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jrichards60 02-10-2007 03:04 PM

Attic Frost?
Hi. I'm new to the forum. We have a new home located in Wisconsin. The temperatures at night here have been below zero and days haven't gone above 10 degrees for a couple weeks. I noticed today in the attic on the north side of the inner roof has a layer of frost. There is still snow on the outside of this side of the roof (north side). Is this normal to have frost on the plywood of the inner roof?

There is about a foot of blown-in insulation & baffles at the eaves.

Thanks for your help.


Square Eye 02-10-2007 05:11 PM

Check your bathroom vents, make sure the exhaust is ducted out of the attic space. This is a MAJOR source of moisture and can cause severe damage in an area that isn't ventilated well.

mudmixer 02-10-2007 06:29 PM

Also, check the fit and insulation of the hatch into the attic, if you have one. This can be a major source of moisture that can accumulate over the period of the last cold spell.

I assume you have made sure your soffit vents are clear. With your prevailing NW winds after a snow, I would not expect an appreciable snow accululation that would plug any box type roof vents, but you never know.

CraigFL 02-11-2007 11:33 AM

You should also verify you have a vapor barrior on the ceiling surface. So many older homes just had insulation blown in the ceiling joists. Ventilation is the key here too-- so as said, make sure the vents are not plugged-- especially if you have snow covered ridge vents.

jrichards60 02-11-2007 08:21 PM

Thanks on attic frost suggestions
Thanks for your help and suggestions. I followed the bathroom vents and they are vented outside. There was some small leaks in the fan box that I sealed. I also made sure there were no leaks where the flexible vent tube mounts to the fan box.
As far as the insulation, I have blown in insulation that is about 18" thick that continues until it hits the roof as the roof angles down on the outsides. There are baffles located on every other truss. I looked down the baffels and can see a clean shot down to the wood (where the gutter would mount). I do have vents under the roof over hang; however, don't know if those are covered with insulation. I could pull one from the outside and see if I get covered with insulation. I also have a full roof vent along the top of the roof.
On the same side of the roof where I have frost is the attic access door. This door is an 18" square of drywall. I insulated this panel today and ran a seal around the outside edge of it where it hits when in place. Also, I checked my garage attic. I have the same roof set up with blown in insulation and an attic access door (drywall).
As far as a celing mositure barrier, the celing in the house is actually tounge and groove wood. The house is a log home with a beautiful wood ceiling. Should this wood be placed over drywall? I can move the insullation in the attic and check. If drywall, is that a good enough barrier? I would hope I don't see the back of the wood ceiling.
If you guys are still following up on this post, do you think I should pull the outside vents under the over hang to see if the blown insulation falls out? If it does, should I clear a path along the inside of the roof so that the vent breaths? What should I be looking for when digging through the insultaion (drywall)? The house is brand new and I have a 1 year warrranty. However, I try not to bother having someone come out unless I can't handle it.
Thanks again,

glennjanie 02-11-2007 09:07 PM

Hello Jeff:
A good vapor barrier would be polyethylene plastic. When you stick your hand down through the insulation the plastic should be a slick surface. I suppose your ridge vent is covered with snow for now but you should get sufficient ventilation across from soffit to soffit. When warmer weather comes and melts the snow off you could check to see if there is moisture dripping off the same spots that are now frosty. If that's not the case, forget it, its just the hyper cold causing the frost.

inspectorD 02-14-2007 01:05 PM

I second what Glennjanie said... sometimes it gets so cold you cannot beat the problem.
Any leaks from hatchs, vents recessed lights or pull down stairs will let air leak into the attic which is just going to condensate at the attic boards.

Like a cold soda on a hot day....:D

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