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Consideration of Envelope Airtightness in Modelling Commercial Building Energy Consumption



Lisa C. Ng, Andrew K. Persily, Steven J. Emmerich


As various strategies for improving building envelope and HVAC equipment efficiencies are increasingly used to reduce building energy use, a greater percentage of energy loss will occur through building envelope leakage. Although the energy impacts of unintended infiltration on a building’s energy use can be significant, current energy simulation software and design methods are generally not able to accurately account for envelope infiltration and the impacts of improved airtightness. The airflow analyses capabilities of several energy simulation software tools were investigated and summarized, including whether the program calculates airflow rates or considers them to be inputs. The theory behind these calculations are summarized and evaluated for their physical soundness and accuracy. A new strategy to more accurately incorporate airflow calculations into energy software is also proposed, which is based on relationships between building infiltration rates calculated using detailed multizone airflow models and building characteristics, weather conditions, and building envelope airtightness.
Air Infiltration and Ventilation Centre


Envelope airtightness, energy, infiltration, indoor air quality, commercial buildings


Ng, L. , Persily, A. and Emmerich, S. (2013), Consideration of Envelope Airtightness in Modelling Commercial Building Energy Consumption, Air Infiltration and Ventilation Centre, [online], (Accessed April 19, 2024)
Created June 24, 2013, Updated February 19, 2017