Insulation Gap OK? beteen int. wall and insulation?

[spam4us]

My pole building has 5-1/4 inch poles. I already have 4-1/2 inch rigid foam sheets I want to put in the walls of my pole building. I would put the foam against the exterior girts, then the 4-1/2 inch foam then put interior girts up and cover it up with OSB. This would leave an air gap of about 3/4 of an inch between the rigid foam and the interior girts and a total 2-1/4 inch air gap from the foam to the osb.(3/4 air gap + 1-1/2 inch for the girt). The wall would look like this.

(Exterior Metal) - (exterior girt) - (4-1/2" foam) - (3/4" air gap) - (1-1/2 interior girt) - (OSB)

Is this ok to have an air gap like this on the interior side or should I take another approach?

I already have the foam.
Thanks

 

[rieferman]

Air gaps are common in pole barn construction because the girts create a space between siding (or interior wall surface) and the insulation. Dead air is a good for your total R-value as it helps combat thermal bridging and this is considered a benefit of post-frame construction.

In other words, your approach will work well.

An interesting article that touches on this topic

 

[Elginz]

Bays are not required to be filled, just to meet the "R" value. An air space is fine, just as you suggest. I would see that the edges of the foam is sealed. I have seen the foam sheets foamed in place to make an air tight seal.

 

[Rookie2]

Bays are not required to be filled, just to meet the "R" value. An air space is fine, just as you suggest. I would see that the edges of the foam is sealed. I have seen the foam sheets foamed in place to make an air tight seal.

Yes I agree ! You can not believe how much air will blow in around those outside sheetmetal panels. I used house wrap. Def. make them as air tight as you can.

 

[spam4us]

Thanks to everyone for the replies. I'm also thinking of doing the same setup but reducing the insulation in the walls to 2-1/2 inch thick foam sheets. These sheets are rated about r-12. (That way I would have enough to do the ceiling.) The setup would look like this.
(Exterior Metal) - (exterior girt) - (2-1/2" foam) - (2-3/4" air gap) - (1-1/2 interior girt) - (OSB)

If I go this route, would the air gap of 2-3/4 plus the 1-1/2" for the interior girt be too large? Would it be better to put the foam panels closer to the interior girts or just place them against the exterior girts.

Thanks

 

[bmxdad]

Curious . .I too have 4x6 beams and used 4" R-13 WMP-50. This is leaving me about a 2" air gap between the batting and the inside of the metal siding.

This is good right? Inside is sealed with the WMP sealing tape, so no air gaps. Person I bought the insulation said the air gap is a must have on pole buildings. His explination made alot of sense, but sometimes I wonder.

 

[larry4406]

The problem with air gaps is that usually the wall or floor cavity is not air tight. This allows air movement within, thus convective currents, which may result in cold walls/floors. The linked article makes the statement "Air films are layers of air that are assumed to be static on each side of a building envelope.." which is rarely the case.

Although I don't build pole barns, the houses my company builds, we always fill the wall/floor cavity 100%, even if that exceeds the R-value requirement.

Personally, I would fill the cavities full, and air seal properly.

Good luck.

 

[Aldershot]

Thats what I did on my pole-barn ever spot I could I put insulation than used a 6 mm vapour Barrier I have r 40 it's a bit over kill but I can heat it with a candle stick

Sent from my iPhone using Tapatalk

 

[Jlbc212]

It's not the material, fiberglass, cellulose or foam, that insulates; it's the trapped air that provides insulation. For instance, if fiberglass insulation that's 6" thick is crammed into a wall space that is only 3-1/2" deep, much of the insulating value is lost. As others have suggested, any air space between the wall or ceiling layers should be "dead" air space, tight enough so that there is no air movement.