# rigid insulation or fiberglass???



## chopper6322 (Oct 17, 2011)

So I am finally getting around to insulating my shop and am curious as to which route i should go with money being the biggest factor. I have a metal building with 2×4 framing in South Texas where it gets extremely hot in the summer. i plan to finish it with 7/16" OSB but am not sure if i want the R-13 Fiberglass insulation for 2×4 walls, or if the 1/4 inch rigid foam would give me good enough results. I have a small air conditioner and as of right now it doesn't seem to drop the temprature at all in the shop. I guess my goal would be to drop it maybe from 100 degrees outside to 80ish in the shop. Any input would be great, thanks a lot.


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## a1Jim (Aug 9, 2008)

If you have the budget a spray on foam would give you the best insulation and stop a lot of air infiltration, of course this is done by a insulation contractor. If your budget won't allow that then use high density fiberglass R15 for walls and blown in in the attic (if you have one)or R30 batts in the roof. you can buy expanding foam to fill any holes you might have.


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## Oldtool (May 27, 2012)

Chopper,

I'm no expert, but I found this web site that may help in your decisions:
http://web.ornl.gov/sci/roofs+walls/insulation/ins_02.html


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## Dez (Mar 28, 2007)

I agree with a1Jim! They do have do-it-yourself kits in some areas.


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## crank49 (Apr 7, 2010)

Chopper, you asked if R13 fiberglass would work or if 1/4" rigid foam would be OK.??
1/4" rigid foam would have less than an R value of 1 so are you planning to put in 12 layers of the foam? 
That's how much you would need to equal the fiberglass.

I have heard that having a skim coat of spray in foam and then putting the 3" fiberglass batts in would give a good wall for not too much more than just the standard fiberglass.

But in Texas I'd think you want at least a full fiberglass insulated wall and as much as you can afford in the roof. More the better.


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## chopper6322 (Oct 17, 2011)

crank- I miss typed, and meant 3/4" but yes i see your point i would still need 4 sheets to equal the R value of fiberglass. Thanks for the info guys looks like fiberglass it'll be  Another question i have, and there may not be a simple answer, but which side do i want the paper facing?


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## DrDirt (Feb 26, 2008)

No such thing as too much insulation…. it would be like owning too many clamps.


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## DrDirt (Feb 26, 2008)

No such thing as too much insulation…. it would be like owning too many clamps.


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## Arminius (Dec 27, 2007)

A bit puzzled by the comparison - EPS board is R5 per inch of thickness, R14 fiberglas is around 3.5 inches thick. EPS board is a little more expensive on a per R-unit basis, but it is a lot easier to airseal. A wall with fiberglas insulation will always be a little thicker, because any sort of compression on the insulation compromises effectiveness.


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## Gene01 (Jan 5, 2009)

Maybe not in your budget but foil backed fiberglass is what I'd recommend. It's designed to reflect heat back into the room. But, just put the foil facing the exterior wall to reflect the heat out. 
Foil backed insulation can be dangerous if ever an electrical wire shorts across it. Not much of a concern if The foil is tight against the exterior wall. 
I went with R16 in the walls and R32 IIRC, in the ceiling. Here in AZ, the shop stays tolerably cool with no A/C.
My exterior walls are stucco over plywood and the roof is Pro Panel, a metal roofing.


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## Dark_Lightning (Nov 20, 2009)

The paper faces the side with the least moisture, which you will have to figure out. How is your shed designed? You can use a radiant barrier product if you have the right ventilation scheme, and save a pile of money. I have radiant barrier insulation in the roof of my house, and it paid for itself in less than two years. The foil backed foam has a similar effect on insulation. The heat rejection from the foil may exceed the insulation value of the foam in the right application.


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## Grandpa (Jan 28, 2011)

Fiberglass with the paper side to the inside. I live in SW Oklahoma and believe this is what you want. They make some stuff today that is better and still designed for 3-1/2 inch walls. Get that. You want about 16 to 18 inches in the attic. They call it the point of diminishing returns. You reach a point where you can add 6 inches and not see it on the utility bill so there is a possibility of too much insulation. A lot is good but too much does no more good than a lot. Ventilation is important in your attic also but you didn't ask about that.


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## chopper6322 (Oct 17, 2011)

My shop has a barn style roof and so there is no attic and i haven't thought about ventilation at all, no soffets or anything, I suppose maybe there is more to this than i thought  maybe i need to put an attic in and install some roof vents? will that do any good without airflow from the bottom of the attic as well?


