At an inspection today, there was heavy frost and condensation on the underside of the attic sheathing. The ventilation was minimal. Would you think that this is a ventilation only problem, or possibly related to the roof coverings? We’ve had snow and ice on our roofs for about a month now (which is quite an event down here).
This condition is usually indicative of warm, moist air infiltrating the attic from below, and this occurs through wiring openings in the top of wall plates, from poorly sealed access door openings or other penetrations from chases, pipes, flues, chimneys, cables, wires, or other openings from the conditioned space below.
The solution is to seal these openings against warm, moist air inflitration from the conditioned space where it can condense on colder sheathing.
It is an energy loss issue as well.
Lack of ventilation can exacerbate the situation but even in properly ventilated attics, you can get the same symptoms when air infiltration to the attic is not prevented.
mansard style roofs can be very problematic, heat and moisture are coming into the space probably from the second floor area, a bathroom, laundry room, kitchen, was this the west side of the building ??