The actual building energy performance essentially depends on the building occupant's behaviour, the real performance of the installed energy systems and the in-use performance of the building envelope. The thermal performance characterization of in-use building envelopes, based on monitored data, represents a crucial step towards bridging the gap between the designed and as-built energy performance of buildings. The main indicator to analyse the performance gap of building envelopes is the Heat Loss Coefficient (HLC); when measured, it commonly shows considerable differences when compared with the design value. This research goes further and proposes a method, based on monitored data from in-use buildings, for the decoupling of the HLC of in-use buildings into its transmission (UA) and infiltration (C_v) heat loss coefficients, in order to identify the origin of the heat losses. The identification of this origin will facilitate the reduction of the performance gap. Therefore, a multi-storey occupied office building of the University of the Basque Country has been monitored and analysed, where the in-use HLC for each floor and for the whole building have already been estimated using an average method. Then, based on the ASTM D6245-18 Standard, the decay method of the metabolic CO₂ of the building's occupants has been successfully applied in this paper to obtain the Air Change per Hour (ACH) rates due to infiltrations. These ACH values have been used to decouple the estimated HLC values into their transmission and infiltration parts.

实际建筑物的能源性能基本上取决于建筑物使用者的行为，已安装的能源系统的实际性能以及建筑物围护结构的使用性能。基于监视的数据，对在用建筑围护结构的热力性能进行表征，是弥合建筑物设计和建成后的能源性能之间差距的关键一步。分析建筑围护结构性能差距的主要指标是热损失系数（HLC）。当进行测量时，与设计值相比通常会显示出很大的差异。这项研究进一步进行，并提出了一种基于在用建筑物的监控数据的方法，用于将在用建筑物的HLC解耦到其传输（UA）和渗透（C _v）热损失系数，以识别热损失的来源。识别此来源将有助于缩小性能差距。因此，对巴斯克地区大学的一栋多层占用的办公楼进行了监控和分析，其中已经使用平均方法估算了每层楼和整个建筑物的使用中HLC。然后，基于ASTM D6245-18标准，已成功地采用了建筑物中居住者的新陈代谢CO ₂的衰减方法，以得出渗透引起的每小时换气率（ACH）。这些ACH值已用于将估计的HLC值解耦到其传输和渗透部分。