Batt insulation vs spray foam?

[cfk]

What's the general consensus here on using batt insulation in a pole shed vs having it spray foamed?

I haven't gotten actual numbers to put to the project yet, but the spray foam will obviously be significantly more expensive.. but is it worth it?

 

[Yankee2bbq]

Just had my shop spray foamed. I was debating between batt vs foam too. My builder highly recommended spray foam. I talked to others about what to do and everyone said spray foam is the way to go.
I believe its well worth it. My shop is sealed up tight.

 

[sz0k30]

One thing that spray does that batt does not do is solidify & windproof.

 

[Dumber than lumber]

Seems to be a Buy Once, Cry Once thing.

 

[cannuck]

I will try to remain reasonable and polite in responding, but it will be hard.

Glass or rock wool fiber batts are rated for their insulation value with ZERO air movement and perfectly dry. That, sadly, is a condition only possible in the test lab at manufacture. The only way you can get half-assed performance from insulating batts is with a full and effective vapour barrier. Now, in a house behind protective drywall, that IS possible (and the outer wrap used these days takes care air and moisture leakage and circulation from the outside of the envelope. IF you can do these things, you can achieve what is claimed for batt type wall or roof insulation. However, my experience with shop buildings is that you will be hard pressed to maintain that (my own home shop was done with 6" foil-backed glass fiber 38 years ago, but the foil backing has all failed and I need to remove it all and will replace with sprayed-in-place foam). BIG job!!!!!

When it comes to sprayed foam, however you need to know with certainty the characteristics of the foam being applied. Look at the table below and you can see that P/U foam can be open or closed cell. In my experience, very low density foam (i.e. lowest cost) tends to be open cell. You need to know you are getting closed cell from a reliable, honest and technically competent contractor.

Now, you are not exactly up here beside me where the Canadian National Research Council has established best practice for insulating an energy efficient building is an R value of 60 in the roof, 40 in the walls and I forget the value under the pad (assuming slab-on-grade construction). IIRC, the US NRC is somewhere around 50 roof, 40 wall for Iowa. To reach these values, a Canadian or US wall in perfectly done fiber batts would be 12" thick and a Canadian roof more like 18 vs. US under ideal conditions 15". You could reach the same values with CLOSED CELL PU 6" walls and 8 US or 10 Cdn roof. The big upside to sprayed foam is fantastic vapour barrier. Movement of air is exceedingly important to achieving target insulation values.

What I see most often is retrofits of 2x6 glass batt walls (R20) with 2" foil faced polyisocyanurate board on the outside (R16) and replacing glass batts in ceiling/attic with 6" of closed cell spray foam (still only R50).

I have been debating what to do in my next (last) shop and think the only way I can reach R60 on roof is with a built up roof of 2 layers of 4" foil back board. Want to build in MIPs, but nobody seems to make anything beyond 6" (that DOES give a workable R50).

Don't forget the underside of the pad. Our resident concrete guys will give their reccommendation, but mine would be 2" of PU board...NOT styrene (IMHO not stable enough and too easily absorbs water). I will be using PFCC (cellular, very light weight concrete) under my pad instead of plastic materials.

Yes, decent insulation is EXPENSIVE, but energy costs are going to go nowhere but up. I am not in the insulation business, but have a friend who is to do so reality checks with.

For those who really want to know, here is the NRC Energy Star programme information: https://www.nrcan.gc.ca/energy-effi...gy-starr-new-homes-standard-version-126/14178

