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Air Quality and Heating

​A Passivhaus building requires very little additional space heating. On very cold days, the air in the ventilation system can be heated or a small heating system with a few very small radiators can be used. Extensive heating systems with large radiators, underfloor heating or heat pumps are not necessary. With the drive towards zero carbon, heat pumps are effective, and gas boilers can be avoided.​


For most days, heat from sunlight, occupants and equipment within the building is sufficient to keep it warm.


Once fully commissioned, the ventilation system will require regular filter changes. How often this is needed depends on the air quality inside and out, and could be required between 1 and 4 times a year. Good quality ventilation systems will include an automatic alert when the filters need changing, and will also allow warm air to be expelled during hot weather to prevent overheating.

Properly installed heat recovery ventilation systems are very efficient. To save 10 watts of heat being lost, only 1 watt of energy may be needed. This means that the ventilation system saves more than 10 times the energy it requires for operation. Air quality is very good, and many residents find their homes are less dusty.

Windows can of course be opened in a Passivhaus. It's just that in winter it's no longer necessary to worry about airing on a regular basis.  When windows are opened frequently, energy consumption will go up, but in a Passivhaus it will still be much lower than any conventional new building.  Outside winter it is obviously reasonable and sometimes even necessary to open the windows more often, in order to get rid of any excessive heat.  External shading attachments are particularly important at this time of year.  When it is really hot outside, it is best to keep the windows closed and rely upon the ventilation system.

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