A study on non-calorimetric method for assessing the equivalent thermal resistance of building enclosures

A novel method for assessing building energy performance was studied experimentally and theoretically. The investigation was focused on the correlation coefficient of the indoor temperature history and the outdoor temperature history (CITOT in abbreviation). A number of tests for determining the CITOTs were performed on a simple building model separately with four different enclosure wall configurations, including block board, block board with a layer of XPS board as outer wall insulation, block board with a layer of XPS board as inner wall insulation and block board with XPS board on both sides. The temperature histories were recorded using a PC based DAS system with Pt100 sensors. The results from the tests indicate that the CITOT depends significantly on the equivalent thermal resistance of the building enclosure and the CITOT decreases as the thermal resistance of the enclosure increases. Simplified mathematical models, with and without the heat capacity of the enclosure taken into account, were developed and solved analytically to validate the generality of the dependence of CITOT on the thermal resistance of the enclosure. It is demonstrated that the CITOT increases monotonously as the thermal resistance of the building enclosure decreases according to the analytical solutions to the mathematical models. It is also shown that the CITOT tends to be zero as the thermal resistance approaches to infinity and to be unity as the thermal resistance approaches to zero. Both experimental and theoretical results show the possibility to use the CITOT used as an index to represent the total energy performance of buildings.