My air handler is in my 3rd floor walk up attic. The ductwork that supplies the 2nd story of my house is also in the attic, but there are no supply vents or return vents in the attic, so at least theoretically the system is sealed from the attic air except for leakage. The HVAC system has a MERV-11 Aprilaire media filter, but they make a MERV-13 that fits the filter housing.

I’m going to have some walls framed in the attic to prepare it to be finished. My carpenter says he prefers to do most of the wood cutting in the attic, rather than doing it outside. He says he has a large dust collection hood that integrates with his saw and vacuum, so dust creation is minimal. He says he can also setup fans with filters to capture dust.

Under these circumstances, would it be OK to continue running the HVAC while the carpenter is doing work in the attic? At this point it is only unfinished framing that will be done. No drywall or drywall dust yet (I will definitely shut the system down for the drywall.)

Thanks.