Frost in Attic After Installing Coal Stove in Basement

CapeCoaler
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Post By: CapeCoaler » Tue. Jan. 02, 2018 1:09 pm

That is why i recommended 4" of the foam insulation...
the condensing point will be inside the foam...
Where the moisture will never migrate to...
it should be closed cell foam board...
as the foam is the vapor barrier because vapor is not able to migrate thru the foam...
No moisture issue...
And you will have r-40 in the attic!
Make sure you get those last 2 feet covered to seal the bay...
Ya still need to vent properly...
Bonus, in the summer the ceiling will not heat soak the second floor...


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Post By: lincolnmania » Tue. Jan. 02, 2018 2:45 pm

Qtown1835 wrote:
Tue. Jan. 02, 2018 12:39 pm
Be careful with installation of the foam board in the attic. Any water vapor that is trapped between hot/cold will not be able to escape like it can with fiberglass. It may be a good idea to make sure you have adequate ventilation in the attic first. You need 1sqft for every 150sqft of attic balanced between intake and exhaust. All the insulation in the world wont help if the moisture has nowhere to go.
i can see daylight at the eaves and the ridge lol no problems there.

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Post By: freetown fred » Tue. Jan. 02, 2018 3:52 pm

Sounds like my old farm house attic L. :)

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Post By: CapeCoaler » Tue. Jan. 02, 2018 7:21 pm

check with the local utility's, up here it is a service provided for 'free'...
via a conservation charge on our electric bill...
That is why partly our electric rate is about 0.25 kw/hr...
HVAC contractor or a specialty service...

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Post By: D-frost » Tue. Jan. 02, 2018 7:41 pm

Brandon,
I just read your other thread.(100lbs./day) Someone mentioned insulation on the outside wall above the concrete, to the first floor. If this house is 2x4 wall construction, this is probably a big leak to the attic, especially, where the electrician ran the wiring up the wall from the circuit breaker box. (This leaves very little room for insulation)If you buy rolled tinfoil backed insulation, cut and staple(tinfoil in) above the concrete, between each floor joist, all the way around, it will help a bunch. And, where the wires go up through the floor, get a couple cans of spray foam to seal it, and, also spray where the plumber ran the pipes up. Best of luck to you.
Cheers

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Post By: Qtown1835 » Tue. Jan. 02, 2018 10:11 pm

CapeCoaler wrote:
Tue. Jan. 02, 2018 1:09 pm
That is why i recommended 4" of the foam insulation...
the condensing point will be inside the foam...
Where the moisture will never migrate to...
it should be closed cell foam board...
as the foam is the vapor barrier because vapor is not able to migrate thru the foam...
No moisture issue...
Must have missed where you said 4" of foam. Even still, if you place 4" of foam in the ceiling joists as a vapor barrier, where does the RH from the interior of the house go? Won't the moisture condense on the joist itself or in any air voids between the 4" of foam where air and migrate? Installing foam board is much different than installing spray urethane since spray foams acts as the air barrier and insulation.

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Post By: lincolnmania » Tue. Jan. 02, 2018 10:27 pm

i have been working on rim joist insulation down in the basement, found a roll of r-19 in the attic! my dad had about 1/3 of the rim joists insulated with foam. there is no insulation in the crawl space, none on the basement walls. house is at least 80 years old. the old part is 2x4 wall framing, 2x8 joists, 2x4 rafters.....it's all used lumber has plaster lath marks and nail holes and knob and tube holes. the sheathing is random width boards, theres tarpaper over that, then my dad put 6 mil plastic on the outside under the vinyl siding.
the siding is shot, i am going to put 1/2" foam board on the outside when i replace the siding.
if we didn't have so much stuff that needed storage i would seal out the attic staircase and blow in 12" of insulation from the other attic entrance. short of gutting the house and starting over, doing what i can to make the house better.
i don't need the 500 year house either! if i am lucky i got another 40 years left, that's all i need.

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Post By: CapeCoaler » Wed. Jan. 03, 2018 12:43 am

This is the link from the DIY in Freddy's place...
https://www.energyvanguard.com/blog/54110/You-Don ... r-Probably
most of the moisture comes from penetrations, not passing through the drywall...
Seal the penetrations with expanding foam, stops most of the moisture...
The floor is already plywood except last 2 feet...
two layers of 2" closed cell foam staggered and taped, minimal air flow expected...
I like the polyisocyanurate...

https://www.jm.com/content/dam/jm/global/en/build ... ced_DS.pdf

The condensation point is interior of the foam sandwich to which negligible moisture will travel...
The bottom layer will be warm and stay above condensing point...
So long as the bays are capped on the last 2 feet no air movement will be below the foam boards...
if the last 2 feet of open bay is not sealed with rigid foam board and sealed tight with expanding foam...
air will circulate under neath and negate any insulating value of the foam above...
bonus is the vermiculite is sealed in place and no wind will disturb the nasties held within...


