What is a sensible up-charge for better performing windows? – GreenBuildingAdvisor

Howdy folks, 

This is perhaps a topic that is discussed to death, but never the less, the opinions of GBA members (and experts) would still be be appreciated for my particular situation. 

I’m building a Pretty Good House (or slightly better) in NW Ontario. We are currently receiving quotes from 2 Canadian window and door manufacturers. Access Windows (near Winnipeg, MB) manufactures windows using the 86mm Geneo profiles. Innotech (Langley, BC) uses the 88mm Kommerling profile. Both are PH rated although the Innotech windows receive a better PH score. 

For our particular build we’ve been quoted between $50,000-$70,000 for windows/doors for various performance levels from these two manufacturers, between U-0.18 to U-0.13. 

I’ve seen some folks (much smarter that I) calculate ROI’s based on heat lost difference between a couple U-value points. I do not know our heating loads yet unfortunately. I also realize that ROI’s for high performance windows is pretty much none existent. 

What would you consider an “acceptable” markup to go from a U0.18 to U0.15 for a $60,000 order?