Opinions on "foil bubble insulation" install method

Dawgfan77 · May 14, 2017

I would like some opinions from you guys on something I've been kicking around. I'm at the point where I'm about order and install my vapor/radiant/insulation barrier over my pole barn purlins for my roof. I describe it that way because that's what the manufacturer calls it, I realize that's a complicated subject. This is an enclosed concrete floor pole barn garage.
Floor-6-8mil plastic under the slab
Walls and roof- 5-10mm thick closed cell foam faced with foil on both sides
full length ridge vent and vented overhangs
Every pole barn contractor I've talked with installs it the same way-pulled directly across purlins snug to the metal roof. I suspect because this is the quickest/easiest method... not necessarily the best.
On the contrary, the red iron type steel building guys around here install it similar, except with an intentional sag (4-8") in it between the purlins to provide an air gap.
Everything I read about radiant barriers (or insulation) seams to point towards requiring the air gap between them and the roof metal in order to be effective
My question is 2 parts,
1) do you guys agree with the "air-gap" method
2) if so, would it be worth my time to go 1 step further and instead of just a loose sag of the material, actually tack it to the bottom of each purlin as it crosses. Effectively turning the loose arch of insulation into a tight pan with 90 degree angles. I figure a good pile of fairing strips would make it a little less tedious.
I've attached a crude drawing to help describe this a little better. The middle is the typical way its installed around here, the black squares are the purlins(side view) and the red line being the radiant/foil bubble /insulation blanket

Hope the drawing helps. Am I just completely overthinking this? My plan is to start slowly adding rigid foam board to the bottom side of the purlins in the future as budget allows, but honestly that will depend on how bearable the climate is in the shop now. Thanks

Marctrees · May 14, 2017

Rigid foam board?? Why?

Get the insul done as the building is constructed.

You really need to search this Forum, and also seperately Google to learn that bubble foil radiant insul is very debatable.

Try to read tech articles, not what Grandma sez.

There should be NO difference metal frame compared to wood, it's the same building insulation wise.

We built a 4800 ft sq steel frame Mueller brand building on the coast of TX.

10 years till we moved, the insul worked great.

I specifically chose against bubble foil after my research.

In TX, we put in 3" poly faced fiberglass batt wide roll PERFORATED face insul being in a "hot humid climate" kinda like yours.

Perforated so the face does not work as a vapor barrier, in this part of the country.

Would be the reverse if I was still back in MN.

Read about it. Marc

Bamafan · May 14, 2017

Radiant barriers can be effective in some, hotter climates. However, the "bubble wrap" kind is by far the least effective. There are brands with actual insulation bonded to them--SolarGuard is one--that are much more effective and safe. That being said, if you are going through that effort, I recommend actually insulating the structure. There is pole barn and metal building insulation made for just such a purpose.

readhead · May 14, 2017

Bubble wrap is worthless and will fail eventually. We use a version of solar guard and it does require a little sag to be effective. Just a few inches. The thin radiant barrier insulation, whatever version, has a single purpose and that is to keep heat out. In your climate that may be a good choice. The down side is that it doesn't keep heat in very well. Places we have used it are storage buildings and farm buildings where it will maintain some what of an even climate without huge temperature swings. Where it doesn't work well is if you have a heated environment. It is better than nothing but barely. Most of these products have an R value between 6-9.

If you want to actually insulate the building use blanket insulation. It will take the same amount of time but when you're done you're done. Most suppliers will precut, roll, mark and bag it giving you very little waste. Barrier insulation will come usually in 100' rolls and you will have to deal with end seams that never fall in a good place.

Bamafan · May 14, 2017

@readhead: Much better put than my post. If taking the effort, go ahead and insulate with blanket insulation.

cajunfirehawk · May 14, 2017

Marctrees said:
In TX, we put in 3" poly faced fiberglass batt wide roll PERFORATED face insul being in a "hot humid climate" kinda like yours.

Can anyone show me links to said perforated face insulation, I have a muller building and would love to use this versus the cost of spray foam.

Bamafan · May 14, 2017

http://www.silvercote.com

3rdgendslmech · May 14, 2017

Dawgfan for what its worth, here's my .02 I'm about to be in the same building stage as you..... Think about it like this, if you take a piece of aluminum foil and hold it a few inches above a hot pan on a stove there's a pretty good difference in temps on the 2 sides. Now take that same piece of foil and lay it in the pan....its going to get just as hot as the pan. So in my opinion there should be an air gap. I think builders put it on top of the purlins and girts because its easier for them to install this way but it kind of defeats the purpose. Specially on the roof side.
I'm planning on doing it with the air gap. I've got galvalume roofing and siding for my build. I should have all of that done by mid June, I live in Md so sometimes our summer days can be a little hot and humid, winters are hit and miss. I'll probably ride out the summer with a bare building then decide what to do about insulation and what not from there. I went with full run ridge vent and vented eave soffits.

ard · May 14, 2017

You need an airgap for the radiant to be most effective. In a hot climate where it is keeping heat out, the sag in the rafters combined with a contiguous air path to allow the heat to escape is the best method.

