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wannabe
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2,283 Posts
Discussion Starter · #1 ·
Some of you are familiar with my current project...we just finished weathering in the roof (continuous Grace I&W) of our SIP project.....sub-floors, framing etc... have been brutalized, everything is wet. (we did the best we could to keep the SIP panels dry)

We are not venting the roof, and are using closed cell spray foam directly to the roof sheathing. We're doing 2 phases....1 skim coat to seal the structure and dry it out, and final before drywall.

The insulation contractor wants us to warm up the lumber before he sprays, so we sealed off the rafter bays, window openings etc...had a temp. furnace installed and cranked the heat.

The real question coming up.........
 

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wannabe
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2,283 Posts
Discussion Starter · #2 ·
Now it's nice and toasty...PM is very concerned about the moisture level of the roof sheathing. He's afraid with the closed cell foam with the Grace will trap moisture and rot the sheathing.

We pretty much just rolled our eyes yesterday, but we went through the motions by getting a moisture meter (anyone know the proper moisture of OSB?...we don't)....anyway, after 12-15 hours of heat, we came in today and found a good amount of condensation on the bottom of the roof.

We pretty much determined the condensation is from the moisture evaporating from what's already inside the house.....

Typically, we wouldn't pay much attention to the moisture level of the framing, we just crank the heat until we're ready to hang board and keep an eye on the sub-floor.

PM wants us to wait to insulate (1st phase) until all levels of moisture are consistant....who knows how long that may take???

I guess the question is....what level of moisture is OK to foam over, and what's the best way to dry out a frame?....right now we have fans and the furnace running 'til atleast Tuesday when the Insulater is scheduled to spray?

Sorry for the long post/s....
 

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KemoSabe
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14,233 Posts
My first question is, what are you heating with? Propane will dump more humidity into the house. I believe Kerosene will as well. I'd suggest dehumidifiers if you want to pull the moisture level down.
 

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wannabe
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2,283 Posts
Discussion Starter · #5 ·
My first question is, what are you heating with? Propane will dump more humidity into the house. I believe Kerosene will as well. I'd suggest dehumidifiers if you want to pull the moisture level down.
We were using propane until our gas furnace was installed. We still were using the heaters for ourselves, but now it's the weekend.....The furnace is running as we speak, along with fans (no propane) and nothing will change for 72 hours....A lot will be riding on the conditions Tuesday.
 

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KemoSabe
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14,233 Posts
We were using propane until our gas furnace was installed. We still were using the heaters for ourselves, but now it's the weekend.....The furnace is running as we speak, along with fans (no propane) and nothing will change for 72 hours....A lot will be riding on the conditions Tuesday.
As long as the air is stirring and the unit is vented to the exterior, at least you won't be adding moisture to the air and it will eventually dry out, but I would consider dehumidifying as well to speed the drying time.:thumbsup:
 

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wannabe
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2,283 Posts
Discussion Starter · #8 · (Edited)
Thanks!....you're starting to narrow down my questions, I wasn't sure what to ask at first...

We're only spraying the roof system....would you be concerned about the roof sheathing not drying, or rotting if we sprayed before it reached the optimum moisture level?

IMO, as long as we get the roof to stop condensating we should be okay to insulate (partially)....waiting until the roof is the same as the subfloor for hardwood seems completely ridiculous....EDIT(unnecessary)
 

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KemoSabe
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14,233 Posts
I think I'd wait to get it down to where the roof deck is giving readings that the insulation contractor is comfortable with for spraying. I don't know much about the Grace I&W product or spray-foam insulation, so I can only guess the outcome of applying foam in less than suitable conditions. If it was felt on the roof and the sheathing was spaced, I'd be more inclined to push the issue with the IC, but with I&W, trapped moisture will definitely cause problems, so I would value his professional opinion.:thumbsup:
 

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topsail's trimcat
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5,026 Posts
lots of heat being electric, a few dehumidifiers and a few very large fans, keep the air moving so that the building will dry ouit quicker and reduce the chance of mold
 

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Registered
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3,951 Posts
OSB isn't very good for letting water vapor through, it's technically not a vapor barrier, vapor passes through it just not very much. That's what Zip System sheathing panels are for, they allow more water vapor to pass through than OSB allows. That's probably why you're seeing condensation on the OSB, if the house was wet then that partial vapor barrier in OSB will catch some of that condensation.

