Metal roof over deck insulation - advice needed.

wish2fish

wish2fish

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Dec 19, 2006
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Locust Creek, Ohio River mm 433
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2003 220BR
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I'm installing a metal roof over my deck at my camp. I'm trying to figure if I need insulation under the metal roofing to mostly prevent heat radiation down to the deck area. The metal roof will be 9 feet above the deck at its closest and 12 feet at the peak. The deck is currently open on 3 of 4 side with the trailer being on the 4th side. I can't find anything online for situations like mine. I did notice that the sheds with metal roofs for sale in my area use the foil bubble wrap as a radiant barrier but everything I read online says there should be an airspace between the metal and the radiant barrier. The lumber yard where I bought the metal said he has seen no insulation and the bubble wrap used. He said folks use the bubble wrap to prevent condensation from forming and dripping.


Wondering if anyone has expertise in this area or has a similar situation.
trailer roof.jpg
 
I'm in now way a professional just a do it yourself kind of guy. But I would suggest just sticking yhe metal roof up there and seeing if you like it. If it's to hot or too loud when it rains than maybe stick up some strip of rigid insulating up there in the future.

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Like said above try it first. My guess is that it will get warm when the sun hits it. I did something like this years ago. It only to cover a shop truck so really didn't spend any time out under it so can't say if it was warmer. If you do decide to insulate I would have an air space and ventilate.
 
sdarc said:
Like said above try it first. My guess is that it will get warm when the sun hits it. I did something like this years ago. It only to cover a shop truck so really didn't spend any time out under it so can't say if it was warmer. If you do decide to insulate I would have an air space and ventilate.
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Did you say anything here Steve?

I have a 24x30 metal carport I store my boat under. When working in the boat during the summer months, I never noticed heat from the roof while in the boat working.
 
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I actually think the biggest problem with no insulation is going to be the noise when it rains. Metal roofs can get loud when you get a good hard rain. Than again some people like that sort of white noise.

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My screened in room has an aluminum roof (interlocking panels) and it's 3 1/2 inches thick. It's filled with styrafoam to dissipate the heat and to quiet it down during rain storms.
 
islandhopper00 said:
Did you say anything here Steve?

I have a 24x30 metal carport I store my boat under. When working in the boat during the summer months, I never noticed heat from the roof while in the boat working.
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I wonder then if the height has a lot to do with it? Is yours in direct sun?
 
Lot of variables. How much direct sun? I see a lot of trees. It the metal going to extend over the trailer or is that area to be sealed off? Ditto the low end. If extending, you have a natural chimney of sorts for the heat to escape.

I think you are going to be fine. However if not, you can lay some of the stiff insulation sheets as Night swimmer mentioned. All they have to do is lay in there on some firring strips at the base of the rafters.

Hold them in place with Duck Tape. It can't be a guy project without Duck Tape. :grin:
 
I would look at your needs as being in preventing condensation, sound deadening, and insulation last. Something like Thermax rigid foam, foil covered…I think they make products that are foil on one side and a washable surface on the other. Putting this on foil up seams taped would protect against condensation, deaden sound, and insulate some. The purpose of the airspace is largely to cut down on conductive heat. Being that you’re open on 3 sides I don’t believe being ’hotter’ under your roof should be a worry. If you're ever going to do it, do it now right under the metal roofing.
 
dpmulvey said:
Lot of variables. How much direct sun? I see a lot of trees. It the metal going to extend over the trailer or is that area to be sealed off? Ditto the low end. If extending, you have a natural chimney of sorts for the heat to escape.

I think you are going to be fine. However if not, you can lay some of the stiff insulation sheets as Night swimmer mentioned. All they have to do is lay in there on some firring strips at the base of the rafters.

Hold them in place with Duck Tape. It can't be a guy project without Duck Tape. :grin:
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Roof over trailer as well. There will be a ridge vent where they meet.
 
Without any hesitation you should insulate under the metal. The most important reason for this is the constant dripping of condensation with the sunrise on cold days!!!!!!!!!! The metal gets cold at night and when the sun hits it in the morning or when the ambient temperature comes up fast you will have considerable dripping all over anything sitting beneath the roof. My boat gets a drenching during these times. My patio furniture gets a good drenching under my aluminum awning on the back of my home. It's like at times you don't even have a roof. So why go to this trouble and expense if you are not going to insulate it and prevent condensaton????
 
Color is another factor with the heat.
Our garage roof has silver galvanized metal sheeting which reflects all the heat - stays cool.
Also no insulation and no condensation issues.
Our shed on the other hand has brown sheeting and gets hot real quick.
 
I had put up one sheet to test fit on Tuesday. Went back yesterday and it was so hot I couldn't hold my hand on the metal underneath. I'm going to go ahead and used the foil bubble insulation under and see how that goes. I assume the foil bubble insulation acts as vapor barrier so the moisture doesn't get to the metal.
 
I am by no means a roofing expert. But, over the years I have done considerable research on heat losses on refrigerated containers and trailers, basically big metal boxes with sheet metal skins, so I have a pretty good grasp of solar heat losses involving metal and insulation.

One comment I can make with certainty is that as long as the roof is a light color; white, silver/aluminum, light grey etc. there will be less heat transfer than darker colors. Sounds like a no brainer, the interesting point is that all of the light colors work at about the same level of efficiency. So shiny aluminum is not going to perform better than grey in any practical sense.

The other comment is that there will be condensation even if insulation is used. It may not drip down on your head, but it will be up there between the metal and the insulation. If the moisture stays trapped it will lead to premature corrosion failure. There are two courses of action; glue the insulation to the metal, or set off the insulation so there can be either drainage, or air flow.

Henry
 
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