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--- basics:building_physics_-_basics:humid_air [2024/05/18 10:55] – [Literature] wfeist
+++ basics:building_physics_-_basics:humid_air [2026/02/10 00:41] (current) – wfeist
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 ====== Humid air ======
-Air humidity - everyone can sense it.... but very often in an incomplete way at best, unfortunately. We will explain this here; here is also a {{ :picopen:sattdampf.gif?linkonly |short film}} on this.(( The relevant explanation in the German version of Wikipedia unfortunately isn't very clear and the focus of the text changes often; nevertheless, it is correct: [[https://de.wikipedia.org/wiki/S%C3%A4ttigungsdampfdruck|saturation vapour pressure.]]))
+Air humidity - everyone can sense it.... but very often in an incomplete way at best, unfortunately. We will explain this here; here is also a {{ :picopen:sattdampf.gif?linkonly |short film}} on this.(( The relevant explanation in the German version of Wikipedia unfortunately isn't very clear and the focus of the text changes often; nevertheless, it is correct: [[https://de.wikipedia.org/wiki/S%C3%A4ttigungsdampfdruck|saturation vapour pressure.]]. But, there is also a nice introdution by the manufacturer of humidity sensors: [Sensirion 2009].))
 |{{ :picopen:humid_air_01.png?600 |}}|An absolutely airtightly sealed container is partly filled with a liquid. The entire thing is kept at a constant temperature.|
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 |{{ :picopen:humid_air_03.png?600 |}}|A couple of molecules in the gas space then become slow enough again to return to the liquid.This is referred to as "condensation at the molecular level"|
 |{{ :picopen:humid_air_04.png?600 |}}|A steady-state equilibrium eventually results:the number of molecules leaving the liquid constantly is the same as those returning to it.|
-|{{ :picopen:humid_air_05.png?600 |}}|The water vapour volume which is then present in the gas space is called the saturation vapour volume.Its density is the saturation vapour density (at this temperature) and the pressure of the water vapour on the wall of the container is called the "saturation vapour pressure".|
+|{{ :picopen:humid_air_05.png?600 |}}|The amount of water vapour which is then present in the gas space is called the saturation vapour mass.Its density is the saturation vapour density (at this temperature) and the pressure of the water vapour on the wall of the container is called the "saturation vapour pressure".|
-Moisture/humidity is simply another word for water and is used when it is present in other substances mixed as water. We speak of air moisture (the amount of water vapour present in the air) or of material moisture (the water which is contained in microscopic empty spaces in a material called "pores"). Moisture - that is water - is present almost everywhere in our surroundings, usually in a beneficial proportion: neither too moist (which allows mould growth), nor too dry (which is not good for our mucous membranes). First it must be stated: **the relative humidity in the air in indoor spaces** that are occupied by humans should be within the range of **35 to 60% (( It just depends on an average value of over 1 to 2 h - shorter fluctuations can certainly be compensated by our bodies. Thus even if the relative humidity drops below 10% for a short time (e.g. during airing), this won't be a problem. Temporarily remaining in e.g. a bathroom with a higher level of air humidity is quickly compensated again.)) on average.** (It will be explained in this section what relative humidity actually is – many errors are based on a false understanding of relative humidity).
+Moisture/humidity is simply another word for water and is used when it is present in other substances. We speak of air moisture (the amount of water vapour present in the air) or of material moisture (the water which is contained in microscopic empty spaces in a material called "pores"). Moisture - that is water - is present almost everywhere in our surroundings, usually in a beneficial proportion: neither too moist (which allows mould growth), nor too dry (which is not good for our mucous membranes). First it must be stated: **the relative humidity in the air in indoor spaces** that are occupied by humans should be within the range of **35 to 60% (( It just depends on an average value of over 1 to 2 h - shorter fluctuations can certainly be compensated by our bodies. Thus even if the relative humidity drops below 10% for a short time (e.g. during airing), this won't be a problem. Temporarily remaining in e.g. a bathroom with a higher level of air humidity is quickly compensated again.)) on average.** (It will be explained in this section what relative humidity actually is – many errors are based on a false understanding of relative humidity).
 Let us start with water: for practical use, it is enough to know about the three states of matter of water. Solid in form like ice, liquid (as **liquid water** from the tap) and gas (**water vapour**).
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 |**[Schnieders 2009]** |Schnieders, J.: Influence of basement insulation on moisture concentrations in basements, German only; Passive house institute; Darmstadt 2009. free Download (German only) from [[https://passiv.de/downloads/05_kellerraeume.pdf|here]]|
+|**[Sensirion 2009]** |Remark: This is a nice introduction given by the manufacturer of modern humidity sensors (Sensirion) to the topic on "humid air", linked here [[https://sensirion.com/media/documents/8AB2AD38/61642ADD/Sensirion_AppNotes_Humidity_Sensors_Introduction_to_Relative_Humidit.pdf|Introduction to Relative Humidity (pdf).]]|
-Remark: There is a nice introduction given by the manufacturer of modern humidity sensors (Sensirion) to the topic on "humid air", linked here [[https://sensirion.com/media/documents/8AB2AD38/61642ADD/Sensirion_AppNotes_Humidity_Sensors_Introduction_to_Relative_Humidit.pdf|Introduction to Relative Humidity (pdf).]]
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