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.

本文通过回顾过去的研究和监测高度绝缘的建筑围护结构的性能，研究了建筑围护结构的原位 U 值监测。过去的具体研究得出的结论是，在原位测量时，建筑结构的性能过高和过低。目前的研究发现，在对整个包络 U 值范围内的所有研究和结果进行分析时，没有证据表明性能过高或过低。然而，当高度绝缘的信封（U 值 <0.3 (W·m ^-2 ·K ^-1)) 进行单独调查，表现不佳的明显趋势变得明显，过去研究中 93% 的测试报告表现不佳。本研究的现场监测结果得出结论，对具有极低 U 值（<0.2 (W·m ^-2 ·K ^-1 )）的包络进行的 10 次测试中有 9 次导致性能不佳，平均偏差超过 100 %。这一发现的意义有两个方面。首先，这意味着一些隔热材料是多余的，会增加建筑物的隐含能量，而不会有益地增加热阻。其次，将导致低能耗建筑中供暖系统的尺寸过小，进而导致效率降低和整体能耗增加。