What is “Passive Design”?
It is a design that requires the least mechanical heating or cooling system by using the natural elements (wind, sun, water and land topography) to design a building. By designing a passive house, the designer allows cross ventilation indoor, bring the sun or daylight to indoor spaces, and sometimes use thermal mass properties to cool or heat the indoor spaces as well.
Homes that are passively designed take advantage of natural climate to maintain thermal comfort all year round. This is a good link to better understand what Passive Design is all about: http://www.yourhome.gov.au/passive-design