12
FRESH AIR DUCT CAPACITIES FOR DUCTS SUPPLYING FRESH AIR TO
BOILER IN TIGHTLY CONSTRUCTED HOUSES
FRESH AIR FOR COMBUSTION
TABLe 3: FResH AiR duCT CAPACiTies
THRouGH LouVeRs
Fresh Air
duct size
¼” Mesh
Screen
Wood
Louvers
Metal
Louvers
(Btuh)*
(Btuh)*
(Btuh)*
3 ½” x 12”
144,000
36,000
108,000
8” x 8”
256,000
64,000
192,000
8” x 12”
384,000
96,000
288,000
8” x 16”
512,000
128,000
384,000
*Btuh = British Thermal Units per hour based on
opening covered by ¼” mesh screen , wood louvers,
or metal louvers.
Figure #2B
