A furnace can be installed various places in a house -- in a basement, an attic, a garage, a ground-floor utility room or outside the walls. Furnaces in basements or garages often are enclosed in cabinets or closets to block noise from the unit and protect it from accidental bumps. There are many ways to build furnace enclosures, varying with the location of the unit, its size, the location of distribution ducts and the air supply and venting requirements. Each furnace comes with a list of specific clearance requirements, but there are some general guidelines for furnace enclosures.
Build an enclosure before installing a furnace, if possible, to simplify access to wall studs and other elements. Make any enclosure large enough to provide easy access to the utility connections. Enclose any furnace cabinet with gypsum drywall, which is fire resistant. Provide a door with a vented front large enough to provide the necessary air supply. Refer to the furnace installation manual for specific clearances and openings.
Elevate an enclosure in a basement or garage. Use concrete blocks or a concrete pad to set the base of the furnace at least 4 inches above the floor, to prevent any water from reaching it. Make the base high enough in any enclosure so the ignition and burner on a gas furnace are at least 18 inches above the floor. Allow at least 6 inches from any wall to a flue or vent taking exhaust heat to the roof.
Make a common enclosure for furnace, washer and dryer in a basement or ground floor installation. Separate the furnace from the other appliances with a vertical wall framed with 2-by-4-inch studs and covered on both sides with drywall. Provide separate utility connections and vents for each appliance.
Use basic wall framing for a furnace enclosure: a bottom plate, top plate and studs on each side. Put horizontal blocking boards in side walls to brace them. Frame a door with horizontal header and sill plates between side studs Make headers with doubled 2-by-4s and support them with side studs between the header and sill. Place the door where its vent will not draw exhaust air from any other appliance.
Things You Will Need
- Furnace installation manual
- Concrete blocks or base
- 2-by-4-inch framing lumber
- Door with vent opening