Replies

1. 
   jberks | Nov 16, 2019 03:19pm | #1

   I actually argue the opposite. Caulk can be harder to deal with than canned spray foam when removing from wood.

   Canned spray foam is not hard to remove. Its pretty light sfuff. Do some tests if you'd like. It pulls off with your fingers and then a quick sanding or rasping to get the residual off the wood.

   Funny enough, I prefer to do both with my windows. I spray around the windows with low expansion spray foam, then when it sets, cut off any excess, then push the foam I with my fingers to make space caulk over top of it.

   This is like a hacks version of a backer rod. But this does 2 things, it insulates and aid seals around the window, then the caulk water seals and backdams the rough opening to block moisture and water ingress and guide a path outward should the window leak.

2. 
   ohioandy | Nov 16, 2019 03:22pm | #2

   I've hacked through spray foam when replacing windows and doors, it's not so bad. A handheld Sawzall blade will do the trick. What's worse is removing far too many nails from the flange, or having to cut through too much caulk. When used as an air seal, the spray foam need not--and SHOULD not--entirely fill the cavity. Best practice would be laying in a single bead around the inside perimeter of the window; despite our reputation for NOT doing the right thing, most contractors know that spray foam is too expensive to waste.

   I don't leave a drainage gap on the sill, since the foam bead is on the inside edge. The sloped-sill concept guards against window failure; it doesn't anticipate water intrusion coming from the trim stool or casing.

   FWIW, I also like the structural rigidity that the foam lends to the window unit.

3. 
   maine_tyler | Nov 17, 2019 10:10am | #3

   Alright, good to know its not too much of a hassle.

   "When used as an air seal, the spray foam need not--and SHOULD not--entirely fill the cavity."

   I am assuming this is for the reasons of drying that I mentioned above? That's kind of the reason I felt like mineral-wool/fiberglass etc. would be nice since it will provide insulation but not clog up moisture flow. I know insulation in that tiny space is really secondary to the air-seal and arguably not worth trying to shove fluffy stuff into (depends on how large a gap I suppose).

   Thanks for the thoughts.

4. Expert Member
   BILL WICHERS | Nov 17, 2019 10:19am | #4

   Mineral wool doesn’t give you an air barrier, spray foam does. Spray foam is really a good way to seal around windows and doors. Anytime I’ve needed to trim it, I just use a hacksaw blade that I bend a bit as a handheld trimmer. Even handheld, the hacksaw blade makes quick work of trimming many access foam and doesn’t have much risk of damaging anything.

   Bill

1. 
   maine_tyler | Nov 17, 2019 10:47am | #5

   Spray foam does offer the full package. To be clear, when I mention rock-wool, I mean to say that air-sealing would take place with gaskets, caulks, and /or tape.
   My intuition (wrong perhaps?) is that all three of those things are a more durable air-seal than the spray foam (if they are of high quality and installed properly). Moreover, if going belt and suspenders by using two of those methods — say, gaskets and tape— then spray foam would feel beyond redundant (unnecessary).
   But my mentality is surely different than those building full-time year round for their bread and butter (which I'm not). Spray foam does seem to have a high level of effectiveness for its cost and ease of use. I just like to overthink it a bit.

1. Expert Member
   MALCOLM TAYLOR | Nov 17, 2019 01:21pm | #6

   Tyler,

   My own preference is to under-frame the rough openings of windows so that you never end up with a gap wider that 3/16". That is easily air-sealed by the combination of exterior flashing tape and interior caulk. The void can be filled with mineral wool or a very small amount of foam. The choice makes no difference.