planning:building_services:ventilation:basics:types_of_ventilation
Differences
This shows you the differences between two versions of the page.
Both sides previous revisionPrevious revisionNext revision | Previous revision | ||
planning:building_services:ventilation:basics:types_of_ventilation [2012/11/07 21:53] – sarah | planning:building_services:ventilation:basics:types_of_ventilation [2023/06/06 11:40] (current) – yaling.hsiao@passiv.de | ||
---|---|---|---|
Line 1: | Line 1: | ||
+ | ====== Types of ventilation ====== | ||
+ | |||
+ | For occupants, the most important planning aspects are health and comfort. Excellent air quality is especially essential and can only be achieved if " | ||
+ | |||
+ | ===== Ventilation through leaks in the building envelope ===== | ||
+ | |||
+ | Gap ventilation through leaks is not adequate in the heating period at all (see also [[Planning: | ||
+ | |||
+ | * 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). | ||
+ | |||
+ | * 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. | ||
+ | |||
+ | * Apart from that, condensation damage can occur due to the warm air escaping through cracks. | ||
+ | \\ | ||
+ | |{{ : | ||
+ | |//**Wind and weather fluctuate - so does the air exchange in " | ||
+ | \\ | ||
+ | |||
+ | ===== Purge ventilation through windows ===== | ||
+ | |||
+ | Without comfort ventilation, | ||
+ | |||
+ | Accordingly, | ||
+ | * If ventilation is insufficient, | ||
+ | |||
+ | * If too much ventilation takes place, the air will become too dry and energy consumption will become excessively high. | ||
+ | |||
+ | => One of the reasons for home ventilation is to reduce the air humidity in the home slightly, because a high level of moisture in the air often causes building damage. | ||
+ | |||
+ | The right level of air humidity is not the only requirement for an adequate exchange of air. Pollution of indoor air, due for example to the radioactive inert gas Radon, must be reduced to safe levels by adding fresh air. ((A long discussion could ensue here about the " | ||
+ | \\ | ||
+ | However, " | ||
+ | Certain volatile substances are always being released into the air – from detergents, clothing, foodstuffs, building materials and basements (e.g. radon). Just the air that is breathed out by people alone causes indoor air pollution; this would quickly become unbearable if no ventilation takes place. That was exactly what Max von Pettenkofer realised already in the 19th century. | ||
+ | \\ | ||
+ | There are two other things that have changed: | ||
+ | - Buildings are more airtight; draughts are not acceptable any more. | ||
+ | - There are no stoves any more in the homes. From the ventilation perspective, | ||
+ | \\ | ||
+ | Consequently, | ||
+ | \\ | ||
+ | |||
+ | ==== Why opening the windows twice a day isn't enough ==== | ||
+ | |||
+ | It's quite simple: | ||
+ | |||
+ | * 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' | ||
+ | |||
+ | * 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< | ||
+ | |||
+ | 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? ==== | ||
+ | |||
+ | |{{ : | ||
+ | |//**This diagram illustrates why sufficient ventilation is so important: | ||
+ | excessive humidity in a bedroom of an old building without thermal insulation.**// | ||
+ | \\ | ||
+ | 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. | ||
+ | |||
+ | * 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). | ||
+ | |||
+ | **Conclusion: | ||
+ | \\ | ||
+ | // Note 1//: the situation depicted in the graph above is not an isolated case, in fact it is the general rule in lots of existing buildings in Central Europe - and we have heard about this from other Winter cold climates in the world, too. This explains why there is so much damage due to moisture in homes in Germany. | ||
+ | |||
+ | //Note 2//: The effects of insufficient air exchange shown in the graph were based on the concentration of water vapour (humidity). | ||
+ | \\ | ||
+ | |||
+ | ==== How often should the windows be opened? ==== | ||
+ | |||
+ | Well, the answer to this is difficult: the general conditions, size of windows, location of the house etc. vary in individual cases. The best solution is a ventilation system which always ensures an adequate supply of fresh air. | ||
+ | |||
+ | Because most people don't yet have comfort ventilation in their homes, we have also studied | ||
+ | |||
+ | This doesn' | ||
+ | \\ | ||
+ | ===== The simplest solution: exhaust system ===== | ||
+ | |||
+ | The function of comfort ventilation is to supply fresh air in "just the right" quantities to the living space. ** The simplest solution is an exhaust fan system**, that extracts the stale and humid air from the kitchen, bathroom and toilet. At the same time, fresh air (cold air in winter) is drawn in through outdoor air inlets into the living areas. | ||
+ | |||
+ | 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). | ||
+ | \\ | ||
+ | |{{ : | ||
+ | |// | ||
+ | \\ | ||
+ | |||
+ | ===== 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. | ||
+ | |||
+ | * 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. | ||
+ | |||
+ | * There is a directed flow throughout the house: the fresh air first enters the main living rooms (see illustration), | ||
+ | \\ | ||
+ | |{{ : | ||
+ | |// | ||
+ | \\ | ||
+ | ===== 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. | ||
+ | \\ | ||
+ | |{{ : | ||
+ | |//**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. | ||
+ | |||
+ | 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. | ||
+ | |||
+ | ===== 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 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. | ||
+ | buildings, not just for\\ Passive Houses.**// | ||
+ | \\ | ||
+ | |||
+ | Due to this principle of directed air flow, the fresh air is optimally utilised: | ||
+ | |||
+ | Supply air and exhaust air ducts allow the heat from the extracted used air to be recovered. | ||
+ | \\ | ||
+ | This highly efficient heat recovery system was specially developed for use in Passive Houses. | ||
+ | > ** With such a heat recovery system, the remaining ventilation losses are insignificant: | ||
+ | Thus,due to the heat recovery, the temperature of the supply air is raised to near room air temperature, | ||
+ | |||
+ | An exclusive advantage of the Passive House is that heating using the supply air is possible. | ||
+ | \\ | ||
+ | |{{ : | ||
+ | |// | ||
+ | \\ | ||
+ | The highly efficient ventilation units developed for the Passive House have also proved to be effective | ||
+ | |||
+ | In hot climates, air-to-air counterflow heat exchangers can also help to recover "cool temperature" | ||
+ | \\ | ||
+ | ===== 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 [[https:// | ||
+ | \\ | ||
+ | ===== Literature ===== | ||
+ | |||
+ | **[Feist 2003]** Feist, Wolfgang: Empfehlungen zur Lüftungsstrategie, | ||
+ | \\ | ||
+ | |||
+ | |||
+ | ====== See also ====== | ||
+ | |||
+ | [[planning: | ||
+ | |||
+ | [[planning: | ||
+ | |||
+ | [[planning: | ||
+ | |||
+ | [[http:// | ||
+ | \\ | ||
+ | |||
planning/building_services/ventilation/basics/types_of_ventilation.txt · Last modified: 2023/06/06 11:40 by yaling.hsiao@passiv.de