Diagnose before replacing
Keep a short comfort diary: which room, what time, and what outdoor conditions make the problem noticeable? A draft at the trim can call for a different response than heat through sun-facing glass.
Make comparable specifications
When reviewing bids, put the exact glass package and performance label beside the frame material and installation scope. A broad “energy efficient” description is not enough to compare products.
Plan for your property
A warmer room is not always a window problem. Look at drafts, shade, orientation, and installation details together. Compare documented product ratings instead of relying on a promised energy saving.