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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. [ABSTRACT FROM AUTHOR]

Airtightness is nowadays one of the physical parameters which determine overall building energy performance. In a wide range of states, the upper limit for air change rate at a Pa (na), air permeability rate at a Pa (qa), or specific leakage rate at a Pa (wa) is determined by the formal regulations. It should be highlighted that airtightness requirements are mainly the same around the world, disregarding any site and climatic conditions. The main goal of the presented work was to reveal the effect of individual location and surrounding infiltration rate and heat demand. The analyses were done using numerical techniques and computational models of the three buildings developed and calibrated based on the blower door test results. The compared buildings characterize by a similar geometry but differ in the air change rate at 50 Pa (n50). Analyses done for different locations and levels of sheltering by surrounding elements allow the determination of the real effect of local conditions. The obtained differences in energy demand between two locations from the same climatic zone were from 70% to 90%, depending on the airtightness of the buildings. Considering different sheltered conditions, the differences for the same location can be even 200%. The obtained results allowed for the formulation of the general conclusion that building location and level of exposure could be considered in future airtightness regulations. [ABSTRACT FROM AUTHOR]