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  • adding vapour barrier

    I have a room where the ceiling is insulated with rock wool and finished with acoustic tile stapled to strapping. There's no sign of a vapour barrier so I guess I should add one.

    Several factors are going to complicate the job. The room is primarily used for storage, but it also serves as a passageway, so the centre can't be obstructed for any length of time. Boss-lady has to have access to the stored items, so she has to know where they are, so I can't move them out of the room, so I have to work around them. To be practical, there's no place to put them even if I could get permission to move them. There are also a couple of partial partitions that I have to work around. All this means I'll have to use small sections of material. Also, I have to work alone, so the material I use will have to be rigid enough to stay in place while I hold it up with one hand and fasten it with the other.

    The one thing that will make the job easier is that appearance is a minor consideration, so I have no problem with taping seams, or screwing through the tile into the strapping. Removing the tile will involve so much extra work and mess I'd rather not contemplate it. I assume the tile has no strength, so gluing the vapour barrier to it wouldn't be a good idea, no matter how light it is.

    Is there a light, vapour-tight, fairly rigid material that I can install in (say) 2' x 4' sections, and then seal with tape or caulking?
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  • #2

    Re: adding vapour barrier

    You do not need a vapour barrier unless it is cold on the other side of the insulation. Is there sign of damage to the rock wool caused by moisture through the ceiling now? It is easy to cover the entire ceiling with 6 mil plastic in full 10' width and then strap it so you can install whatever new covering you want. You will lose an inch of height in the room but save a huge mess.
    Rob

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    • #3

      Re: adding vapour barrier

      Indeed, if the ceiling is warm on both sides, there is no need for a vapour barrier, if it IS cold on one side and warm on the other, then yes, you need a vapour barrier/retardant.

      Shamelessly lifted from Jon Eakes website:

      "Benjamin Moore has a "Super Spec" primer K206-00 that is a latex paint and comes in at less than 0.5 perms; Sherwin Williams has a "Moisture Vapor Barrier" latex paint B72W00001 that comes in at less than 1 perm. Others look promising but the data sheets don't list perm ratings.

      The company Zinsser makes a shellac based white primer called BIN that is primarially used for hiding difficult stains, but it too rates in at less than 1 perm and this company, depending who is working in their labeling department this month, occasionally identifies it as a "vapour barrier paint". Although more expensive per gallon, you can easily find this product in most paint departments."

      Further on Jon's page regarding vapour barrier paint, apparently 2 coats of oil based paint would also be quite effective. Of course, we're talking about an acoustic tile ceiling, which would drink up that first coat... but it would seem to me to be the most effective way of getting it done if absolutely required. Rolling on some paint would be the easiest way to accomplish the task... but change the appearance of the ceiling... something you are stuck with no matter what you do. The joints between the tiles might be an issue though... tough to seal up with paint and caulking it would take forever and use a lot of caulk.

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      • #4

        Re: adding vapour barrier

        Paint is a very good vapour barrier.

        My question involves the rock wool installation. Normally rock wool was applied in Paper Back Batt form or loosely blown in like cellulose or fibreglass. Whatever is above this ceiling may suggest the type of installation. If it's an attic space it could have been blown in. If not blown in, then Batts are likely. Are you sure the application does not include tar backed paper which is in fact the vapour barrier. I'm asking because many people do not know the paper was the vapour barrier and my reasoning is predicated on this: WHAT HELD THE INSULATION UP IN THE CEILING? You describe tile stapled to furring strips. That tile would have had to be in place before anything was blown in or it would simply fall thru the ceiling joists onto the floor. Is there something else like screening holding it up or do you believe it would fall down if you removed the tile?

        BTW, yes you could apply plastic vapour barrier and drywall right over the tiles which are insulation as well. My point is you don't need anything if there is tar backed paper batts up there!
        "Do it Right!"

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        • #5

          Re: adding vapour barrier

          Originally posted by Rusty View Post
          Paint is a very good vapour barrier.

          BTW, yes you could apply plastic vapour barrier and drywall right over the tiles which are insulation as well. My point is you don't need anything if there is tar backed paper batts up there!
          Or, IMO, if there is no sign of condensation damage. If there is water coming from the roof above, the VB will not help it will hinder.
          Rob

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          • #6

            Re: adding vapour barrier

            Originally posted by iamtooler View Post

            Or, IMO, if there is no sign of condensation damage. If there is water coming from the roof above, the VB will not help it will hinder.
            Rob
            Agreed. Condensation is a definite concern. A roof leak is another concern. Neither condition was mentioned by the OP. Is there a roof above? Unfortunately that was not mentioned either. Could this be soundproofing between a room under a room?
            "Do it Right!"

