I’m located in climate zone 5B and looking to replace about 20 windows while considering the implications of importing vs. buying from a local manufacturer. Imported tilt and turn windows may be lower priced, but aren’t generally available with a nailing flange so I’m looking at how to deal with sealing and trimming the windows out without replacing the siding… We have older vinyl siding and can’t buy anything that matches.

   One idea that’s occurred to me is that it would be possible to install flangeless windows at a recessed wall depth that would then allow re-installation of the old window frame and screen in front of the new windows.

   I realize this may sound like a jury-rigged install at 1st glance, but the more I think about it the more it seems like a reasonable option. I’d like some constructive criticism/feedback about whether this is/isn’t a viable option.

   To start with, the existing windows have an IGU that fits into the same “track” as the screen. If we remove the IGU and some of the other vinyl separators we would be left with a frame that has a nailing flange and can hold a screen the size of the frame. This would fit the existing siding/trim dimensions perfectly and would look like it does today (except it would have a full width screen instead of a 1/2 screen for sliders and single/double hung windows).

   By installing the new windows at a depth allowing the old frame to be re-installed it would put them in the middle 1/3 of the wall (2×6 framed) and offer the best efficiency. They would be installed using the recommended sealing methods (Sloped sills, back dams, liquid flashing, or tape, with appropriate tapes and sealants at the heads, jambs, and sills).

   From here the old frames could be installed with sealant and tapes at/on the flange as is typical with U.S. homes. They could also be installed with a barrier sealing the space between the new window and old frame (Not sure what would be appropriate here and would appreciate thoughts on this). Water should be able to escape through both window frame’s weep holes (Likely with the new/inner window draining into the old frame because it’s narrower/thinner and the old frame draining to the outside). If any water somehow made it’s way behind the flanged frame and the inner window’s frame it would drain to the outside as with any quality window install.

   Longer-term, when we/future owners are able to replace the siding, the old frame could be removed and the windows could be trimmed out using best methods for the new siding at that time.

   A couple of side benefits would be re-using the old uPVC frames instead of throwing them in the landfill and part of the old screen frames could be re-used when building the new frames.