Lumped parameter models for building thermal modelling: An analytic approach to simplifying complex multi-layered constructions

There are many sophisticated building simulators capable of accurately modelling the thermal performance of buildings. Lumped Parameter Models (LPMs) are an alternative which, due to their shorter computational time, can be used where many runs are needed, for example when completing computer-based optimisation. In this paper, a new, more accurate, analytic method is presented for creating the parameters of a second order LPM, consisting of three resistors and two capacitors, that can be used to represent multi-layered constructions. The method to create this LPM is more intuitive than the alternatives in the literature and has been named the Dominant Layer Model. This new method does not require complex numerical operations, but is obtained using a simple analysis of the relative influence of the different layers within a construction on its overall dynamic behaviour. The method has been used to compare the dynamic response of four different typical constructions of varying thickness and materials as well as two more complex constructions as a proof of concept. When compared with a model that truthfully represents all layers in the construction, the new method is largely accurate and outperforms the only other model in the literature obtained with an analytical method.

► A 3R2C RC-network can represent multi-layered constructions accurately.
► An analytical method to create a 3R2C model is presented here: the DLM.
► The DLM produces dynamic responses with an error smaller than 0.1 °C in this paper.
► The DLM of a construction can be found solving a set of simple algebraic equations.
► This methodology constitutes a building block to create LPMs of complete buildings.