When I looked at bubble, the very slight R value from the miniscule amount of trapped air was WAY overpriced. Simple barriers are fine, get your R value elsewhere.

Marctrees · May 14, 2017

Cajun - You can order it from Mueller.

We did.

Some of the sales guys don't know they can get it - You need to educate them - Tell them yes they can, and tell them it is what IS proper to use in "hot humid climate".

Those that do not install perfed in hot humid, are making a mistake.

Not my idea - Google it. "vapor barrier hot humid"

The plastic facing contains the glass fibers, a white bright cleanable surface, but the tiny holes make it very permeable.

Read engineering related articles, not some trash on Houzz or whatever BS fluff website.

Lamtec is a primary company in US to make insul facings.

Perforated available from them, through a distributor. Marc

From Lamtec website -

4. CAN I ORDER PERFORATED PRODUCTS?
Yes, LAMTEC can perforate its full line of insulation facings. Perforations are available in the following options:

Marctrees · May 14, 2017

3rdgen - If your building in MD is not yet skinned, why would you not use poly faced wide roll batts??

In northern location, you would NOT want perfed as in LA. Marc

3rdgendslmech · May 14, 2017

Marc I will eventually. The goal right now is to get the actually building up and functional. Being how its an aluminum shell I'm kind of curious to see how hot it'll actually get this summer. The bubble foil is just for a radiant barrier to block some of the heat. I dont really have a set plan for heating or cooling it just yet. I'm pretty tolerant of hot and cold temps. But yes sooner or later I'll frame out the walls put R-21 insulation in and look into probably a mini split system.

Marctrees · May 14, 2017

3rdgen - Well, if you put the wide rolls on before you skin it, you will save a TON of labor compared to doing it afters.

MUCH more pain to do it later - Picture it in your mind - Scaffold, trying to keep insul up while you support it, fighting gravity, PIA.

Have the crew roll it out over the frame, WAYYY less labor overall.

Figure the 3" poly faced wide roll batts insul will cost you about 45 cents/ ft2 for material.

I'm assuming you are using one of the standard "R" panel steel sheets.

One thing to keep in mind is - If you do batts over girts and purlins, you kinda need to go w the heavier sheet, not the 29ga or whatever thin stuff, otherwise some wavyness may result. Marc

Marctrees · May 14, 2017

And, why get on the latest greatest minisplit bandwagon unless you are dividing up the building into small sections requiring different temps ????????

Marc

3rdgendslmech · May 14, 2017

Marc are you talking about regular roll or batt insulation or XPS boards?
I get what you're saying about framing out the walls on the ground, then insulate, then raise it and nail it into place between the posts. But if you've got electric run you're kinda limited on doing it this way, maybe on some walls where there's nothing.
As far as minisplit, I'm not completely sold on them but I've seen a few used and if it'll knock the chill out and cool it down some I'm happy. I dont have natural gas in my area. Heating oil could be a possibility, I see a few people selling old oil systems fairly cheap on C/L.

Dawgfan77 · May 15, 2017

Marctrees said:
Rigid foam board?? Why?

Get the insul done as the building is constructed.

You really need to search this Forum, and also seperately Google to learn that bubble foil radiant insul is very debatable.

Try to read tech articles, not what Grandma sez.

There should be NO difference metal frame compared to wood, it's the same building insulation wise.

We built a 4800 ft sq steel frame Mueller brand building on the coast of TX.

10 years till we moved, the insul worked great.

I specifically chose against bubble foil after my research.

In TX, we put in 3" poly faced fiberglass batt wide roll PERFORATED face insul being in a "hot humid climate" kinda like yours.

Perforated so the face does not work as a vapor barrier, in this part of the country.

Would be the reverse if I was still back in MN.

Read about it. Marc

OK, let me try to answer all of these...
I realize the bubble stuff is poor insulation at best, but again, I'm not trying to insulate right now. I am on a budget, I'm building this myself out of pocket, If I were financing or paying a contractor it may be different. My thoughts are, If I can get a radiant barrier and a moisture barrier in one product for under $2000 now, and then insulate from underneath later as funds allow, then I will.

I say "rigid foam" later on because of the PITA I know it will be for me to insulate from the bottom side of the ceiling by myself from ladder, scaffold, etc... I figure buying 1 stack of foam at a time will be easiest on the wallet, and installing it from underneath 1 sheet at a time will be the easiest on me. I definitely not set on rigid, and will continue to research.