Material	R-value/in	3 1/2"	5 1/4"	10"	12"	15"
Fiberglass (batt)	3.1 - 3.4	10.8 - 11.9	16.3 - 17.8	31.0 - 34.0	37.2 - 40.8	46.5 - 51.0
Fiberglass blown (attic)	2.2 - 4.3	7.7 - 15.0	11.5 - 22.6	22.0 - 43.0	26.4 - 51.6	33.0 - 64.5
Fiberglass blown (wall)	3.7 - 4.3	12.9 - 15.0	19.4 - 22.6	37.0 - 43.0	44.4 - 51.6	55.5 - 64.5
Mineral Wool (batt)	3.1 - 3.4	10.8 - 11.9	16.3 - 17.8	31.0 - 34.0	37.2 - 40.8	46.5 - 51.0
Mineral Wool blown (attic	3.1 - 4.0	10.8 - 14.0	16.3 - 21.0	31.0 - 40.0	37.2 - 48.0	46.5 - 60.0
Mineral Wool blown (wall)	3.1 - 4.0	10.8 - 14.0	16.3 - 21.0	31.0 - 40.0	37.2 - 48.0	46.5 - 60.0
Cellulose blown (attic)	3.2 - 3.7	11.2 - 12.9	16.8 - 15.0	32.0 - 37.0	38.4 - 44.4	48.0 - 55.5
Cellulose blown (wall)	3.8 - 3.9	13.3 - 13.6	19.9 - 20.8	38.0 - 39.0	45.6 - 46.8	57.0 - 58.5
Polystrene Board	3.8 - 5.0	13.3 - 17.5	19.9 - 26.2	38.0 - 50.0	45.6 - 60.0	57.0 - 75.0
Polyurethane Board	5.5 - 6.5	19.2 - 22.7	28.9 - 34.1	55.0 - 65.0	66.0 - 78.0	82.5 - 97.5
Polyisocyanurate (foil-faced)	5.6 - 8.0	18.2 - 28.0	29.4 - 42.0	56.0 - 80.0	67.2 - 96.0	84.0 - 120.0
Open Cell Spray Foam	3.5 - 3.6	12.2 - 12.6	18.4 - 18.9	35.0 - 36.0	42.0 - 43.2	52.5 - 54.0
Closed Cell Spray Foam	6.0 - 6.5	21.0 - 22.7	31.5 - 34.1	60.0 - 65.0	72.0 - 78.0	90.0 - 97.5

 

[Showkey]

The merits of each have been stated.
So………….Depends on your budget and is this your forever home (shop). Going to move for work is 3-7 years ? The insulation is value to you in energy saved ……..resale recovery $$$$ is not there.
Are your heating all the time ?
Are you cooling it ?
Ball park foam is going to 3-5 times the cost batt.
It can not be overstated……….foam installs can be screwed up. Pick the installer carefully for both. Batt can be DIY for a fraction of the cost.

 

[billconner]

The combination of the two is also common. an inch or two of spray foam on inside of exterior wall and then batts (or dense packed cellulose).

 

[theoldwizard1]

The combination of the two is also common. an inch or two of spray foam on inside of exterior wall and then batts (or dense packed cellulose).

Yes ! You see this more and more. 2" of spray foam and then fill the cavity with batts.

If you are planning on finishing the interior with something, you can hang skrim and blow in fiberglass or cellulose. Cheaper and faster than batts.

 

[theoldwizard1]

It can not be overstated……….foam installs can be screwed up. Pick the installer carefully for both. Batt can be DIY for a fraction of the cost.

Pole buildings are inherently have many air leaks even if you have used house wrap. Nothing seals a building like spray foam.

As said, "Buy once, cry once !"

 

[Showkey]

Pole buildings are inherently have many air leaks even if you have used house wrap. Nothing seals a building like spray foam.

As said, "Buy once, cry once !"

Agree……..but………That only works if you have budget ( aka money or resources) ……….if its not in the budget, you can’t buy it. The difference from $3000 to $10,000 can be significant for some…….so it‘s easy to spend other peoples money

Since foam is sold by the board foot:
That might make combo of foam and batt the winner ??????

 

[cfk]

I have been doing a little research and came across someone talking about how spray foam (specifically closed cell) should not be used in a post frame because when moisture gets behind the metal, the closed cell foam doesn't allow any air movement to dry out the girts..

Any thoughts on this?

 

[billconner]

Watched an R&R builders YouTube on this. They make a good case for not using spray foam in new construction.

In a closed wall - like sheathing and drywall - I think it's hard to beat dense packed cellulose.

