I am planning a new home construction. Naturally, I am looking to make it as energy efficient as possible and worry free. I plan to use the closed-cell spray foam insulation on 3/4 inch sheathing. Will I be looking at any problem with going to a metal roof?
Guest User
2011-08-19 12:02:13.000000
I am hearing that spray foam under the plywood deck and peel and stick membrane on top of the plywood deck and then metal roofing, is causing the plywood to deteriorate. Comments?
Guest User
2013-07-22 13:34:46.000000
It seems to have been a while since you posted, Bill boulrice. I am wondering if you found any remedy to your problem?
It sounds like they may have used some setup similar to the Madden Industry with double the foam. Foam can be expensive. When you installed did you do any research on the EPS? I'm going to go out on a limb and say that the white stuff that they sell at Lowe's as a 4x8 sheet @2" thickness is awful. It's not as well made as the EPS that some consumer electronics are packed with and may not provide the desired r value.
Guest User
2014-04-28 18:41:31.000000
There should be a space between the metal wrap and another layer collecting heat, shingles or metal
Guest User
2014-08-05 12:12:19.000000
I am installing a metal roof over synthetic felt on 5/8 OSB, MS Gulf Coast. Plan to go with closed cell foam on the underside of the OSB to include the roof as it extends over three porches. My contractor said I have two options. 1. Leave the roof over the porches uninsulated and insulate only the roof line in line with the conditioned living space below. Or 2. Insulate the entire envelope to include the porch ceiling. Which is best. Would number 1. Leave a super heated dead space on 3 sides of house since no soffit vents due to potential high wind entry leading to roof failure.
Guest User
2015-02-05 11:13:51.000000
This site seems difficult to enter questions, if one is not currently a contractor or provider of materials.
It's kinda mind-blowing that foam insulation and metal roofing has been around so long, yet so many roofers are still not doing it?! Can only think there might be reasons why most roofers are not yet including foam insulation under the metal?
We want to increase insulation any good way we can; our roof, as-is, generates tremendous heat-gain in summer, and loads of heat loss in winter. The roof trusses are bottom-grade [read: smallest possible wood parts possible]. Climate: SW WA State. Two old layers of old comp. roofing must come off.
Only one contractor so far, could address placing 2" solid foam insulation panels Between Roof Underlayment and a new Standing Seam Metal roof; says he's installed numerous; some's been in place for over 20 years, no problem, applied like this. He didn't mention purlins.
A few of our concerns/questions have yet to be answered by any source:
---How well do 2" foam insulation panels withstand heating/cooling cycles .over time., in this application?
---Do some types of foam insulation panels work better than others [i.e., open vs. closed-cell]?
---This type of application: good or bad idea? [if it's bad idea, why?]
---Is it necessary to place Purlins on top of the foam, to give an air-space between the insulation and the metal?
---Is a Stick-down, or Non-Stick-down, Synthetic Underlayment the best choice, for this application?
---Is there a better way to do plumbing roof vents, than putting holes through metal roofing? [We're trying to minimize roof penetrations!]
---Does anyone usually install permanent eye-bolts at the roof ridge, to hook on safety equipment?
---The contractor who says this is a good idea, also said he'd have to remove the gutters, replace those and raise gutters higher on new facia boards...yes or no necessary to change location of gutters? Or replace them at all [they seem to be working OK] ?
I really appreciate advice!
Thanks!
Guest User
2015-07-25 17:22:15.000000
It's about 2600 s.f of roof on a '79 housing-boom, single-story, "flipper-special-lipstick-on-a-pig-bank-repo-special" house;
"... roof generates... heat-gain in summer, and... heat loss in winter....
"roof trusses... bottom-grade [read: smallest possible wood parts possible], average-pitch... "
"Two old layers of old comp. roofing must come off."
Add: Olympia area;
A few frank leaks, a few threatening leaks; shingles age-worn.
We want to get rid of existing plastic roof vents, to use Ridge-venting.
An unknown number of roof-deck pieces need replaced, per some contractors, but last one said decking seems fine.
Modest gable-end vents x 3, and eave/soffit vents about every-other truss.
Chimney is at edge of roof, w/leaking flashing and spalling bricks.
Unsure what else?
