Ventilation in 2 or 3 unit multifamily buildings before and after weatherization.

This study investigates the fresh air distribution in 2 or 3-unit multifamily buildings before and after weatherization and evaluates the effectiveness of exhaust-only ventilation in providing the minimum recommended fresh air flows to dwellings in such buildings. Lowrise multifamily buildings often have no mechanical ventilation system and rely on the air leakage through the exterior envelope to provide outdoor air to occupants. Weatherization of the roof space, a common energy conservation measure applied to 2 or 3-unit multifamily buildings (also known as Duplex or Triplex) in Quebec can greatly reduce the equivalent leakage area of the exterior shell and change the location of the neutral pressure plane. Consequently, this has a major impact on the outdoor air supply to the building and how it is distributed on a unit-per-unit basis. Field test data characterizing the shell leakage and inter-zonal leakage of a case study building was used to define various pre-and post-weatherization airflow models. Airflow models were introduced in CONTAM, a software developed by the National Institute of Standards and Technology (NIST), to determine the air change profiles (fresh air change & total air change) for the individual dwellings. The results of simulations presented herein shed light on the most popular mechanical ventilation strategy used in weatherized low-rise multifamily buildings.