Air leakage through the building envelopes is responsible for a large amount of energy use. The US Department of Energy Windows and Building Envelope Research and Development Roadmap for Emerging Technologies states that, in 2010, air infiltration was responsible for 20% of primary energy consumption attributable to the fenestration and building envelopes of commercial buildings. Despite this fact, improving airtightness is not always recognized by commercial building owners, as they have been slow in acknowledging and diminishing the detrimental effects of air leakage on energy use, comfort, indoor air quality, and building material durability.
The design and construction industry would benefit from a credible, easy-to-use tool that estimates potential energy and financial savings in a standardized manner so designers and contractors can give building owners compelling reasons to invest in reducing air leakage. In 2016–2017, Oak Ridge National Laboratory, the National Institute of Standards and Technology, the Air Barrier Association of America, and the US-China Clean Energy Research Center for Building Energy Efficiency collaborated to develop an online calculator. This user-friendly calculator is free to the public and uses the simulation results of the whole building energy simulation tool EnergyPlus and the airflow simulation tool CONTAM. In 2018–2019, the calculator was expanded to add moisture transfer calculations given that air leakage through the building envelope can have a significant impact on moisture transfer and associated impacts. Four more commercial building types were also added to the existing database of three building types as part of this update. This paper describes the procedure used to calculate moisture transfer due to air leakage and provides examples that demonstrate the moisture transfer for each of the seven commercial building types that are currently part of the calculator.