Insulation which is more effective?

[Turkey Creek]

I am building another walk in cooler, probably 8' x 12'. Here is a question I am pondering. I am going to use foam board because it fits my design and needs the best. However, I am wondering would the R value be higher if I use 2 layers of foam board with the a closed air pocket between them or would the insulation R factor be higher with a solid wall of foam board? From my understanding air makes the best insulation as long as it is in a "sealed" void.

 

[MoBuckChaser]

Only if it is sealed does air work. I would not think you could get it sealed properly unless you make windows for a living.

 

[Jordan Selsor]

Chris
I dont know if this helps but when they spray foamed my house they started with closed cell (more dense) then they come over the top of it with open cell foam which contains more air within the foam. So I guess Im with you on the concept. I imagine with a heck of allot of silicon caulk you could seal the void between the two but my gut tells me the void is better to be filled with either blown or bat insulation. I think the insulation between the two foam boards would slow the hot/cold transfer from one side to the other...

 

[Turkey Creek]

Well I dont make windows for a living! :) If I did leave the gap I was thinking about sealing the seams with foam in a can. I dont want to use bat or blown in insulation because of it possibly gathering moisture and then mold growing, the room will be high humidity as well. I will use it for cold storage only part of the year.

 

[Bowsnbucks]

If the room is going to be high humidity, I'd staple on a layer of heavy plastic sheeting to keep the moisture from condensing on the foam panels as well. Any water makes insulation less efficient.

 

[John-W-WI]

Turkey Creek - sounds like you've built them before... but for those that don't know building walk-in coolers can be tricky. You need a vapor barrier on the INSIDE of a walk-in, not the outside of the wall like your home. If you don't, the walls will be water logged in no time and experience a complete failure. I believe commercial walk-ins have a barrier on the inside and outside meaning the wall is fully sealed.

-John

 

[birdog]

Turkey Creek - sounds like you've built them before... but for those that don't know building walk-in coolers can be tricky. You need a vapor barrier on the INSIDE of a walk-in, not the outside of the wall like your home. If you don't, the walls will be water logged in no time and experience a complete failure. I believe commercial walk-ins have a barrier on the inside and outside meaning the wall is fully sealed.

-John

I believe this is incorrect. It is my understanding that you want your vapor barrier on the outside of the wall. Condensation is pulled from the warm (outside) air towards the cold (inside) air. If your vapor barrier is on the inside of the wall like your home then the super cold air inside the cooler will pull moisture into the wall and cause mold.

storeitcold.com

 

[John-W-WI]

I stand corrected birdog (I bought my walk-in used, I didn't build it).

Where I went wrong was based on a conversation I had with a local builder who said someone was considering converting a regular building to a drive-in cooler. He told them not to as the walls would get water logged.

I have to be honest, I'm still confused (I'm slow many days, bear with me). Isn't TYPAR (the fabric stuff they put on the outside of a house) a vapor barrier? I assumed it was and that's why I gave the wrong info above. Sorry for any confusion I caused!

Thanks,

-John