Understand the sightlines
Visible frame widths differ between fixed windows, opening sections and combined elements. Review drawings of your own arrangement. An inspiration photograph cannot confirm which profiles will be used in the actual windows described in your proposal.
Discuss comfort
Ask how the proposed system addresses heat loss and the joints around the opening. Compare complete-window performance and discuss solar exposure. Facade orientation and glazing deserve attention alongside the choice of frame material.
Specify the finish
Record colour, gloss, texture and any different internal finish in writing. Ask what cleaning and periodic checks suit your location. Have the distributor confirm that your chosen dimensions and opening arrangements are feasible within the specified system.