Star ratings are a good start if you're building an energy efficient home - but there's plenty more that can be done if you're serious about it. How well it's actually built, how big it is, what sorts of materials are used and how much waste is generated (among other things) all add to the equation too. These days, addressing those things often isn't as hard or expensive as you might think.

A bit of research and a few questions can go a really long way - have a chat with prospective architects, building designers and builders to see what they offer.