Air, or air and water? I can't decide. I like the WF envision unit, I believe it would work well for my 2400 sq ft retrofit using existing ductwork and well for the 1500' addition I am planning to put on. But, the more I read about hydronic heat the more interesting it sounds. Warm floors in the bathrooms and some rooms of the new addition would be a nice and unacustomed luxury after years of feeling chilly. However, I understand that hydronic's much more expensive to install than plain hot air heat & air cooling. Also, it would mean I would have to switch from the envision with its 30 EER/5COP to a WF synergy unit which seems to have 23 EER/4.5 COP. Or, go with another company altogether. One installer has been trying hard to interest me in a Hydron combination unit that would give me air throughout and also hydronic heat. He told me WF didn't have such an animal, but when I looked through the WF site just now, it seems he's wrong. Are both company's units comparable? Is one better than the other? Is one unit louder than the other? I think I heard or read that Hydron was a bit noisier. Is one brand, or type less prone to problems than the other? What would the difference in the EER and COP numbers mean to me, the user. Is it that the all air unit would be more efficient, and a combination less so? Would it be noticable to me comfortwise? Does it mean the combination unit would have to work harder and longer to heat the house? And, does it mean the combination unit would cost more to run, as well as more to install the piping? Roughly, what would the difference in the cost of adding hydronic heating to 1500 sq ft of new building be. Are there ways of saving when putting it in? I know I have lots of questions and probably didn't express them very well, but I certainly would appreciate any advice. Thanks.