 

[toyotadriver]

Polyiso also doesn’t have the same R value in cold temps as it does in hot temps.

My house is insulated with cellulose in the walls, foam sheets on the outside, and cellulose in the attic. It’s impressive how cheap it is to heat and cool.

 

[Treasure]

Watched an R&R builders YouTube on this. They make a good case for not using spray foam in new construction.

In a closed wall - like sheathing and drywall - I think it's hard to beat dense packed cellulose.

I thinks that's an old vid. He praises spray foam in his latest vids.

 

[65Goat]

^^^

 

[Dandy1008]

Yes ! You see this more and more. 2" of spray foam and then fill the cavity with batts.

If you are planning on finishing the interior with something, you can hang skrim and blow in fiberglass or cellulose. Cheaper and faster than batts.

If you fill walls with blown in insulation, does it not have a tendency to settle? I thought that was always an issue with blowing in the wall cavities. I am preparing for a new shop and home build and starting to research options. I am hoping to get the shell of the shop put up and do as much on the inside as possible myself to create sweat equity.

 

[mgbbob]

I will try to remain reasonable and polite in responding, but it will be hard.

Glass or rock wool fiber batts are rated for their insulation value with ZERO air movement and perfectly dry. That, sadly, is a condition only possible in the test lab at manufacture. The only way you can get half-assed performance from insulating batts is with a full and effective vapour barrier. Now, in a house behind protective drywall, that IS possible (and the outer wrap used these days takes care air and moisture leakage and circulation from the outside of the envelope. IF you can do these things, you can achieve what is claimed for batt type wall or roof insulation. However, my experience with shop buildings is that you will be hard pressed to maintain that (my own home shop was done with 6" foil-backed glass fiber 38 years ago, but the foil backing has all failed and I need to remove it all and will replace with sprayed-in-place foam). BIG job!!!!!

When it comes to sprayed foam, however you need to know with certainty the characteristics of the foam being applied. Look at the table below and you can see that P/U foam can be open or closed cell. In my experience, very low density foam (i.e. lowest cost) tends to be open cell. You need to know you are getting closed cell from a reliable, honest and technically competent contractor.

Now, you are not exactly up here beside me where the Canadian National Research Council has established best practice for insulating an energy efficient building is an R value of 60 in the roof, 40 in the walls and I forget the value under the pad (assuming slab-on-grade construction). IIRC, the US NRC is somewhere around 50 roof, 40 wall for Iowa. To reach these values, a Canadian or US wall in perfectly done fiber batts would be 12" thick and a Canadian roof more like 18 vs. US under ideal conditions 15". You could reach the same values with CLOSED CELL PU 6" walls and 8 US or 10 Cdn roof. The big upside to sprayed foam is fantastic vapour barrier. Movement of air is exceedingly important to achieving target insulation values.

What I see most often is retrofits of 2x6 glass batt walls (R20) with 2" foil faced polyisocyanurate board on the outside (R16) and replacing glass batts in ceiling/attic with 6" of closed cell spray foam (still only R50).

I have been debating what to do in my next (last) shop and think the only way I can reach R60 on roof is with a built up roof of 2 layers of 4" foil back board. Want to build in MIPs, but nobody seems to make anything beyond 6" (that DOES give a workable R50).

Don't forget the underside of the pad. Our resident concrete guys will give their reccommendation, but mine would be 2" of PU board...NOT styrene (IMHO not stable enough and too easily absorbs water). I will be using PFCC (cellular, very light weight concrete) under my pad instead of plastic materials.

Yes, decent insulation is EXPENSIVE, but energy costs are going to go nowhere but up. I am not in the insulation business, but have a friend who is to do so reality checks with.

