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  • Steel roof sweating!

    We are in the process of building a new shop. It has a steel roof and we were told there would be no problem with condensation from the roof. That advise has not proved to be accurate as we are getting the drip, drips.
    We plan to insulate across the ceiling joists with fiberglass battens and of course are concerned about this condensation dripping onto the fiberglass and wetting through onto whatever ceiling we put in.
    We are thinking of running construction felt from the peak down across and stappled to the perlins continuing to the soffits. The idea being the water would run down the felt and drain out the soffit.
    Anyone got a better suggestion or see a problem with our plan?
    Thanks......Ray
    Last edited by roadrashray; 11-07-2008, 09:26 AM.

  • #2
    Re: Steel roof sweating!

    you need a vapor baror to keep the moisture from getting to the steel in the first place, most of the rolls of insulation used in steel roof farm buildings is plastic sheet on the insided face,

    Likewise, insulation not properly tucked in under the roof and at the top of the wall panels can be exposed to condensation and wind-blown rain, causing underside corrosion of the roof panel.

    (picture in origional post),


    Installation practices that allow the insulation to become continually wet simply should be avoided. Fiberglass blanket insulation under GalvalumeĀ® roofs needs to be installed in such a way that all vapor barrier seams are sealed, and punctures, penetrations or holes in the vapor barrier are repaired. Condensation of water vapor on the underside of the roof, along with saturation of the insulation, can cause inside-out corrosion.

    Certain types of field-applied spray-on insulation contain chemical fire retardants that may be corrosive to GalvalumeĀ® sheet. Check with insulation manufacturers before using such products.
    http://www.steelroofing.com/trade_prepaint_job.htm
    spray on foams may be the answer in your situraion, I know many of the old steel buildings were spray on foamed and with good sucess, it may need to be pressrue washed /cleaned,if there is any oils on the tin yet,
    Push sticks/blocks Save Fingers
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    PUBLIC NOTICE: Due to recent budget cuts, the rising cost of electricity, gas, and oil...plus the current state of the economy............the light at the end of the tunnel, has been turned off.

    Comment


    • #3
      Re: Steel roof sweating!

      Is there an an adequate airspace with adequate venting? Insulation is certainly a good idea, but if there is no proper venting you'll just end up with moldy insulation.

      As well, vapour barrier is just seal everything up tighter, so proper venting with a proper cavity to vent is extremely important.

      I assume it's sheet steel/panels - depending on your airspace, if there is one, you might be good with low profile vents along with your soffit vents, assuming the soffits are vented.

      If it's cathedral ceiling style, ridge vent is the only way to go.
      I'm on "The List" and I love it!!

      Comment


      • #4
        Re: Steel roof sweating!

        Originally posted by tinmack View Post
        Is there an an adequate airspace with adequate venting? Insulation is certainly a good idea, but if there is no proper venting you'll just end up with moldy insulation.

        As well, vapour barrier is just seal everything up tighter, so proper venting with a proper cavity to vent is extremely important.

        I assume it's sheet steel/panels - depending on your airspace, if there is one, you might be good with low profile vents along with your soffit vents, assuming the soffits are vented.

        If it's cathedral ceiling style, ridge vent is the only way to go.
        There is venting from the soffit on the bottom up to the ridge vent at the top. We had planed a attic space above the flat ceiling which was to have the fiberglass insulation layed in the space between the joist's on top of the ceiling.
        The steel panels were installed with no vapor barrier and are now screwed to the top of the perlins running across the 40' span of the roof. My explanation that we would run felt from the ridge under the steel and stappled to the underside of the perlins and continuing down to the soffit was a brain fart of course. That installation would block any draining of water at the stappling at the perlins and in fact would create a series of mini dams at each perlin. This would also stop any air flow from the soffit up to the ridge under the steel panels.
        We don't want to remove the steel panels. Maybe a spray foam is the best approach?
        Thanks for the help....Ray
        Last edited by roadrashray; 11-07-2008, 09:27 AM.

        Comment


        • #5
          Re: Steel roof sweating!

          Since you have in essence a "hot"roof, the spray foam might be your only option. I had an Icynene contractor tell me once that they were using it on old homes with no soffit venting/converted third floor attics to living space. Steel is colder in winter and hotter in summer, so the moisture thing will be ongoing otherwise. I also thought about breathable underlayment, which allows flow both ways. But if the structure is uninsulated you'll still be back to the same problem. Regardless, hope it works out for you.
          I'm on "The List" and I love it!!

          Comment


          • #6
            Re: Steel roof sweating!

