Windows were installed last week. We purchased the casement 7100 series windows form Starline Windows. We got their Smartglass for their energy efficiency and durability. They have double low emissivity coatings, and argon filled spaces between both panes of glass, for the best energy efficiency in Vinyl windows. We looked at using a fiberglass window with an insulated frame, and triple glazing with low e coatings, but the budget had been set for this project, and we couldn’t make the jump in price. I will definitely consider it on my next project. They are to my knowledge, the most energy efficient windows on the market today and several manufacturers are offering products for both the residential and commercial construction industry. You can get excellent fiberglass windows form Cascadia windows, based out of Langley, BC.