For those who really want to know, here is the NRC Energy Star programme information: https://www.nrcan.gc.ca/energy-effi...gy-starr-new-homes-standard-version-126/14178

Material	R-value/in	3 1/2"	5 1/4"	10"	12"	15"
Fiberglass (batt)	3.1 - 3.4	10.8 - 11.9	16.3 - 17.8	31.0 - 34.0	37.2 - 40.8	46.5 - 51.0
Fiberglass blown (attic)	2.2 - 4.3	7.7 - 15.0	11.5 - 22.6	22.0 - 43.0	26.4 - 51.6	33.0 - 64.5
Fiberglass blown (wall)	3.7 - 4.3	12.9 - 15.0	19.4 - 22.6	37.0 - 43.0	44.4 - 51.6	55.5 - 64.5
Mineral Wool (batt)	3.1 - 3.4	10.8 - 11.9	16.3 - 17.8	31.0 - 34.0	37.2 - 40.8	46.5 - 51.0
Mineral Wool blown (attic	3.1 - 4.0	10.8 - 14.0	16.3 - 21.0	31.0 - 40.0	37.2 - 48.0	46.5 - 60.0
Mineral Wool blown (wall)	3.1 - 4.0	10.8 - 14.0	16.3 - 21.0	31.0 - 40.0	37.2 - 48.0	46.5 - 60.0
Cellulose blown (attic)	3.2 - 3.7	11.2 - 12.9	16.8 - 15.0	32.0 - 37.0	38.4 - 44.4	48.0 - 55.5
Cellulose blown (wall)	3.8 - 3.9	13.3 - 13.6	19.9 - 20.8	38.0 - 39.0	45.6 - 46.8	57.0 - 58.5
Polystrene Board	3.8 - 5.0	13.3 - 17.5	19.9 - 26.2	38.0 - 50.0	45.6 - 60.0	57.0 - 75.0
Polyurethane Board	5.5 - 6.5	19.2 - 22.7	28.9 - 34.1	55.0 - 65.0	66.0 - 78.0	82.5 - 97.5
Polyisocyanurate (foil-faced)	5.6 - 8.0	18.2 - 28.0	29.4 - 42.0	56.0 - 80.0	67.2 - 96.0	84.0 - 120.0
Open Cell Spray Foam	3.5 - 3.6	12.2 - 12.6	18.4 - 18.9	35.0 - 36.0	42.0 - 43.2	52.5 - 54.0
Closed Cell Spray Foam	6.0 - 6.5	21.0 - 22.7	31.5 - 34.1	60.0 - 65.0	72.0 - 78.0	90.0 - 97.5

VERY good information.

 

[mgbbob]

If budget allows do everything. For sure spray the roof and things up high. I am happy. with my 3 1/2" batts in the sidewalls. I started there before I found the spray foam. Spray foam has gotten pretty pricey with the oil situation so take a look.

 

[billconner]

If you fill walls with blown in insulation, does it not have a tendency to settle? I thought that was always an issue with blowing in the wall cavities. I am preparing for a new shop and home build and starting to research options. I am hoping to get the shell of the shop put up and do as much on the inside as possible myself to create sweat equity.

If dense packed - 3 pounds per cubic foot - it shouldn't settle.

 

[theoldwizard1]

If you fill walls with blown in insulation, does it not have a tendency to settle? I thought that was always an issue with blowing in the wall cavities. I am preparing for a new shop and home build and starting to research options. I am hoping to get the shell of the shop put up and do as much on the inside as possible myself to create sweat equity.

No first hand experience, but I would say, over several years, yes cellulose insulation will settle. Less with fiberglass.

Last time I checked there was not a huge difference between DIY blown in fiberglass vs cellulose

 

[theoldwizard1]

If budget allows do everything. For sure spray the roof and things up high. I am happy. with my 3 1/2" batts in the sidewalls. I started there before I found the spray foam. Spray foam has gotten pretty pricey with the oil situation so take a look.

Do you put house wrap on the outside ?

I see more and more DIY home builders using Zip System sheathing. No wrap required.

 

[kj_mustang]

Any good business decision should include cost benefit analysis. If you can afford the spray foam expense up front and you will be in the property long enough to recoup some of the differences in cost in saved utility expense, then it may be a good decision for you. I used closed cell spray foam on mine because I planned on this being my home until I die and we lived in the building at first so it really needed to be air and pest tight. It takes very little to heat and cool my building.

