Field testing of the QUB method for assessing the thermal performance of dwellings: In situ measurements of the heat transfer coefficient of a circa 1950s detached house in UK

Abstract

In this paper the findings from a long-term field study of the thermal performance of a circa 1950s dwelling are presented and discussed. The study aimed at evaluating the robustness of the QUB method in the field under UK climatic conditions. A series of 147 QUB tests were performed during the whole heating period (September 2016 -March 2017) in a detached house located in the University Park campus, University of Nottingham considering two distinct conditions: as-built and with increased airtightness.The QUB method was able to provide consistent and robust estimates of the Heat Transfer Coefficient (HTC) of the whole dwelling with approximately 80% of the results within ± 10% from the mean and more than 95% of the results within ± 15%. The need to treat heat losses occurring through the ground when assessing the thermal performance of buildings through experimental diagnostics methods was highlighted, especially in uninsulated concrete slab floors. The method devised to isolate the ground floor heat losses from the whole building losses resulted in reduced dispersion of the adjusted Heat Transfer Coefficient with a coefficient of variation of 5% and 98% of results within ± 10% from the mean.

Evaluation of the precision and accuracy of the QUB/e method for assessing the as-built thermal performance of a low-energy detached house in UK

“…These results were consistent with the findings reported in an uninsulated property [31]. It also suggests that the precision of the QUB/e method is similar regardless of the levels of thermal insulation of the building investigated.…”

“…Such effect of the external temperature on the HTC was not found in this case (Figure 8a). This appears to be inconsistent with the findings reported in the uninsulated property [31]. However, in this case the test was conducted differently than it was in the previous case study; both the starting internal temperature and the power input were adjusted to achieve the recommended values of the α-parameter.…”

“…Robustness of the method in determining the HTC of the building was investigated in terms of the effect of specific testing conditions on the obtained results. In the first long-term study conducted in an uninsulated property [31], it was found that the results obtained were not correlated to common occurring wind and solar conditions. However, the internal starting temperature was found to have an effect on the results due to the ground floor losses that were not consistent with the losses occurring from the rest of the building envelope that was in contact to the external temperature (ibid).…”

“…This was attributed to the methodology followed where the internal starting temperature was adjusted to the external one in order to maintain a desirable temperature difference and consequently the value of the α-parameter within the recommended limits (as there was no option to adjust the power input); this led to increased heat losses through the ground and consequently at higher values of HTC [28]. A methodology was proposed to deduct the heat losses from the floor and it was found that the external temperature had no effect on the adjusted HTC [31].…”

“…The ability of the QUB method to provide reliable results, has been demonstrated numerically [13,25,26] and experimentally in a climate chamber under steady conditions [13,24,27]. Several studies have also reported on the precision and accuracy of the method under actual climatic conditions in different regions of Europe (e.g., see [13,24,[28][29][30][31]). These studies highlighted the ability of the method to provide reliable results and its applicability as a research tool.…”