CONTAM

Following the pandemic of Covid-19, the scientific interest in ventilation rate of buildings, and especially in spaces with high occupancy, has increased. The creation of a healthy and acceptable internal environment, especially at workplaces is considered necessary, both to deal with the sick building syndrome, or the spread of various diseases, as well as to improve the comfort of employees.

In residential buildings, the indoor air quality can be significantly affected by ventilation measures initiated by occupants, including the operation of windows and in-unit exhaust fans in kitchens and bathrooms. The outcome of these measures can be highly variable and difficult to accurately characterize in building simulation frameworks. Consequently, many simulations simplify these factors by disregarding window opening behaviours and using fixed schedules for exhaust fan operation across all residential units.

An approach has previously been developed to estimate space-specific carbon dioxide (CO2) levels that can serve as metrics for the adequacy of outdoor ventilation rates. These metrics are based on the CO2 concentration expected in a space given its intended or expected ventilation rate, volume, and occupant information (i.e., the number of occupants, their CO2 generation rates, and duration of occupancy).

Buildings account for approximately 40 % of energy use in the European Union, as well as in the United States. In light of the European Energy performance of buildings directive, efforts are underway to reduce this energy use by targeting zero or nearly zero energy buildings. In such low energy buildings in cold climates, ventilation to ensure suitable indoor air quality is responsible for half or more of their energy use. The use of heat recovery and demand-controlled ventilation are potential solutions to reduce ventilation-related energy consumption.

With increasing building airtightness, the design of an adequate ventilation system gains importance. The first generation of ventilation systems, based on continuous supply of the nominal airflow rate, are now being replaced by Demand Controlled Ventilation (DCV). These systems, often H2O and/or CO2 controlled, do not take into account the emissions of Volatile Organic Compounds (VOCs) to the indoor environment.

In an extensive simulation study using a multi-zone airflow and contaminant transport calculation software (CONTAM) recommendations for the supply air rates for residential housing were derived as input for the revision of the Austrian standard ÖNORM H 6038 (2014). The floor plan, the occupancy and the contaminant and humidity sources are modelled to represent a typical Austrian housing situation. A humidity buffering model is also implemented. Based on common thresholds for CO2, relative humidity (r.h.) and TVOC the so-called relative threshold deviation is determined.

Methods of manipulating building envelope wind pressure distributions for application in the natural ventilation of high-rise buildings are presented using computer simulation methods. CFD was used to simulate the external flow while the multi-zone method was used to compute the flow distribution in the building interior. First, a 2-D CFD study was conducted to explore various techniques of manipulating the building envelope wind pressure distribution.

The importance of adventitious air leakage under normal operational conditions and its reduction in order to save energy is highlighted by the relvant building standards of many countries. This operational leakage is often inferred via the measurement of air permeability, a physical property of a building that indicates the resistance of its fabric to airflow. A building’s permeability is the measure of airflow rate through its envelope at a constant pressure differential of 50 Pascals.

The paper presents the whole year simulation of humidity based demand controlled hybrid ventilation in multiapartment building. The simulation was performed for NAPE (National Energy Conservation Agency) multifamily residential reference building. This allowed the authors to compare obtained results with earlier investigated behaviour of the NAPE building with passive stack ventilation and mechanical exhaust ventilation.