We're thinking, condensation on underside of decking [in attic] will be largely Reduced, if foam boards are placed between metal and underlayment on roof deck. That is, doing that reduces the temperature-changes thru the large roof surfaces, so that should nicely reduce incidence and severity of condensate under the decking [in the attic]? As well as taking a bite out of our indoor air tempering costs until we can do more. [[Our roof needs fixed this summer; insulation in ceiling/walls must wait, due to budget constraints. We're looking for viable ways to keep things "spackled together" for a generous several years until we can afford to do things right. ]]
Thanks!
Guest User
2015-07-27 15:41:09.000000
I am looking at installing a new metal roof on new trusses (closed attic/sealed Attica). Roof will be 35'x70'. I would like to not have to sheath the entire roof just to put the metal roof on. I plan to have runner every 2 foot and the truss company said we could go in on a 4 foot center for trusses. I would like to spay foam to the underside of the metal roof. What will I need to do to do this? Vapor barrier on top of the trusses under the metal? Can you spay the metal directly with out a vapor barrier?
Guest User
2016-01-03 17:22:00.000000
How can I tell if the contractor is using open or closed cell foam?
Guest User
2016-01-03 21:13:57.000000
Old Farmhouse Restore.. 1850 build, Upstate NY climate.
A recent reno to the upstairs of my old farmhouse has left us with bigger problems. Our roof is tin over osb and clap boards with MINIMAL air circulation . We installed 8" of batten insul. to the bottom of the roof deck & a knotty pine the ceiling. now that the house is more air tight condensation has developed b/w the underside of the roof deck and batten insulation thus saturating the insulation. The obvious start is to pull down the pine (which breaks my heart to do) & insulation to expose the underside of the roof deck.
Question 1.) will 4" to 5" of closed cell spray foam applied to underside of roof deck be enough of a moisture barrier to prevent further condensation from forming on the bottom of the roof deck? (would that create the thermal break we need to stop the dew point from being reached?)
Question 2.) If i spray foam will that just isolate condensation b/w the bottom of tin and closed cell foam and rot out the roof deck faster.
Im trying to come up with solutions that dont involve complete reconstruction of the roof.
Guest User
2016-01-09 14:35:15.000000
not enough space to get r 49 in there 5-1/2" is ALL i can get in there. the ceiling is nailed onto 2x6 nailers i added. original "rafters" if one can call them that are 3" x 4" roughcut @ 3-4 feet on center!! I dont know how these old houses stood for so long with the snow loads we get here!
May i ask what the rigid-foam will accomplish that the spray foam wont?
Guest User
2016-01-09 14:55:56.000000
I'm hoping someone can give guidance. We are building a new smaller (about 750sf on main floor) home in mid-Missouri, so zone 5. We want it very energy efficient , at least as much as practical and we can afford. But we can sacrifice surface stuff to get the structure right.
No attic- the whole space is a loft open to below. There is a big front porch that extends over the front room's roof about 6' in, and there is a dormer in the front also. Otherwise pretty simple with a 8/12 pitch. We plan on doing a red metal roof, over I think 3/4" OSB and roof is site built with16" on center spacing. The house faces south/east but there are some trees that might shade a little. The north west side is uninterrupted except for a vent pipe.
We aren't planning on VHAC on the loft unless we find we need it, But are doing a ductless minisplit system downstairs . It does dehumidify, which is needed here. Will also have a wood stove. The bath, stove and shower are vented outside. It has a concete floor but we did put R 5 insulation blankets under the slab and will insulate the outside of the slab edges. Only 2 of us, so may not generate a lot of internal moisture, but we do keep our windows open a lot on spring and fall and we have humidity here. The house has a fairly open floor plan. We were going to install wood "car siding" as the ceiling rather than drywall.
Worried about best way to insulate, protecting the roof structure from moisture, and possible leaks and how that might be to repair , though the metal guy says it won't. So, what is the best way to insulate this?
