Living in a unit, instead of a house.

I am always looking at ways to become more efficient and from my last post I talked about choosing a place to live. This post is about what type of living I hope to accomplish. My whole life I have spent living in single family homes (except for a duplex) and am now investigating whether it would be worth my while to live in a unit rather than a house. The main reason is efficiency. I don't really do anything with a lawn, so it doesn't make sense to have one. I especially don't need a driveway or garage, because I don't own a car. I like the idea of having shared walls to reduce heating and cooling costs and would like a building that isn't too high up to access my room with a flight of stairs (not a fan of elevators). The building must have secure bicycle parking in their garage and should be close to a grocery store, my workplace and a library. I am a big fan of ownership and have no interest in renting. I am looking for a permanent place. I would like to have a flexible association willing to investigate conservation measures such as adding extra insulation, having solar hot water panels on the roof, as well as allowing rooftop gardening. This is my American dream.