Tempo:
the rooms of the house. The simplest example is that of a forced air heating system that has a duct running from outside to the return air trunk duct. The operation of the furnace fan draws outdoor air into the forced air system where it mixes with the return air and is then distributed throughout the house by the forced-air system ductwork. Exhaust fans are used to vent bathrooms and the kitchen. A more efficient option involves connecting a heat recovery ventilator (HRV) to the furnace ductwork system so the heat of the air exhausted from the house is recovered to warm the incoming outdoor air. The ventilation and heating system controls are interlocked so that the furnace fan mixes and circulates the outdoor air that is delivered to the distribution ductwork. Installation costs are lower because one duct system serves both heating and ventilation. Operating costs may be higher depending on the efficiency of the furnace circulating fan (brushless direct current motors are best). If an HRV is not used, proper design is necessary to ensure that outside air is mixed and adequately warmed before entering the furnace heat exchanger so that it is not damaged. Ventilation system not coupled with a with a forced-air heating system (stand-alone ventilation system)—This system consists of fans, ducts, grilles and controls that exhaust air from selected rooms in a house and supply air to rooms that are not being exhausted. It is usually installed in houses with baseboard, radiator and in-floor radiant heating systems that do not use forced-air heat distribution. It is designed for ventilation only, independent of the need to deliver heating or cooling. Incoming outdoor air must be tempered (warmed) during the cold season to maintain a comfortable air supply temperature. Heat recovery ventilators are often used as it is important to raise the temperature of the outdoor air as much as possible before it is delivered to a room to prevent comfort problems and reduce heating costs.
Exhaust-only ventilation system—This system expels air from a house and relies on leakage through the building envelope into the house for replacement air, resulting in some depressurization of the house. Consequently, exhaust-only ventilation systems should not be used in houses that have fuel-fired appliances that use natural draft and unsealed venting systems to vent combustion products. This includes wood fireplaces and woodstoves, naturally aspirated gas furnaces with draft hoods and oil furnaces with barometric dampers. It should also be noted that exhaust-only systems rely on the availability of air leakage through the envelope to make-up the air being exhausted. As it is not possible to ensure uniform air leakage around the house, it is also not possible to predict with any certainty that an exhaust-only system will be able to adequately ventilate any given room in a house. In the case where interior pools and tubs are installed, those with an area less than 10 m2 (107 sq. ft.) must be equipped with a pool cover, and those with larger areas are required to have exhaust fans capable of recovering at least 40 per cent of sensible heat.
Heat and Energy Recovery Ventilators A heat recovery ventilator (HRV) is a device designed to recover heat from the exhaust air and transfer this heat to the incoming outdoor air during the winter. In air conditioned houses in the summer, the process is reversed where the cold is recovered from the outgoing exhaust air and helps reduce the temperature of the incoming air. This not only brings down heating and costs, but, in the winter it also helps bring the temperature of the incoming outdoor air up to a point where it can be introduced into the occupied space with little risk of comfort problems. In addition, HRVs temper incoming air and reduce the risks of the colder outdoor air damaging furnace heat exchangers for coupled systems. Numerous studies have concluded
Exhaust-only ventilation system—This system expels air from a house and relies on leakage through the building envelope into the house for replacement air, resulting in some depressurization of the house. Consequently, exhaust-only ventilation systems should not be used in houses that have fuel-fired appliances that use natural draft and unsealed venting systems to vent combustion products. This includes wood fireplaces and woodstoves, naturally aspirated gas furnaces with draft hoods and oil furnaces with barometric dampers. It should also be noted that exhaust-only systems rely on the availability of air leakage through the envelope to make-up the air being exhausted. As it is not possible to ensure uniform air leakage around the house, it is also not possible to predict with any certainty that an exhaust-only system will be able to adequately ventilate any given room in a house. In the case where interior pools and tubs are installed, those with an area less than 10 m2 (107 sq. ft.) must be equipped with a pool cover, and those with larger areas are required to have exhaust fans capable of recovering at least 40 per cent of sensible heat.
Heat and Energy Recovery Ventilators A heat recovery ventilator (HRV) is a device designed to recover heat from the exhaust air and transfer this heat to the incoming outdoor air during the winter. In air conditioned houses in the summer, the process is reversed where the cold is recovered from the outgoing exhaust air and helps reduce the temperature of the incoming air. This not only brings down heating and costs, but, in the winter it also helps bring the temperature of the incoming outdoor air up to a point where it can be introduced into the occupied space with little risk of comfort problems. In addition, HRVs temper incoming air and reduce the risks of the colder outdoor air damaging furnace heat exchangers for coupled systems. Numerous studies have concluded
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