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## Dark_Lightning (Nov 20, 2009)

2X4 only gives R-11 at the roof. I bet for your area the recommended insulation is around R-30. I'm in So Cal and that's what is recommended here (building code required for homes). In your case I'd recommend foam, since 3.5 inches is about R-21. Stuff it in the bays between rafters and nail light straps across them if they don't have nailing strips of some sort around the perimeter.


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## Gene01 (Jan 5, 2009)

A ceiling at 8-10' might be wise. Especially if you want to insulate it. There are numerous ways to vent an attic. 
Static vents at each end, electric fan vents at one or both ends, a "whole house" fan in the ceiling with static vents in the ends, or one or more of those globular like roof vents that spin as the attic heats up.
The main idea is to prevent heat build up in the attic which will transfer to the space below. 
We have the "whole house" fan in our home. We open a few windows and run it a 10 or 15 minutes before going to bed so it pulls in the cooler night air and cools the house (at least those rooms with the open windows) and it cools the attic. Mine is controlled by a wall switch only. One could put it on a timer or use a thermostatically controlled switch.


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## Grandpa (Jan 28, 2011)

The best system is ridge vents on the ridge. This has no moving parts or bearings to wear out. It is at the apex of the roof. remove the ridge cap if you have composition shingles. cut an inch off the decking on each side of the ridge pole then put on the cap. Get the kind that comes in 4 ft. sections. Put on a new ridge cap. Go to the lower edge of the roof and decide where the insulation will no longer touch the decking. Install "turtles" there to all air to circulate in. The system should draft from bottom to top like a chimney. If you use gable vents with the ridge cap it will circulate up there and never exchange the air below. The insulation needs to be kept dry (and the structure too). I would consider installing some joists like a scissor truss would offer. This can be stick built. Then install a ceiling on that. That will do as much good as the insulation since you don't have that barrier. In a home you figure 1 sq ft of open ventilation for every 150 sq ft of attic floor. You divide that in half and put half of it near the ridge and half near the bottom of the attic or in the soffit area. By installing the joists you also lower the insulation away from the roof and decking. You will like that better in 15 years. The insulation can trap moisture and ruin the decking. You want to keep the attic for storage if you can build it strong enough. by putting in the scissors you have moved the insulation away from the wall and still kept most of the space open for storage. By using a whole house or attic fan, you only cool the building when the fan is on. If that is at bed time or the end of the day then the heat is built up for all the afternoon sun shining on the roof all afternoon. The turbine system works but they have only 113 sq inches of opening for a 12 diameter opening. Takes a lot of them if you need 2 or 3 feet. BTW the wind turns them and not the heat. The air would have to flow out at about 5 mph per hour to spin them from heat. In my area the wind wears the bearings out in a couple of years. If you choose to use those be sure the base is vertical. Those that lean out of in have a short bearing life since the bearings are not designed for a side load. Sorry this is so long but I inspect homes and I see a lot of ways to do thing wrong or poorly. I also see a lot of ruined homes. Our thinking has changed drastically since we build better homes today than those from the 1920's. That is an old house in my part of the country.


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## craftsman on the lake (Dec 27, 2008)

Here in Maine we do insulation! The fiberglass will be much less expensive. The white foam stuff is cheap but doesn't insulate much. The denser pink and blue sheets are pretty good but pricy. Just look at the cost compared to the R value. The paper faces the inside, the moisture side. It's also a good idea if you use fiberglass to put up a sheet of plastic on the inside but it isn't mandatory. Never put plastic or the facing on the outside wall unless you want water condensing and dripping inside the walls.

Fiberglass is good stuff and will give you more bang for your buck. It also seals edges better than the foam stuff and you can use it to stuff in gaps where windows and doors are.


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## Grandpa (Jan 28, 2011)

What Craftsman said


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## chopper6322 (Oct 17, 2011)

Wow, I love the detailed information, thanks so much guys, you probably just saved me lots of headaches in the future


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## changeoffocus (Dec 21, 2013)

chopper,
It's not just about wall insulation it's the entire building envelope. for instance you can put R19 in the walls but if you have 25% of your exterior wall surface in single pane glass, you are going in the wind. 
If you get the entire envelop right you can heat and cool dirt cheap. Oh yeah, until you turn on an exhaust fan or a vented dust collector. 
Craftsman on the lake covers it very well in his reply.


