So what exactly is a passive home?  It is a home designed to gain all of it’s heating and cooling energy from completely passive (ie. natural) resources.  It accomplishes this through a virtually air-tight building design that is heated through solar energy and heat gains from people and electrical equipment.  Conversely, heat gain is avoided when necessary through shading and window orientation.  An energy recovery ventilator provides a constant, balanced fresh air supply. The result is a system that is able to heat and cool itself independent of traditional energy sources and also provides a uniquely terrific indoor air quality.  Today, this system is used mostly in Europe, with over 15,000 buildings created using Passive Standards over the past 10 years.  This method of building is carefully regulated, similar to our LEED standards in the US.  If you are interested, you can read more at the Passive House Institute US.