Inspect the closed seal
A casement closes against its perimeter seal. Hardware adjustment and installation affect that contact; product ratings should be reviewed for the actual model and size.
Plan for outdoor conditions
Choose the opening direction around prevailing exposure and nearby obstructions. Ask how the sash should be secured during windy weather and how to maintain its hardware.
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.