Insulating replacement windows with nail fins

[oceanengineer]

I have ordered a few of my replacement windows (Simonton Prism Platinum) with nailfins to replace windows in siding with no overhang (I convinced myself that if properly installed it would provide the best water infiltration protection). I have also specified that the window be insulated using non-expanding foam.
The question I have is how do you inject the foam and ensure that the rough opening is filled when the window has nailfins?

Thanks

[randy]

You can't, unless you want to remove the sheetrock on the inside.

If the installers are properly sealing under the nailing fin, and using window wrap over the nailing fin, it shouldn't be needed.

[XSleeper]

Insulation may not be needed in parts of Texas, but where I live it is!

I'm just guessing that your replacement windows with nailing fin will not be as thick as the windows you currently have... but I could be wrong. Depending on where the nailing fin is located on your new windows, they may only project 1 5/8" in past the sheathing level (the surface they are mounted on). If that's the case, there will be a gap between your existing drywall (or trim) and the new window so you can inject the foam in there, but I suspect you may be removing and replacing it anyway, and you just haven't come to that conclusion yet?

[randy]

Why didn't I think of that? Tear off the sheetrock return, replace the sheetrock, apply texture, prime and paint in order to spray a 1/4" line of foam insulation beside the window frame. And if the room hasn't been painted in a couple of years, what the heck, just repaint the entire room. If you're already spending $7500.00, what's an additional $1500.00!

Sounds reasonable to me.

[oceanengineer]

The windows I am replacing are single pane aluminum framed windows from the early 80's - but you are right - I don't know how the new ones will line up in the existing opening. The installer said that he would have to modify the opening/ replace sheetrock if there is a gap so I guess if the opening is large (from the inside) I may be able to inject the foam from the inside. If not I guess we'll be doing what Randy has indicated.

Anyway, I guess I'll find out on thursday as the first windows should arrive then.

Thanks for all the input.

[randy]

Your installers will most likely have to cut the sheetrock back. This is commonly required here with the way houses are constructed.

You would only notice the difference if you have blinds which require the full depth that you have now.