I am getting ready to put a metal roof on my house it presently has 1 layer of shingles on a 6/12 pitch and Iam in florida I am think of putting r-foil under 1 x 4s battens or the styrofoam boards between the battens and also a solar attic fan w/elec option and the metal will be a light color from douglas metal roofing does this sound like a good plan?
Guest User
2013-08-31 01:04:52.000000
Todd you are most helpful. I am thinking about a metal roof over shingles on a singlewide trailer. I am looking to hopefuly put the metal roof on an never have to worry about it again. Thanks for all the info.
Guest User
2014-06-11 10:40:16.000000
Todd, earlier in the post you said you would not recommend foam under metal but here you are telling Steve that 'it sounds reasonable'. I've been told not to put foam under the metal because of the condensation from the metal will deteriorate the foam. I believe there are more burdens than benefits by so doing.
Is there any way to insulate when you install metal over existing shingles on a one with 'cathedral' ceilings and with very little existing insulation and therefore a low R-factor. The home owner feels there has to be a way but I have never seen an effective solution. Your thoughts?
Guest User
2015-07-09 19:52:37.000000
if you are installing a standing seam panel, use a 4" x 4" bearing plate with a rigid foam.
Guest User
2015-07-10 22:11:28.000000
Eric, Thanks for your reply. We are using R-panel and intend to use 1x4 battens. My main concern is whether or not the R-factor gained from using foam board is worth the expense. Do you know what the R-factor is for the foam board? (I can't seem to get accurate answers from anyone locally) Any idea what a realistic monthly savings would be (percentage wise) after foam is installed? From what I've been able to determine the difference between installing r-panel on battens vs the same install but adding the foam board is minimal yet the cost is much greater. Also, Should one expect that condensation might cause damage to the foam over time or is this a myth? Your thoughts?
Guest User
2015-07-12 18:11:23.000000
thanks for this forum it really helped me a lot.
I want to use the rigid foam under the metal sheet to provide some thermal insulation and i'm planning to use bitumen as a kinda of glue between the metal sheet and the foam; my question is : Can it work?
Thanks
Guest User
2016-04-06 09:36:29.000000
We built a log home a couple years ago. The main part of the house has a vaulted roof with SIP panels with 7" of insulation, synthetic underlayment and 29 gauge standing seam metal and we have had no problems. The wings of the house have scissor trusses with synthetic underlayment and 29 gauge metal and insulated to code with regular insulation attached to the bottom of the trusses and the ceiling is tongue and groove cedar. In the winter the roof decking condenses and drips through the insulation and ceiling. I was told that I did not have enough venting through my soffit to my vent ridge, so I added more vents. The problem continued last winter. Should I have closed cell sprayed on the underside of the deck and close off all outside vents and roof vent? There is barely enough room to crawl around in the trusses. Is there a way to spray in that confined an area? Do I need to take out all of the original insulation?
Dave
Guest User
2016-07-11 20:22:45.000000
OK we bought a used mobile home after a house fire 10 yrs ago. The homes roof was at that time already 18 yrs old. I am attempting to put a metal roof on it and am worried that IF I don't put styrofoam sheets 3/4 inch under roof panels, during a rain storm it will be so noisy you can't hear yourself talk much less sleep. I am nervous cause I have only one attempt at this and want to do it right. I don't have the money for this so I want to do the job right the first time.
Guest User
2016-07-25 14:13:50.000000
I have a metal roof over 1x4 purlins and the living space underneath has r21 paperback insulation underneath which is 2 by 6 24 on Center the roof Rafters are 8 are true 8 inch two by 8s so there's about two and a half inches of room between the insulation and the metal roof I have plastic over the ceiling down to the walls I cut holes above the soffits to let air in up behind the insulation but my sofit on the outside don't have any vents so I have to put vents in my soffit my issue is my metal roof sweats and drips on my insulation and leaves wet spots it hasn't happened in a couple days but I think if I open up the soffit to allow air to come in up above the soffit and up behind the insulation that allow air to circulate am I correct so it shouldn't sweat I just started to renovate it and insulate the whole upstairs I only noticed it since I insulated the roof rafters in the summertime it doesn't sweat but in the winter now that it is insulated and it is 65 degrees up there moisture is still being trapped behind the insulation and the metal roof even with the plastic a little bit should I put a dehumidifier and once I sheetrock it will that help prevent the moisture in going through as well I don't want to cover it up without knowing it won't sweat once I put vents in the soffit I think that will help with allowing it to breathe and not trapping the moisture am I correct any other ideas would be appreciated. the upstairs is its own separate living space so there is no attic there's a loft and is fully insulated. thank you again the red arrow shows where I put holes in each bay to allow air to get up between the insulation and the roof those are true 2x8s so with 5.5inch of insulation there is 2.5 inch of room.
