Map the uncomfortable rooms
Note when a room becomes too warm and which windows receive direct sun. Record exterior shade, nearby trees, overhangs and blinds without assuming their effect is constant through the year. The aim is to describe the room’s pattern so the professional can compare glazing and shading options in context.
Use the right performance measures
Solar heat gain coefficient relates to admitted solar energy, while visible transmittance relates to daylight. U-factor addresses heat transfer. These measures cannot be collapsed into one statement that a window is more efficient. Ask for the actual proposed glass package and whole-window ratings, then discuss the tradeoffs for each elevation.
Consider the full room design
Glass area, ventilation, shading, room use and the home’s heating and cooling systems all influence comfort. A large fixed window may emphasize the view while requiring a separate ventilation plan. Avoid promising that a glazing change will eliminate cooling needs without assessing the wider design.
Look at samples and written specifications
If appearance matters, compare tint, reflections and daylight through a representative sample. Ask whether different elevations will use different glass and how that looks from outside. Keep coatings and model numbers in the final schedule; a phrase such as energy-efficient glass does not define the product that will be manufactured.
Questions worth asking
- When and where is the room uncomfortable?
- What do SHGC, visible light and U-factor show?
- Have shading and ventilation been considered?
- Is the exact glass package recorded?
Further reading
Natural Resources Canada: window technology ↗Source checked October 16, 2026. Current requirements and eligibility need separate project-specific verification. This guide is an original planning explanation, not a product certification or installation instruction.
