A Trio of Window Air Sealing Detail


One of the things we learned from our first unofficial blower door test was that our window sealed with Tremco’s ExoAir Trio alone did not perform perfectly.  This may be a issue of level of expectation than about the performance of the tape.  I think we were expecting it to be completely air-tight but in the end it was not.  It sealed most of the potential air-infiltration but when the home was depressed at 50 Pascal, you can definitely feel a small stream of air leaking in all around the windows.

We decided that this was not good enough and sought out a better solution.  Also, we decided to make some comparisons, so we know what choices we have for future projects.

Window Installed and Sealed with Trio

Window with Trio

Cost: $27 for Trio

Installation Time: 15 minutes

Sealing Time: 0 minutes

Here’s the first alternative, we call it:

Quick and Foamy

Window sealed with GreatStuff sprayfoam

This is the quickest and easiest way to remedy the problem.  Take a can of GreatStuff and carefully seal the entire gap with it.

Cost: $3.00 of foam (Rough estimate, also we have really thick walls.

Installation Time: 15 minutes

Sealing Time: 2 minutes (one minute to spray and one minute to check).  It will probably take another 3 minutes to trim away the excess foam when we drywall.  So, 5 minutes.

and the “Slow and Sticky”……

Window taped with Tescon Tape

This is the most time consuming.  We start with stuffing the gap with fiberglass insulation (next time, we’ll use mineral wool or Roxul).  Then we place the tape on the window frame We had to be mindful of how this will be finished and be sure to only tape 1/4″ or less of the window frame, so when the drywall goes on, the tape won’t show.  The application takes a long time and the tape being SOOOOO sticky does not help.  However, the strong adhesion is one of the reasons this tape performs so well and provides a long-lasting seal.  Finally, we patch the corners to be sure that there are no holes or wrinkles on the tape.

Cost: Tescon Profil ($6.16), Fiberglass insulation ($1)

Installation Time: 15 minutes

Insulation Time: 5 minutes

Air-Sealing Time: 20 minutes

How do they perform?

Jim and Andy of Elysian Energy did another unofficial blower door test yesterday.  We were especially interested in how each of these windows fared.

Andy starting up the Blower Door

Under negative pressure, with the window installed and sealed with just Tremco trio, I felt a small amount of cold air all around the window with the back of my hand.  The Quick and Foamy and Slow and Sticky both performed well, I did not feel any air-infiltration.

We also used an infrared camera to see if there was a big drop in temperature in the installation gap.  Under the scrutiny of the IR Camera, there was a 4to 5 degrees drop in the installation gap with just Trio.  Quick and Foamy showed about 0.5 degree of difference, while Slow and Sticky had a small fraction of degree drop in temperature.

In conclusion, Slow and Stick is probably the most long-lasting and air-tight detail.  It is also the most time consuming.  Quick and Foamy is not a bad solution, but sprayfoam should not be completely trusted to get into every void you are trying to fill.  Additionally, the longevity of the air-tight seal created by sprayfoam is unknown.


22 responses to this post.

  1. Nice research! Like your conclusion too…..
    Go slow & sticky (and durable).


  2. Thanks Floris! Now the question is, where do I find someone who will tape the windows like this for me?


  3. Wondering if you considered SIGA Corvum for the slow & sticky? I like the way it is prefolded so that only 1/4″ goes onto the frame.


  4. Thanks Jack. Actually the Tescon Profil has similar divided release backing paper like in Corvum.


  5. Ah, cool…. Also: sorry I didn’t know my link would embed the video.

    I’m curious, with the ExoAir Trio do you need to enlarge your R.O. sizes?



  6. Jack,
    Here’s the spec sheet. The tapes comes in 2 different thicknesses (there may be three now). The expand to fill different opening ranges. So, within normal situations, you shouldn’t need to enlarge R.O.


  7. Oops Jack. I meant to upload the spec sheet. Let me know if you want to look at it and I can email it to you.


  8. roger,

    so were you guys at the high end of the r.o. spacing around the window frame? i’m wondering if the tolerances were tighter, if leakage would be such a big deal…


    • Mike,

      You are right. We were on the higher end of the tolerance but still within acceptable range. I agree, if the spacing is a little smaller or if the tape was a little thicker, there would be less air.

      As I told Joerg, this may be an issue of expectations too. This is from it’s data sheet: ” an airtight, thermal, vapor permeable weather seal in one product.”

      As Albert pointed out below, as a group, PH people are “obsessive”. “Airtight” on the spec sheet means something different than our definition of “airtight”. As I described, it was a small amount of air coming through the Trio. Probably not much to really warrant resealing every window but when you do a blower door test and you know this is a known weak point, why not try to make it perfect?

      Additionally, the original intent with the Trio was that I was looking for a way to minimize labor and minimize human errors. I wanted something that can be done quickly with a perfect result every time. That was perhaps naive of me to be searching for something magical.

      When it didn’t perform to expectation, I was curious about what would make a really good detail that I can get someone else to replicate. It was based on those reasons, I decided to do my trio of window sealing tests.

      This is not me trying to bash any particular product. I think The Trio will work very well in a large project where you can’t be taping every single window. Or at least, quickly or cost-effectively.


  9. A couple of notes:

    We are still learning how to use the Trio. At 50pa depressurization, it can move some air (we are learning). -It is after all, an open cell foam. Being towards the middle of the range helps since there is more compression. If it was “good work” it wouldn’t be an issue. Since it’s us “PH folk” (look up obsessive in Webster’s) I think that we may need to consider a backup along with it. Your Tescon Profil or the Siga Corvum should do it.

