Trying to decide between Pella Architect series windows and Kolbe Ultra windows. The Pella windows have a U-factor of 0.30 (I have no idea what that actually means). I don't yet have the U-Factor number of the Kolbe windows. Aesthetically, they are very similar to me. If anyone can compare their performance, I would love to hear all about it. My contractor likes the Kolbe windows better and they are about $5K less all in, so if we could go that route without big issues, I'd like to try that. Anyway, appreciate any thoughts on this.