[KevinEldon]

I think we agree. I meant inefficiency in building density not energy use. I was thinking about row houses in San Francisco and brownstones in New York City. Old short and inefficient buildings could be torn down and replaced with tall, dense, efficient structures; but people who own row houses, or rent apartments with high rents, or like the way their neighborhood is now don't seem to want this kind of transformation.

[Udik]

And over what time period would you finally offset the excess co2 introduced in the environment by tearing down and rebuilding existing buildings? They're already medium-density buildings, with considerable historical and urbanistic value. Seems a crazy idea to me.