 

[Showkey]

What is the opportunity cost of going with spray foam? Does spending $10K versus $3K keep you from purchasing something else for $7K that has great importance?

It’s the total project cost as price creep up in each category or feature/upgrade …………thats how a garage/shop/shed build creeps up to $120-200/sqft

common creep items
4-5-6“ floor thickness $10k
HVAC $12k
full plumbing/bath/shower, septic/well connections. $10k
insulation and wall covering. $7k-$15k
100-200-400 amp service $5k
sub panel or new service. $3-6k
gutter/overhang and roof material. $5k
attic/office/mezzanine/loft. $2-20k

 

[bluedog225]

Fiberglass and cellulose is cheap. Really cheap. It works.

People can make money installing foam.

 

[cannuck]

I have been doing a little research and came across someone talking about how spray foam (specifically closed cell) should not be used in a post frame because when moisture gets behind the metal, the closed cell foam doesn't allow any air movement to dry out the girts..

Any thoughts on this?

To begin with, if you are going to use foam, you need to have it done as a completely sealed system - and pole barns especially difficult to do that. The foam IS the vapour barrier, but screwing around with something thin such a 1" sprayed by someone who may not have access to a full surface to connect the whole thing into a barrier - or some just isn't that good at it. If not a complete barrier, air and moisture are going to come through. If foam too thin the inner surface could become cold enough to condense moisture (thinking foam and batt now = someone trying to cheap out). Rule is simple: vapour barrier must be INSIDE of the location of the freeze zone ( the point along the temperature gradient from inside to outside where it hits zero C = 32 F).

Now, if from this business of moisture coming in can't dry out....uhhh....there is obviously movement since the water came IN - and the air can and will circulate through that same pathway. But again, as I said you need to design for the kind of insulation and conditions, and this is extremely hard to do well on a pole barn as the skin is usually stuck on by putting holes in the skin and the joints are likely to be a lot less than air (or water) tight as well.

If you want to do foam well, buy MIP (or IMPs = Insulated Metal Panels) where high quality, factory controlled closed cell foam connects the inner and outer skins of a STRUCTURAL metal panel. Most now are attached by clips on the inside skin. Smaller building can be done with IMPs as self framing.

The only way I would ever do foam combined with batts would be to build a stick frame 2x8 wall with staggered 2 x 4 or 2 x 6 studs, batt insulated from each side and with a 100% sealed vapour barrier. Then do 2" of isocyanurate foil backed board on the outside to make a thermal brake for the plates and corners.

 

[aggie113]

Glad I went with spray foam. Helped firm up the walls a great deal and damn near made the garage air tight. I would have liked to go more than 2" but the cost for that was 7k (30x40x18). Hopefully it pays off again when I get the minisplit installed and don't have to pay out the nose to keep the place comfy.

 

[Hobby_Man22]

One thing that spray does that batt does not do is solidify & windproof.

How does the fiberglass Batts not windproof when they put that silverback white covering on the outside of it that covers it. On a steel building the Batts are placed on top of the pulling, then the panels are putting and and it's pinched in place.

 

[sz0k30]

How does the fiberglass Batts not windproof when they put that silverback white covering on the outside of it that covers it. On a steel building the Batts are placed on top of the pulling, then the panels are putting and and it's pinched in place.

You answered your own question when you said they put silverback over the batts, so the silverback covering may do some windproofing, the batts DO NOT.

And the original poster never said anything about a steel building.

 

[Hobby_Man22]

You answered your own question when you said they put silverback over the batts, so the silverback covering may do some windproofing, the batts DO NOT.

And the original poster never said anything about a steel building.

Regardless the insulation is typically covered by something. Drywall, silverback covering, etc. Nobody puts up fiberglass insulation and just leaves it exposed.

 

[billconner]

How does the fiberglass Batts not windproof when they put that silverback white covering on the outside of it that covers it. On a steel building the Batts are placed on top of the pulling, then the panels are putting and and it's pinched in place.

