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--- planning:building_services:ventilation:basics:types_of_ventilation [2015/09/01 10:02] – [The simplest solution: exhaust system] wfeist
+++ planning:building_services:ventilation:basics:types_of_ventilation [2015/09/01 10:13] – [The convenient solution: supply and exhaust air systems with heat recovery] wfeist
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 |{{ :picopen:fresh_air_valve_cold_air.png?400 }}|
-|//**Thermographic image of an external air inlet of an exhaust\\ system. The minimum investment for air hygiene 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)**//|\\
+|//**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)**//|\\
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 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.
-**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 90 %. 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.\\
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 |{{ :picopen:heatrecovery.png?400 }}|
 |//**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 unused) 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
+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.**//|\\
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 |{{ :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 perceptible 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).**//|\\
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 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.
-An additional possibility for improving the efficiency of ventilation systems is offered by the **subsoil heat exchanger**: on average, the ground is warmer in winter than the surrounding air, and colder in summer.  Fresh air can therefore be pre-heated or pre-cooled using the earth.  This can take place directly through air ducts (air-to-soil heat exchanger) or indirectly by means of a hydraulic system (brine-carrying subsoil heat exchanger).\\
 In hot climates, air-to-air counterflow heat exchangers can also help to recover "cool temperature" from the exhaust air and to reduce the temperature of the supply air, if the fresh air is uncomfortably hot. But this requires low energy fans in order to reduce heat loads caused by the ventilators. Humidity recovery, which is possible with special types of heat exchangers, is another highly efficient option in extreme cold and/or extreme hot and humid climates.\\