Tempo:
Fuel-fired (oil, natural gas, propane) furnaces require a supply of combustion air from outside. Therefore, a hole of sufficient size has to be roughed into the foundation wall, rim (header) joist or exterior wall through which a combustion air duct can be passed. It is preferable to provide this hole when framing so that the duct can be properly integrated into the air and vapour barrier, exterior moisture protection and insulation systems of the building envelope. If not provided during construction, the mechanical contractor may damage the wall when the combustion heating appliance air duct is installed. The air intake must be situated where snow and drifting snow will not block airflow into the combustion air duct. The air intake must also be located to avoid contamination from local sources such as automobile exhaust or other exhaust vents including those serving clothes dryers, central vacuums or other fuel-fired appliances. Except for approved concentric vents, the separation between the air intake and other vents must be at least 900 mm (36 in. ). Concentric vents must be installed in accordance with CAN/CSA B149.1 Natural Gas and Propane Installation Code. Fuel-fired systems must also be connected to a combustion venting system that is either side-wall vented or vented through a chimney. For side-wall vented systems, plan where the vent must be passed through the foundation wall, floor rim (header) joist or exterior wall. Certain clearances from combustible material may be required if the vent conducts hot combustion gases. As is the case with the combustion air duct, it is important that the hole for the combustion venting system be roughed in such that the vent is easy to install and that there is continuity of the air and vapour barrier systems, exterior moisture protection and insulation around the opening. Some fuel-fired appliances use one-piece concentric, combustion air/combustion venting equipment that helps limit the number of holes required in the building envelope and simplifies the installation.
For furnaces connected to chimneys and flues, a framed space must be provided to allow the passage of the chimney or flue vent up through the house to the roof. Provisions must be made to ensure the continuity of the attic air and vapour barrier and insulation around the chimney or flue in such a way that also respects the clearances required between the chimney or flue and combustible materials. Framed chimney chases may also be provided up an exterior wall, though the cooler location may undermine venting performance under certain conditions (see Chapter 18). Earthquake vibrations can rupture fuel supply lines to heating appliances and cause appliances to tip or move enough to break fuel lines. In areas subject to earthquake vibration, appliances must be secured (strapped or braced) to the structure to resist overturning and displacement. Even in areas not subject to earthquakes, local regulations may require the securing of appliances. Therefore, it may be necessary to rough in framing or other structural support prior to the installation of the heating appliance. If they are located on an exterior wall, also provide the air and vapour barrier and thermal insulation in the support framing so continuity of all materials can be maintained when the rest of the wall area is finished. Sometimes humidification equipment may be added to the forced air system. It is typically connected to the furnace supply and return plenums so that it can add moisture to the air being circulated around the house through the forced air system. When a humidifier is added to maintain specific humidity levels, an automatic humidity control device must be provided.
Ductwork and Grilles The main supply and return air plenums connected to the furnace are typically suspended immediately below the main storey floor joists. Branch ducts leading to and from the plenums are usually located between studs in partition
For furnaces connected to chimneys and flues, a framed space must be provided to allow the passage of the chimney or flue vent up through the house to the roof. Provisions must be made to ensure the continuity of the attic air and vapour barrier and insulation around the chimney or flue in such a way that also respects the clearances required between the chimney or flue and combustible materials. Framed chimney chases may also be provided up an exterior wall, though the cooler location may undermine venting performance under certain conditions (see Chapter 18). Earthquake vibrations can rupture fuel supply lines to heating appliances and cause appliances to tip or move enough to break fuel lines. In areas subject to earthquake vibration, appliances must be secured (strapped or braced) to the structure to resist overturning and displacement. Even in areas not subject to earthquakes, local regulations may require the securing of appliances. Therefore, it may be necessary to rough in framing or other structural support prior to the installation of the heating appliance. If they are located on an exterior wall, also provide the air and vapour barrier and thermal insulation in the support framing so continuity of all materials can be maintained when the rest of the wall area is finished. Sometimes humidification equipment may be added to the forced air system. It is typically connected to the furnace supply and return plenums so that it can add moisture to the air being circulated around the house through the forced air system. When a humidifier is added to maintain specific humidity levels, an automatic humidity control device must be provided.
Ductwork and Grilles The main supply and return air plenums connected to the furnace are typically suspended immediately below the main storey floor joists. Branch ducts leading to and from the plenums are usually located between studs in partition
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