Tall buildings in cold climates have unique challenges in maintaining indoor air quality due to stack effect. During the heating season, interior air buoyancy creates large pressure differentials in vertical shafts that can drive airflow from lower floors into upper floors. This pressure differential can result in the spread of contaminants throughout a building. Most recently, concern over COVID-19 has increased attention to the potential spread of airborne diseases in densely populated buildings. For many multi-unit residential buildings, suite ventilation has traditionally relied upon fresh air supplied through a mechanically pressurized corridor. In cold climates, large pressure differentials created by stack-effect can reduce the effectiveness of this approach. Multizone and CFD simulations are employed to analyze airflow and contaminant spread due to stack effect. Simulations are conducted on an idealized model of a 10-storey building using a range of experimentally derived airtightness parameters. Simulations demonstrate stack effect can reduce corridor ventilation to suites and even reverse the airflow for leakier buildings. Reduced airflow to suites can result in the accumulation of contaminants. Reversal of the airflow can allow contaminants from a suite to spread throughout the building. Contaminant spread is illustrated as a function of mechanical ventilation, building airtightness, and ambient temperatures. Strategies to reduce the influence of stack effect on mechanically pressurized corridors are discussed.

Numerical simulations capable of predicting the behavior of fire in the built environment are of increasing importance in environment design and safety analysis. The study of polyether polyurethane foam (PUF) is important as it is one of the most abundant materials present in the built environment and poses significant risk of fire and toxic gas. Several attempts to develop pyrolysis models for PUF have been made over the past decade with limited accuracy in replicating experimental result. Observations of PUF decomposition has led to a proposed model describing its kinetics, thermo-physical properties and fuel representation in a computational fluid dynamics (CFD) environment. The proposed model describes the physical observations and addresses many of the limitations of previous models. The model is validated with an array cone calorimeter experiments on different size specimens for two types of PUF. The purpose of this paper is to further improve the PUF pyrolysis model so that it can be applied in larger simulations of varying geometrical fuel arrangements.