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Relative humidity

This is a discussion on Relative humidity within the New Growers: Ask the Senior Members forums, part of the New Growers category; Relative humidity /humidity, are they the same? My little indoor micro environment shows 74% Relative ...

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  1. #1
    Jeff Rutledjd's Avatar
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    Default Relative humidity

    Relative humidity /humidity, are they the same? My little indoor micro environment shows 74% Relative humidity @77 degree's I have 21 plants growing in it.

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    espranch is offline Senior Member
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    I try to keep my humidity at about 60 %, with good air movement. ( in my greenhouse ) With higher humidity, I have found that there is a chance that mold/fungus can occur on orchids. Just my opinion...Betty :-)

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    Quote Originally Posted by espranch View Post
    I try to keep my humidity at about 60 %, with good air movement. ( in my greenhouse ) With higher humidity, I have found that there is a chance that mold/fungus can occur on orchids. Just my opinion...Betty :-)
    Another question ??? how would be the best way to reduce the humidity, i have most of my plants in S/H sitting in 14X18 trays, I have two fans blowing on high.

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    Quote Originally Posted by Jeff Rutledjd View Post
    Another question ??? how would be the best way to reduce the humidity, i have most of my plants in S/H sitting in 14X18 trays, I have two fans blowing on high.
    If you want to decrease humidity, move the plants further apart. Also, using air conditioning will remove moisture from the air. The best way to avoid problems is not to worry about too much humidity, it is to increase air movement. JMHO

    Cheers,
    BD

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    Quote Originally Posted by Jeff Rutledjd View Post
    Relative humidity /humidity, are they the same? My little indoor micro environment shows 74% Relative humidity @77 degree's I have 21 plants growing in it.
    Jeff there is a difference between humidity and relative humidity.

    Humidity is the amount of water vapour in the air, where as the relative humidity is the percentage of humidity at a particular temperature, saturation factor plays an important role here. To simplify here is an example.

    Assume that at 25 0C, 100 litres of air has 1 litre of water vapour in it. No more water can evaporate, if there is more evaporation, then simultaneously equal amount of water vapour will condense into water. i.e The air is saturated with water vapour or in other words the relative humidity(RH) is 100%

    If instead of 1 litre only 700 ml of water vapour is present then the RH is 70 %.

    Now as you increase the temperature this saturation point increases so at 30 0C instead of 1 litre of water, 1.5 litre of water is needed to saturate 100 litres of air.

    so at 30 0C 1 litre of water vapour corresponds to 66 % RH where as at 25 0C the same humidity of 1 litre water vapour corresponds to 100 % RH

    So at the same humidity the RH is different.

    I hope I didn't complicate it LOL

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    Quote Originally Posted by Halloamey View Post
    Jeff there is a difference between humidity and relative humidity.

    Humidity is the amount of water vapour in the air, where as the relative humidity is the percentage of humidity at a particular temperature, saturation factor plays an important role here. To simplify here is an example.

    Assume that at 25 0C, 100 litres of air has 1 litre of water vapour in it. No more water can evaporate, if there is more evaporation, then simultaneously equal amount of water vapour will condense into water. i.e The air is saturated with water vapour or in other words the relative humidity(RH) is 100%

    If instead of 1 litre only 700 ml of water vapour is present then the RH is 70 %.

    Now as you increase the temperature this saturation point increases so at 30 0C instead of 1 litre of water, 1.5 litre of water is needed to saturate 100 litres of air.

    so at 30 0C 1 litre of water vapour corresponds to 66 % RH where as at 25 0C the same humidity of 1 litre water vapour corresponds to 100 % RH

    So at the same humidity the RH is different.

    I hope I didn't complicate it LOL
    LOL. Yes you complicate it. Every one talks about having the humidity right, I am not sure i have it right? Let put it this way, what would be the best Relative Humidity to grow mostly Phal's. Thanks for all the info, I am new at this, but i am having fun.

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    Sounded good to me Amey!! Thanks

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