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FAQ

Are there different Passive House Standards for different climates?

Whether in Siberia or Southern Spain, one of the beauties of the Passive House Standard is its consistency (see the Passive House Criteria).:

  1. The Space Heating Energy Demand is not to exceed 15 kWh per square meter of net living space (treated floor area) per year or 10 W per square meter peak demand. 
    In climates where active cooling is needed, the Space Cooling Energy Demand requirement roughly matches the heat demand requirements above, with a slight additional allowance for dehumidification.
  2. 2The Primary Energy Demand, the total energy to be used for all domestic applications (heating, hot water and domestic electricity) must not exceed 120 kWh per square meter of treated floor area per year.
  3. In terms of Airtightness, a maximum of 0.6 air changes per hour at 50 Pascals pressure (ACH50), as verified with an onsite pressure test (in both pressurized and depressurized states).
  4. Thermal comfort must be met for all living areas during winter as well as in summer, with not more than 10 % of the hours in a given year over 25 °C. For a complete overview of general quality requirements (soft criteria) see Passipedia.

These criteria are functional and based on the ability to heat the house soley through the supply air. They are not climate dependent. Instead, the design of each Passive House 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 Passive House in Siberia, for example, would likely require better thermal protection than a Passive House in Southern Spain.

 

Can a building really stay warm without a conventional heating or cooling system?

Time and again, Passive House certified buildings have proven that it is possible to build structures requiring so little energy, that convential 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 Passive House at a comfortable temperature. During warmer periods, strategic shading and aeration is typically enough to keep a Passive House comfortably cool, although in warm, humid climates, some type of small scale air conditioning may be required. Measurements in Passive House subdivisions have proven that Passive Houses keep energy requirements consistantly and predictably low: the expected consumption agrees well with average actual consumption, even given a great variety of occupant habits and lifestyles.

 

Can you open windows in a Passive House?

Passive House occupants may open windows whenever they want. The beauty of Passive House design, however, is that they won't have to. A Passive House 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 ever could. This has advantages: unlike just opening the windows, fine filters in the ventilation system keep dirt and pollen out- a blessing for those who suffer from allergies and respiratory problems. Indoor air quality is always excellent, even when occupants are away and/or windows are never opened. Of course, as with all houses, if windows are left open for longer periods with extreme outdoor temperatures, the inside air temperature will be affected and energy consumption for heating / cooling will increase.
 

Aren't Passive Houses expensive?

Passive Houses not only save money over the long term, especially in light of rising energy costs, but are surprisingly affordable to begin with. The investment in higher quality building components required by the Passive House standard is mitigated by the elimination of expensive heating and cooling systems. The financial support increasingly available in many countries makes building a Passive House all the more feasible.

Even so, Passive Houses do cost more upfront than their conventional counterparts. On average, someone building a Passive House in Germany might expect to spend about 8% more, and this cost differential is likely more in countries where Passive House components are not yet readily available. As the number of Passive House suitable components on the market increases, however, prices in these other countries will drop. Financial support for Passive Houses, as currently available in a number of countries, further reduces their cost. In this light then, building a Passive House may even be more affordable over the long term than building a conventional home.

 

People often express reservations about the need for a ventilation system: are there problems with bacteria, noise and drafts?

The ventilation system in a Passive House 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.

 

How does Passivhaus construction prevent moisture damage?

In Passive Houses, airtight construction and thick insulation 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.

 

Isn't a Passive House a complicated, high-tech building?

Not at all! More than anything, a Passive House utilises higher quality versions of the same building concepts and components that are utilised in typical buildings. The ventilation system, not common in conventional buildings, is user-friendly and easy to operate with fewer controls than a normal television. Passive House technology is so simple, there's no need to hire someone to perform annual air filter changes; you can do it yourself.


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