fran wrote:
If this is a common problem, what can people do about this before their roof rots away. I don’t even use my bathroom fan and I always have my furnace fan on.
Well, not using your exhaust fan, especially in the during cold weather is the perfect solution and leaving the furnace fan on the ON setting to keep air moving in the home also helps.
To see if you have excess moisture in the attic during the winter - a person would need to use the exhaust fan(s) as normal and then look into the attic from the hatch with a good flashlight. Try to identify the exhaust ducts and see if there is excess moisture, soaking wet roof sheathing, etc. If conditions are bad then the whole attic may be wet with water dripping from the thousands of roof shingle nails that are exposed in the attic.
When called out as a warranty issue builders often slap copious quantities of vapour barrier tape around the leaky connection between the exhaust duct and the roof sheathing. Of course this is a slap-stick "repair".
During very cold weather I would consider a small amount of condensation to be normal. But - this is not the 70's and mold, rot, and excessive moisture in new homes at any time of year is IMO not an acceptable condition.
Here is another lovely image I took in an attic showing frost on the roof sheathing as a result of warm exhaust air leaking from the exhaust duct.