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Post By: Qtown1835 » Wed. Jan. 03, 2018 8:17 am

CapeCoaler wrote:
Wed. Jan. 03, 2018 12:43 am
most of the moisture comes from penetrations, not passing through the drywall...

Seal the penetrations with expanding foam, stops most of the moisture...

The condensation point is interior of the foam sandwich to which negligible moisture will travel...

So long as the bays are capped on the last 2 feet no air movement will be below the foam boards...
if the last 2 feet of open bay is not sealed with rigid foam board and sealed tight with expanding foam...
air will circulate under neath and negate any insulating value of the foam above...
I think this is the bigger issue with trying to effectively 100% seal off an existing attic. If there are any holes or pathways for air to infiltrate the new "cap" of insulation, OP is in for a world of hurt. It has been said that a "leaky" house is far better than a "tight" house regarding structural longevity, why then would we try to work backwards and seal off an area that would create a potential failure in the insulation system?

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Post By: CapeCoaler » Wed. Jan. 03, 2018 11:03 am

It won't get "wet" if the condensation point is internal to closed cell foam board...
That is the point of putting down 2 layers to bring the total to 4"...
The closed cell insulation is almost vapor proof...
Nothing is '100%' vapor proof...
But it can be reduced to the point so it is irrelevant as far as condensation is concerned...
Think of it this way the bottom side of the foam will be 'semi-conditioned space'...
And the vermiculite will breathe back to the house to adjust with the seasonal humidity of the house...
In a perfect world it would just get spray foamed...
Encapsulating the vermiculite along with the associated asbestos and sealing the bay...
They do have DIY spray foam kits that are reasonably priced...
And that is the way i would go for the 2' perimeter space...
Any moisture that is in the vermiculite will just adjust with the interior house conditions...

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Post By: Qtown1835 » Fri. Jan. 05, 2018 11:29 am

Was doing some more digging and found this tidbit.
http://strunk-albert.com/wp-content/uploads/2014/ ... Attics.pdf

"Along with the air barrier at the ceiling line, a Class II vapor retarder should be installed
in Climate Zones 6 or higher (See Photo 4). Installation of Class I vapor retarders (vapor
barrier) can be installed in Climate Zone 6 or higher but is not recommended in other
climate zones because top-side condensation can occur during air conditioning season.
For example, if the outdoor air conditions are 90 degrees F 70% rh then the dewpoint is
79 degrees F. If the inside conditions are 75 degrees F and air permeates through the
fiberglass insulation it will condense on the attic side of the vapor barrier."

After all of this discussion i decided to take a look around in my attic since we have been having some extreme cold temps. To my dismay, i found that the plywood decking in the attic was trapping and condensing some moisture on the "warm side". My next project will be to remove the plywood decking and cover the balance of the attic in insulation. Im not surprised however, considering there is only maybe 3" of insulation under the decking. I was intrigued by the lack of vapor barrier suggested in the aforementioned source above, but it does make sense.

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Post By: brandonh98 » Sat. Jan. 06, 2018 5:30 pm

Thanks for all the replies everyone. I spent all day yesterday up in the attic foam sealing everything that penetrated the attic. There were massive holes where the plumber put drain vents though the attic and up through the roof. It was pretty obvious that a lot of the moisture was coming from these spots. Insulation was black and there was actually no frost on the sheeting in these areas because it was so warm.

I also installed a new bathroom fan yesterday. I believe the previous one was grossly undersized. When I would take a shower it was not uncommon for water to be running down the walls, even if the fan was on. I took a nice hot shower last night with the new fan and there wasn't even moisture on the mirror.

It was a lot of work but between these two things I'm hoping the moisture stays out of the attic. The test will be when this melts and (hopefully) dries out and wait for the next freeze.

Thanks again everyone for the replies. I'll keep you posted on any updates.

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Post By: CapeCoaler » Sun. Jan. 07, 2018 9:41 am

Thanks for the follow up...
Doing IT and running data cables...
I see what bad plumbers, electricians and even framers can bury...
Keep sealing the leaks and soon your moisture problems will be history...

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Post By: Rob R. » Sun. Jan. 07, 2018 10:47 am

Nice job. Fix the moisture and burn less coal at the same time.

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Post By: rberq » Sun. Jan. 07, 2018 11:05 am

brandonh98 wrote:
Mon. Jan. 01, 2018 2:20 pm
I fear that I will be tearing out all the attic insulation to seal for leaks and replacing it. I can image when this melts it’s going to be pretty wet up there.
That might be overkill. The guy who insulated my place said, flatly, moisture in the house is going to make its way to the attic. Period. Can’t completely avoid it. Seal up where practical, check that attic ventilation paths haven’t been blocked. And it does make sense that last summer’s changes somehow are involved, since it’s a new problem. But like Qtown said, be careful of making drastic changes that you don’t understand (and you probably don’t). You could go from the frying pan to the fire.


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