I'm confused by the motives of going for triple glazing as I like to do the maths behind these sorts of things. I see two primary reasons economic, reduced energy bills, and environmental, reduced 'carbon footprint'. I am pro green tech so start from a bias of wanting to include them.   Improved U-value: The U-value of a 1m2 window might typically improve from 1.2 W/m2K for double glazing to 0.8 W/m2K and so an improvement of 0.4 W/m2K. Based on heating the house for the coldest 6 mont