Tempo:
Heat or rotary wheel heat exchanger—This type of heat exchanger is used to transfer both heat and moisture. Indoor air passing through the heat wheel deposits heat and moisture into a desiccant material. As the wheel rotates into the outside air stream, the moisture and heat are released into the air supply (Figure 163). ERVs or HRVs may be installed as a stand-alone ventilation system or as a ventilation system coupled to a forced-air heating system. In most areas of Canada, high indoor relative humidity is more of a problem than low indoor relatively humidity. For this reason, heat recovery ventilators tend to be the ventilator of choice. Properly installed, HRVs and ERVs deliver a balanced flow of supply and exhaust air, neither pressurizing nor depressurizing the house. Moreover, some types of HRVs can operate in a recirculation mode to even out room to room temperature and humidity conditions. Recirculation mode can also help distribute heat from wood-burning appliances throughout the house.
Ventilation System Ductwork The installation of mechanical ventilation system ductwork involves many of the same considerations for builders as do forced air heating systems. Supply and exhaust duct runs through joist spaces and wall stud cavities must be as direct and straight as
possible to limit pressure losses along the system. Ventilation system motor fan sets do not have the same pressure flow characteristics as forced air furnace fans, and they are particularly sensitive to pressure losses due to turns, abrupt transitions and leakage. Penetrations of the building envelope for exhaust fan ducts or HRV ducts should be carefully planned to ensure the continuity of the air and vapour barriers, external moisture protection and insulation in the building envelope. Except for exhaust ducts, all ducts and plenums forming part of a heating, ventilating or air conditioning system and located outside the building envelope must be sealed and insulated to the same level required for exterior walls. Ducts or openings intended to discharge air to the outdoors must be equipped with a motorized damper or gravity or spring-operated backflow damper.
Operation and Maintenance To be effective, mechanical ventilation systems must be appropriately maintained and operated by occupants. This typically includes cleaning screens and filters, as well as servicing the equipment according to manufacturer’s instructions. It is important to provide enough space to access the equipment. Consult with the heating contractor prior to finalizing the house design so that the mechanical ventilation system may be properly integrated within the house.
SUSTAINABLE HOUSING INSIGHT Healthy Indoor Environment
Keep construction drywall dust and debris out of ductwork. Ventilation is required to remove stale air and excessively moist air.
Houses equipped with electric baseboards would benefit from a fully ducted ventilation system to supply outdoor air to each room and to exhaust air from kitchen and bathroom areas.
Ventilation System Ductwork The installation of mechanical ventilation system ductwork involves many of the same considerations for builders as do forced air heating systems. Supply and exhaust duct runs through joist spaces and wall stud cavities must be as direct and straight as
possible to limit pressure losses along the system. Ventilation system motor fan sets do not have the same pressure flow characteristics as forced air furnace fans, and they are particularly sensitive to pressure losses due to turns, abrupt transitions and leakage. Penetrations of the building envelope for exhaust fan ducts or HRV ducts should be carefully planned to ensure the continuity of the air and vapour barriers, external moisture protection and insulation in the building envelope. Except for exhaust ducts, all ducts and plenums forming part of a heating, ventilating or air conditioning system and located outside the building envelope must be sealed and insulated to the same level required for exterior walls. Ducts or openings intended to discharge air to the outdoors must be equipped with a motorized damper or gravity or spring-operated backflow damper.
Operation and Maintenance To be effective, mechanical ventilation systems must be appropriately maintained and operated by occupants. This typically includes cleaning screens and filters, as well as servicing the equipment according to manufacturer’s instructions. It is important to provide enough space to access the equipment. Consult with the heating contractor prior to finalizing the house design so that the mechanical ventilation system may be properly integrated within the house.
SUSTAINABLE HOUSING INSIGHT Healthy Indoor Environment
Keep construction drywall dust and debris out of ductwork. Ventilation is required to remove stale air and excessively moist air.
Houses equipped with electric baseboards would benefit from a fully ducted ventilation system to supply outdoor air to each room and to exhaust air from kitchen and bathroom areas.
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