Comparing operational energy use between masonry and cross-laminated timber (CLT) buildings: Considering dynamic U-values of walls

Cross-laminated timber (CLT) walls have received increasing attention recently because of lower carbon emissions than conventional masonry walls. However, it remains unanswered whether CLT buildings also demand less energy to operate compared with conventional masonry buildings. Building energy simulation is widely adopted when studying building operational energy use. As a required input, the thermal transmittance (U-value) of walls can significantly influence the simulation results. Theoretical U-values (U_theo) have been employed in a number of related studies. Nevertheless, the U-values of walls fluctuate because of a variety of environmental influences. It means that the dynamic U-values (U_dy) of walls need to be taken into account in the simulation. In this study, the operational energy consumption of both masonry and CLT buildings was compared based on U_dy. Firstly, the in-situ U-value measurements of the masonry and CLT walls were carried out in Sheffield and Ninghai. Secondly, the measured datasets were applied to develop the U-value prediction models for the masonry and CLT walls using hierarchical linear regression. Thirdly, three case study cities with different climatic characteristics were chosen to predict the U_dyof masonry and CLT walls. The predicted U_dyof two walls were used for energy performance simulation. The findings indicated that the CLT buildings needed less energy to operate in heating-dominated zones, yet they required more operational energy in cooling-dominated zones when considering U_dy. Meanwhile, the U_dyhad greater energy implications in heating-dominated zones than in the cooling-dominated zone.