As the outdoor temperature sinks yet again this season we are reminded of the financial importance of conserving heat energy in our home or apartment. We turn down the thermostat and cringe every time the furnace kicks on. But what if we could save money AND be comfortable? What if we could reduce our heating costs by as much as 90%? This is what the Passive House Institute claims to achieve with their stringent building standards. A passive house is designed to be extremely energy efficient without using “active” energy supply sources such as photovoltaic or solar thermal hot water systems. Instead, it utilizes natural renewable resources such as sun, shade and natural breezes to heat and cool the building’s interior. It also relies on architectural Features such as large south facing windows that allow the sun to heat the building. High ceilings trap the heat during heating months. During the summer, skylights allow this heat to escape through the roof. A Passive house is also insulated extremely well. Typical values of resistance are as high as R-60. This is possible because of the building envelope’s thickness. In addition to preventing heat loss, the building’s thick walls act as a thermal mass which stores heat both gained from solar radiation during the day and heat generated within the building. Further heat loss is reduced by sealing all air gaps with caulk or tape to avoid air leakage. A typical blower door test for a passive house is as low as 0.15/h. Although most people couldn’t afford to bring their home up to Passive House standards, we can all be reminded in this age of “thinking Green” that you don’t have to have fancy technology to use less energy.