Heatilator BIR42 Owner's Manual page 19

WARNING! Risk of Fire! -
DO NOT
Storm Collar
Roof Flashing
Shaded areas
represent
2 in. (51 mm) min.
air space clearance
required around pipe
(attic)
Attic
Insulation
Shield
(insulation)
(ceiling)
Offset/Return (secured
2 in. (51 mm) min.
with hanger straps)
(ceiling)
Ceiling Firestop
Must have 2 in. (51 mm)
minimum clearance
to header
Transition
48 in.
1219 mm
1-1/2 in. (38 mm) to back &
sides of appliance
0 in.
(except at nailing flanges
to floor
where it is 1/2 in. [13 mm])