Date
Inquiry
Does the furnace need to have closed combustion if it is installed in the attic? Unless there is an attic fan, there does not seem to be a lot of evidence for vented attics to be negatively pressurized, causing potential backdraft problems.
Ruling
Yes. It is acceptable to install an atmospherically vented furnace in the attic if the attic if properly vented with no fan in the home that could cause negative pressurization. This kind of installation is discouraged because the IEQ risks are unclear and it is very difficult to find high-efficiency, atmospherically-vented furnaces. Applicable Internationally.
Internationally Applicable
On
Campus Applicable
Off