            Originally posted by roadrashray View Post
            We are in the process of building a new shop. It has a steel roof and we were told there would be no problem with condensation from the roof. That advise has not proved to be accurate as we are getting the drip, drips.
            We plan to insulate across the ceiling joists with fiberglass battens and of course are concerned about this condensation dripping onto the fiberglass and wetting through onto whatever ceiling we put in.
            We are thinking of running construction felt from the peak down across and stappled to the perlins continuing to the soffits. The idea being the water would run down the felt and drain out the soffit.
            Anyone got a better suggestion or see a problem with our plan?
            Thanks......Ray
            Some of the answers in this thread are/could be accurate but a few bits of information are missing:

            1. Where is this building located? Nearest large city and in what state?
            2. Is the building conditioned? That is to say is there an HVAC system in place?
            3. What is the roof structure comprised of (from outside to inside)?
            4. What is the wall construction (from outside to inside)?
            5. What is on the floor? Exposed concrete? Carpet? Tile?
            6. When was the slab poured?

            The issue seems to be condensation causing it to 'rain inside'... this is all about dew point and probably less about insulation (at this point).

            Once you button-up a building the inside RH (relative humidity) rises and causes more moisture in the air. The first condensing surface is probably the steel roof and/or walls as the glass probably has some insulative value or is double/triple paned. In the summer the RH would lower as the AC would be dehumidifying the air (after all that's what an AC unit does). In the winter, the RH can/will skyrocket as heaters do not dry the air. If the building is leaky and allows loads of cold air inside then the building will dry.

            One of the tell-tale signs of a leaky house is a dry house in a cold winter.

            If you plan on adding in dropped ceilings and such yopu can probably get away with laying R-19 to R-38 (depending on climate zone) on top of the ceilings. That coupled with some sort of soffit and roof venting will keep the rest of the steel structure more equalized from inside to out (much like a traditional house is built). Adding a layer of Icynene (or an open-celled spray foam insulation... Icynene is a trade name) would certainly help push the dew point further out towards the roof as opposed to inside. That said you can get water to condense on insulation... which takes us back to my other points about a leaky house and/or insulating the dropped ceilings.

            Comment


            • #7
              Re: Steel roof sweating!

              Another thought.... many of you are suggesting a vapor barrier.

              Before you do this I would STRONGLY suggest you seek other alternatives (depending on where you are geographically). IN N. America there are only a few spots where vapor barriers make sense and that is in northern Minnesota and northern Wisconsin. For 99% of other areas vapor barriers are just not needed (even some AHJ's require vapor barriers where they should not) and in a majority of cases they can be a HUGE mistake if installed (especially incorrectly).

              From the company I used to work for:

              Moisture Management:
              Water management shall be provided as specified in the Energy and Environmental Building Associationā„¢ (EEBA) Water Management Guide. Moisture that enters building assemblies shall be allowed to dry either to the interior, exterior or both sides.
              Low permeance paints (less than 1 perm, ASTM E96), vinyl wallpaper, sheet polyethylene, foil-backed gypsum board, or any other low permeance material (less than 1 perm ASTM E96) shall not be used on the interior of walls and ceilings in Climate Zones 1-3.
              Very low permeance materials (less than 0.1 perm, ASTM E96), such as polyethylene, shall not be used on the interior of walls and ceilings in Climate Zones 4-5.
              Climate Zones shall be defined by the U.S. Department of Energy Climate Zone Map below.
              The text above and map illustrating the climate zones can be found here: http://www.eflbuilder.com/ProgramSpe...oisture_manage

              Comment


              • #8
                Re: Steel roof sweating!

                Originally posted by Keyser Soze View Post
                Some of the answers in this thread are/could be accurate but a few bits of information are missing:

                1. Where is this building located? Nearest large city and in what state?
                2. Is the building conditioned? That is to say is there an HVAC system in place?
                3. What is the roof structure comprised of (from outside to inside)?
                4. What is the wall construction (from outside to inside)?
                5. What is on the floor? Exposed concrete? Carpet? Tile?
                6. When was the slab poured?

                The issue seems to be condensation causing it to 'rain inside'... this is all about dew point and probably less about insulation (at this point).

                Once you button-up a building the inside RH (relative humidity) rises and causes more moisture in the air. The first condensing surface is probably the steel roof and/or walls as the glass probably has some insulative value or is double/triple paned. In the summer the RH would lower as the AC would be dehumidifying the air (after all that's what an AC unit does). In the winter, the RH can/will skyrocket as heaters do not dry the air. If the building is leaky and allows loads of cold air inside then the building will dry.

                One of the tell-tale signs of a leaky house is a dry house in a cold winter.

                If you plan on adding in dropped ceilings and such yopu can probably get away with laying R-19 to R-38 (depending on climate zone) on top of the ceilings. That coupled with some sort of soffit and roof venting will keep the rest of the steel structure more equalized from inside to out (much like a traditional house is built). Adding a layer of Icynene (or an open-celled spray foam insulation... Icynene is a trade name) would certainly help push the dew point further out towards the roof as opposed to inside. That said you can get water to condense on insulation... which takes us back to my other points about a leaky house and/or insulating the dropped ceilings.
                For additional info this is a woodworking shop.
                Answers to questions this post:
                1-state and nearest city-Syracuse,NY 35 miles NE
                2-Building will be heated in winter with coal stove. No AC Building will contain commercial dust collection system.
                3-Steel roof panels screwed to wood 2x4 perlins. Ceiling will be particle board with 10" fiberglass battens layed in bays above.
                4-Wall is larch 1x boards nailed to framing. with 6" fiberglass and particle board.
                5-Floor is exposed concrete, poured yesterday.
                Thanks very much for the help......Ray

                Comment


                • #9
                  Re: Steel roof sweating!