I don't think it's a big deal, just get a dehumidifier in there and give it time to dry out. And I believe 15% moisture or lower is good for framing, I am not sure though.
 

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Contractor
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4,733 Posts
12% would be a real nice number, 13-14% may be more realistic, but I would be concerned about making a high moisture sandwich: with Grace on one side and foam on the other, the only point for moisture to escape would be the ends (eaves). If it's open cell (I'm not knowledgable enough on this...) the moisture may be able to escape-someone correct me.

I wonder if you'll need to get the snow off the roof to help w/ the condensation issue (?)
 

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Capra Aegagrus
Remodeler
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24,799 Posts
I wonder if you'll need to get the snow off the roof to help w/ the condensation issue (?)
With the current cold and windy weather, I'd think snow on the roof would actually help keep it a bit warmer.

WNY, like many I have no experience with your particular scenario. But considering what you have riding on this, I'd definitely want the insulation guy to be happy (and taking the responsibility) with the moisture level.
 

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wannabe
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2,283 Posts
Discussion Starter · #14 ·
Thanks for the input!

The foreman is going in Mon. to asses the situation, I'm guessing we'll probably put off insulation for another week and bring in a dehumidifier.

One of the problems we were having was getting an accurate reading from the meter....Knowing what % moisture we needed didn't help. We had to program 'species', 'temperature'....(neither I nor the Foreman really knows how to use a moisture meter:sad:)

My best guess was to set the meter for SPF, and we guessed the temperature.....yesterday afternoon the air temp we figured indoors was 45*. we were looking for a constant to compare to, so we probed a recent delivery of 7/16....6, Then we checked the sip sheathing, 26, then the framing, 18, the roof deck was 36, and the subfloor @the entry was 76 LOL....each of which we guessed the temperature.

We generally only use a meter for the hardwood flooring that has been acclimating for a couple weeks in a dry house at 60-65*...

Any advice as to how we should calibrate the meter to actually understand what the differences in moisture content is in our building materials?
 

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Capra Aegagrus
Remodeler
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24,799 Posts
As I said, you're in a situation I haven't had to deal with (thenk yew!). But it seems obvious that your first step in "calibrating" is to know for sure what temperatures you're dealing with. That I could do--I always carry a $10 digital thermometer so I can tell just how miserable I am. :laughing:

Sorry I can't help with the meter, but if your WAG method is anywhere near accurate, 6x the moisture in a recent delivery does sound like you have some serious drying to do. :sad:
 

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Curmudgeon
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11,706 Posts
That Grace sounds like
a real problem for you.
You have effectively put
a vapor barrier on the wrong side
of the OSB, and saturated
the other side with condensate.
I would want to give it as long
as it takes to come down to 12-14%.
Once you spray the closed cell
with the Grace on top there is
no where for the water to go.....
 

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Maker of fine kindling
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6,199 Posts
When you get the dehumidifierS working you will be amazed how much water you haul out of that house.

I'll start the pool at 32 gallons.
 

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KemoSabe
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14,233 Posts
When you get the dehumidifierS working you will be amazed how much water you haul out of that house.

I'll start the pool at 32 gallons.
I say 25:thumbsup:
 

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Registered
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2,254 Posts
Oh don't we love winter construction in the North.......:rolleyes:
We've used closed cell PU foam with many of our projects.
I wouldn't try to guess on this one.

If you have a fire and water damage restoration outfit nearby, I would call on them to set you up with the proper equipment to dry out that roof.

They do it all the time and have calibrated moisture meters so they can assure you and the insulators that the foam can be applied without causing future damage to the structure.

Be safe with this one:thumbsup:
 

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KemoSabe
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14,233 Posts
Oh don't we love winter construction in the North.......:rolleyes:
We've used closed cell PU foam with many of our projects.
I wouldn't try to guess on this one.

If you have a fire and water damage restoration outfit nearby, I would call on them to set you up with the proper equipment to dry out that roof.

They do it all the time and have calibrated moisture meters so they can assure you and the insulators that the foam can be applied without causing future damage to the structure.

Be safe with this one:thumbsup:
That's a good eye deer:thumbsup:
 
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