-Closed cell at least 2" under roof deck? If so, is it ok to leave the rest of the cavity empty? Is it best to fill the cavity with open cell or rock wool or combination? -Or Maybe put 2" rigid foam boards between the cavity and spray either open or closed after that( thicker and could do the board part ourselves and so if there was ever a leak, could access that easier???) -Could look at foam board on top of the roof deck/ vapor barrier but not built for that now and not sure how to modify it and if our metal roof would be ok with that method. -One foam installer recommended about 3 1/2 " of open cell but recommended closed cell for the walls so would probably have both equipment if we want to combine it( most of his work was Florida- no cold issues like here-but R factor of that not up to code). -Would open cell be ok if we dry walled and painted the ceiling with a bathroom paint ( not my favorite idea)? Any better ideas? Is it needed to still caulk everything (air seal) if doing any of these methods?- does that mean every crack? This is a one shot deal for us, so any help would be greatly appreciated.
Guest User
2016-03-06 08:38:06.000000
I have enclosed a pole barn with metal skin all the around. The dimensions are 32 x 48. I plan on spraying foam insulation directly to underside of metal roof and to the inside of the metal walls. Do I need open or closed cell? I have been told use open it will allow moisture to escape and also use closed because it will create moisture barrier.
Rusty
Guest User
2016-04-12 12:00:49.000000
Hi Guys,Ok we bought a home in May 2015,we live in southwest Louisiana.Well here is the cold weather about 35 degrees and we start to see wet spots on our ceiling,we are all confused about what's going on so that's when I went to do research,here I am trying to figure out what is condensation.....sweat in my attic.....we still not really understanding so we call a roofer and he says we need more air flow in our attic so we get 3 turbines hoping this would help our situation but it didn't.....We had a cold day today an guess what my metal roof is still sweating..... please tell me what I can do.We don't have any sheathing on the underside of our metal roof and we would really like to get this situation solved.....In our area I need help!!!
Guest User
2016-11-21 20:13:42.000000
Jerry T
I have been reading your forum. I am an an HVAC contractor but am looking to do battens over existing comp my house and interested in the best way to do insulation or if best not to? some open attic and some cathedral ceiling The cathedral ceilings has a lot of heat loss and I would like to insulate if possible?
Guest User
2017-02-18 19:56:26.000000
I am having a hard time deciding about this insulation issue. I am about to install a metal roof over a layer of comp with purlins..I am trying to figure out which insulation is best for the space and should I use 2x4 or 1x4 ....some of the forum appears to be leaning towards solid closed cell and some seem to lean towards spray foam The ceiling is open with gable vents and truss vents...blown in insulation . Open attic in 50% of the house and the other cathedral ceiling all has 1/2 in omb lid
Guest User
2017-02-18 20:48:55.000000
Question
I have a barn / shop that gets hot in the summer and cold in the winter. The walls are insulated to R20 but I have this metal roof that seems to radiate heat into the the space. The metal roof is of a "mini v " used on MD horse Barns. If I were to use Expanded Polystyrene Foam Board Insulation either attached to the metal roof or suspended below the roof would this help. Second what direction should I point the metal side of the Expanded Polystyrene Foam Board Insulation?
Thanks you in advance
Guest User
2017-05-03 17:15:26.000000
I live in central virginia, we built our house in 2013. We have ceiling, 6 mil plastic vapor barrier, r-38 fiberglass, 2 x 10 rafters, 5/8 in roof deck, Grace underlayment and the screwed down metal roof. We also have soffit vents and ridge vent and gable vents.Screwing the metal roof to the deck was the manufacturers instruction. In the past I have used 2x4 purlins, reflectix insulation and never had any condensation issues. With this install we have had problems at the chimney which is at the eaves. We caulked the cricket valleys even though there is 24" valley flashing underneath, caulked where the metal meets the chimney and reflashed the chimney, and sealed the stone on the chimney 3 times now.
Thinking that maybe it was coming through the masonry I cut the ceiling away from the chimney and painted 2 coats of high quality masonry sealer from the ceiling joist header up as far as I could get to which was to the underside of the decking.
The big clue came when I realized that water comes down the chimney face inside the house hours after it starts raining and only when we have a frog strangler that lasts for many hours and the air becomes liquid outside. Like when the air turns greenish outside. Then we get a quick burst of water, usually about a half cup, as though it has been condensing and breaks loose all at once, (it's an 8/12 pitch). I'm tired of replacing the drywall around the chimney, 3 times now, taping, mudding, etc.
