All the data that describes the proposed building design,including climate, shading, ventilation are entered into the PHPP to create an accurate model of the proposed design. Once set up correctly it is possible to vary elements of the design in the model to assess accurately what effects they will have on its energy performance. Careful design using PHPP guides the appropriate use of orientation, solar shading, thermal mass, and bypass of the heat recovery ventilation system in order to reduce heat gains. The costs to incorporate passive design into a new building are relatively low, and these are recouped in a very short period of time. The benefits are greatest when passive design principles are incorporated into the entire design & build process, from site selection onwards.