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Table 501.4.3(2)
Procedure to Determine Makeup Air Quantity for Exhaust Appliances in Existing
Dwellings
(Refer to item 5 in section 501.4.3 to determine applicability of this table)
One or multiple power One or multiple fan- One atmospherically Multiple ap
vent or direct vent assisted appliances and vented gas or oil atmospheri
appliances or no power vent or direct appliance or one solid or oil applia
combustion appliancesAvent appliancesB fuel appliance� appliances°
1. Use the Appropriate Column to Estimate House Infiltration
a) pressure factor 0.25 0.15 0.10 0.05
(cfm/sf)
b) conditioned 4900
floor area (sf) — —
(including unfinished basements)
Estimated House
Infiltration (cfm): _735_
[1a x 1b]
or
Alternative
Calculation (by
using blower door
test)E
c) conversion
factor 0.75 0.45 0.30 0.15
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d) CFM50 value
(from blower
door test)
Estimated House
Infiltration (cfm):
[1c x 1d]
2. Exhaust Capacity
80% of exhaust
rating = Exhaust 600x.80=480
Capacity (cfm):
(not applicable if recirculating system or if powered makeup air is electrically interlocked with exhaust)
3. Makeup Air Requirement
a) Exhaust
Capacity (from _480_
above)
b) Estimated
House Infiltration 735
(from above)
Makeup Air
Quantity (cfm): 480-735=(-255)
[3a - 3b]
(if value is negative, no makeup air is needed)
4. For Makeup Air Opening Sizing, refer to Table 501.4.2
AUse this column if there are other than fan-assisted or atmospherically vented gas
or oil appliances or if there are no combustion appliances.
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BUse this column if there is one fan-assisted appliance per venting system. Other
than atmospherically vented appliances may also be included.
�Use this column if there is one atmospherically vented (other than fan-assisted)
gas or oil appliance per venting system or one solid fuel appliance.
°Use this column if there are multiple atmospherically vented gas or oil appliances
using a common vent or if there are atmospherically vented gas or oil appliances and
solid fuel appliances.
EAs an alternative, the Estimated House Infiltration may be calculated by
performing a blower door test and multiplying the conversion factor by the CFM50
value.