The attic is not receiving undue humidity from inside the house and there is no staining on the underside of the decking. We are going to sell the house and I don't want to stick a new owner with this issue. What I'm thinking is that an inch of closed cell foam to the underside of the deck would solve the problem. Other than that it seems like the metal needs to come off and it needs to be replaced with insulation between the metal and the deck.
Ideas are most welcome!
Guest User
2017-05-14 12:43:46.000000
Thanks Todd,
We haven't tarped it yet, we did try having a guy on the roof with the garden hose try to replicate the situation by flooding the area with water and we couldn't get it to leak.
Guest User
2017-05-15 06:59:58.000000
I am converting a metal roofed barn into living space. The roof is in great shape, so I don't want to replace it, therefore I will be retrofitting the insulation. I am in West Virginia, we have moderate winters, some days below freezing and some snow every year and plenty of humidity in the summer months. I will probably be heating/cooling with a mini-split. The metal roof is laid on 1x6 purlins which are nailed at 2 foot centers on 2x8 rafters on 16 in centers. There is no vapor or moisture barrier between the metal and the purlins. I have purchased 2" closed cell rigid foam boards that have a fiberglass covering on it which I plan on cutting and caulking in between the rafters and then filling the rest of the space with fiberglass batts. I have continuous soffit vents and gable end vents that equal about 570 sq. in. There are collar ties creating an opening below the ridge that will tie all the vents together. So, should I leave space between the rigid insulation and the purlins for air flow? If so how much space should I leave? Should I put anything on top of the rigid insulation as a vapor or moisture barrier? Would roofing felt be a good thing to use for this? Should I put a vapor barrier between the rafters and the drywall that I'll be using to finish the ceiling? If so what? Thanks for your help.
Guest User
2018-01-09 14:32:35.000000
No, in fact metal is very well suited to hot roof applications like this.
Todd Miller
2011-08-19 12:53:43.000000
Thanks Ray. Feel free to call me anytime at 1-800-543-8938 ext 201 and I will be happy to talk it through.
My reference to not all systems being compatible with foam was referencing situations when the foam is installed on top of the roof deck. I am not at all a fan of that application unless battens are involved. I will not allow my company's products to be installed that way.
This particular forum posting, however, is referencing foam sprayed to the bottom side of the roof deck. That is a different situation entirely and all metal roof systems can be compatible with that.
I do apologize for any confusion I may have created but I saw this post and yours as two very different situations, hence my different answers.
Todd Miller
2011-08-22 08:06:46.000000
I should give a little extra clarification here ... the issue with foam on top of the deck is that many panels can "walk" into the foam, causing deformation of the panels. Additionally, the foam can allow fasteners to be over-driven which also can have damaging results.
On metal panels that can be installed over battens, though -- that can work well with foam on top of the roof deck. The battens provide the support for walkability and for fasteners that does not exist if only foam is there.
I hope this helps.
And, again, to reiterate -- "hot roof" or "hot attic" assemblies where the foam is beneath the roof deck, are okay.
Todd Miller
2011-08-22 08:31:06.000000
I agree that some ventilatuon would be a good thing. Also, do you have high humidity levels inside the home for some reason? Are there any unusual large sources of moisture inside the home? Those could be contributing to a feeling that it is warmer because now that moisture is not escaping perhaps.
Todd Miller
2013-10-22 11:17:43.000000
If you use a closed cell foam you do not need an additional vapor barrier. However, should the roof ever need replaced, having the vapor barrier will be very helpful so I would suggest it.
Todd Miller
2016-01-03 17:27:18.000000
They will be able to tell you. They are two very different products.
Todd Miller
2016-01-03 21:39:58.000000
It does sound like you need ventilation in the attic. The turbines you added are to act as exhaust vents. Do you have adequate intake vents, usually in the eave soffits / overhangs to feed air to the turbines? A great source of venting information is www.airvent.com
Also, look for ways to reduce moisture levels in the living space of the home. Also, are things like dryer vents, bathroom and kitchen fans, plumbing stacks all vented to the outside rather than just into the attic? Additionally, if your home has a furnace with a fan, try keeping the fan running all the time, not just when the furnace is on.
