Modelling building infiltration using the airflow network model approach calibrated by air-tightness test results and leak detection

Abstract

This paper presents a computational approach to air infiltration modelling and simulation validated by the blower door test results. In order to evaluate the potential of the airflow network method, three simulation models of the infiltration test were developed and calibrated by field measurements of leaked air change rate per hour at 50 Pa. Models were developed for existing building designs and constructed in low-energy standards differing in construction type and tightness. All leaks were precisely measured during field tests, defined as openings or cracks, numerically described and included in the model. The simulation results of calibrated models for other pressure differences revealed that the models’ accuracy is satisfactory. The differences between field tests and simulation results do not exceed 2.5%. Additionally, the calibrated models were used to estimate the infiltration heat losses of buildings in three different locations under continental climatic conditions. The results were compared with the steady-state method calculations made for the same building models and climatic conditions. It was proved that the steady-state method gives higher results of heat demand to cover infiltration losses than the simulation method. The final results depend on building location and vary between four and nine times.

Practical application: The computational modelling and building performance simulations are increasingly commonly used in engineering design. The proposed method of air-tightness modelling and calibration can be used at any phase of a building’s lifecycle, from design and construction to exploitation and maintenance. Using the proposed techniques, it is possible to estimate more realistic processes of air infiltration and its effect on a building’s energy consumption in comparison with the steady-state method. Moreover, the analysis includes the dynamic effect of boundary conditions (external air temperature, wind speed and direction), as well as the effects of the building site and the surroundings.