Evaluation of a modified co-heating test for in-situ measurements of thermal transmittance of single family houses

Within two years after commissioning the energy use for heating and operation of new buildings in Sweden should be verified by measurements. These have to be corrected for energy usage deviating from what has been defined normal during the building design, e.g. excessive venting and hot water use. This is practically difficult since the transmission losses of the building in use cannot be verified due to lack of a standard practical methods for their evaluation. Designers and producers of low-energy houses would benefit of such a method as the design of well-insulated envelopes is an essential quality of these buildings. A recently reintroduced method, the so called co-heating test, could be used for the verification of the overall thermal transmittance of buildings. To test the applicability of the co-heating test in-situ, measurements were performed on two test objects. A two years old low-energy house and a new summer cottage were tested. During the measurements, the latter was placed in a laboratory environment with a stable climate. Air tightness was measured on both houses. The overall average heat transfer coefficients were obtained and compared to theoretical values. This paper describes how the co-heating test has been modified to be used in in-situ conditions. Findings from both the measurements and following analyses are presented. The results obtained indicate that there is a clear potential for further simplifications of the co-heating test in future.