Ventilation needs and strategies differ according to occupancy patterns and building type. Main considerations are:
Dwellings: The ‘dominant’ pollutant in dwellings is often moisture which is best extracted directly at source from wet zones using mechanical extract ventilation or ‘passive’ stacks. Fresh supply air is needed in living rooms and bedrooms to meet the needs of metabolism. Additional airing may be necessary if smoking takes place. Further air supply in the form of vent openings is necessary to meet the combustion needs of ‘open’ flue and ‘flueless’ combustion appliances. Special care is needed to avoid flue down-draughting resulting from the use of extract systems. In high radon areas, special attention to sealing the foundations is necessary, combined with sub floor venting.
Offices and other non-domestic buildings: Important pollutants in non domestic buildings include metabolic carbon dioxide, volatile organic compounds from furnishings and fittings, and ozone and carbon emissions from printers and photocopiers. In many of these buildings, metabolic carbon dioxide may represent the dominant source of pollutant. High heat gains may affect the choice between minimum ventilation combined with mechanical cooling or maximum ventilation for passive cooling. Industrial processes require special ventilation provision to prevent the discharge of contaminated air both internally to the occupants and externally to the atmosphere. Other special applications include provision for hospital and clean room ventilation design to avoid contamination.