I'm not apposed to the blanket, or batts, or anything. But I really don't want 2-3" of insulation between my purlins and metal. This is 29 gauge metal. But I will explore that more.

I realize its much easier to insulate now than later, and I realize I would probably be happier in the long run. But again, I'm on a budget. When I was setting my budget and deciding on building size, the quotes I was getting for insulation were in the $3-5K range, so that will have to wait. I don't "NEED" a fully insulated building now... But I NEED a dry building that's not gonna drip on everything.

readhead · May 15, 2017

When the bubble wrap disintegrates after you eventually insulate you could end up with a real mess.

Maddog10 · May 15, 2017

Air gap is essential to the insulation working. In nearly all practical heat transfer calculations, conduction (if applicable) is the dominating percentage of heat gain/loss. Radiant barrier insulation offers very little resistance to conduction, so if there is no air gap heat will go right through it. However, if you eliminate conduction by adding an air gap it becomes all convection/radiation, which results in much less heat gain/loss.

Marctrees · May 15, 2017

3rdgen - I am talking about the very common like 4' wide faced fiberglass batts used on wood pole buildings and also steel frame buildings.

Frame is all erected, then before the r panels, they roll out the pre cut per order to length rolls. Marc

Marctrees · May 15, 2017

Sorry guys - I confused 3rdgen w dawgfan few times above.

Too tired right now to fix it. Marc

lakeroadster · May 15, 2017

Dawgfan77 said:
When I was setting my budget and deciding on building size, the quotes I was getting for insulation were in the $3-5K range, so that will have to wait. I don't "NEED" a fully insulated building now... But I NEED a dry building that's not gonna drip on everything.

As others have stated, use insulation blankets under the roofing.

It has a poly facing with tape / adhesive at the seams. It is fairly easy to install and when finished gives a nice sanitary white light reflective surface from inside the barn.

As I recall it was about a $2,000 adder (materials and Labor) on my 30' x 44'.

Dawgfan77 · May 15, 2017

Maddog10 said:
Air gap is essential to the insulation working. In nearly all practical heat transfer calculations, conduction (if applicable) is the dominating percentage of heat gain/loss. Radiant barrier insulation offers very little resistance to conduction, so if there is no air gap heat will go right through it. However, if you eliminate conduction by adding an air gap it becomes all convection/radiation, which results in much less heat gain/loss.

Thanks for that info, that's what I was wanting confirmation on :beer:

Dawgfan77 · May 15, 2017

lakeroadster said:
As others have stated, use insulation blankets under the roofing.

It has a poly facing with tape / adhesive at the seams. It is fairly easy to install and when finished gives a nice sanitary white light reflective surface from inside the barn.

As I recall it was about a $2,000 adder (materials and Labor) on my 30' x 44'.

Thanks, That is exactly the type I want to put in, love the white inside face... but my estimates were quite a bit higher. My roof is 57'Wx39'D with a 6/12 pitch.... so I guess I need to decide if I should rethink my budget. I did have $2000 budgeted for a 2 post lift like yours.... damn I hate to toss it out, but maybe I should for now. By the way, love the red siding on your exterior! Mine will be the same, but with gray roof and wainscoting!
:beer:

Dawgfan77 · May 15, 2017

Marctrees said:
Rigid foam board?? Why?

There should be NO difference metal frame compared to wood, it's the same building insulation wise.

We built a 4800 ft sq steel frame Mueller brand building on the coast of TX.

10 years till we moved, the insul worked great.

I specifically chose against bubble foil after my research.

In TX, we put in 3" poly faced fiberglass batt wide roll PERFORATED face insul being in a "hot humid climate" kinda like yours.

Perforated so the face does not work as a vapor barrier, in this part of the country.

Would be the reverse if I was still back in MN.

Read about it. Marc

Marc, I am exploring this option and trying to get my price comparisons together.

So you're saying ONLY the 3" batt PERF rolls, no vapor or radiant barrier??
If so, that would change things significantly price wise.

I have read a ton between here, google, tractornet, green(something), etc... And it seemed to be general opinion that I still need the vapor and radiant barriers in an un-sheeted metal roof, so I factored those costs into my budget as well.

Also, did you use BETWEEN the purlin rolls (ie 24" wide) or are you referring to the wider rolls, rolled OVER the purlins with sheet metal screwed through it?
thanks,
Phil

Marctrees · May 16, 2017

Dawg - Not sure what you mean "un-sheeted roof" ??

You mean framed, but R panels not yet applied?

Yes, the very wide like I don't remember like 4 ft. rolls rolled OVER girts and purlins.

And then the R panels. screwed down touching the naked side of the batts.

Again, I think you need to go w the heavier gauge metal option to eliminate all waviness.

Our was flat as a laser everywhere when done, and we actually got 3.5", not 3.0".