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## woodchuckerNJ (Dec 4, 2013)

Spray on foam, look online for do it yourself kits.
The spray on is the best bang for the buck.
Wish I had done my shop with it. I did it Fiberglass R13 and it's useless.


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## teejk (Jan 19, 2011)

Full circle with a topic that earned me "ignore" status for many here (shoot the messenger). I was told by a pro that "spray foam" and "metal buildings" are a bad combination. Sit in a metal building sometime and listen to it expand and contract (you'll hear it). The issue seems to be with creating crevices where moisture can get into and lead to premature rusting of the metal.


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## Whiskers (Nov 6, 2012)

Noone mentioned this, but I was told at one time that if you want to put the blown in insulation into a attic area, if you buy a certain amount from one of the big box places they will rent you a blowing machine for free to install it. Just a FYI.


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## woodchuckerNJ (Dec 4, 2013)

teejk, I wonder what experience the pro had. There are so many pro's who really know diddly squat.

See Ron Walters videos, he's in Canada, and uses a metal building with spray foam.. he goes over the build..
woodgears.ca 
Search for foam insulation Ron Walters https://www.youtube.com/user/RonaldWalters47/videos
good videos.


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## teejk (Jan 19, 2011)

Jeff, the "pro" was somebody that has been selling steel buildings for years. I guess his experience comes from processing warranty claims. Canada seems to be a little more advanced on spray foam and perhaps they have a more flexible product that will expand and contract with the building. Our stuff is pretty ridgid once it cures.

As an aside, the people that construct steel buildings seem to learn a lot from warranty claims! The guy that built mine employed some rather interesting techniques because of warranty claims, one of which was using a punch on a stack of panels to mark the screw locations. Measure and mark the top sheet, then punch hard enough to dent several sheets below it. When the dents start getting faint, add new sheets below and punch again. He only has to measure one time and is assured of a perfect horizontal screw line (self-tapping pole barn screws) around the building. He learned to do that because drilling the holes caused premature rusting at the screw locations.


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## kelvancra (May 4, 2010)

The facing of the insulation changes with climate.

Putting on a metal roof over ply or OSB, you must have tar paper to deal with the condensation that will form. Obviously, a vapor barrier may be a good idea any time you are dealing with metal.

Notice your stainless kitchen sink, for example, That black or white on the bottom is there for a reason - to reduce condensation. As such, it may be a coat of paint on the inside, before you seal things up, may be a good idea.

When painting out of the way areas that will never be seen, you don't have to buy expensive paint. For example, I painted a rental by buying miss-mixes of top quality paint for around five a gallon. When the pastels were mixed in a fifty-five gallon drum, I got a nice, light gray.

A lot of housing construction has vapor barrier, of sorts, on both sides. For example, you put tar paper or Tyvex on the outside, then install insulation with a vapor barrier an cover that with rock, then seal it with paint. All this retards the movement of air into the walls from either direction.

I've done a few remodels and get annoyed at the lack of infrared resistance of the newer rolls. for that reason, I stopped at the local Cash and Carry restaurant supply and bought the industrial rolls of aluminum foil. One roll will do around a couple hundred square feet.

I cut cardboard strips, then staple through the strips to hold the aluminum about 1/4" to 1/2" off the wall. This creates another air space, so the foil will not conduct heat, in addition to reflecting it back.

Try a test piece of foil on a ceiling, both with it touching and with an air gap, and you'll note a huge difference in heat transfer.

The remodel I was working on had a bathroom right off a meeting hall. Not a place someone might want to find his or her self contemplating the wisdom of the burrito they just had. I started looking into sound transfer. I knew sound was air movement and could be transferred by vibration (e.g., moving siding and walls or windows, or speakers), but was also caused by air movement through gaps and things.

Since caulk is cheap when you buy it by the case, I caulked all the 2x's to the sheathing before I installed the insulation or rock in a kitchen, which had one outside door and four new windows. I didn't realize what a difference it made, stopping noise transfer, until I opened the door to, only then, discover a wind storm was taking place.


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## kelvancra (May 4, 2010)

I should add, around here, all the shops big enough to drive combines into and the potato sheds (there are a lot of both) have spray foam interiors and they are nice places to work, summer or winter.


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