Call me if you'd like to talk this through further. Todd Miller. 1-800-543-8938 ext 201
Todd Miller
2016-11-22 05:20:12.000000
This can be difficult and to some degree depends upon where you live and what the risks are there. You basically have thermal break, vapor barrier, insulation and ventilation to play with and all can be necessary in some cases. Ideally I like from the bottom up, ceiling, vapor barrier, insulation, vented air space, decking, underlayment, roofing. I'd be happy to talk to you sometime if you would like to call me at my office at 1-800-543-8938 ext 201.
Todd Miller
2017-02-19 05:49:01.000000
Adding insulation and/or an enclosed ventilated airspace would help dramatically at creating a situation that helps block heat. Radiant barriers need to face an air space ... no major different whether they face in or out.
Todd Miller
2017-05-03 20:09:57.000000
This really doesn't sound like condensation to me but, of course, you are much closer to the situation. I am sorry for what you have experienced. I will say this ... anytime a ceiling is opened up, a lot of moisture does get through. Anyway, I still feel like this sounds like a masonry or flashing issue. Is there any way to tarp off the chimney and see what happens? Feel free to send me photos of the chimney and flashing if you like. todd@asktoddmiller.com
Todd Miller
2017-05-15 05:27:05.000000
Gotta agree with Todd - most panels directly over foam are a bad idea. Insulation between battens, or sandwiched between two layers of plywood/OSB is a better options.
Nate Libbey
2011-08-23 08:22:52.000000
hey todd'
i dont unnerstand.
when i asked you the same question u said that not all metal roofs were compatible with foam.
the guys at two foam spray companies got a laugh out of that cus they couldnt figger what metal roof would be incompatible with foam.
metal is metal and foam is foam and never the twain shall conflict.
as for bsbs approval your response to guest seems to have been remarkably free of this.
btw
if u need someone to defend your status as a tech expert and not a salesman for a company the website is already in trouble.
dont worry about any more offensive posts from me.
im outa here.
ray t
ray tartakoff
2011-08-22 07:37:33.000000
I have an older single wide mobile home in Arizona where the heat is. Several friends I know had new roofs installed by a contractor by putting 4 inches of hard foam than wrapping it with metal across the whole thing. They all state how energy efficient this makes the mobile plus it's a good roof for weather as there's no nail or screws except on the very outside edge.
However I seem to be the only one with the following problem. instead of being efficient my electric bill increased once the roof was installed. The air conditioner was checked and is working fine but it runs a lot trying to cool the mobile. I feel it runs more than it did before and I think the new roof is trapping the hot air in the house. There never were any vents anywhere on these units but I'm wondering if it would be beneficial to open both ends and let the air flow through between the roofs and even putting a small fan in there if needed to remove the heat between the old and new roof. There isn't much space maybe 8 to 10 inches at the highest point but anything is better than nothing.
I might add that the mobile only has a 7 foot height inside and I have insulated the outside over the years put new windows and siding on this unit to upgrade it. I don't think all my efforts made that much difference.
Bill Boulrice
2013-10-22 11:11:07.000000
Sorry I reposted a new topic before I saw your response. The roof is galvanized steel with a fresh coat of elastomeric paint. I do want to add fiberglass batts between the foam and the drywall, does that change your thought on a vapor barrier? Anything on top of the foam (that is between the air space/steel and foam)? Thanks again for your expertise.
David Fleming
2018-01-10 13:12:00.000000
Not at all.
Best of both worlds in both insulation and and roof choices.
Rigid foam to the exterior surface can be a bit more cost effective as compared to applying the insulation depth to the underside of the sheathing in the total R-Value depth required and create a true thermal break between the roof and the structure below.
A polyisocyanurate foam and system of battens can give you the overdeck venting and 100% thermal break that is ideal.
Eric Novotny
2011-08-19 20:08:17.000000
+1
Todd's advice is spot on.
Eric Novotny
2011-08-25 08:50:20.000000
This is not true in my observations if the foam on the underside of the deck is closed cell or treated with a vapor retarder paint.
If, however, you spray the underside of the roof with what is a vapor open foam (open cell) and you have enough moisture in the air, it can collect on the cold underside of the sheathing, condense, and rot the roof deck from the bottom up.
