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TOPIC: Energy Efficiency

insulate beneath metal roofing outside and seal roof

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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
An informed customer is the Best Customer!

4/6/2016
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

7/11/2016
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
Isaiah Industries, Inc.

7/11/2016
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

7/25/2016
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
Isaiah Industries, Inc.

7/25/2016
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

8/9/2016
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

12/26/2016
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
An informed customer is the Best Customer!

12/27/2016
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

3/26/2017
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
An informed customer is the Best Customer!

3/27/2017
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

9/9/2017
Steveo, what is the pitch of the roof?
Todd Miller
Isaiah Industries, Inc.

9/9/2017
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

11/18/2017
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
An informed customer is the Best Customer!

11/18/2017
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

11/18/2017
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

11/26/2017
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?
Eric Novotny
An informed customer is the Best Customer!

11/26/2017
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

1/10/2018
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
Isaiah Industries, Inc.

1/10/2018

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