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Community and Q&A

Roflex substitute

Trevor Lambert | Posted in Green Products and Materials on

I need a flexible gasket for my upcoming mini split install. Roflex comes in such a small piece that I’d need two of them, one inside and one outside. That’d be about a hundred bucks with shipping. Meanwhile, I see EPDM rubber sheeting of the same thickness on eBay for less than half that for ten times the material. Is there something special about Roflex, or will the generic sheeting do the same job?

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  1. Expert Member
    Malcolm Taylor | | #1


    I would guess that a carefully cut piece of EPDM stretched around a pipe or duct would seal as well as Roflex. But then, I've never used it. Maybe someone with experience can tell us what is magical about it.

    I use peel & stick membranes in those situations. They don't end up looking as neat though.

  2. Expert Member
    Zephyr7 | | #2

    A quick check of the Roflex datasheet pretty much shows it’s a piece of EPDM with a hole punched and an adhesive backing applied. I thought there might be some fire testing or approvals but it doesn’t list any. It looks to me like it’s mostly a time saving product and not really all that special in terms of the materials used.

    I think you’re safe using a sheet of “regular” EPDM. To get a good seal, you’ll need to cut the holes as cleanly as possible. If you have access to a metal punch, that would be the best way to do it. Next best is a SHARP knife and a template. You’ll want to undersize the hole a bit to get a tight fit on whatever you’re sealing. Any nicks in the perimeter of the hole will open up and leak (I’ve made gaskets this way before, clean cut edges are important).

    For the adhesive, use a spray adhesive like 3M 74 or 90, both of which should adhere to the EPDM and wood/metal surfaces. 90 might be a bit better in this application.


  3. Trevor Lambert | | #3

    I'm starting to wonder whether this type of gasket even solves my problem. I need to seal the bunch of lines that come out of the back of the indoor unit (couple of refrigerant lines, at least one electrical cable) to where it goes through the wall. The access to the hole in the wall goes away as you mount the unit, so the seal has to be something that happens automatically as you push the pipes and wires through. The EPDM gasket is automatic, but its sealing ability over multiple separate pipes is questionable. I just can't think of another way. The wall is too thick to try to access this from the other side after the unit goes on the wall. If there was a wide enough flat space on the back of the unit where the pipes come out, I could imagine having a foam gasket that meets up with a pre-installed pipe going through the wall. If I could find a detailed diagram of the unit, or see it in person I could wrap my head around the problem. The installer isn't going to be very interested in proper air sealing (or waiting for me to figure it out), so I have to have this more or less "ready to go" when he arrives.

  4. Expert Member
    Zephyr7 | | #4

    I think you might need to change your thinking a little, like what you’re saying about sealing the unit instead of the pipes. You’ll have a very difficult time sealing multiple lines (I’m guess three, refrigeratent in and out and electric supply), especially when they have to move as the unit is slid into place. You might be able to use some of the silicone D profile weather stripping to seal between the wall and the back of the unit, that type of weather stripping can seal a pretty wide gap but still squish down in tight areas without too much force.

    The other option might be to borrow from the telecom industry. Data centers used raised floors as a cooling plenum, so there is a need to air “seal” around multiple cables where they exit the floor under equipment racks. There are two common options: one is something of a double brush that the cables pass through. The brush closes the larger square hole in the floor tile (usually around 4x4”, but can be quite a bit larger) to limit loss of air pressure under the floor. The other is similar, but uses flaps of EPDM or foam rubber. Neither will make a “seal” the way you’re probably thinking of though, you’ll still have leaks, but not as much as a large hole would have.

    Another option might be a multiple aperature cable gland seal similar to those shown here:
    These are normally tightened into a round clamp assembly, but they can also be used inside plastic pipe if you cut a slit and use a large stainless hose clamp around the perimeter.

    There are a lot of weather seals for the utility industry to seal around multiple cables in manholes and the like. It might be possible to make one work for your application. If you can provide some pics I might be able to suggest something. You could potentially make your own seal too out of a thick (1/2” or so) slab of EPDM. Drill holes slightly smaller than each pipe/cable in a straight line, then cut a straight line down the center of the slab bisecting all the holes. You can clamp with a square bracket.


  5. Expert Member
    Rick Evans | | #5


    I used this (EPDM used for RV roofing).

    We cut the holes smaller than the mini split 2 refrigerant lines and signal cable, stapled the sheet to the sheathing , and then sealed edges with Zip Tape. We then covered it with a trim board. (See photo)

    The mini split installers pushed the lines through without trouble. I also did this for our water hydrants and ERV port.

    I suspect the seals were effective as our home achieved o.24 ACH @ 50 Pascals.

    Hope this helps!

  6. Expert Member
    Rick Evans | | #6


    My wife read my reply and corrected me. (She was there when they installed the mini split.)

    Turns out the installers had a hard time with the EPDM. They were worried the openings were too tight and would restrict flow. Too loose and the epdm wouldn't make a proper seal.

    To improvise, my wife had them push a 4" pvc pipe through the EPDM sheet to serve as a conduit for the lines and cable. She then filled the pipe with low expansion spray foam.

    Sorry for the false information! :-)

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