Peanut-brittle method for walls of a pole barn?
Looking to find out if I should remove the current 3/4″ expanded poly styrene insulation from between the interior girting of my pole barn before spraying Dow froth-pak @1″ thick. So, the girting actually has 2 types of foam board used inside the barn, one type is 1″ foil faced poly iso which makes up about 1/8 of the overall and the other 7/8 is 3/4″ foil faced expanded polystyrene. Can I apply this froth pack insulation over all the existing foam (both types), will it cause any product adhesion issues? Or should it all be removed before spraying? Also wondering if since spraying the walls with froth pak should I do the bottom side of the roof. It is a well vented pole barn in northern Michigan, and I do intend on heating and cooling (when applicable) year round.
Any comment or questions would be greatly appreciated as I’m quite the novice homeowner with grand ideas of insulation. I am confident I can spray the froth pak insulation, as I’m an automotive paint tech by trade and have plenty of experience applying even coats of a wide variety of automotive finishes.
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Replies
TKO,
The short answer is that you can leave the rigid foam in place and spray over it.
There are other questions here that are worth addressing here, though.
1. "Pole barn" can mean a lot of things. Are these natural round poles (peeled logs) or milled posts?
2. Does the building have sheathing?
3. What material will you use on the interior to protect the sprayed foam and limit the fire hazard?
4. What R-value are you aiming for? It might make sense to thicken up the rigid foam before you install spray foam.
5. Does the barn have a level ceiling? Or do you intend to insulate the sloped roof assembly?
6. Have you compared the cost of hiring a spray foam contractor to buying lots of Froth-Pak kits?
-- Martin Holladay
1. Pole barn was built approx. 15yrs ago and has milled posts as well as some treated lumber.
2. Sheathing? Yes, from what I can tell is 1/2" Osb with tyvek house wrap and vinyl siding.
3. The foam is class A foam with a fire retardant, I had planned on using 5/8 Osb to seal/cover the sprayfoam and to give me the ability to mount tools and cabinets where I see fit.
4. I was hoping to get close to r-20 in the walls. Does that sound like enough?
5. Their is no ceiling there yet... only the 6-12 sloped roof which I was thinking to spray foam...your thoughts?
6. No money is kinda tight around here and I have no plans of using contractors. I wanna do this myself!
Thanks for the response Martin!
TKO,
1. You told us that you plan to cover the 1-inch thick rigid foam with 1 inch of spray foam. If you do that, you won't have R-20. You'll have about R-11. So adding more rigid foam would be a good idea.
2. If you want to insulate your sloped roof assembly, you don't have to use spray foam. (Spray foam is usually an expensive way to insulate.) To learn about all the ways to insulate a sloped roof, see this article: How to Build an Insulated Cathedral Ceiling.
3. You wrote, "Money is kinda tight around here." That is why I urge you to compare the cost of hiring a spray foam contractor with the cost of buying lots of Froth-Pak kits. For a large job like yours, the spray foam contractor will be cheaper.
-- Martin Holladay