1

If a regular vinyl window is replaced, and the foam is applied from the inside around the window, should it be also sealed / caulked from the outside before the capping is done?

2

Yes.

You should silicone the flange top and sides (not the bottom), and use flashing as wide as practical for the top and sides as well.

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  • Foam is no substitute for weather-tight caulking and sealing against moisture intrusion. It serves as an air barrier and to replace lost insulation volume in voids only. – Fiasco Labs Nov 2 '12 at 2:19
  • @matthew-pk all contractors I talked to assure me that sealing from the outside is not necessary because there is also capping that protects from water / air to get in. I suspected this may not be true, and sealing from the outside is a must. Just to confirm: are you saying the one should always seal from the outside no matter what e.g. whether the capping is done? – tolitius Nov 2 '12 at 15:37

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