Got a call to inspect an attic, homeowner stated he hasn’t gone up there in a long time, when he was up there he noticed the underside of the roof sheathing had frost on it. He recently had a new heat pump, and Aprilaire humidifier installed (in basement). He wondered if that could be the cause.
Its been 20 degrees or less here for a couple days, house is a 3500sq. ft. colonial. He said the HVAC contractor set the Aprilaire and said this is the setting to leave it on.
I was planning on looking for vents improperly terminating in attic, poor ceiling insulation, and poor attic venting.
Anything else I should look for?