I am a contractor for custom homes, and have had a lot of experience with an array of windows. The windows that penguin offer are superior to any other I have worked with. I have had penguin windows in my home for 3 years now and could not be more pleased with my investment. My energy bill has not decreased by 40% though. It decreased by more than 50%!!!!! I thought the sales guys were great and very knowledgeable, but the product sales it self as far as I'm concerned. They dont tell you about the tax write-offs you get with there window either, I get roughly 300 credit every year. Thank you Penguin!!!!