Multi-dimensional heat transfer through complex building envelope assemblies in hourly energy simulation programs.

States that most whole building thermal modelling computer programs use simplified, one-dimensional, parallel path descriptions of the building envelope, which may generate serious errors in building load estimation for several structural and material configurations of building envelope components which have high thermal mass and/or two- and three dimensional thermal bridges. The paper presents the method of coupling three-dimensional heat transfer modelling and dynamic hot-box tests for complex wall systems with the whole building thermal simulations, a method which can increase the accuracy of the whole building thermal modelling. Current popular building envelope designs, utilizing modern building technologies and large fenestration areas and floor plans with multiple exterior wall corners are often overestimated in their actual field performance with current thermal modelling and calculation procedures. States that some frequently used computer codes were calibrated with field data sourced from lightweight wood frame buildings. They are now used in high mass buildings with notable heat accumulation effects. Also suggests that the effects of extensive thermal shorts on the whole building thermal performance is not accurately shown by one-dimensional energy simulations.