The sustainable architecture blog Jetson Green shows just how green an alley house can be. This example from from Seattle, Washington is rated LEED Platinum and includes such green features as solar hot water, radiant heat, a green roof, and insulated concrete construction.
Louisville has a sizable stock of alley housing, most of it historic. This housing type increases the density of a neighborhood in an unobtrusive way and allows for a more varied neighborhood composition. Perhaps we could learn from the Seattle example in redeveloping our historic neighborhoods? Read the full article at Jetson Green (many more photos).