                  Originally posted by roadrashray View Post
                  For additional info this is a woodworking shop.
                  Answers to questions this post:
                  1-state and nearest city-Syracuse,NY 35 miles NE
                  2-Building will be heated in winter with coal stove. No AC Building will contain commercial dust collection system.
                  3-Steel roof panels screwed to wood 2x4 perlins. Ceiling will be particle board with 10" fiberglass battens layed in bays above.
                  4-Wall is larch 1x boards nailed to framing. with 6" fiberglass and particle board.
                  5-Floor is exposed concrete, poured yesterday.
                  Thanks very much for the help......Ray
                  Ray-

                  Here's a few of your problems.....

                  1. Near Syracuse. Move south to a freer society
                  2. Woodworking shop: how much wood will be stored and how 'fresh' is the wood? Wood retains water as we all know... as it ages it dries (releasing moisture into the air).
                  3. Green concrete = ENORMOUS amounts of water!!! So you had an enclosed space and THEN you poured the floor? Or was this happening previously? If previously was this on bare ground? That too would hold and release copious amounts of water.
                  4. Move south - we have less problems here...

                  Comment


                  • #10
                    Re: Steel roof sweating!

                    [QUOTE=Keyser Soze;187661]Ray-

                    Here's a few of your problems.....

                    1. Near Syracuse. Move south to a freer society .......Maybe move south to a warmer society.....or at least warmer women!!

                    Comment


                    • #11
                      Re: Steel roof sweating!

                      Originally posted by roadrashray View Post

                      1. Near Syracuse. Move south to a freer society .......Maybe move south to a warmer society.....or at least warmer women!!
                      Yep and yep!

                      Actually we have family in the Binghamton area just S of you. Beautiful part of the state.

                      Comment


                      • #12
                        Re: Steel roof sweating!

                        Hello all,
                        Here's my 2 cents worth, if you can afford it, FOAM it. It's the only real satifactory way I've seen to keep metal roofs from condensing. That said there are TWO types of foam out there, closed cell (better for most apps, but more spendy, you get what you pay for) or open cell. I spray both
                        And NO I don't just spray foam, have been building for years, commercial, indust, res. And I do have to agree with some of the others, isn't NY some "foreign" country back east?!!

                        Comment


                        • #13
                          Re: Steel roof sweating!

                          Originally posted by shugabuddy View Post
                          Hello all,
                          Here's my 2 cents worth, if you can afford it, FOAM it. It's the only real satifactory way I've seen to keep metal roofs from condensing. That said there are TWO types of foam out there, closed cell (better for most apps, but more spendy, you get what you pay for) or open cell. I spray both
                          And NO I don't just spray foam, have been building for years, commercial, indust, res. And I do have to agree with some of the others, isn't NY some "foreign" country back east?!!
                          Shug........Thanks for the info. Our plan (based on the advise in this forum) is to foam.
                          We are to busy right now to research types and brands. Do you have a favorite brand and could we rent the equipment and spray it ourselves? What is the minimum temp that it can be applied?
                          Yep! It's the foreign country where most of the manufacturing in the US was that is now residing in China. It was taken from here and put there by the same wall street geniuses that gave us the meltdown we are in now.
                          Of course they were aided and abeted by the US and NYS government's, however thats a whole other can of money isn't it?
                          Thanks boys....Ray
                          Oh.....and Shug, welcome to the forum. It looks like you have the right combination of know how and zaniness to fit right in!!!!
                          Last edited by roadrashray; 11-24-2008, 04:25 PM.

                          Comment


                          • #14
                            Re: Steel roof sweating!

                            I agree with roadrashray! haha
                            metal canopies | carports | metal carports

                            Comment


                            • #15
                              Re: Steel roof sweating!

                              You know Ray,
                              I posted a longer reply to your questions yesterday but for some reason it hasn't showed up. So I will wait and see if it does show up for fear of sounding redundant. But the quick answer is, NO, I don't think you could ever "rent" the equipment. Too easy to screw up, and the parts are a total rip. My personal opinion is most brands out there are pretty even. I've sprayed various. Just make sure you are comparing apples to apples, ie, closed cell to closed cell. Be careful because ALL poly foam is flammable. Yes I know, "but it has a flame retardant in it". The flame is "retarded" compared to what?,burning gasoline, then yeah it burns slower. Really though, foam is excellent when used with a little thought. Just don't forget to use your brain around it, no HOT objects next to it, no flames. You would be amazed at what people do. Oh, and really the substrate should be above 55F, can be lower, has to be specially formulated for it. Have done it many times, but you waste more and will probably end up paying more Take care

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