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planning:building_services:ventilation:basics:types_of_ventilation [2019/02/21 12:53] – cblagojevicplanning:building_services:ventilation:basics:types_of_ventilation [2025/11/27 16:58] (current) – [See also] yaling.hsiao@passiv.de
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 For occupants, the most important planning aspects are health and comfort. Excellent air quality is especially essential and can only be achieved if "used" air is regularly replaced by fresh air. Opening windows twice a day is not enough (see [[[planning:building services:Ventilation:Basics:Types of ventilation#Purge ventilation through windows]]). Comfort ventilation based on the requirements for fresh air is therefore indispensable in every [[basics:what_is_a_passive_house|Passive House]]. A regular, guaranteed and adequate exchange of air in winter is only possible by means of comfort ventilation –  this also applies for ordinary new buildings. The issue here is not energy efficiency, but the health of the building's occupants; Indoor Air Quality (IAQ) has a much higher priority than energy conservation - but it turns out that there is no conflict at all, if efficient components are used. For occupants, the most important planning aspects are health and comfort. Excellent air quality is especially essential and can only be achieved if "used" air is regularly replaced by fresh air. Opening windows twice a day is not enough (see [[[planning:building services:Ventilation:Basics:Types of ventilation#Purge ventilation through windows]]). Comfort ventilation based on the requirements for fresh air is therefore indispensable in every [[basics:what_is_a_passive_house|Passive House]]. A regular, guaranteed and adequate exchange of air in winter is only possible by means of comfort ventilation –  this also applies for ordinary new buildings. The issue here is not energy efficiency, but the health of the building's occupants; Indoor Air Quality (IAQ) has a much higher priority than energy conservation - but it turns out that there is no conflict at all, if efficient components are used.
  
-===== Gap ventilation =====+===== Ventilation through leaks in the building envelope =====
  
 Gap ventilation through leaks is not adequate in the heating period at all (see also [[Planning:Airtight construction]]): \\ Gap ventilation through leaks is not adequate in the heating period at all (see also [[Planning:Airtight construction]]): \\
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   * Apart from that, condensation damage can occur due to the warm air escaping through cracks.   * Apart from that, condensation damage can occur due to the warm air escaping through cracks.
-\\ + 
-|{{ :picopen:nat_ventilation.png?400 }}| +[{{ :picopen:nat_ventilation.png?400|Wind and weather fluctuate - so does the air  exchange in "free"\\ ventilation. If this is sufficent on wind-free days, the heat losses\\ during strong winds will be intolerably high. Gap ventilation is\\ therefore no longer accepted by occupants in colder climates.}}]
-|//**Wind and weather fluctuate - so does the air  exchange in "free"\\ ventilation. If this is sufficent on wind-free days, the heat losses\\ during strong winds will be intolerably high. Gap ventilation is\\ therefore no longer accepted by occupants in colder climates.**//|\\ +
-\\+
  
 ===== Purge ventilation through windows ===== ===== Purge ventilation through windows =====
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     * If the window is opened wide for long enough, the stale indoor air will be replaced by fresh outdoor air.     * If the window is opened wide for long enough, the stale indoor air will be replaced by fresh outdoor air.
- 
     * When the air replacement is complete, the windows doesn't need to be kept open any longer (replacing of fresh air with fresh air?).     * When the air replacement is complete, the windows doesn't need to be kept open any longer (replacing of fresh air with fresh air?).
- 
     * Window ventilation provides this kind of just one complete air exchange each time it takes place.     * Window ventilation provides this kind of just one complete air exchange each time it takes place.
- 
     * If this is done twice a day, this means two air replacements in 24 hours or an average air change of 2 / 24 h<sup>-1</sup> which is less than 0.1 h<sup>-1</sup>.     * If this is done twice a day, this means two air replacements in 24 hours or an average air change of 2 / 24 h<sup>-1</sup> which is less than 0.1 h<sup>-1</sup>.
- 
 There is no doubt that 0.1 air exchanges per hour is insufficient for good health and comfort (see following illustration).\\ There is no doubt that 0.1 air exchanges per hour is insufficient for good health and comfort (see following illustration).\\
-\\+
  
 ==== Why is an adequate supply of fresh air so important? ==== ==== Why is an adequate supply of fresh air so important? ====
  
