Insulating a metal porch roof

Discussion in 'Homestead Construction' started by BarbadosSheep, Nov 7, 2011.

  1. BarbadosSheep

    BarbadosSheep Well-Known Member Supporter

    Messages:
    2,032
    Joined:
    Jun 27, 2011
    Location:
    South Carolina
    I built a porch on my house last year and made a big mistake. The framing is treated wood and the roof is metal. In the summer, that metal roof turns the porch into an oven. I can't spend time out there at all....it's just too hot! I'd love to insulate it but I am afraid of creating a moisture problem between the metal and whatever I use for insulation. Any suggestions?

    Thought about spray foam insualtion right against the metal. Might be pretty expensive though.

    also though about installing a ceiling on the bottom of the treated roof rafters, but this would create a dead air space between the ceiling and the metal roof.
     
  2. fishhead

    fishhead Well-Known Member Supporter

    Messages:
    15,177
    Joined:
    Jul 19, 2006
    Location:
    northcentral MN
    Is your roof sloped?

    What if you created a double roof with an air space between the roofs and the ends open so that air could flow between the rafters? If it's got a slope the heat should create an air current that would take away the heat.
     

  3. VaFarmer

    VaFarmer Well-Known Member

    Messages:
    138
    Joined:
    Mar 2, 2011
    Location:
    Virginia
    Yes there is reflective material made for use under metal roofing of all types. Can't find the brousher or name of 1 product where going to but under a dormer area next yr. The material must not be aluminum, alum absorbs heat does not reflect it like you need, stuff at lowe's is alum. need to get from commercial metal roofing company, don't remember price but for a 18 sq area was about $1500. a porch you probably have 2.5 sq. Sean samples & demos on the material and looks like a good thing.
     
  4. texican

    texican Well-Known Member

    Messages:
    12,325
    Joined:
    Oct 3, 2003
    Location:
    Carthage, Texas
    Hopefully you used some regular wood between the metal roofing and the pressure treated wood... otherwise, the chemical reaction is going to eat the metal away.

    BTDT. Seen it also on a 100K + boat house...
     
  5. Seymour

    Seymour Well-Known Member

    Messages:
    92
    Joined:
    Dec 15, 2011
    Location:
    ont Canada
    ya the new pressure treated wood (they took out arsnic and added more copper) will eat through any metal. thats why people use the ceramic deck screws. but for insulation i would tack up some 1" foil faced rigid foam sheeting and then cover it with wafer board or plywood which you could paint or whatever. the foil will reflect the heat from the roof and the foam will keep any cool air down, you will also be able to keep the airspace which is absolutely essential with the steel roofing. just my .02
     
  6. Seymour

    Seymour Well-Known Member

    Messages:
    92
    Joined:
    Dec 15, 2011
    Location:
    ont Canada
    ya the new pressure treated wood (they took out arsnic and added more copper) will eat through any metal. thats why people use the ceramic deck screws. but for insulation i would tack up some 1" foil faced rigid foam sheeting and then cover it with wafer board or plywood which you could paint or whatever. the foil will reflect the heat from the roof and the foam will keep any cool air down, you will also be able to keep the airspace which is absolutely essential with the steel roofing. just my .02
     
  7. BarbadosSheep

    BarbadosSheep Well-Known Member Supporter

    Messages:
    2,032
    Joined:
    Jun 27, 2011
    Location:
    South Carolina
    Thanks for the suggestions. The roofing I used is painted so that should help with the contact agaist the treated lumber. And I did use the kind of screws that are for the new treated wood so hopefully that will work ok too. I think gluing some foam insulation to the back side of the tin is a good idea. That will still leave the groves for an airspace.