closed cell foam/humidity/pole barn roof

[lowell66dart]

I am getting ready to pull the trigger on a 40x80 Robilt polebarn. I am going to have a metal ceiling in it and need to address the insulation before that ceiling goes up. I want to spray the underside of the roof. The walls will have bookshelf girts so I will probably batt them, maybe. I called a local spray foam only contractor (15 years doing foam) and he recommended open cell. I just wanted to do an inch but he said it's hard to do less than 2 inches and 3 would be the most cost effective for the results that you achieve. He quoted me $4200 for 3 inches. I know from searching here that almost everyone says go closed cell but with the humidity here in Louisiana I am worried about trapping moisture between the roof and foam and ending up with wood rot. My next step is to check out buidings he has done locally and sreak with the owners. Any experience out there with similar conditions?

 

[willymakeit]

I would do closed cell. We did a roof with about 3'' and havent had moisture problems yet, its been about 5 years.
Ive worked in La. and understand your concerns. As you suggested check some local projects with time on them.
I would think the open cell would let more moisture to acess your deck where closed is sealed off and remains that way. I would definetly check with your local contractors.

 

[lowell66dart]

I think closed cell can work IF it really is a vapor barrier. Some say it isn't and if thats true then I will have condensation between the metal and wood and problems.

The open cell in my mind would allow some air movement and eventually dry out.

Performance wise I think closed cell works better but open cell is more forgiving but this is just my internet educated opinion

 

[willymakeit]

Have you researched it on the internet yet? I know its not the same as knowing or seeing the reults first hand.
I will look into it, since Im curious myself. Ive wondered about using closed cell on my crawlspace walls to help with temps.

 

[willymakeit]

Ok in a nutshell open cell is not recommended against wood roof decking because of allowing moisture migration, which would be the same for metal decking.
Closed cell is heavier [ higher density] and has a gas inside it that retards moisture migration and increases the r value. Closed cell also has a higher perm rating and works as a adhesive in helping hold the roof membrane together.
Open cell has a higher sound rating and is not recommended for exterior applications.
I googled open cell vs.closed cell and found a lot of info.
My vote is closed cell since there is a low moisture migration. Any moisture that is present at time of application wouldnt pose a problem.

 

[lowell66dart]

Found this.......

install spray foam insulation in California and Nevada. We install open cell in metal buildings and on the underside of metal roofs on a regular basis. A radiant barrier only works if there is a airspace of an inch or so. Otherwise it is just more metal to radiate heat. If the spray foam is applied directly to the underside of the roof the use of a radiant barrier or air space is not recommended. Open cell spray foam is an air barrier and does not allow moisture laden air to pass through it. For condensation to occur you need to have moisture reach an area that is equal to or below the dew point. The underside of the spray foam never reaches the dew point and since the moisture can not reach the area above the insulation you do not have moisture problems.

We actually apply open cell spray foam to the underside of metal barns just to stop the condensation. The balance of the barn is nor insulated and quite often does not even have full walls. It works great.

We do this in all areas of California and Nevada and in all weather zones from the coast to the mountains

 

[willymakeit]

I would still look at info for your area,they are in a low humidity area.
I about sweated everything that was in me out in La. Worst humidity I was ever in.Love the food tho.
I lived in Ca. at one time and their moisture levels are not even close to yours even on the coast.
Check some of your local commercial warehouses or shops that are using spray foam.
I work in the const. industry but every area of the U.S. is different in climate and soil conditions so I usally defer to the locals who live with it every day.
Hope all of this helps.

 

[lowell66dart]

Yep, I think the best route is to see what I can locally. I was hoping there would be someone local on here with some experience. I have only had the time to call one contractor so I am curious about the price also.

 

[nehog]

... and he recommended open cell. ...

Why did he recommend open cell? I'm sure he had a reason, whether to lower costs, lessen the potential for moisture damage, or something.

 

[buddyboy]

Open cell spray foam is an air barrier and does not allow moisture laden air to pass through it.

i see a lot of people thinking the moisture 'moves' into an area, so you need to keep it out.

take a clear bottle.

make sure it's dry inside... (don't have to bake it or anything) just make sure it's dry.

put a cap on the bottle and make sure it's air tight

put it in the hot sun for a few hours

how'd all that moisture laden air get in the bottle?

moisture is already in the air.

I'm thinking getting rid of air space is like getting rid of moisture.

good luck

 

[lowell66dart]

Found another local guy. 13 years in the business. BASF product, 2lb. density closed cell, 1 1/2 to 2" thick. $5600.

 

[djkeev]

Yep, I think the best route is to see what I can locally. I was hoping there would be someone local on here with some experience........

How in God's name do you expect local feedback when you have not disclosed where you are? If you would mention a major local town or city but even a State, it would help you in your quest for local information.



Dave

 

[lowell66dart]

Hi Dave.

First post did mention Louisiana but your right I should be a little more specific. South Louisiana. About midway between Baton Rouge and New Orleans right off I-10.