If you live in an old house, a cold, windy day often means wearing an extra sweater, checking the thermostat to make sure the heat is actually on, and maybe even a discussion or two with your roommate about who keeps turning the heat up ( or down). Even modern homes can be susceptible to hot and cold spots, as upstairs rooms become uncomfortably toasted and first-floor spaces lose heat due to high ceilings or draft fireplaces.
But in a passive house, these problems of cold in winter (or heat in summer) are a thing of the past. The temperature is comfortable and constant from room to room: no additional layers or subterfuges of the thermostat are required. In fact, there is no thermostat at all, because a passive house maintains its comfortable conditions without a conventional heater, boiler or HVAC system. So what exactly is a passive house and how is it different from a traditional house or other houses with alternative energy?
A passive house is one in which a comfortable indoor climate can be maintained without active heating and cooling systems [source: Passivhaus Institut]. While other houses may employ a passive solar design or use alternative energy sources such as wind and solar energy to minimize their environmental impact, the passive house is a specific certified building standard conceived and maintained by the Passivhaus Institut in Germany.
Passive house features include the following:
Heavy insulation: the most important component of a passive house is a highly efficient insulation layer that continuously wraps the building envelope, even under the concrete slab in the basement, reducing heat transfer between indoor and outdoor spaces
Design without thermal bridges: the heated air inside a house will follow the path of least resistance to the outside of the house, known as “thermal bridge”. Conventional houses offer many of them, in the form of inefficient windows, poorly insulated walls or cracks under doors, but the passive design of the house eliminates them through superior insulation and efficient windows and doors.
Airtight construction: Passive homes feature airtight construction to prevent humid room air (or humid outdoor air, in warmer climates) from penetrating the home construction where it can cause mold, affect indoor air quality, and even structural damage.
Ventilation: Another important component of the passive house design is its efficient central ventilation system, which continuously exchanges humid, “contaminated ” indoor air with fresh, filtered outdoor air to maintain a comfortable and constant temperature and humidity level.
Passive heating technology: Perhaps the most ingenious part of the passive house concept is its ability to heat (or cool) indoor spaces with nothing but fresh outside air. As fresh and cold air enters the house through the ventilation system, it is heated by the hot air that comes out as it comes out.
High efficiency windows: Efficient windows are essential for passive house design. The specific windows used vary from climate to climate, but triple pane windows with low-e glazing, argon gas and insulated frames are common.
Passive solar gain: passive solar gain, that is, good heat from the sun, is the main source of heat for a passive house, so the situation of the house on the lot and the size and position of the windows are important factors.