I think you're talking about materials on inside that would stop air movement but - at least my take - is wind outside washing the fiberglass towards the exterior. I think it's desirable to prevent as much air movement near the fiberglass (or rockwool or cellulose or any of the "green" fuzzy materials used) to maximize its insulative capabilities.

 

[My Old Tools]

Are you going to heat and cool? How much? I have been extremely happy with plastic faced fiberglass roll insulation in my building. I heat and cool for pennies. I keep my building at thermostat at 47 unless I'm in there. I seldom see it drop low enough to run the unit. In summer I keep it about 80 unless I'm in there. That keeps the humidity down and I can pull it down further very quickly. More insulation or foam would be money wasted in my case.

 

[rburke65]

If your energy cost jump 100%, the foam will look like a great investment

 

[cfk]

A few things to add since I started this thread..

I do have house wrap on my shop, which I did for 2 reasons; 1) to help mitigate some drafts and wind through the steel, which should help the effectiveness of batt insulation, and 2) if I decide to spray foam, I don't stick the foam to the exterior metal, in case it ever needs replacing.

Lumberyard sells 8' wide rolls of unfaced fiberglass insulation.. It would be about $1600 to do all the walls in my 40x48x14. I've left a couple messages with the local spray foam guy and haven't been able to get a call back yet, but I'm guessing its going to be at least $6,000?

Are you going to heat and cool? How much? I have been extremely happy with plastic faced fiberglass roll insulation in my building. I heat and cool for pennies. I keep my building at thermostat at 47 unless I'm in there. I seldom see it drop low enough to run the unit. In summer I keep it about 80 unless I'm in there. That keeps the humidity down and I can pull it down further very quickly. More insulation or foam would be money wasted in my case.

I will likely keep the shop in the low to mid 40s using the radiant floor heat just to keep everything from freezing, and then use a hanging heater to heat it up to 65 when I want to work in there. No cooling (as of now anyways).


An additional question to add: If I do batt insulation, there is a solid sheet of insulation between the posts, but there would be a 4 1/2" wide void of insulation behind the posts - would sticking a piece of 1 1/2" foam board back there (or sticking some fiberglass insulation behind the posts) accomplish anything? I'm unsure if it would prevent much cold infiltration, or if the cold just goes around it?

 

[billconner]

I don't know if spray foam over the fibreglass will ever pay back. You do want the thickest batts that will fit. And I think either in space between metal and post would be beneficial. I'd use EPS and maybe anchor it with foam in a can. My 2 cents.

 

[Jakemedic]

Used 8’ wide insulation specifically made for post frame construction. Best investment I made to insure my shop was warm. Of course used vapor barrier and house wrap too. Minimal thermal break.

 

[Hobby_Man22]

They wanted 10k just to do my little 1500 sq ft steel building. What do you do when it leaks? All steel buildings leak at some point. Mine is 3 years old and it will leak if the rain and wind blows the correct direction.

 

[yeldogt]

I can tell you on a stick building there is just no comparison to the foam .... builders who have done both will tell you. I went to a high end development 20 years ago where the builder upgraded some of the insulation using different types and there was no question what was the best system .. closed foam.

I have never built a pole or metal building -- so I can't comment on best practice on how to foam

 

[billconner]

They wanted 10k just to do my little 1500 sq ft steel building. What do you do when it leaks? All steel buildings leak at some point. Mine is 3 years old and it will leak if the rain and wind blows the correct direction.

Isn't that the purpose of housewrap under it?

 

[Hobby_Man22]

Isn't that the purpose of housewrap under it?

How does it adhere to the panel if you have house wrap?

 

[billconner]

Sorry, I thought the 'what do you do when it leaks' was if it was fibreglass. I don't know what you do when water infiltrates metal siding with spray foam. I also don't know what it sticks to other than housewrap when the housewrap is installed under metal, as reported in other posts here (so the siding can be replaced when damaged.) I also dont know how you replace a damaged metal panel when sprayed in place.