It appears that we don't have enough ventilation in the attic because the
roof nails are wet. Nothing is leaking so far and the roof is only nine
Is this a problem that requires an immediate attention? There is snow on the
Should I put new vents now, or wait untill the spring?
How is your insulation up there? I ask this because for condensation to
occur, warm air has to hit the cold of the nail. The snow on the roof will
tell you where the cold is coming from leaving the origin of the warm as
your primary concern. Check around exhaust fans, vent pipes, light fixtures
and any other item that might be letting warm air into the attic. I would
definitely have an insulation contractor come in to take a look.
Disclaimer: All my advise is based on logic and very little know-how.
I don't think it is unusual for frost to form on the roof nails where they
poke thru into the attic. The humidity inside the attic in cold weather
will always be somewhat higher than that outside even with a good vapor
barrier. I have an extremely good vapor barrier, 12" of insulation, and
ridge and soffit venting--I never get an icycle on the roof even with over a
foot of snow sitting there, but I have seen frost on the shingle nails.
They are always going to be significantly colder than the air inside the
attic. So you may not really have a problem. Do you have frost forming on
the rafters and roof decking, or just on the nails?
Rafters are dry, there is only one spot, maybe a couple of sq.ft. where the
roof decking is frosted.
The reason I started worring about it, is that I found a couple of water
stains on the first floor ceiling (one in the corner and another by the
chimney). I thought maybe the condesation from the attic causes that, by why
the second floor ceiling is dry?
Cold nails + humidity = condensation.
The question is where does the humidity come from.
Is there a vapor barrier at the ceiling level?
Ate the tops of wall cavities sealed?
A lot of humidity will move up through the walls and up through the ceiling.
If that is taken care of, look at the amount of ventilation.
A little is OK and normal under some conditions. However a lot means
too much moisture is up there. Bad or missing vapor barrier or very likely
too little ventilation. The attic must be ventilated as much in winter as
in the summer.
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