Anyone believing the real-estate hype these days is hearing that the market is turning around. Never mind the real indicators we'll skip that discussion for the moment.
Energy Star homes are built to have a more efficient "envelope" to help keep the house comfortable while using less energy. It is a part of the same program that rates appliances, computers etc. The process of getting a home qualified is pretty straight forward. Build to a standard, use the right materials and get the house inspected. The EPA has a nice description of the process and differences.
The problem is that just because a builder has a design that meets the specs doesn't mean it will really be very efficient. Sure if the standards are followed the envelope will be good. However, it doesn't mean the design is good. Take for example the house we're in now. To be clear it doesn't seem that this house actually was qualified with an inspection rather it's a design built to the standard.
When you come tour the home while it's empty it's always comfortably heated or cooled. However what isn't often noticed on those visits are things like window placement. This house in particular has several rooms with no operable windows. Instead they have sliding glass doors. Sliding glass doors are nice enough but they aren't windows. In particular it's quite hard to find a "window fan" that fits well in a sliding glass door. Worse than having a house where you have to leave the doors open to get ventilation, is having one that seems designed to prevent effective cross-ventilation. Lacking rooms with two windows it's not possible to get good flow-through ventilation.