Replies

1. Expert Member
   DCcontrarian | Jan 23, 2023 05:11pm | #1

   Spray foam isn't appropriate for exterior applications, it's not weather durable nor will it keep out pests. At a minimum, proper sealing of a hole like that is something rated for exterior use and then spray foam on the interior to seal air and restore the continuity of the insulation. Silicone is rated for exterior use but it has a limited ability to bridge large gaps. There is a putty that is commonly used on the exterior whose name escapes me right now.

   I say "at a minimum" because depending on the size of the hole, the siding material and the exposure you may want to flash the opening. That usually means mounting a block, running the pipe through the block and then flashing around the top and sides of the block. In that case you can usually cut the hole in the block close enough to the size of the pipe that silicone can bridge the gap.

2. 
   plumb_bob | Jan 23, 2023 05:40pm | #2

   If the gap you are trying to fill is not too big I would remove a bit of the spray foam from the exterior, and then caulk on top of it flush to the siding with a good quality exterior product. But if the gap is large then flashing is your best bet as above.
   Is the hole at the bottom of the wall close to ground? The lower on the wall the more prone to water infiltration.

3. 
   an123 | Jan 23, 2023 05:57pm | #3

   Thanks. The lineset hole that is filled with silicon is high on first floor wall. A second heat pump was installed today by a different installer, heat pump for basement so the hole is closer to the ground. For that lineset, installer used spray foam on inside of cavity and silicone around the exterior.

4. Expert Member
   BILL WICHERS | Jan 23, 2023 06:09pm | #4

   My preference for larger holes with irregular stuff in them like this is to use canned foam to seal, then cut the canned foam flush with the exterior wall and use “duct seal” (a clay-like material) to seal the exterior. This gets you the better insulating value of canned foam, and a better chance at having a good air seal, but also the durability and critter resistance of duct seal on the exterior where you need it.

   Bill

5. 
   an123 | Jan 23, 2023 07:10pm | #5

   Thank-you.