Humidifiers

Hi David
the low humidity is caused by the water in the atmosphere condensing on cold surfaces. therefore you would need a very well insulated house to add humidity or you run the risk of mould growing on cold walls and water collecting on windows. If anything it is more usual to dehumidify at this time of year.
Regards
Dan

Whenever I go skiing, I take a small, portable humidifier that I bought at The Sharper Image along; one of the few items actually worthwhile I have ever seen there. I find that it helps my dry skin condition immensely. Living in the central valley of California, temps usually don't get so low that the indoor humidity at home is that much of a problem, though I do on occasion find that a reservoir style humidifier helps. I don't quite agree with Dan's analysis: if the air is dry to begin with, it would be very hard to add enough humidity to the air to cause mold to grow on inside surfaces. Most homes turn over the ambient air often enough so that should not be a problem. As I understand it, low humidity found in homes in the winter is related to the relative moisture carrying capacity of room temperature air compared to the outside air you have just heated to room temperature. I recently acquired one of those home weather summary stations that incorporates a wireless outdoor temp sensor and find that relative indoor humidity of 52-55% is much more comfortable than if the humidity is under 50%. I suspect that if I were to measure the relative humidity of the hotel I stayed at last weekend in the mountains, it would have registered under 30% before adding moisture.

Norman

quote:

the low humidity is caused by the water in the atmosphere condensing on cold surfaces

Condensation is an indication of a cold object in a warm atmosphere with humidity and is not a cause of low humidity.

Low humidity inside during the winter is caused by central heating. To add too much humidity, coupled with poor ventilation, could cause mould. I wouldn't use a humidifier. Open your windows for a few minutes a day to let fresh air in.

quote:

Originally posted by count.d:
Condensation is an indication of a cold object in a warm atmosphere with humidity and is not a cause of low humidity.

Surely that condensation is removing moisture from the inside air?

quote:

Low humidity inside during the winter is caused by central heating. ... Open your windows for a few minutes a day to let fresh air in.

Again, the central heating is not removing moisture from the air, it is heating the air which is therefore able to hold more weater vapour.

Therefore the relative humidity goes down (ie same amount of water vapour, but a lower percentage of the maximum that the warmer air can hold).

Presumably water vapour needs to be added to bring the RH up to a comfortable level.

cheers, Martin

PS I guess water condenses on cold glass because the air next to the glass cools, the RH goes over 100%, and the excess condenses out.

Hi David
Perhaps I was too vague with my initial responce but I don't imagine you want a lesson in dew points or relative humidity.
My point is that you can add a considerable amount of water to the atmosphere in a ski lodge because it is so well insulated and a house in California is rarely exposed to frost. If you live in the UK I believe it would cause you problems. So where exactly do you live?

Regards
Dan