As you know, I posted a survey the other day asking for feedback from folks who use Green Building Advisor . At the end of the survey I asked a couple of open-ended questions in order to get some comments. While not nearly enough of you have filled out the survey (if you don’t vote, you can’t complain), a couple of good comments came in. Thanks for filling out the survey and sharing your thoughts with us.One comment, I think, can make a good conversation starter.It criticized us for being unjustifiably critical in terms of payback assessment of some energy-related solutions, and that we don’t have enough good info on solar thermal.The reader says,“Payback scenarios are fleeting and mostly a lot of rubbish to begin with…” and that we “hardly ever address solar thermal (like solar hot water space heating), and even criticize it, again for bad ‘payback.’ ”So what is the cost of building green? Some folks, like Bill Reed , say that if you go far enough you can practically tunnel through the cost barrier — that you can build a superior house for the same cost as a regular house, or even less.Some of the houses in our Green Homes section list sq. ft. prices that are very much in line with what people think is the “right” square foot price—$100/sq. ft. (the same price as when I was framing houses 15 years ago).Some examples from our Green Homes section illustrate that you can spend as much (or as little) as you want to spend. These homes are very high performing homes—the kind with extremely small utility bills.New construction:$94/sq. ft. — The First U.S. Passive House Shows That Energy Efficiency Can Be Affordable$96/sq. ft. — Super Energy-Efficient Home in Vermont$150/sq. ft. — Teenagers Build an Affordable LEED-Platinum Home$196/sq. ft. — Vermont LEED Platinum Home$230/sq. ft. — Sustainable Spec House in Coastal Maine Grabs LEED’s Highest RatingRemodels/retrofits/renovations:<$50/sq. ft. — Deep Energy Makeover$126/sq. ft. — Green Renovation: Same Footprint, Twice the Space$223/sq. ft. — Michigan’s First LEED Platinum Gut-Rehab$250/sq. ft. — Connecticut’s First LEED Gold HomeWe’d love to hear more from our readers on green building costs and payback.What do _you_ think?