Build it Solar has an extensive collection of power projects including photo voltaic, passive heating and cooling, solar water heating and more. If you are considering building a passive solar house you will need to draw a sun chart . You will need to know the latitude and longitude of your plot's location. If you are considering building a passive solar house in Europe you will need to know the solar radiation for your site. The best site for Europe is the European Commission Joint Research Centre . Another site providing solar data is SolAngles . This one draw sunrays in plan and sections. The drawings can then be superimposed on architects plans or sections to help studying overshadowing between neighbouring buildings.