Cross-laminated timber (CLT) buildings have recently received increasing attention owing to their lower carbon emissions. However, the question of whether CLT buildings demand less energy to operate compared with conventional buildings remains unanswered.
Building energy simulation is widely applied when studying building operational energy use. As a required input, the thermal transmittance (U-value) of building envelopes can significantly influence simulation results. Theoretical U-values have been employed in most related studies. However, the U-values of envelopes fluctuate owing to temperature and relative humidity (T/RH). This means that the dynamic U-values of building envelopes need to be considered in simulations.
In this study, the energy impacts of dynamic U-values were studied. The operational energy consumption of CLT and three conventional buildings was compared by considering dynamic U-values. First, in-situ U-value measurements of the CLT and three conventional envelopes were conducted. Second, different U-value calculation methods were applied to calculate dynamic and average U-values of the four tested envelopes. After validation, the optimal U-value calculation methods were proposed. Third, based on the calculated dynamic U-values, the U-value prediction models for the four tested envelopes were developed by linear and non-linear regression methods. The linear model was proven to be the optimal U-value prediction model. Finally, the theoretical U-values, predicted average U-values, and predicted dynamic U-values were used in operational energy simulations of CLT and three conventional buildings.
The results showed that the dynamic U-values had significant energy impacts in climate zone D. The dynamic U-values had more significant energy impacts in the CLT and masonry buildings than in the reinforced concrete (RC) and brick buildings. The CLT building with insulation consumed the least operational energy in climate zone D, and conventional buildings consumed the least operational energy in climate zones A, B, and C.
