This might be better suited to to Heating/Cooling forum.
However, I recall Mish commenting that ppl often opt for big windows and then have to spend large amounts of money covering them.
We've found that the large expanse of comfort plus windows in our house hasn't solved the heat loss / cold transfer, so we are now in the process of ordering blinds for all our rear windows and blockout, sheers and pelmets for the bedrooms and rumpus.
We probably would have been better off saving the cost of the comfort plus and putting it into external blinds.
Oh well .. lessons learned .