses have been conducted to compare thermal performance of the new design and the available normal roofing with the same materials and color. A general mathematic equation system, which can be used for further evaluation and prediction of the new design with varied parameters, has been derived for the thermal process through the roof. The results show that the new design can effectively reduce the downward thermal flow through the roof into the house. As a consequence, the cooling load of the house can be lower and more electricity for cooling attempt can be saved.

► We develop a new design for metal-sheet roofing structure by using Phase change material (PCM).
► The design helps to reduce inward heat flow through roof to indoor space.
► The indoor comfort can be maintained much longer.
► The peak-load of indoor air conditioning can be shifted purposely by modifying PCM amount.
► We reported thermal performance of the new design in different weather conditions.