Bad condensation in attic


Old 01-24-16, 09:11 AM
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Bad condensation in attic

I live in the home my great grandfather built. The attic has always been finished insufficiently. My dad redid it a few years ago and did not properly ventilate so the already existent mold got much worse. The rafter are mostly rotten and the roof is in terrible shape.
Long story short there is absolutely no money to put a new roof on.

This summer I doubled up the rafters, ran baffles and put r13 insulation in. The previous leaks are much less but wherever I put soffit vents in I have condesation again. I am in Wisconsin and was going to put r19 in this summer.

The condensation is dripping into the room where I put in knee wall cabinets and everywhere there is a soffit vent outside. I'm pretty sure the cold air is entering thought the vents and warm air inside is condensing. It leaks much less than previous years and the room is much more comfortable.

Someone suggested, even though I am using Kraft faced insulation, to run a plastic barrier over as well. Is 19 going to be enough? I have no idea how to get r30 or more up there. Insulation is cheap enough for me to afford. I am just trying to get this attic to be more liveable, without my stuff constantly getting ruined, for a few years until I get our of school and can afford to buy the house and rehab it.

P.s. the walls are covered with 1/4" plywood because drywall is too heavy for the weak roof. Also, the rafters are 2x6
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Old 01-24-16, 09:40 AM
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Hi Who, as you know you have a lot of issues, been there in my early days. It sounds like you have living space in the attic with plywood across the bottom of the rafters and r-13 in the rafter bays.

Two issues, moisture and heat. That condensation/dripping is coming from moisture in the air OR ice dams on the edge of the roof. Let us know if there are lots oc icicles but for now I will address the moisture in the air.

Any warm air that leaks through to those rafters will be a problem. Plus, the plywood is difficult to seal and it needs a complete vapor barrier under it.

Give us a better description of what you have and be sure to rake the snow off given the condition of the roof.

Old 01-24-16, 09:51 AM
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Your story reminds me of a multifamily house I was once involved in selling (as a Broker).

The attic was well ventilated . . . . but it also had to deal with the vent pipe for the waste water disposal system being open right into the unfinished attic.

In the winter, brown colored icicles formed on the rafters in the attic. The Owners didn't even know about this, they seldom ventured into the attic . . . . I only learned of the issue because I was showing the property during the winter, and my Buyers noticed these stalactites.

Apparently, the Sellers had wanted to save money in the past by not adding another roof penetration when a new roof was installed years earlier, so this is what they wound up with.

I hope that's not your problem.

Last edited by Vermont; 01-24-16 at 10:37 AM.
Old 01-24-16, 09:52 AM
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thank you very much. The roof is snow free at the moment. We have a split level house. The upper roof, which has the attic, did have ice dams my entire life. Until I put the soffit vents in. Now I have only seen 1 icicle this year. The gaps I sealed with Spackle. But that will be easy to break. Also in between the rafter I used 1x4s and pocket screws to put in more area to screw into and prevent the plywood from sagging.

Thanks for your time
Old 01-24-16, 12:00 PM
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Sounds like the whole problem is summed up in two words... "attic" and "finished". You say the attic has always been finished insufficiently. Got news for you. Attics aren't usually meant to be "finished" at ALL... especially in cold climates.

If you are using what was originally designed as an unconditioned attic as a partially conditioned living/storage space, you are creating your own problem.

Is there an air barrier to prevent air on the cold side from getting in? I doubt it.

Is there a vapor barrier and air sealing on the warm side to prevent moisture from getting to the cold air where it will condense? Doesn't sound like it... and if you tried, it's woefully inadequate.

Are there heat registers and cold air returns to circulate air, mixing it with the air in the rest of the house and to prevent warm moist air from building up in the attic to high levels of humidity? I doubt that too.

In adding ventilation, you may have solved one problem but caused another. It sounds like you have made the roof colder, but in doing so you have brought the warm air and cold air in closer proximity to one another. With inadequate insulation... inadequate air sealing... inadequate vapor barrier and inadequate ventilation/air exchange, it is a recipe for failure. All these things are the common problems people encounter when they try to create usable space in the wrong way, using the wrong methods, in a space that was not designed to be used in that manner.

The proper way to treat an attic if you plan to use it for storage, is to insulate the floor with as much insulation as possible, and build an elevated platform above the insulation, which can then be used as cold storage. This allows plenty of room for ventilation and maximum separation of what is warm (the house below) and what should be cold (your attic space and roof deck).
Old 01-24-16, 06:53 PM
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I spoke to my grandma some more, this part of the house was added on when she was a child, she said the walls were open to the roof decking at first. After a bit her dad covered it in ship lap and several years later a tree limb damaged the roof and they had to remove the ship lap to repair it.

Her dad never got to finish it back up again and when she and her second husband moved in they redid the attic for her stepson. He didn't have water damage for several years but at time went on they began noticing various drips. They assumed it was the bad roof. They shingles were torn off in 2005 but the original, rotted roof deck was left on. That is when my dad redid it again and thats when the severe problems happened.

Around this time as well my dad said the boards where the soffits now are were open at the ends and had a large gap running the length of the soffit board. My dad built a box and hung it from the house, closing up the gaps.

While there are no icicles hanging from the roof there are a couple of small ones hanging from the soffit vents and frozen water stains on the siding. This only is happening in the front of the house, the back has a pine tree nearly against the house and not issues except 1 tiny spot on the wall and nothing outside. Yesterday was in the upper 30's so the humidity was high, that's when these condensation problems occur, in the 35-45 range and snow on the ground.

Since i redid everything this past summer this is the worst it has been up there this year. I actually thought things were good because all i had so far was a tiny spot in the hall and I solved it by closing up a rather large gap near this spot.

There is a heat vent up here, always has been, and a cold air return. The cold air return is in the hall though so I am also running a dehumidifier right now to try and remove some moisture.

Also the floor is insulated and I was told the floor joists were beefed up to support weight.
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