If you need to stick to a tight budget you may want to look into vinyl windows.
Insert windows for existing vinyl windows.
Your question if you can use replacement windows would be no.
Fix it with a replacement window to seamlessly match the existing windows in your home.
Just to get it out there you could use them but only after you remove the vinyl window completely and install them like it was new construction.
Push them into the opening inside your existing windows to create an insulating pocket of air.
If they re rotten or badly out of square the whole unit including the frame may need replacing.
Write down the measurements and use the smallest measurements for width and height to buy your new window.
However before deciding to tackle the how to install replacement windows job yourself check the condition of your existing window frames.
To do it that way would be a little counterproductive.
Add skylights to let in additional daylight.
Next measure the width at the top middle and bottom.
Necessary when existing window frames are old and deteriorating.
Even relatively new vinyl windows less than ten years old can suffer from seal failures and degradation from exposure to weather and may need to be replaced.
Insert windows preserve the original frame exterior trim exterior siding and interior casing.
One solution that has been around for a while is the window insert an acrylic window that fits inside your existing windows often held in place with snap.
The extrusions of the vinyl windows would not allow that.
More advanced project because you have to remove interior and exterior trims and sometimes the siding.
Insert windows install directly into the existing frame of the window being replaced allowing you to get the latest window performance features while minimizing disruption to your home.
Energysavr window inserts are effective interior window insulation panels.
This is a much bigger and more complicated job than installing a vinyl window insert and may require a pro.
You have two choices for vinyl replacement windows.
The window insert to the rescue.
An insert window is a great option when you re happy with the size shape and operating style of your existing window.
Keep the cold air out in the winter.
Sliding windows slide open horizontally saving space while offering a clean modern design.
They will stop drafts dust air infiltration.