Guest User
2016-12-26 11:40:23.000000
I want to put a metal roof on 1×4 battens & install styrofoam insolation between the battens. Will the styrofoam "sweat" & cause my boards to rot or any other damage due to condensation? It's a 32×76 mobile home with a layer of shingles. I live in Louisiana & my light bill in the summer is outrageous!
Guest User
2017-03-26 05:26:05.000000
i have 1950 built home using 2" celotex/homasote type material over beam ceilings. On top prior owner put rock tar roof and by the looks of some window wood droop, and some of the celotex sagging from the inside, I deduced that rock roof was too heavy for that product. Therefor, I am removing the rock roof and want to put standing seam metal roof directly over the celotex. When I take off the rock am planning on replacing the celotex product with homasote product of same dimensions. Is this a proper application for a metal roof? Type of fasteners to use? Should I try to use a 3" screw to go though the celotex and sink into the beams which are 32-34? inch centers, or just forget using a metal roof, and go with asphalt shingles? thanks
Guest User
2017-09-09 10:59:27.000000
Hi
I plan to install as part of a hurricane induced roof rebuild the following. This is in tropical climate in the Turks and Caicos Islands.
Existing roof 2x6 T&G with cathedral ceiling underneath
We will use Grace Ice and Watershield as underlayment.
Then use 2x2 pressure treated strapping vertically and place 1.5" Polyiso boards between
Then use white .032 aluminum standing seam metal as final layer.
Does this make any sense? Also for the Polyiso, should they be foil faced and or fiber/paper faced? My supplier has the Carlisle Insulbase in stock which is fiber/paper faced ... will this work in terms of moisture exposure? Is it recommended to go with a foil faced product like Rmax Thermaroof?
Guest User
2017-11-18 14:05:17.000000
Thank you Sir
The standing seam metal will serve as the radiant barrier in this concept. The metal installer has mentioned that he will prefer to put straps on top of the T&G to better anchor his fasteners. He has concerns the T&G is on the thin side and does not want his nails to break through on the finished inside ceiling.
The polyiso is something we came up with to avoid air spaces between the straps and prevent uplift in a storm. Then of course the Polyiso adds R-Value under the standing seam. I have seen this done on island multiple times and it seems to work. All installers have used foil faced polyiso and I wonder if this is to avoid moisture problems. The paper facers on the board that my supplier suggested just look like they are not made for this climate. My thinking is that a foil faced polyiso will have much less area to soak up potential condensation or storm water. I am not sure however if this is really an issue or maybe I am over thinking it. My understanding is that polyiso does soak up water and that moisture does damage it in the long term.
On the positive side the temperatures under an aluminum roof should help to dry out the panels fairly quickly too?
What is your opinion on this?
Guest User
2017-11-18 19:09:21.000000
Our log home has a metal roof with no vapor barrier or decking. The insulation was blown in. The inside ceilings are tongue and groove. We’re having condensation through the covered porch tongue and groove. What would be the most cost effective solution to our problem?
Guest User
2018-01-10 00:12:21.000000
Thanks for your post.
First of all, I think you need to choose your metal roofing product and then work out the details with the manufacturer. Not all products can / should be installed over foam. Additionally, some products can be installed over battens.
In my opinion, you need ventilation beneath the new roof more than insulation. Ventilation will help avoid ice dams and also allow moisture that is generated inside the home to be vented out.
I would suggest choosing your product and then working with the manufacturer to determine how to install it with ventilation and possibly with insulation as well.
Todd Miller
2011-08-19 05:34:44.000000
Thanks Ray.
Honestly, I personally do not recommend any installations over foam. However, there are some manufacturers who are probably okay with it. I really do not know specifically who is and who is not. Sorry.
First of all, I think the rooftop is the wrong place to insulate, and second installing over foam can lead to the product interlocks and overlaps being distorted and rendered not watertight.
