A study carried out jointly by the authors to develop design tools and a methodology which would apply to the feasibility stage of a design and to produce guidelines which would enable architects to become aware of the consequences of their planning decisions at a very early stage in the design process. Chart is presented which shows the relationship between insulation (U value) ventilation, internal temperature and the annual energy demand, for a typical 5. 4 by 8. 1 m, two-story house.