The peal and stick on the top surface does not really decrease the permeability of the plywood though as it is not tremendously permeable anyway.
If you didn't spray the right foam or application, the roof deck can rot out regardless of peal and stick vs felt.
Eric Novotny
2013-07-24 11:27:49.000000
If you don't insulate the underside of the porch roof, you will need to allow for a bit of convection to happen in there by providing some vents on the gable ends or otherwise to the exterior.
I would probably incorporate some rigid foam to the roof deck to help that SPF work that much better.
Eric Novotny
2015-02-09 10:08:43.000000
Chi,
Tell me about your home currently. Questions (some already answered but in list format):
Location of the home: SW WA
Attic Type: Vented or non-Vented
Roof construction: Trusses or Rafters
Eric Novotny
2015-07-26 09:21:48.000000
Chi,
If the roof is vented, insulating the roof deck won't impact condensation formation at the end of the day. The attic needs to be air sealed and insulated and you need to up the venting. If there isn't any HVAC in the attic, going with a lighter color (while it will keep some of the radiant heat out of the attic) is entirely inconsequential.
You have to stop the moisture from migrating into the attic and if/when it does, the roof/attic needs to be properly ventilated to remove it.
If you were putting foam on the roof deck and then spray foaming the underside of the roof (i.e. making he attic a conditioned space), that is all fine and good but we aren't doing that here.
http://apps1.eere.energy.gov/buildings/publications/pdfs/building_america/ba_airsealing_report.pdf
Eric Novotny
2015-07-27 15:53:18.000000
4-5" would be enough and would give you sufficient R-Value as well. Opt for the 5" range and code may require that you put R-38/R-49 (whatever that equates to).
https://energycode.pnl.gov/EnergyCodeReqs/?state=New%20York
The moisture is coming from the home. You will fix that via the spray foam.
I would stick some rigid foam inside the joists and then spray the backside of the rigid board.
Eric Novotny
2016-01-09 14:47:54.000000
Poly-Iso has a higher R-value per inch and will also allow the room to to serviced at a later date without destroying the foam.
The framing will still be the weak point in the thermal system but plenty of roofs have been converted to insulated and do quite well.
You will need to condition that space when you are done though. It is now part of the interior space and envelope.
Eric Novotny
2016-01-09 15:05:29.000000
Best bet here is going to be to incorporate right foam to the outside layer (i.e. sheathing side).
This will help uncouple the framing from the thermal boundary and make the entire assembly more resistant to condensation formation.
Eric Novotny
2016-03-06 14:50:22.000000
Rusty,
Depends on where the barn is, but the prescriptive recommendation on roofs is usually Close Cell (CC SPF). We have done open cell before and it works quite well as long as the application is left exposed and uncovered.
If you aren't covering the foam (FYI...it will need to be covered with an intumescent barrier of some sort), it is best being closed cell.
Eric Novotny
2016-04-12 16:25:14.000000
Jerry,
How do the vaulted sections tie in with the vented sections? How about some pictures?
Eric Novotny
2017-02-19 09:11:52.000000
Ideally, you want about a 1" clear (minimum) vent space.
You could cut some small blocks to install to the back side of the purlins to give you your space and then hang your foam inside the rafters. Seal them up really well and very little moisture should make it to the roof at that point.
What type of metal roof is it?
As long as the finished ceiling is night and airtight, I don't see a need for a vapor barrier with the seal up foam board. You should insulate to the underside of the collar ties and make that small flat space your air barrier and allow that area about to work with the gable end vents and soffit venting.
Eric Novotny
2018-01-09 16:39:44.000000
If the foam is sealed tight to inside the rafters (i.e. caulk and foam) you should not need an additional vapor control layer. Just make sure the drywall is nice and airtight, you have continuous ventilation, and the foam is not moisture sensitive. You might get (with the right exterior weather conditions) some condensation on the backside of the metal that might drip on the foam.
In a perfect world, you have a full layer of underlayment that will take any of the drips/drops that might happen and keep them draining off the roof. That isn't possible here without removing the roof though.
You should be good though if you haven't seen the roof sweat much before, it shouldn't get any worse now.
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