Passivhaus certified buildings have proven that it is possible to build structures requiring so little energy, that conventional heating and cooling systems are rendered unnecessary. During cold periods, the small amount of heat that can be added to incoming fresh air through a ventilation system is sufficient to keep a Passivhaus at a comfortable temperature.

During warmer periods, strategic shading and aeration is typically enough to keep a Passivhaus comfortably cool, although in warm, humid climates, some type of small scale air conditioning may be required.

Measurements in Passivhaus subdivisions have proven that Passivhaus buildings keep energy requirements consistently and predictably low: the expected consumption agrees well with average actual consumption, even given a great variety of occupant habits and lifestyles.

Whether in Siberia or Southern Spain, one of the beauties of the Passivhaus Standard is its consistency (see the Comfortable, healthy homes Passivhaus Criteria). These criteria are functional and based on the ability to heat the house solely through the supply air. They are not climate dependent. Instead, the design of each Passivhaus building must be adapted to the particular climate in which it will be built, meaning that these criteria may sometimes be more or less difficult to fulfil. A Passivhaus in Siberia, for example, would likely require better thermal protection than a Passivhaus in Southern Spain.

Passivhaus’ not only save money long term but are surprisingly affordable to begin with. The investment in higher quality building components required by the Passivhaus standard is mitigated by the elimination of expensive heating and cooling systems.

Passivhaus occupants may open windows whenever they want. The beauty of Passivhaus design, however, is that they won’t have to. A Passivhaus is continuously supplied with fresh air via the ventilation system, which does a far better job of consistently bringing fresh air in than simply opening the windows. Fine filters in the ventilation system keep dirt and pollen out ensuring excellent indoor air quality, even when occupants are away and/or windows are never opened. If windows are left open for longer periods with extreme outdoor temperatures, the inside air temperature will be affected and energy consumption for heating and cooling will increase.

The ventilation system in a Passivhaus is a fresh air supply system, not an air conditioning system that recirculates inside air. Bacterial growth is only a problem in poorly maintained recirculating air systems. The fan and valve noises resulting from the ventilation system are almost completely eliminated by sound control measures such as vibration isolation mounts, low air speed and acoustic lining in ducts. Jet nozzles guide incoming air along the ceiling, where it uniformly diffuses throughout the room at velocities that are barely perceptible.

Air tight construction and thick insulation in a passive house maintain even indoor temperatures at around 20°C (dependent on user preference) throughout, thus preventing condensation and mould growth. Airtight construction also prevents leaks through which moist air can enter the building envelope.