-|{{ :picopen:2mal_fensterlueften_reicht_nicht_muenzenberg_k.png }}|    + 
-|//**This diagram illustrates why sufficient ventilation is so important:\\  +[{{ :picopen:2mal_fensterlueften_reicht_nicht_muenzenberg_k.png?400|This diagram illustrates why sufficient ventilation is so important:\\ excessive humidity in a bedroom of an old building without thermal insulation.}}] 
-excessive humidity in a bedroom of an old building without thermal insulation.**//||\\+ 
 \\ \\
 Moisture is continuously being released into the room, especially at night. Moisture is continuously being released into the room, especially at night.
   * If the air is not replaced, the relative air humidity increases – these periods of increased humidity can be seen clearly.   * If the air is not replaced, the relative air humidity increases – these periods of increased humidity can be seen clearly.
- 
   * One can also see that each time the window is opened for air exchange, the humidity level drops (valleys). The residents open the windows for airing more than twice a day  - but in spite of that the humidity keeps increasing and for long periods of time it remains above 60%.     * One can also see that each time the window is opened for air exchange, the humidity level drops (valleys). The residents open the windows for airing more than twice a day  - but in spite of that the humidity keeps increasing and for long periods of time it remains above 60%.  
- 
   * The green curve shows the indoor air humidity near the inner surface of the external wall.  A relative air humidity level of more than 80% is often present here.  These are the conditions which encourage mould growth (area in blue).   * The green curve shows the indoor air humidity near the inner surface of the external wall.  A relative air humidity level of more than 80% is often present here.  These are the conditions which encourage mould growth (area in blue).
  
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 For the Passive House, however, this simple system can't be considered because the incoming air is cold, the **ventilation losses will therefore be too high** (see thermographic image).  For one thing, a correspondingly high output heat supply near the inlet will then be necessary and for another, the annual heating demand will be at least double that of a Passive House.  Less ventilation doesn't come into question because energy conservation should not mean less hygienic conditions ore worse indoor air quality.\\ For the Passive House, however, this simple system can't be considered because the incoming air is cold, the **ventilation losses will therefore be too high** (see thermographic image).  For one thing, a correspondingly high output heat supply near the inlet will then be necessary and for another, the annual heating demand will be at least double that of a Passive House.  Less ventilation doesn't come into question because energy conservation should not mean less hygienic conditions ore worse indoor air quality.\\
-\\ + 
-|{{ :picopen:fresh_air_valve_cold_air.png?400 }}| +[{{ :picopen:fresh_air_valve_cold_air.png?500 |Thermographic image of an external air inlet of an exhaust system. The minimum investment for indoor air quality that is indispensable for every new building and for every modernisation of existing buildings. An acceptable solution for a low-energy house if the heater is located under the inlet. For a Passive House the cold incoming air is not acceptable - and also the high heat losses are inacceptable.(Photograph and thermographic image: ebök)}}]
-|//**Thermographic image of an external air inlet of an exhaust\\ system. The minimum investment for indoor air quality that is indis-\\ pensable for every new building and for every modernisation of\\ existing buildings. An acceptable solution for a low-energy house\\ if the heater is located under the inlet. For a Passive House the\\ cold incoming air is not acceptable - and also the high heat los-\\ ses are inacceptable.\\ (Photograph and thermographic image: ebök)**//|\\ +
-\\+
  
 ===== Controlled ventilation ===== ===== Controlled ventilation =====
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   * There is a directed flow throughout the house: the fresh air first enters the main living rooms (see illustration), from here it flows through the transferred air zones (usually corridors) into the humid areas. The humid areas have relatively high air changes so that e.g. towels can dry more quickly.\\   * There is a directed flow throughout the house: the fresh air first enters the main living rooms (see illustration), from here it flows through the transferred air zones (usually corridors) into the humid areas. The humid areas have relatively high air changes so that e.g. towels can dry more quickly.\\
-\\ + 
-|{{ :picopen:cross_ventilation.png?400 }}| +[{{ :picopen:cross_ventilation.png?500 |Ventilation only functions properly if used air is continuously\\ being removed from the kitchen, bathroom, toilet and other\\ rooms with high pollution and humidity. In return, fresh,\\ unused external air is supplied to the living room, bedrooms\\ and functional rooms. (diagram: PHI)}}]
-|//**Ventilation only functions properly if used air is continuously\\ being removed from the kitchen, bathroom, toilet and other\\ rooms with high pollution and humidity. In return, fresh,\\ unused external air is supplied to the living room, bedrooms\\ and functional rooms. (diagram: PHI)**//|\\  +
-\\+
 ===== The convenient solution: supply and exhaust air systems with heat recovery ===== ===== The convenient solution: supply and exhaust air systems with heat recovery =====
  
