Hello, was curious about the insulating properties of Microfoil vs. 2" spray foam insulation. In getting my quotes for a 48'x36'x16' post frame metal RV garage, two separate builders offer these two different types of insulation. Both quotes are for insulating the walls and roof but at different cost. The microfoil is: $3500 and the 2" spray foam is: $8,800. Not knowing anything about either one, what are the pros and cons? I would ask about other alternatives and lie to myself that I will just do it myself, but honestly I just need to get it done when the building goes up. The building will be in NW Montana so I'm told that it won't matter what I do without a heat source, it's going to get below freezing in there. Thanks for all of the help guys.
Differences between spray foam and microfoil insulation
- Thread starter nomad10th
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Marctrees
Well-known member
First off, why not consider Poly faced wide fiberglass batts rolled onto outside of framing before steel panels?
Second - I am no expert on this, but seems to me "Microfoil" VS Foam is TOTALLY apples to orange.
Isn't one mostly a radiant barrier, and the other just plain insulation?
The below link is from a reputable website, not just some content writing fluff **** -- Marc
http://www.greenbuildingadvisor.com/blogs/dept/musings/stay-away-foil-faced-bubble-wrap
More good reading -
http://www.sawmillcreek.org/showthread.php?101035-anyone-use-radiant-guard-foil-insulation
Second - I am no expert on this, but seems to me "Microfoil" VS Foam is TOTALLY apples to orange.
Isn't one mostly a radiant barrier, and the other just plain insulation?
The below link is from a reputable website, not just some content writing fluff **** -- Marc
http://www.greenbuildingadvisor.com/blogs/dept/musings/stay-away-foil-faced-bubble-wrap
More good reading -
http://www.sawmillcreek.org/showthread.php?101035-anyone-use-radiant-guard-foil-insulation
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Marctrees
Well-known member
AND, IF you are planning on never heating, even to just like 40f, then I have no idea how to insulate at all, if any insulation of anykind is needed.
But I would look into making provisions to allow convective venting.
At least a basic ridge vent during construction, and you can always cut in some low intakes anytime later if wanted.
Not those big boxy spensive ridge vents, just low almost no added cost Scotchbrite like "closure strips" where your ridge V shaped to pitch sheet metal goes against the roof steel.
Instead of the solid foam ones.
The coarse "Scotchbrite" like material easily allows air flow, keeps out critters.
And leave a few inches minimum gap of your roof sheeting at the very peak of course.
Whether you insulate in any way or not, either way.
Marc
But I would look into making provisions to allow convective venting.
At least a basic ridge vent during construction, and you can always cut in some low intakes anytime later if wanted.
Not those big boxy spensive ridge vents, just low almost no added cost Scotchbrite like "closure strips" where your ridge V shaped to pitch sheet metal goes against the roof steel.
Instead of the solid foam ones.
The coarse "Scotchbrite" like material easily allows air flow, keeps out critters.
And leave a few inches minimum gap of your roof sheeting at the very peak of course.
Whether you insulate in any way or not, either way.
Marc
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matt_i
Well-known member
What is "microfoil" exactly? Is that 1" thick polyiso R-6 board? Or is this the reflective bubble-wrap?
The spray foam has the nice property of air-sealing any gaps whereas anything else would have to be caulked or taped to get the same level of air-sealing.
I am planning to help my brother build a post-frame building and I drew the plans with commercial/bookshelf 2x6 girts on 24" vertical centers. This way Roxul batts can be direct-fit into most of the cavities with minimum cutting.
I would make sure your trusses are set on 48" centers for metal skin ceiling or 24" centers for drywall or osb/plywood.
The spray foam has the nice property of air-sealing any gaps whereas anything else would have to be caulked or taped to get the same level of air-sealing.
I am planning to help my brother build a post-frame building and I drew the plans with commercial/bookshelf 2x6 girts on 24" vertical centers. This way Roxul batts can be direct-fit into most of the cavities with minimum cutting.
