Speaking of concrete houses, I was under impression that ZEGO offers a unique solution – but actually that they have many competitors.
All of them offer ICF – insulated concrete forms – as a building system. Here’s the list of the first ones I found:
From their websites I learned about additional advantages of this kind of building. Apart from being energy efficient (because it is better insulated) and easy made plumbing/electrical works (no need to drill in concrete), the house is also fire-rated (has much better chance to survive a fire), termite-proof, has better acoustics (as in sound-proof), won’t crack and all of that adds to its resale value.