As far as brands of metal roofing ... certainly I am a believer in all of the MRA member manufacturers. ABC, ATAS, Fabral, MBCI, McElroy, and Metal Sales are manufacturers that may offer good fits for what you wnat to do.
Todd Miller
2011-08-19 09:43:09.000000
I would also suggest looking for products that meet the Premium certification level of the Metal Construction Association certified metal roofing program.
Todd Miller
2011-08-19 09:43:54.000000
Yes, that sounds reasonable. Make sure that the product you choose to install is accepted / approved for this type of installation. Also, if your ran vertical battens first followed by horizontal you could potentially vent a portion of the chamber, bringing air in at the bottom and exhausting it out at the ridge, This would be very effective for energy efficiency as well. Also, as an option, the metal shingle style modular products create their own integral airspace as a thermal break, even when installed over solid decking.
Todd Miller
2013-08-31 06:03:09.000000
Thanks for the kind words, John. I also have an educational site at www.asktoddmiller.com
Todd Miller
2014-06-11 21:36:01.000000
Ideally, I would have liked to have seen a vapor barrier behind the tongue and groove. Is there any way to reduce the home's moisture level? Is it high for some reason? Spray foam probably is a good option ... I am not sure about the access thing though.
Are you sure the ventilation is functioning well? Have you ever tried a smoke pen test in the attic to check for air flow?
Todd Miller
2016-07-11 20:26:54.000000
Thanks. Really, I can't confirm nor deny your fears. I assume the roof is not metal now. Is that correct? If you do want to insulate, not all metal roofs can be installed that way. Also, you need to choose a metal product that is appropriate for the pitch of your roof.
Todd Miller
2016-07-25 14:22:58.000000
Steveo, what is the pitch of the roof?
Todd Miller
2017-09-09 13:58:01.000000
Carole, I assume it's impossible to add ventilation. Can you spray closed cell foam to the back side of the roof deck, or, worst case, to the ceiling itself?
Todd Miller
2018-01-10 02:38:06.000000
i want to roof my 800 sq ft cathedral ceiling house on outside with metal roofing. i converted the ceiling to cathedral in 1999. it was an old bungalow from the 30's. it has open eaves and insulation was blown into the walls. i replaced the sash windows with energy saver inserts and am concerned that snow melts off my roof quicker than id like. on the inside ceiling i installed 6" fiberglass, foam battens and a ridge vent. outside is 1 layer of shingles and tar paper. i want to put foam insulation under the metal roofing. what kind of insulation will give best r for the money? should i go thicker than a 2 by four? would it be cost effective to take off the layer of shingles (pain in the neck) and tarpaper and seal the roof surface before putting down foam? if it is, what is the best material to do this with? thank you in advance. i went onto dan perkins website and it scared me into joining this website before i get into trouble. i cant tell you how much i appreciate this website.
ray tartakoff
2011-08-18 21:32:43.000000
hi
that was a good answer for a salesman/marketing type. now, what brand of metal roofing would you recommend or choose that allows for foam insulation?
ray tartakoff
2011-08-19 09:35:09.000000
how about something like ice dam shield material directly over entire roof? maybe foil backed. then i dont need battens and the compressibilty wont dimple the screws enough to compromise watertightness.
presently i use 100 gallons oil and 4 cords wood. per winter
the foamco guy can install 3 inches high density between two by four battens on edge.
estimated $3600. for r 35 total.
figure $7k for entire job as opposed to $2k for just steel and some type of ice dam over entire roof.
not much r but the amortization cost is more than 20 years.
i like the ice shield idea.
anybody manufacture anything like that?
already have a roof vent and rafter mates so ventllation isnt an issue.
what materials are out there?
ray tartakoff
2011-08-19 11:29:16.000000
When insulating your home, you can choose from many types of insulation. To choose the best type of insulation, you should first determine the following:
1. Where you want or need to install/add insulation
2. The recommended R-values for areas you want to insulate.
The maximum thermal performance or R-value of insulation is very dependent on proper installation. Homeowners can install some types of insulation -- notably blankets and materials that can be poured in place. Other types require professional installation. But, Radiant barriers are more effective in hot climates, especially when cooling air ducts are located in the attic. Some studies show that radiant barriers can lower cooling costs 5% to 10% when used in a warm, sunny climate. The reduced heat gain may even allow for a smaller air conditioning system. In cool climates, however, it's usually more cost-effective to install more thermal insulation.