I would make sure your trusses are set on 48" centers for metal skin ceiling or 24" centers for drywall or osb/plywood.
Voi
Well-known member
A structure that size with a typical 4:12 pitch roof would be around 4500 square foot of wall space and roof deck. That doesn't account for overhead doors, man doors or windows that wouldn't be insulated with spray foam or foil but is a good starting point for estimating how many square feet of insulation you'll need.
If the microfoil is the radiant barrier stuff that looks like aluminum foil over bubble wrap I'd skip it all together.
As far as spray foam, at that price and thickness I'd assume you're getting closed cell spray foam. At 2" thick you'll have an excellent vapor and air barrier that you won't get with fiberglass.
The "problem" with 2" of closed cell spray foam in your climate is that it might not be sufficient for dew point control if you plan to add more insulation over it, particularly at the roof deck. The more R value you want the more foam depth you need for the dew point control. At some point it becomes a cost issue and you lose much of the economical advantages of a pole barn. Even with the price of closed cell coming down at some point you're better off building a more traditional structure.
I've posted in your other thread but don't recall what your heating goals are exactly? Do you have a need for keeping the trusses open and insulating the underside of the roof deck?
Thanks for the replies. My hopes are to keep the building above freezing without any additional heat source for as long as I can through the fall. I know that's not possible once temps get down in the single digits (from what I'm told), but this would allow me to not have to winterize my motorhome until later in the season. We do a lot of fall and even winter camping and it's just a pain to have to winterize every time we come back.
73RR
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The dew point control is important. You might also ask the bidder about the cost of using 4-5" of open cell foam as an option.
If the building has enough insulation then you may only need minimal heat to keep the interior above freezing.
If the building has enough insulation then you may only need minimal heat to keep the interior above freezing.
Voi
Well-known member
I hear you on winterizing.
Can you skip the spray foam on the roof deck and put in a ceiling and a thick layer of blown cellulose? Then spray foam the walls?
I'm guessing the roof deck portion of your spray foam bid is a third or more of the cost. That would go a long way towards a ceiling and insulation (and trusses engineered to hold them).
I love open trusses in pole barns but with a ceiling you get a much more R value per dollar and it can make the place easier to light.
I live in a poplar RV area and I know some people only blow their lines out during the early winter season and don't bother with anti-freeze until it gets really cold. But we're warmer than your area.
Voi
Well-known member
I agree with this. I didn't ask about the price of open cell the last time I had something sprayed but I think I've heard 1/3 to 1/2 of closed cell.
I probably wouldn't use it on the roof deck but it should be a less expensive way of air sealing the walls.
rburke65
Well-known member
So what exactly is "micro foil " insulation?
I posted a link to the microfoil in my garage questions thread in general discussion. Don't know how to link it to here.
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Radix2
Well-known member
The main difference between the "microfoil" and spray foam is that the spray foam is actual insulation and will give you about 10x the r-value.
The other difference is that the microfoil is a scam and the spray foam is not.
The other difference is that the microfoil is a scam and the spray foam is not.
73RR
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microfoil is a radiant/reflective barrier....not exactly insulation.
There are many ways to build a roof and just as many ways to insulate it based on the rest of the construction.
If you have a fully sheathed roof then you could use something like this to seal the sheathing and act as a radiant barrier.
It all comes down to how much money you want to spend and what results you expect or demand.
Like some others, I am a big fan of fully sheathed roofs and lots-o-spray foam.
There are many ways to build a roof and just as many ways to insulate it based on the rest of the construction.
If you have a fully sheathed roof then you could use something like this to seal the sheathing and act as a radiant barrier.
It all comes down to how much money you want to spend and what results you expect or demand.