    I think what we want the trio to do in the application is to move with the opening which the LEF won’t do, and, absorb and release vapor. It’s not a “all in one” application with zero air movement for PH work. If it was, through it’s application width, it would trap moisture. A tricky balance.

    The two tapes are a little differant. The SIGA Corvum is worth a try. It’s doesn’t just have a split back. It is pre-folded and has one backing removed. That means it lays off the roll faster and makes precut corners easier.

    Rodger was nice enough to let us know of the difficulties that he had with the trio. I appreciate that. We are still learning what to expect from it.

    Pardon this commercial interruption.


  10. Hi Albert,

    Thanks for your notes. I agree with you about the compression. Perhaps we are a little obsessive too. There’s a certain PH in NB coming in at 0.17 ACh 50 and the guys are still making it tighter! Their details are great and I applaud that effort.

    I think Trio is not a perfect product. As I wrote to Mike above, it comes down to expectations. It also comes down to cost, when it costs so much, you kind of expect perfection without a backup measure.

    The biggest issue I see with the tape is from our experience it really absorbs water and it actually released the water to the inside. So, I think that statement in the Spec sheet that it is a “weather seal” is questionable. Joerg is trying to figure out what happened. I really don’t think it is an issue of installation since Joerg flew in to show us how to do it (great customer service BTW) and we watched the video prior to the install to make sure we followed the directions.

    Thanks for pointing out the difference between the different tapes. We are not wedded to any particular products and are perfectly happy to try the SIGA too. We are constantly trying to figure out the easiest, cost effective and highest performing way to do things.



    • Rodger,

      Fair enough. I know I’m still learning how to use it.

      No one is Naive in this game. It’s not for the timid. We don’t always get it right the first time, but I that’s the life of the “early adopter”.

      keep plugging…



  11. Thanks Albert!


  12. Posted by Peter on 2012/03/31 at 11:45 pm

    How do you like your Intus Windows? Any problems?


    • Hi Peter,

      We like them.

      Haven’t had any serious issues with them. but you might want to keep the following in mind.

      1. Be sure to order screens though, we assumed they would have screens but they didn’t so had to order them at a later date.

      2. Installation is very different from American style windows. There are no flanges that you screw in. You either use the metal brackets they come with or you drill the frames. I don’t like the bracket system. I think the windows should be pre-drilled or fabricated with the holes in it for installation.

      3. These windows are extremely heavy, so if you have some large ones, be sure to figure out the installation steps ahead of time. We had a 5×10, that needed 8 guys to install.


      • Posted by Peter on 2012/04/01 at 2:38 am

        Thanks for the info! Why don’t you like the brackets? How are the tilt & turn? Do they stay open without being propped? The largest windows I will have are 5×7 fixed. Were they able to do a 5×10 window WITHOUT a center mullion?

  13. Hi Peter,

    The brackets present a number of challenges:

    1. They are not easy to insert into the frames, but you’ll get the hang of it after a few.
    2. Once attached to frame, in order to bend it against the R.O., you need to shim each bracket, which create a difficult surface to finish. Give me your email and I can send you some pictures of what it looked like.

    What I would do different next time is to pre-bend the brackets before attaching them to avoid this problem. Also, I would make my R.O. larger to allow for a “sub rough opening”. This will give me more room to work with when installing drywall.

    The tilt & turn work well. They stay open without being propped. Although, when the windows are open in the regular casement way, a stiff wind can cause them to close.

    5×7 should not be a problem. our 5x10s are without a center mullion. I think you may be referring to a Canadian manufacturer that require a mullion?


  14. Peter,

    If it helps… We are a fan of installing wood windows with special frame screws rather than clips etc. It makes the interior air sealing easier by not having to go around clips etc, by what ever means you plan to seal.

    For this purpose we import a range of small head 7.5mm window screws from Dresselhaus in Germany. These work on their own or with the GRK adjustable shim screw. If you’re curious, you can find them on our website under the window installation section.


    • Posted by Peter on 2012/04/02 at 3:46 pm

      Will those screws work with an ICF wall utilizing vinyl window bucks? Or must one have wood bucking around the windows if using an ICF wall system?

      Why doesn’t Intus install a nailing flange on their windows? Seems strange?!!?

      How strong are those brackets? Would it not be stronger to have the window frames screwed to the framing?


      • Peter,
        You may want to ask Intus directly these questions. I am interested to know if you could use vinyl window bucks too.

        Window nailing flange is mostly something that North American manufacturers use because those windows are installed on the outter face of the exterior wall. In Europe, windows are installed recessed in the wall. The benefits of which you can find on this blog and other places too. Most European windows do not use window nailing flanges.

        The brackets are an alternative to screwing, so, it’s either screws or brackets but not screws and brackets.

  15. Peter,

    I will send you pictures later today.

    Also Albert is correct that shim screws are a better option. Here’s a quick video on them http://youtu.be/XKT4upXeEiw

    Other than Smallplanet, you can also get them here. http://www.conservationtechnology.com/building_shimscrews.html

    With Intus, you will need to drill your own holes. But perhaps you can get them to pre-drill them in the factory. This option works with all the operable windows. With fixed windows, you may not have the options because Intus and at least some of the others glue the window sash into the fixed window frames, in that case, you will still need to install with brackets. We did exactly that.


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