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General Forestry => Drying and Processing => Topic started by: Tree Dan on March 25, 2019, 03:34:41 PM

Title: Air space needed with spray foam?
Post by: Tree Dan on March 25, 2019, 03:34:41 PM
A dehumidification type kiln 20 x 8 x 8
If the roof is flat could this be foam sprayed, with no air space like a sloped roof?

Or even if the roof has a slope with a steel roof, could this be foam sprayed with no air space?

I think it can, but Im not a expert on this...what's your thoughts on this?

Thanks

Tree D
Title: Re: Air space needed with spray foam?
Post by: tacks Y on March 25, 2019, 03:48:58 PM
I would, air space would mean ventilation also. It should keep the ceiling from raining condensation. This being said I do not always work to code.
Title: Re: Air space needed with spray foam?
Post by: Southside on March 25, 2019, 05:57:43 PM
Make sure the foam is rated for the temperature it will be exposed to also. 
Title: Re: Air space needed with spray foam?
Post by: rjwoelk on March 25, 2019, 06:08:14 PM
When we did the cabin I sheeted the roof, covered it with water shield membrane. 
Strapped it then put my tin exterior roofing on.
Then the underside of the roof was spray foamed  with 4 inches.  This is called a cold roof. The attic is part of the interior of the cabin .
Title: Re: Air space needed with spray foam?
Post by: offrink on March 25, 2019, 06:47:40 PM
My brother sells buildings. His advice when I asked him about this exact thing, even if it is code, how will you replace that section if it ever gets damaged? You canít exactly remove the steel roof panel without destroying the insulation. 
Title: Re: Air space needed with spray foam?
Post by: Tom the Sawyer on March 25, 2019, 08:24:14 PM
I had a similar question when I had the metal roof replaced on my barn (hale damage claim).  The salesman's recommendation was to install vapor/condensation barrier under the new roof panels.  If I have spray foam done later, the roof can still be removed for replacement.  Otherwise, you have to replace the spray foam too, and that can be a big mess and quite expensive.
Title: Re: Air space needed with spray foam?
Post by: Mike W on March 25, 2019, 08:33:16 PM
x2 Tom the Sawyer, can be done without issue if there is a membrane installed below the metal or other roofing and the spray foam insulation, can be of any moisture barrier material like Tyvek, asphalt felt or plastic sheeting to give you an isolation barrier between the roofing structure and the insulation.  if ever needed the material can be removed and replaced or repaired without disturbing the spray in insulation.
Title: Re: Air space needed with spray foam?
Post by: Tree Dan on March 26, 2019, 02:45:23 PM
Thanks for the input guys...that's what I needed to hear.

I guess plastic on the walls in-between the foam and steel would be a good idea too,
just in case I drove the skid steer into the side walls ;D

Cheers

Tree D
Title: Re: Air space needed with spray foam?
Post by: jimbarry on March 27, 2019, 07:07:52 AM
I spray foamed the floors level to the floor joists because I put down a plank floor afterwards. The walls and ceilings I had sprayed full and enough to cover the studs.


(http://forestryforum.com/gallery/albums/userpics/20037/20181103-kilnbldg-sprayfoam.jpg?easyrotate_cache=1553684792)
 
Title: Re: Air space needed with spray foam?
Post by: woodshax on March 28, 2019, 08:35:45 AM
So.....I used to have a spray foam insulation company....and had to learn me all there is about the products and applications.    Never use .5 Lb open cell foam on a metal building....it is like a sponge.... Used closed cell 2lb foam.... it is a complete moisture barrier at 2 inches and that is all you should use in depth...it also adds 50% of the racking strength of a 5/8" plywood.... they use it in areas like Houston  and the foam roofs are intact after a hurricane and the building around them without it end up in the next county.   You could also use 3lb roofing foam... that they put on the exterior of building roofs to protect them from hail, water seal and give insulation......I would not worry about roof replacement.....it will outlast you....if it does not...you just cut out the section sheet on top and then refoam that section....it will be water tight if done right....... if you were doing the walls I would suggest skinning over the foam with metal sheets just as a protection against scorching....foam is just plastic and although it has about a 500 degree F cross over  (dont quote me on the exact temp)...it just makes sense......the roof....depending on the internal temp of the kiln should be fine