Orderable in diff widths, AND pre cut length batts for your roof and wall sections.

They bundle/ bag the diff length pieces, and mark the bundles w installation location in building.

When done installed, about the only scrap is the triangles cut off gable end rake.

When you Google tech articles on hot humid vapor barrier, you will see you do not want a vapor barrier toward inside of building, being in South Carolina.

MN would be the opposite.

Although that's even being questioned in some cases lately.

The metal r panels act as the OUTSIDE vapor barrier sufficiently.

And no, you do not need to seal r panel joints IMHO.

Actually, in the portion we finished into home, that part we used the mastic tape at alll metal lap joints.

But not in the shop side.

In Rockport, near Corpus Christi, we had the building framed, they rolled out the wide batts, pulled em snug. and screwed the r panels over it.

Walls and ceiling done the same.

And, in SC or TX, you do NOT need to tape the insul seams cause again, it is not acting as vapor barrier to inside.

Only tape if needed for support or appearance.

Again, northern states MN would be the opposite.

So no, we did not use any bubble foil, made no sense to me to do that, and we were very happy.

And as I said, figure that roll insul @ ballpark 45 cent/ ft 2.

That's what Texas Mueller quoted me a few weeks ago.

Glad to help w any questions.

But keep doing your study.about this.

And don't listen to opinions, mine included.

LOTS of misinformation going around about this vapor barrier depending ON CLIMATE AREA thing.

AND on the radiant barrier type materials.

Read tech engineer stuff like from Oak Ridge Natl.Labs type stuff.

Both the vapor and radiant questions. Marc

https://www.google.com/search?q=vap...TF-8#q=vapor+barrier++hot+humid+oak+ridge+lab

https://www.google.com/search?q=vap...-8#q=radiant+barrier++hot+humid+oak+ridge+lab

Hdonly0 · May 16, 2017

I am new to the forum, but not new to the radiant heat barrier foil with closed cell foam in between. I started a metal house several years ago. Inside work has been delayed for several years because of being self build and health problems. The foil covered foam does work. My construction uses the foam and will have six inch standard insulation also. Only the foam is up right now and it does make a huge difference inside the building. It has held up very well for 10 years. It does need to sag some to create the airspace. This is located in the Florida Panhandle.

Dawgfan77 · May 16, 2017

Marctrees said:
Dawg - Not sure what you mean "un-sheeted roof" ??

You mean framed, but R panels not yet applied?

Sorry, I meant sheet metal ONLY roof, no OSB or plywood sheeting under the R panals.
Thanks again I'll keep researching. I don't know why, but I just can't wrap my head around it being ok to have naked fiberglass insulation pressed against the R panels. Not saying its wrong, just seems like its begging for a nasty, hanging, sagging mess... For some reason I keep picturing a ratty trailer park with no underpinned trailers and insulation hanging to the ground!

Dawgfan77 · May 16, 2017

Hdonly0 said:
I am new to the forum, but not new to the radiant heat barrier foil with closed cell foam in between. I started a metal house several years ago. Inside work has been delayed for several years because of being self build and health problems. The foil covered foam does work. My construction uses the foam and will have six inch standard insulation also. Only the foam is up right now and it does make a huge difference inside the building. It has held up very well for 10 years. It does need to sag some to create the airspace. This is located in the Florida Panhandle.

When you say "Standard insulation" I assume you mean batts or rolls right? Are they on top of the foam, or were these pics before it was added?

dv8customs · May 16, 2017

I'm in east Texas so I am more concerned with keeping heat out rather than in. My 30x40 has the bubble style insulation and while it is not great, it is indeed better than none at all. I even purchased some to apply to my roll up doors as without it you could feel the heat radiating off of them from a couple feet away. I put in a metal ceiling to limit my airspace and a 24k btu A/C keeps it nice and cool in the shop during the summer months.

Marctrees · May 16, 2017

Dawg -

Must be misunderstanding you.

There is no OSB or ply involved here.

Framing, insulation rolled out poly side to inside, bare glass fiber side to r panels.

Insulation is USUALLY rolled on perpendicular to purlins/ girts.

Over, on exterior side of all framing, not between framing like batts are usually done.

The support straps many use are only necessary to prevent sagging if your purlins are far apart.

In our building being in Hurricane area, and what with plans to rock much of the structure for use as a home, ours were about 42" OC, so we didn't need the little support straps.

Unfaced fiberglass against steel?

Done alllll the time. Marc

https://www.google.com/search?q=met...UICygC&biw=1396&bih=669#imgrc=HwB-pWqZ8cz78M:

Hdonly0 · May 16, 2017

Dawgfan77, I will be putting fiberglass rolls in the walls and in the attic. Not installed yet. No more insulation at the roof, just in the attic above the ceilings.

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