Frost in attic roof

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  #1  
Old 02-13-18, 07:21 AM
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Frost in attic roof

Very cold winter here in Minnesota, and a couple weeks ago we had a unusually warm day. Water started dripping through one of our bedroom door jams. This has happened maybe twice that I know of. I looked up in the attic and found frost on the northern-facing (shaded) part of the roof. It didn't look very extreme to me but it is certainly enough to drip/pool/stream to a low point and eventually drip through into the house. Not good...

A few years ago I broke the seal into the attic to install an antenna.. I did not re-seal it, but it is a good fit, no obvious open gaps. I plan to put some weather stripping on the edge of that access area. It is an insulated cover. attic insulation is blown, about 16 inches.

The attic is vented (at least 10 vents), and the builder installed baffles so that insulation didn't block the soffit vents.. so that looked good to me.

I have a few more ideas that I might try.. local store rents a thermal camera for about 75/day, so I was going to go look for any leaks from light fixtures or vents/pipes. What is the best way to seal these if I find a problem? I assume I have to do that on a cold day, colder it is the more obvious any heat signature would be. Was thinking caulk or foam spray. Or possibly sealing with a layer of plastic and then putting insulation back on top of that.

Was thinking some additional rafter baffles could catch drips and channel them to the edge of the roof instead of letting it drip into the insulation & soak through the roof, into the house..

Alternate is of course to hire someone to fix this for me. But seems like it shouldn't be too difficult, although probably a bit time consuming.
 
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Old 02-13-18, 08:52 AM
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Was thinking some additional rafter baffles could catch drips and channel them to the edge of the roof instead of letting it drip into the insulation & soak through the roof, into the house..

You have a issue that goes way beyond the gap that may exist around the attic opening.

Frost is an indicator of a moisture issue and adding the baffles to control water is definitely not the solution.

You need to find out where it's coming from, like a bathroom, and get that fixed!
 
  #3  
Old 02-17-18, 06:34 AM
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What is the proper way to seal a gap in a ceiling, such as an opening for a light fixture or fire alarm?
 
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Old 02-17-18, 07:21 AM
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What you describe is common and the solution is straight forward but can require some work.

Sealing methods can vary. A large vent pipe may require 2 half moon pieces, one from each side and long enough to overlap. Then caulked in place with a fire rated caulking. Recessed lights can be covered but best if they are IC/AT rated (insulation contact and air tight). If not then a box over the top with drywall and plenty of clearance, caulked and/or foil tape. Then generously covered with insulation. Drywall doesn't burn and lots of space under there helps dissipate any heat. LEDs also generate less heat.

A drop ceiling over the kitchen cabinets or in a stairwell can provide a lot of warm air leaking in. There are many more places but that load of insulation will be a challenge Link on air sealing attached below.

Other issues are bath and kitchen fans dumping air into the attic and the effectiveness of your ventilation. Soffit venting needs to be in every rafter bay and NFA (net free area) needs to reach the minimum recommended amount. We can help. High vents also need to be sufficient.

Bud


https://www.energystar.gov/ia/partne...ide_062507.pdf
 

Last edited by Bud9051; 02-17-18 at 07:22 AM. Reason: added link
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Old 02-17-18, 07:47 AM
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Thank you. I have 3 bathroom fans upstairs and they are all vented to the roof, not to the attic. I counted approximately 20 different light fixtures/fire detectors or other openings to check! (5 bedrooms and 2 bath upstairs). And that doesn't count any other pipes, wires, etc..

i am having the gas company come to do an energy audit, they have a door blower & thermal imaging service to help detect leaks. There are too many potential areas for me to do it on my own.
 
  #6  
Old 02-17-18, 08:12 AM
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Typically they are not going to chase down every leak, but if you are there and nice they might get more involved. Have a complete floor plan of your home and if their camera is a good one it will shoot IR and matching digital images. It also attaches a number to each and if they will share you can note each on your floor plan. Be sure to ask for all IR images and digital ones. They often don't provide them. They should be able to download them right to your computer.

On the blower door test ask for the total CFM50 number (that is the air leakage at 50 Pascals negative pressure.

They should check, but be sure all windows are closed tight. Check all exhaust dampers, dryer, bath fan, kitchen fan to be sure they are not stuck open.

Conduct the IR thermal scan while the blower door is running, maybe at half speed to keep from freezing you out. The longer it runs the more the cold air will infiltrate the walls and ceiling so don't panic it can look bad.

Be sure to inspect for leakage around the basement perimeter rim, a common leakage area.

There are many different energy software packages and some just provide a conclusion, but pry for as much information that is going into his calculation as possible. MN should be good at doing energy audits.

Bud
 
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