I live in the UK, and I have a hygrometer, it says around 50-60% relative humidity.
Is this right? I live in the UK, it isn't very sunny right now, it is quite wet though.
Is this right? I live in the UK, it isn't very sunny right now, it is quite wet though.
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My first question is: do you have your hygrometer inside or outside?
If you have it inside, it shows only the relative humidity (percentage to obtain full saturation) inside your home and it can be very different from outside. Here is an example:
If the temperature is 0 C outside (freezing point) and the humidity is 100 percent, then there are 5 grams of water in a cubic meter of air. If you take that air inside your home and you warm it to 15 C, at that temperature, the same cubic meter of air can now contain 13 grams of water. Because of that, the relative humidity is dropping to 5 / 13 * 100 = 38 percent and that is very dry air.
This is why we feel the air very dry in the winter: First, the absolute humidity (how much water per volume of air) is low when it is cold, then when that air is warmed up inside our houses, the relative humidity drops a lot.
But even outside, when there is no wind and the air masses are not moving, the relative humidity is fluctuating during the course of a day. Here is why: During daytime, the sun heats the earth. At night, the heat radiates back into space. Sunrise is the coldest time of the day because it is at the end of a light long heat loss. Usually at that moment, the temperature has sunk to, or below what we call rightly, the dew point temperature. Rightly because it is the temperature at which the air is entirely saturated, the relative humidity is 100 percent and ... dew forms because water needs first to touch something with a mass in order to condense into droplets.
I think that an indoor hygrometer showing 50 to 60 percent relative humidity is what you will find in most homes. If it is much higher, it helps the growth of fungus and bacteria and it is not really advisable.
If you have it inside, it shows only the relative humidity (percentage to obtain full saturation) inside your home and it can be very different from outside. Here is an example:
If the temperature is 0 C outside (freezing point) and the humidity is 100 percent, then there are 5 grams of water in a cubic meter of air. If you take that air inside your home and you warm it to 15 C, at that temperature, the same cubic meter of air can now contain 13 grams of water. Because of that, the relative humidity is dropping to 5 / 13 * 100 = 38 percent and that is very dry air.
This is why we feel the air very dry in the winter: First, the absolute humidity (how much water per volume of air) is low when it is cold, then when that air is warmed up inside our houses, the relative humidity drops a lot.
But even outside, when there is no wind and the air masses are not moving, the relative humidity is fluctuating during the course of a day. Here is why: During daytime, the sun heats the earth. At night, the heat radiates back into space. Sunrise is the coldest time of the day because it is at the end of a light long heat loss. Usually at that moment, the temperature has sunk to, or below what we call rightly, the dew point temperature. Rightly because it is the temperature at which the air is entirely saturated, the relative humidity is 100 percent and ... dew forms because water needs first to touch something with a mass in order to condense into droplets.
I think that an indoor hygrometer showing 50 to 60 percent relative humidity is what you will find in most homes. If it is much higher, it helps the growth of fungus and bacteria and it is not really advisable.
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Humidity usually changes rapidly day by day, you can always check the met office website for the day-weeks forecasts of humidity, in the uk humidity isn't a big issue
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