planning:building_services:ventilation:basics:types_of_ventilation
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planning:building_services:ventilation:basics:types_of_ventilation [2015/09/01 09:52] – [Why opening the windows twice a day isn't enough] wfeist | planning:building_services:ventilation:basics:types_of_ventilation [2022/05/21 21:47] – wfeist | ||
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* Wind and airflow caused by temperature differences fluctuate too much in Central Europe. In a house which is not leaky enough for sufficient air exchange during periods with small windforces, intolerable draughts are still caused during periods with strong winds (following picture). | * Wind and airflow caused by temperature differences fluctuate too much in Central Europe. In a house which is not leaky enough for sufficient air exchange during periods with small windforces, intolerable draughts are still caused during periods with strong winds (following picture). | ||
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* New constructions in many countries such as Germany are so airtight that air exchange through leaks in the nevelope is insufficient for good indoor air quality. This also applies for modernised buildings with new windows. | * New constructions in many countries such as Germany are so airtight that air exchange through leaks in the nevelope is insufficient for good indoor air quality. This also applies for modernised buildings with new windows. | ||
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Accordingly, | Accordingly, | ||
* If ventilation is insufficient, | * If ventilation is insufficient, | ||
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* If too much ventilation takes place, the air will become too dry and energy consumption will become excessively high. | * If too much ventilation takes place, the air will become too dry and energy consumption will become excessively high. | ||
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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. | ||
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* When the air replacement is complete, the windows doesn' | * When the air replacement is complete, the windows doesn' | ||
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* 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. | ||
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* If this is done twice a day, this means two air replacements in 24 hours or an average air change of 2 / 24 h< | * If this is done twice a day, this means two air replacements in 24 hours or an average air change of 2 / 24 h< | ||
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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. | ||
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* 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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These simple systems are now standard in France; exhaust systems have been used in Sweden for more than 50 years and since 1980 it has become obligatory to have home ventilation. | These simple systems are now standard in France; exhaust systems have been used in Sweden for more than 50 years and since 1980 it has become obligatory to have home ventilation. | ||
- | 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 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). |
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Systematic examination of homes has shown that proper distribution of fresh air in all rooms and safe dehumidification of kitchens and bathrooms is possible through **controlled ventilation**. | Systematic examination of homes has shown that proper distribution of fresh air in all rooms and safe dehumidification of kitchens and bathrooms is possible through **controlled ventilation**. | ||
* In this way the fresh air is directly supplied to the living room, office and bedrooms. These rooms are equipped with at least one supply air inlet. | * In this way the fresh air is directly supplied to the living room, office and bedrooms. These rooms are equipped with at least one supply air inlet. | ||
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* As in exhaust air systems, the kitchen, bathroom and toilet as well as other areas with high humidity and odours are ventilated directly through the extract air outlets. | * As in exhaust air systems, the kitchen, bathroom and toilet as well as other areas with high humidity and odours are ventilated directly through the extract air outlets. | ||
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* There is a directed flow throughout the house: the fresh air first enters the main living rooms (see illustration), | * There is a directed flow throughout the house: the fresh air first enters the main living rooms (see illustration), | ||
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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. | + | 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. |
- | **In Central Europe, Passive Houses only work if a highly efficient heat recovery system is also present** | + | ===== Heat Recovery with a Counterflow Heat Exchanger ===== |
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+ | **In Central Europe, Passive Houses only work if a highly efficient heat recovery system is also present** | ||
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|//**This is how a heat exchanger works:\\ | |//**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. | + | The stale extract air (red) flows through a duct and transfers its\\ heat to the plates above and below. |
buildings, not just for\\ Passive Houses.**// | buildings, not just for\\ Passive Houses.**// | ||
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The highly efficient ventilation units developed for the Passive House have also proved to be effective | The highly efficient ventilation units developed for the Passive House have also proved to be effective | ||
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- | An additional possibility for improving the efficiency of ventilation systems is offered by the **subsoil heat exchanger**: | ||
In hot climates, air-to-air counterflow heat exchangers can also help to recover "cool temperature" | In hot climates, air-to-air counterflow heat exchangers can also help to recover "cool temperature" | ||
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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, | + | 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, |
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===== Literature ===== | ===== Literature ===== |
planning/building_services/ventilation/basics/types_of_ventilation.txt · Last modified: 2023/06/06 11:40 by yaling.hsiao@passiv.de