Recently came across the phenomenon that heating a room apparently decreases the humidity. If it was just that heating the space makes a lot of the water condense out of the air, eg onto window panes or other surfaces, then I could accept that. But the bit my brain can’t get around is that if it’s 80% humidity but 2celcius outside, and it’s say 70% humidity and 15celcius inside, why is it helpful to open a window? The warm air inside would be cooled, but surely the water in the air outside would diffuse in and raise the humidity in the room? I feel like I’m missing something really obvious here :/
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When you heat a space, the air inside becomes less dense and rises. This causes a flow of air from the warmer space to the cooler surroundings, which can carry moisture away from the space.
As the temperature increases, the maximum amount of moisture that the air can hold also increases, so the relative humidity decreases. This is why heating a space can decrease the humidity.
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