 Ventilation will only work properly if used air is continuously being removed from the kitchen, bathroom, toilet and other rooms with high pollution and humidity.  In return, fresh, unused external air is supplied to the living room bedrooms and functional rooms.\\ Ventilation will only work properly if used air is continuously being removed from the kitchen, bathroom, toilet and other rooms with high pollution and humidity.  In return, fresh, unused external air is supplied to the living room bedrooms and functional rooms.\\
-\\ + 
-|{{ :picopen:ventilation_passive_house.png?400 }}| +[{{ :picopen:ventilation_passive_house.png?500 |The principle behind convenient home ventilation: used air (brown) is continuously being removed from the rooms\\ with high levels of pollution and humidity. Fresh air (light blue)\\ is supplied to the living areas. Good quality air is an important\\ prerequisite for a healthy and comfortable living climate.}}] 
-|//**The principle behind convenient home ventilation:\\ +
-used air (brown) is continuously being removed from the rooms\\ with high levels of pollution and humidity. Fresh air (light blue)\\ is supplied to the living areas. Good quality air is an important\\ prerequisite for a healthy and comfortable living climate.**//|\\ +
-\\+
 Just the right quantities of fresh air that are required for the good health and comfort of the occupants are supplied. Only untreated air enters the living areas, there is no recirculated air, thus providing a hygienic air quality.   Just the right quantities of fresh air that are required for the good health and comfort of the occupants are supplied. Only untreated air enters the living areas, there is no recirculated air, thus providing a hygienic air quality.  
  
 Ventilation can also take place if a simple exhaust air system and external air inlets are used.  The external air inlets let fresh (cold) air in the required amounts into the rooms.  However, for the Passive House the ventilation heat losses that would be caused by the disposal of the unused extract air would be much too high.  It would only be possible to adjust the energy balance with a high heating output. Ventilation can also take place if a simple exhaust air system and external air inlets are used.  The external air inlets let fresh (cold) air in the required amounts into the rooms.  However, for the Passive House the ventilation heat losses that would be caused by the disposal of the unused extract air would be much too high.  It would only be possible to adjust the energy balance with a high heating output.
 +
 +===== Heat Recovery with a Counterflow Heat Exchanger =====
  
 **In Central Europe, Passive Houses only work if a highly efficient heat recovery system is also present**  This recovers the heat from the exhaust air and using a heat exchanger, transfers it back into the supply air without mixing the air flows. Today, modern ventilation technology allows a heat recovery rate of  between 75 and 95 %. This is possible due to counterflow heat exchangers and special energy-efficient fans (with so-called EC motors with a particularly high effectiveness), so that the recovered heat is 8 to 15 times the electricity consumed.\\ **In Central Europe, Passive Houses only work if a highly efficient heat recovery system is also present**  This recovers the heat from the exhaust air and using a heat exchanger, transfers it back into the supply air without mixing the air flows. Today, modern ventilation technology allows a heat recovery rate of  between 75 and 95 %. This is possible due to counterflow heat exchangers and special energy-efficient fans (with so-called EC motors with a particularly high effectiveness), so that the recovered heat is 8 to 15 times the electricity consumed.\\
-\\ + 
-|{{ :picopen:heatrecovery.png?400 }}| + 
-|//**This is how a heat exchanger works:\\ +[{{ :picopen:heatrecovery.png?500 |This is how a heat exchanger works:The stale extract air (red) flows through a duct and transfers its heat to the plates above and below.  It cools down and exits as exhaust air (orange). Unused fresh air streams in through separate ducts on the other side of the plates. It takes up the heat and is available as warm (but still fresh) supply air (light turquoise). The counterflow principle makes up for almost 100% of the temperature difference. Saving energy by using heat recovery is not only cost-effective and environmentally friendly but also healthy fresh air is provided constantly without having to keep opening the windows. This applies for all buildings, not just for Passive Houses. }}] 
-The stale extract air (red) flows through a duct and transfers its\\ heat to the plates above and below.  It cools down and exits as\\ exhaust air (orange). Unused fresh air streams in through separate\\ ducts on the other side of the plates. It takes up the heat and is\\ available as warm (but still fresh) supply air (light turquoise).\\ The counterflow principle makes up for almost 100% of the tem-\\ perature difference. Saving energy by using heat recovery is not\\ only cost-effective and environmentally friendly but also healthy\\ – fresh air is provided constantly without having to keep\\ opening the windows. This applies for all +
-buildings, not just for\\ Passive Houses.**//|\\ +
-\\+
  