Like some others, I am a big fan of fully sheathed roofs and lots-o-spray foam.
kj_mustang
Well-known member
Open cell foam is not an air and water vapor barrier, closed cell foam is. Most articles I have read state that a minimum of 2" of closed cell spray foam is required to be an air and water vapor barrier. CC spray foam is rated about R-7 per inch thick but it way outperforms fiberglass of that same rating because of no air infiltration. Shop around for a better price on the spray foam. You should be analyzing your building on how warm do I want to keep it and what heat source choices do I have? If you will be spending a significant amount on heating costs than spending money upfront for better insulation is the smartest move.
matt_i
Well-known member
Reading some more, i would definitely do a ceiling + loose fill.
I don't think its a good idea to think the building is going to trap a lot of heat and be above-freezing any more than the ambient air, without an internal heat source. My shop which is R19 walls, R30 ceiling seems to follow the ambient temp of outside with about a 1-2 day lag, up or down, depending on how large the temp swing is.
I'm going to guess here, but I'd say a 45k BTU unit would keep your space at 35F if you insulate walls and ceiling without a silly amount of runtime. Have to have ceiling fans to distribute the air or keep the tstat down-low. You could run a quick heat input calculation and then translate that to energy costs. Rough, ballpark stuff of course, but enough to get a basic handle on the utility bill.
I don't think its a good idea to think the building is going to trap a lot of heat and be above-freezing any more than the ambient air, without an internal heat source. My shop which is R19 walls, R30 ceiling seems to follow the ambient temp of outside with about a 1-2 day lag, up or down, depending on how large the temp swing is.
I'm going to guess here, but I'd say a 45k BTU unit would keep your space at 35F if you insulate walls and ceiling without a silly amount of runtime. Have to have ceiling fans to distribute the air or keep the tstat down-low. You could run a quick heat input calculation and then translate that to energy costs. Rough, ballpark stuff of course, but enough to get a basic handle on the utility bill.
lakeroadster
Well-known member
FWIW: My 30 x 44 pole barn roof has 2" thick Poly faced fiberglass batts. They were 4' wide and were rolled onto the outside of roof framing before steel panels were placed. The batts have adhesive on their edges to seal each to the adjacent batt.
It looks nice.. whatever that's worth to you.... see photo below.
The bulk of the rest of the barn isn't insulated yet. I have recorded interior temp's and thus far the barn hasn't dropped below freezing during the winter 2016/2017 season. It's gotten as cold as 33 F. though.
Part of that is from the solar advantage of the steel panels, and the heat sink the concrete floor provides.
And full length soffit and ridge vents also allow the interior to warm quickly also.
I considered spray foam. I found out that it voided the steel panel warranty. Additionally subsequent replacement of the steel panels would be a nightmare.
It looks nice.. whatever that's worth to you.... see photo below.
The bulk of the rest of the barn isn't insulated yet. I have recorded interior temp's and thus far the barn hasn't dropped below freezing during the winter 2016/2017 season. It's gotten as cold as 33 F. though.
Part of that is from the solar advantage of the steel panels, and the heat sink the concrete floor provides.
And full length soffit and ridge vents also allow the interior to warm quickly also.
I considered spray foam. I found out that it voided the steel panel warranty. Additionally subsequent replacement of the steel panels would be a nightmare.
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minytrker
Well-known member
I have 2in closed cell in my shop, best money I spent so far. It was night and day difference before and after. Friend has same shop with regular insulation and mine is always cooler in summer and warmer in winter.
73RR
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Some of the manufacturers would disagree with you on that statement.
I have used both, in garages as well as living spaces, and they each have an advantage. They are both air barriers. In my geographical area (just to get picky), the open cell performs as well as closed cell when thickness is near 2x. Yes it gets cold here in the high desert (4000 ft el)...this winter we had a couple weeks below '0'......
As for unheated spaces, I built a 30 x 30 garage for my wife's cars, no heat, and during those ugly cold days the interior temps did not dip below 30°.
This box is sealed, no roof venting, no soffit venting...just a big picnic cooler with all walls and roof covered in foam. Given the abysmal R-rating of OHD and the one window I'd say the performance is pretty good.