Determining FRESH-AIR Flow for Heater Location

AIR FOR COMBUSTION AND VENTILATION

Providing Adequate Ventilation (Cont.) Determining Fresh-Air Flow for Heater Location

AIR FOR COMBUSTION AND VENTILATION

Continued

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 (6 x 10-11kg per pa-sec-m2) or less with openings gasketed or sealed and

b.weather stripping has been added on openable win- dows 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 6.

If your home does not meet all of the three criteria above, proceed to Determining Fresh-Air Flow For Heater Lo- cation, below.

Conﬁned and Unconﬁned Space

The National Fuel Gas Code, ANSI Z223.1/NFPA 54 deﬁnes a conﬁned space as a space whose volume is less than 50 cubic feet per 1,000 Btu per hour (4.8 m3 per kw) of the aggregate input rating of all appliances installed in that space and an unconﬁned space as a space whose volume is not less than 50 cubic feet per 1,000 Btu per hour (4.8 m3 per kw) of the aggregate input rating of all appli- ances installed in that space. Rooms communicating directly with the space in which the appliances are installed*, through openings not furnished with doors, are considered a part of the unconﬁned space.

*Adjoining rooms are communicating only if there are doorless passageways or ventilation grills between them.

DETERMINING FRESH-AIR FLOW FOR HEATER LOCATION

Determining if You Have a Conﬁned or Unconﬁned Space

Use this work sheet to determine if you have a conﬁned or unconﬁned space.

Space: Includes the room in which you will install heater plus any ad- joining 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 20 ft. (length) x 16 ft. (width) x 8 ft. (ceiling height) = 2560 cu. ft. (volume of space)

If additional ventilation to adjoining room is supplied with grills or open- ings, add the volume of these rooms to the total volume of the space.

2.Multiply the space volume by 20 to determine the maximum Btu/Hr the space can support.

____________(volume of space) x 20 = (Maximum Btu/Hr the space can support)

Example: 2560 cu. ft. (volume of space) x 20 = 51,200 (maximum Btu/Hr the space can support)

3.Add the Btu/Hr of all fuel burning appliances in the space.

Vent-free heater		_____________ Btu/Hr
Gas water heater*		_____________ Btu/Hr
Gas furnace		_____________ Btu/Hr
Vented gas heater		_____________ Btu/Hr
Gas ﬁreplace logs		_____________ Btu/Hr
Other gas appliances* +		_____________ Btu/Hr
Total	=	_____________ Btu/Hr

*Do not include direct-vent gas appliances. Direct-vent draws com- bustion air from the outdoors and vents to the outdoors.

Example:		40,000
Gas water heater
		_____________ Btu/Hr
Vent-free heater	+	33,000
		_____________ Btu/Hr
Total	=	73,000
		_____________ Btu/Hr

4.Compare the maximum Btu/Hr the space can support with the actual amount of Btu/Hr used.

____________________Btu/Hr (maximum the space can support)

____________________Btu/Hr (actual amount of Btu/Hr used)

Example: 51,200 Btu/Hr (maximum the space can support) 73,000 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 air. Your options are as follows:

A.Rework worksheet, adding the space of an adjoining room. If the extra space provides an unconﬁned space, remove door to adjoining room or add ventilation grills between rooms. See Ventilation Air From Inside Building, page 6.

B.Vent room directly to the outdoors. See Ventilation Air From Outdoors, page 6.

C.Install a lower Btu/Hr heater, if lower Btu/Hr size makes room uncon- ﬁned.

If the actual Btu/Hr used is less than the maximum Btu/Hr the space can sup- port, the space is an unconﬁned space. You will need no additional fresh air ventilation.

WARNING: If the area in which the heater may be operated is smaller than that deﬁned as an unconﬁned space or if the building is of unusually tight construc- tion, provide adequate combustion and ventilation air by one of the methods described in the National Fuel Gas Code, ANSI Z223.1/NFPA 54 Section 5.3 or applicable local codes.