In-situ U-value monitoring of highly insulated building envelopes: Review and experimental investigation

Abstract

In-situ U-value monitoring of building envelopes are investigated in this article by reviewing past studies and monitoring the performance of highly insulated building envelopes. Specific past research studies have concluded both over- and underperformance of the building fabric when measured in situ. This current research has found that when analysing all studies and results over the full range of envelope U-values together there is no evidence of over- or underperformance. However, when highly insulated envelopes (U-values <0.3 (W·m−2·K−1)) are investigated in isolation a clear trend in underperformance becomes evident with 93% of tests from past studies reporting underperformance. In-situ monitoring results from this study conclude that 9 out of the 10 tests on envelopes with very low U-values (<0.2 (W·m−2·K−1)) result in underperformance with an average deviation of more than 100%. The significance of this finding is two-fold. First, this means that some of the insulation is redundant and adds to the embodied energy of the building without offering a beneficial increase in thermal resistance. Second, under-sizing of heating systems in low energy buildings will result, which in turn will result in lower efficiencies and greater overall energy consumption.