Capturing Building Fabric Thermal Performance and Solar Heat Gains Through a Whole House Heat Loss Test – an In-Situ Study in Poland

Determining a building’s “as built” heat loss coefficient (HLC) is one of the key starting points to understand the role of residents’ practices in heating or cooling-related energy consumption. It is also a starting point for white-box modelling of different behaviour scenarios within a given home environment. Co-heating test is a recognised experimental method to evaluate the building’s fabric thermal performance. It involves a quasi-stationary homogeneous heating experiment performed on an unoccupied dwelling. This paper discusses the results of a co-heating test carried out in a low-energy semi-detached house in Wrocław, Poland between 6th-12th December 2021. The periods of different types of solar operation are captured to evaluate HLC: night-time with no solar gains, daytime with direct solar gains, and daytime with only the diffuse component of solar radiation. Internal solar gains in the building are calculated using the TRNSYS simulation program, assuming detailed modelling of the radiation incident on the vertical partitions (including the anisotropy of the diffused radiation component and complex analyses of the sun path geometry inside the building). Based on the results, the HLC values excluding infiltration and ventilation corresponding to different solar operation types are calculated and compared. This contributes to a more nuanced understanding of HLC under different external conditions.