tion, air for combustion and ventilation shall
be permitted to be supplied by normal infiltra-tion.
5.3.2 If normal infiltration is not sufficient
because of tight construction, air for combus-tion
and ventilation shall be obtained directly
from outdoors or from spaces that freely com-municate
with outdoors by means of a perma-nent
opening or openings having a total free
area of not less than 1 square inch per 5,000
Btu/hr (28 square inches per gal/hr) based on
the total input rating of all appliances in the
space.
5.4 Appliances Located in Confined Spaces.
For appliances installed in confined spaces,
air for combustion and ventilation shall be
provided using one of the methods set forth in
this section.
8 National Oilheat Research Alliance
5.4.1 All Air Taken from Inside the Building.
5.4.1.1 The confined space shall be provided
with two permanent openings, one near the top
of the space and one near the bottom. (Figure
9). For more information reference the current
version of NFPA 31.
Testing to Determine if there is
Sufficient Air Available for the
Appliance
The confined space calculation does not take
into account other factors in the home which
also affect the amount of combustion, dilution
and ventilation air available. These include:
Attic Fan
Central Vacuum
Range Hood
Microwave
Bathroom Exhaust Fan
Clothes Dryer
Fireplaces
NFPA has developed a “worst case draft test”
that enables technicians to determine if a com-bustion
air problem might arise in the future.
Residential Clothes Dryer
How much air does a clothes dryer
exhaust? It depends on what
model of dryer.
An Energy Star Clothes Dryer will
use up to 12,000 cubic feet of air.
With this type of dryer, one 60-minute
cycle will exhaust all the air from a
1,500 square foot home.
A Standard Clothes Dryer will use
up to 6,000 cubic feet of air. This type
of dryer will exhaust all the air from a
1,500 sq. ft. home in two 60-minute
cycles.
Figure 9