Air Leakage: 0.3 is max loss allowed. So most say less than .3. Basically in high winds when the windows are under pressure these will leak max amount allowed. This is the framing system. Double hung windows are a poor design to begin with so they will always have worse numbers.
U-Factor: Energy efficient windows start at .3 or lower. Slider is almost max allowed for energy efficient windows. Double hungs are much better.
All in all I never work residential or your region so take anything I say with a grain of salt. What I will say is that for a tipple pain window to let that much air leakage through - they could of done better. That said - my Anderson Windows I put in my house have the same rating for air leakage, but they are also over a decade old and only double pain. Ill never understand why the window companies put all this time and effort into having the other factors be good when air is leaking through. This is why Ill never use double hungs if I ever move north and build. Sliders are basically the same design as double hungs. Awning windows are the best from what I have read.
Gubment recommendations for your reference (I should be shooting for blue and you red):
@xJuice - what say you fellow glazier? This is your backyard so maybe you could provide better insight to him?
It's sat on the shelf ever since my stepdad bought a Stihl.
