Check out dorocell or sundolitt. They have systems for building extremely well-insulated houses using pre-made polystyrene blocks filled with concrete. I believe the roof insulation should be at least 80 cm to meet the requirements for passive houses. You can read about the requirements for it to be called a passive house by googling. But you don't have to buy the whole concept; you can build something that resembles one and still be close.