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            • #7

              Re: adding vapour barrier

              How old is the place? If its 30 years old or more there is enough paint on the ceiling to make a decent VB dont worry about it.
              https://www.facebook.com/gregsreinventions2016/

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              • #8

                Re: adding vapour barrier

                Greg I believe the ceiling is acoustic tile stapled on and I'm guessing that the house is older than 30 years considering Rock wool is the type of insulation which was apparently used. The last time I saw rock wool installed was many years ago. Perhaps the Original Poster will respond and clarify.
                "Do it Right!"

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                • #9

                  Re: adding vapour barrier

                  There is a roof immediately above the ceiling. The space above the insulation is connected to a vented attic, but I'm afraid there isn't enough space to assure decent ventilation. Another reason to worry about a vapour barrier.

                  The insulation appears to be in batt form, but without a paper backing. It looks like what was called friction fit back when there was a choice of paper-faced or unfaced batts. I haven't seen the paper faced kind recently. It was probably a tight enough fit to stay in place while the strapping was being put up, but I wouldn't want to count on it staying up now, if I removed the tile.

                  I've heard of paints that are impermeable enough to serve as vapour barriers, but I never knew if they really worked. Unfortunately, the tile is the kind with holes in it. They don't go all the way through, but they would make it impossible to get a continuous coat of paint on the tile.

                  I agree that a continuous layer of plastic film is the way it should have been done originally, with an empty room and as much help as needed. Now it doesn't look like such a good idea. Even when I was young and agile, trying to handle a roll of polyethylene film overhead and have it stay in place while I stapled it was a job to be avoided. I always felt like the proverbial 1-armed paperhanger. I don't think I'd even attempt it alone, now.

                  After I wrote my original post, I remembered that I have a stack of small (probably 2'x4') sheets of Arborite (or some equivalent laminate). It's the paper-thin kind, so it will sag as I try to put it up, but not nearly as badly as poly film, and if it's too floppy, I can always cut it into 2'x2' pieces. It should be impermeable, though I'll still have to seal the screw holes and seams. I was hoping to get this job done this winter, but I probably won't be able to get it out of the shed where it's stored until the snow is gone. Unless somebody has a better idea, I'll wait until I can get to it.

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                  • #10

                    Re: adding vapour barrier

                    You never said how bad the condensation problem is in that room. Stapling 6mil is not hard to do because it does not need to be taught and you cover 19' wide.
                    Rob

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                    • #11

                      Re: adding vapour barrier

                      If you need to put up a vapour barrier get a couple of bundles of lathe and slid them in over the strapping when you remove the tile. That should hold bat type insulation in place. Get th vapour barrier up is a pain. Just start the full length of one side and then work underneath the vapour barrier stapling to the strapping as you go. Then reuse your tiles if they are still good.

                      Nails in the bottom truss cords may also work to hold up bats. Just depends on your situation.
                      Egon
                      from
                      The South Shore, Nova Scotia

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                      • #12

                        Re: adding vapour barrier

                        OK here's a couple thoughts. It's probably not Rock wool. If we knew age and colour of the insulation we might be able to help more effectively. Who installed it would help too. SPACE doesn't vent itself regardless of size. Roof vents and clear flow soffit vents will vent the space which by your description does not seem to be a problem regardless. Frankly I don't think you need a VB anyway because you have not told us there is actually a problem. Do you want one simply because you THINK you should have one? The paint on the tile is an acting VB albeit not a great one. If you MUST,,,,,, you have 2 options......[1] leave the tile in place,,,,,,,,rent a sprayer, preferably an airless sprayer and paint the tile. [2] leave the tile in place and staple a layer of Poly VB over the tile, Seal the perimeter with red poly tape [I will explain] and apply drywall or some other ceiling material over the Poly.

                        The red poly taped perimeter is critical. IT MUST BE DONE PERFECTLY. What you do is apply a layer of 2 inch wide masking tape 1/2 inch down from the ceiling on all of the perimeter walls. Staple up the poly. One guy can do it easily. If you choose this method we will walk you through it. Once the poly is up, use the red tape to tape the poly to the wall applying it on top of the masking tape so it does not stick to the wall except for the first 1/2 inch at the intersection of the wall and ceiling. Then cut the tape with a razor knife at the 1'2 inch mark. Peel the masking tape and it will remove the unwanted red tape as well. The reason you have to be so careful is you need a seal and this red tape sticks worse than the stuff on a blanket. You will never get it off the wall without ruining the wall surface, if you don't use the masking tape. You need the perimeter seal as a safeguard because this is where you will suffer air exhaust and infiltration.

                        I'm not sure I would do either but I'm not in your shoes.
                        Last edited by Rusty; 01-08-2018, 04:36 PM.
                        "Do it Right!"

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