Well, if you’re building from scratch then the simplest thing is to follow the passiv haus model.
And if you want to reduce the bills for your existing home, then you could do worse than contact Parity Projects.
They aim to reduce energy and water bills by 75% or more, and have an impressive track record of achieving these aims in some difficult situations.
Alternatively, check out The Yellow House. They turned our 1930s ex-council house into our environmental dream home, reducing energy consumption by two thirds, using sustainable materials, and without losing comfort or style.