When you are in the process of designing and constructing a new building, or planning for the remodeling or retrofitting an existing building, the Natural Order of Sustainability is:
Passive First – Active Second – and Renewables Last.
A “passive” solution delivers desired performance naturally, as a function of design, and continues to deliver that performance over time with little or no intervention other than basic maintenance.
When you design the eaves above a south-facing wall to block the summer Sun, which is high in the mid-day sky, from reaching the windows — but to allow the lower Sun during winter to shine through those windows, you have a “passive solution” that will help keep the home cooler in summer and warmer in the winter. If you also incorporate flooring with thermal mass that the winter Sun warms during the day, you have an additional passive solution that will provide additional warmth on cold evenings.
Another familiar example of a “passive” solution is a thermos, which keeps beverages hot for hours. An alternative “active” solution is a hot plate, which also keeps the coffee hot, but requires constant power to do so. A Passive House is a bit like a thermos, airtight and insulated, so maintains the desired temperature by design.
Important passive measures that are applied to Passive House buildings.
Airtightness of the envelope, including windows and doors:
Conditioned air, warm or cool, is not continuously escaping through leaks — dramatically lowering the energy required for heating and cooling, as well as adding resilience. In the event of a power outage a Passive House building will maintain its temperature much longer.
Strategic insulation and elimination of thermal bridges: 
Dramatically reduces the conduction loss of heat in winter and the intrusion of heat in summer. The thermal image on the right shows that the insulation is working well, but due to the thermal bridging of heat to the balconies, the building is acting as a radiator for the neighborhood.
If you maximize efficiency with passive solutions first, you can reduce operational energy by using smaller and more efficient active systems for heating or cooling and can offset your energy bill with a much smaller renewable energy system. House A not B.
Author: Jay Gentry
