Replacement double hung

Justgaff

Nobody have any experience working with replacement windows?

I am planning on replacing weighted sash DH windows with single hung replacements. I've been told to remove the weights and spray foam the cavities; is that necessary or would fiberglass be adequate?

Do I measure the windows exact or leave an 1/8" around the perimeter and caulk?

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Windows on Wash

Spray foam, while more expensive, if preferable in this case.

Stuffing FG in the cavity requires a larger hole (not a problem) and is usually over compressed and therefore under-performing.

FG does not do anything to stop air movement either.

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Dierte

Im not a window guy by any means but take 3 width and 3 height measurements. Take the smallest dimension and the subtract a quarter inch.

HomeSealed

I like to spray a layer of foam for air seal, then fill the rest with loose fiberglass. Filling the whole cavity with foam can be very costly. You'll need to remove the casing if you want to do a good clean job. If you are just using the access panels in the jamb, you'll probably need to choose one or the other.

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joecaption

I've been using some 1" foam board I had laying around, I install that first, seal around any gaps with spray foam, then install fiberglass to fill the rest of the gap.

I agree it would not be cost effective to try and fill that whole area with spray foam, it also may distort the frame.

If this is a really old house your trying to measure for windows, often times the house has settled and the frame will be a square. I use a level sitting on the sill to check it, if it's out to much I just set the level so it's in the middle of the bubble and measure from the bottom of the level to the top of the jamb.
I hope that makes since.
If you were to not take that into account the window will not fit because it can not be twisted to make up for it.
A window frame that has settled on one side will still measure the same on both sides so it can be misleading.

Justgaff

All good points and all makes sense! Thanx for the help!!