Decoupling the heat loss coefficient of an in-use office building into its transmission and infiltration heat loss coefficients

Abstract

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 CO 2 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. • Metabolic CO 2 concentration decay method for estimating C v value of in-use buildings. • Decoupling the HLC into transmission (UA) and infiltration (C v ) heat loss coefficients. • Identify the heat losses origin in order to understand the building performance gap.