Todays homes are built more energy efficient than ever. New materials, increased insulation, and new construction methods help reduce heat loss in homes. Home owners weather strip and caulk around windows and doors to keep the cold air out and the warm air in. During heating months, home owners want their homes as airtight as possible.
While it is good to make your home energy efficient, your home needs to breathe.
Fresh air must enter your home. All fuel-burning appliances need fresh air for proper combustion and ventilation.
Exhaust fans, fireplaces, clothes dryers, and fuel burning appliances draw air from the house to operate. You must provide adequate fresh air for these appliances.
This will insure proper venting of vented fuel-burning appliances.
PRODUCING ADEQUATE VENTILATION
All spaces in homes fall into one of the three following ventilation classifications:
1. Unusually Tight Contruction; 2. Unconfined Space; 3. Confined Space.
The information on pages 5 through 8 will help you classify your space and provide adequate ventilation.
Unusually Tight Construction
The air that leaks around doors and windows may provide enough fresh air for combustion and ventilation. However, in buildings of unusually tight construction, you must provide additional fresh air.
Unusually tight construction is defined as construction where: a. walls and ceilings exposed to the outside atmosphere have a continuous water vapor retarder with a rating of one perm or less with openings gasketed or sealed and b. weather stripping has been added on openable windows and doors and c. caulking or sealants are applied to areas such as joints around window and door frames, between sole plates and floors, between wall-ceiling joints, between wall panels, at penetrations for plumbing, electrical, and gas lines, and at other openings.
If your home meets all of the three criteria above, you must provide additional fresh air. See Ventilation Air From Outdoors, page 8.
If your home does not meet all of the three criteria above, continue reading.
An unconfined space has a minimum air volume of 50 cubic feet for each 1000
BTU/Hr input rating of all appliances in the space (cubic feet equals length x width x height of space). Include adjoining rooms only if there are doorless passageways or ventilation grills between the rooms.
A confined space has an air volume of less than 50 cubic feet for each 1000
BTU/Hr input rating of all appliances in the space (cubic feet equals length x
width x height of space). Include adjoining rooms only if there are doorless passageways or ventilation grills between the rooms.
DETERMINING FRESH-AIR FLOW FOR HEATER LOCATION
Determining if You Have a Confined or Unconfined Space
Use this worksheet to determine if you have a confined or unconfined space.
Space: Includes the room in which you will install heater plus any adjoining rooms with doorless passageways or ventilation grills between the rooms.
1. Determine the volume of the space (length x width x height).
Length x Width x Height = cu. ft. (volume of space)
Example: Space size 18 ft. (length) x 16 ft. (width) x 8 ft. (ceiling height) =
2304 cu. ft. (volume of space)
If additional ventilation to adjoining room is supplied with grills or openings, add the volume of these rooms to the total volume of the space.
2. Divide the space volume by 50 cubic feet to determine the maximum BTU/Hr the space can support.
... (volume of space) cu. ft. = (Maximum BTU/Hr the space can support)
Example: 2304 cu. ft. (volume of space) 50 cu. ft. = 46.1 or 46,100 (maximum
BTU/Hr the space can support)
3. Add the BTU/Hr of all fuel burning appliances in the space.
Gas water heater*
Vented gas heater
Gas fireplace logs
Other gas appliances*
+ ... BTU/Hr
= ... BTU/Hr
Gas water heater
* Do not include direct-vent gas appliances. Direct-vent draws combustion air from the outdoors and vents to the outdoors.
4. Compare the maximum BTU/Hr the space can support with the actual amount of BTU/
... BTU/Hr (maximum the space can support)
... BTU/Hr (actual amount of BTU/Hr used)
BTU/Hr (maximum the space can support)
BTU/Hr (actual amount of BTU/Hr used)
The space in the above example is a confined space because the actual BTU/Hr used is more than the maximum BTU/Hr the space can support. You must provide additional fresh