I imagine most people who have decided to undertake a self-build will have some concept of what house they want to build but are likely to be scant on a lot of the detail.  For us, the main driver for the design of our house is its eco-credentials - we firmly believe that all new houses should aim to be carbon neutral if not carbon negative. Our other main design goal is to have a modern space to live in, scaling down from our current five bedroom 17th century home.