 Due to this principle of directed air flow, the fresh air is optimally utilised:  it provides high quality air in the living areas, removes any bad air from the transferred air zones (e.g. odours from clothes), and finally dehumidifies the humid areas. Due to this principle of directed air flow, the fresh air is optimally utilised:  it provides high quality air in the living areas, removes any bad air from the transferred air zones (e.g. odours from clothes), and finally dehumidifies the humid areas.
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 An exclusive advantage of the Passive House is that heating using the supply air is possible.  Because the fresh air is supplied to the living room, bedrooms and workrooms in any case, this air can also be used to provide warmth.  Because it is fresh air (not recirculated air), the quantity of this fresh air is limited (because otherwise the air will become excessively dry), and as its temperature may not be increased too much, **the supply air heating method functions only for houses with a very small heating demand** – i.e. Passive Houses.  Therefore, it is possible to provide very elegant and space-saving building services solutions, like the compact ventilation unit.\\ An exclusive advantage of the Passive House is that heating using the supply air is possible.  Because the fresh air is supplied to the living room, bedrooms and workrooms in any case, this air can also be used to provide warmth.  Because it is fresh air (not recirculated air), the quantity of this fresh air is limited (because otherwise the air will become excessively dry), and as its temperature may not be increased too much, **the supply air heating method functions only for houses with a very small heating demand** – i.e. Passive Houses.  Therefore, it is possible to provide very elegant and space-saving building services solutions, like the compact ventilation unit.\\
-\\ + 
-|{{ :picopen:heat_exchanger_ir.png?400 }}| +[{{ :picopen:heat_exchanger_ir.png?400 |Thermographic image of an opened counterflow heat recovery unit. The actual heat exchanger can be seen as a hexagon.It recovers more than 75% of the sensible heat from\\ the extract air. (Image: PHI). }}] 
-|//**Thermographic image of an opened counterflow heat recovery\\ unit. The actual heat exchanger can be seen as a hexagon.\\ It recovers more than 75% of the sensible heat from\\ the extract air. (Image: PHI).**//|\\ +
-\\+
 The highly efficient ventilation units developed for the Passive House have also proved to be effective  in **modernisations of existing buildings**. Here they contribute to the improvement of the air quality, and ensure that mould growth does not occur at weak points in external building components, as well as helping to save energy. The highly efficient ventilation units developed for the Passive House have also proved to be effective  in **modernisations of existing buildings**. Here they contribute to the improvement of the air quality, and ensure that mould growth does not occur at weak points in external building components, as well as helping to save energy.
  
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 ===== Conclusion ===== ===== Conclusion =====
  
-Passive Houses always have an integrated home ventilation system with heat recovery, and often this is the central component of the complete building services. Only high quality ventilation technology is suitable for the Passive House. The Passive House Institute has [[http://www.passiv.de/03_zer/Komp/Lueft/Lueft_F.htm|summarised these (in German) in the requirements for central ventilation units]]: Apart from a high heat recovery rate, low electricity consumption, and hygienically faultless and very quiet operation must be guaranteed.\\+Passive Houses always have an integrated home ventilation system with heat recovery, and often this is the central component of the complete building services. Only high quality ventilation technology is suitable for the Passive House. The Passive House Institute has [[https://passivehouse.com/03_certification/01_certification_components/02_certification_criteria/02_certification_criteria.htm |summarised these (in German) in the requirements for central ventilation units]]: Apart from a high heat recovery rate, low electricity consumption, and hygienically faultless and very quiet operation must be guaranteed.\\
 \\  \\ 
 ===== Literature ===== ===== Literature =====
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 ====== See also ====== ====== See also ======
 +
 +[[planning:building_services:ventilation|Ventilation]]
  
 [[planning:building_services:ventilation:the_ventilation_system_-_there_is_no_alternative|The ventilation system – there is no alternative]] [[planning:building_services:ventilation:the_ventilation_system_-_there_is_no_alternative|The ventilation system – there is no alternative]]
  
-[[planning:building_services:ventilation:flow_rates:flow_rate_adjustment_in_ventilation_systems|Flow rate adjustment in ventilation systems]]+[[planning:building_services:ventilation:flow_rate_adjustment_in_ventilation_systems|Flow rate adjustment in ventilation systems]]
  
-[[planning:building_services:ventilation:flow_rates:automatic_volume_flow_balancing_in_ventilation_units|Automatic volume flow balancing in ventilation units]]+[[:planning:building_services:ventilation:automaticvolumn]]
  
 [[http://www.passivehouse-international.org/index.php?page_id=290#Ducting|Rigid or flexible ducting?]]\\ [[http://www.passivehouse-international.org/index.php?page_id=290#Ducting|Rigid or flexible ducting?]]\\
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