Daawn Merark
2016-08-09 00:36:14.000000
Good afternoon,
We are going to be starting a small reroof, (29 square) soon. We are stripping the composition shingles, installing 2 1/2" ISO with a one inch air gap then sheathing attached. The designer wants to put ice/water shield on T & G decking underneath the ISO, which I don't feel good about. He also wants to seal all the plywood joints on top of the new sheathing, which I am ok with. We have our one inch airspace which will exit into a ridge vent. My question is how can I introduce airflow at the eave into our one inch airspace? There will be fascia board and gutter installed,
Marco Fontana
2017-11-26 15:45:49.000000
Putting foam atop the roof deck will do very little, if anything at all, in the means of insulation because your roof deck is already vented.
If you wanted to add more insulation, you are really talking about ripping off the roof deck or dense packing cellulose.
You could create an over deck venting situation (i.e. battens) and hope that creates enough of a thermal break and air movement to eliminate some of melting.
Eric Novotny
2011-08-19 09:14:08.000000
Todd is 100 correct. Installing directly over foam in not recommended regardless of what the manufacturer says in my opinion. It is about 100 times easier to foul up that kind of install and create issues down the road.
The roof, if you want to apply foam, should be installed on to a system of battens which will benefit you from both the over deck venting aspect and the structure of the roof (i.e. maintaining proper alignment of the installed system).
Foam is not a very resistant to point load deflection and if a fastener is over torqued, the foam will compress and mis-align the fastener and roof.
A batten helps displace the load over a larger surface area and is much more resistant to over compression and therefore maintains proper alignment.
Todd is not a Salesman or Marketeer. He gives quite freely of his time and is more than available to customer to answer questions and help them navigate the complexities of a metal roof decision process. He also helps out quite a few people with problems when roofs are installed improperly or materials have failed.
Eric Novotny
2011-08-19 10:58:42.000000
Ice and water over the entire roof is a great idea and especially if you consider the fact that you are sealing up the envelope (air barrier) across the roof deck.
If you put the 2x4s on end, you should get a 3" foam (will get you an additional R-18) on there and still have a 1/4" above deck airspace. This would be the best of both worlds. Fasten the roof panels the the battens (that is what the 2x4s will be acting as) and you should have little to no melting at that point.
Eric Novotny
2011-08-22 08:08:28.000000
Todd is a great resource and even better person. Always willing to lend a helping hand and thoughtful answer.
Eric Novotny
2014-06-12 19:32:08.000000
JD,
I don't recall Todd saying that he didn't like insulation, just that metal directly over insulation (i.e. rigid board) can easily be over torqued and mess with panel alignment.
I agree to that extent and always recommend a solid deck or some sort of strapping to prevent this.
Rigid foam works great and the metal can be installed directly over the top of it. You just need to be careful not to pull/torque the panels when fastening them.
Eric Novotny
2015-07-10 18:59:11.000000
Foam works great. Depending on the foam, you will have an R-Value of anywhere from 3.5 per inch on the low side and 6.5 on the high side.
As long as the battens and purlins combo will vent, it will work fine and you can skip the foam. The foam is better for non above deck vented options.
Eric Novotny
2015-07-13 12:26:02.000000
What kind of metal?
I would not glue the metal to the foam. It would not allow the metal to move as it will need to.
Eric Novotny
2016-04-06 11:03:34.000000
If you are going to be dropping the ceiling and have access to everything, best bet it so create a vented space if you can and insulate properly.
Here is a great link on some alternate methodologies.
http://www.finehomebuilding.com/pdf/021221068.pdf
Eric Novotny
2016-12-27 14:21:56.000000
Should not make the panels or roof sweat here. Best thing if you are concerned would be to incorporate some above deck venting.
Eric Novotny
2017-03-27 10:11:37.000000
Unless there is an airspace the radiant barrier doesn't serve much purpose. You could do some above deck venting, but in high wind areas, I think it makes better sense to avoid those applications.
Eric Novotny
2017-11-18 18:56:32.000000
You do need to seal the T&G and Ice/Water does a good job of that.
After that, there is no real reason to seal the sheathing in this case as there should be an underlayment over top of it that will be a Class 1 vapor retarder and not allow any air/moisture to reach the metal. Where is the home located?
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