Backer rods
tjones1014
| Posted in General Questions on
Are all closed cell foam backer rods essentially the same for air sealing windows? Or are there some that are higher quality than others?
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I think most backer rod is just poly foam in various sizes, nothing special. You can get a foam neoprene (the black stuff) weather stripping that is square and has no adhesive that can also be useful. Use whatever gets you the best fit.
Bill
What should we be looking for in terms of fit?
Also, is all window & door low expansion foam basically the same as well? We were thinking of doing the spray foam first (only inserting the nozzle about half way into the opening) then backer rod and caulk. Our other option was backer rod and caulk then suga wigluv on top after the caulk cures.
Our insulation/air sealing team usually fills the entire space around the window instead of leaving a small space for drainage if needed. Since we want it done a specific way, they said we should do it ourselves to ensure someone doesn't accidentally do it wrong (since they're not used to doing it that way). Trying to make sure we do it correctly! I appreciate and welcome any and all advice!
I usually just used canned foam, but you want the "low expansion" kind for around windows and doors. The low expansion foam doesn't exert as much force when it cures and expands, and it stays a bit more spongy once cured too. I usually just use Great Stuff brand, which works fine for this, but I've also used Loctite (now GE) brand, and a few others. The OSI Quadfoam has a good reputation too, and while I have not yet used that one myself, one of my commercial spray foam contractors loves the stuff.
Bill
Most backer rods are essentially the same..
You might get higher quality from a glazing supply store compared to the local hardware store but they essentially do the same thing: stuff the gap so you can caulk on top of it.
I usually avoid it all together and just use spray foam as the backer rod. Fill the top and sides with ¾-⅞ of the depth and after it cures, use sealant to make it water and vapour tight.
You can use backer rod and sealant at the bottom, to leave space for water to gather and flow out (hopefully you've sloped your sill).
Or you can use spray foam as the backer rod if you're careful enough not to fill the entirety of the gap but spray just a bit in a zig-zag pattern to keep it near the inside of the sill, which replicates a backer rod.
Hope this helps,
Jamie
Are most window & door spray foams essentially the same as well? Or are some brands better than others?
I do the same thing as Jamie. Spray foam and caulk over it. Key is some practice as not to over-fill the gap so it oozes out and you have to trim. Caulk over big gaps is hard, so if you have gaps of around 3/4" or more I would use tape as backup instead of caulk.
For the bottom, I spray foam the whole thing as canned foam is not liquid tight. Water will still find its way out.
I'm partial to the Dow low expansion foam as it lasts in the gun for a long time without setting. The Sika foam from the box stores also works well.
Canned spray foams have different expansions rates, and some are latex / water based, others are solvent based.
Backer rod serves a specific purpose to compress and expand while the caulk bead does the opposite, without the bead adhesion to the substrate failing. You may find the info at this link helpful: https://metrosealant.com/when-to-use-backer-rod-a-comprehensive-guide/?srsltid=AfmBOorgf3a_FztEcFxm0g7RteVLsiLtE8LrMKPMeMY1rKpztsalzwF7
Our windows have factory-applied jamb extensions. I had no idea that's what we were getting when my contractor placed the order (that's on me for not understanding that at the time, but I'm learning along the way). I just found out that's what they were. Does that change the way I should air seal the windows? They're already installed, so no going back now unfortunately.
No, it doesn't change anything for the sealing around the window.
It just means the windows will be deeper than they normally come.