I have purchased a digital weather station which tells me, among other things, the temperature and level of humidity. Currently inside it is 58% humidity and the temperature is 20 degrees. Whilst my old bungalow never has condensation on the windows, even on the coldest nights, I am wondering whether there is a recommended level of humidity as I sometimes leather goes a bit mouldy if I don't keep vigilant about it.
iluvmuse,
Aug 17, 1:09am
I think art museums try to maintain about 50% as too dry can cause cracking. My dehumidifier displays a mold warning at 75%.
pogram0,
Aug 17, 1:33am
Thanks, iluvmuse - on that figure looks like I am not too bad at the moment. I'll keep my eye on it over the summer when the humid weather arrives.
tweake,
Aug 17, 1:41am
58% sounds a bit low. average for nz homes is 70%. i think auckland is currently 71% (met service) and typically a whole lot more.
last minute thought, check if the gauge reads relative humidity or not.
pogram0,
Aug 17, 1:55am
Well, just located my old barometer and relative humidity is showing 60 and it looks like there is a normal range of 60 - 70. Which begs the question, how does one increase the humidity inside a house? I would have thought though that the more humidity the more likelihood of mould.
johotech,
Aug 17, 2:02am
58% @ 20deg is high. 65-70% or higher @ 20deg and you're going to get a LOT of mould & mildew as well as condensation on walls and windows.
At 20deg it should be around 40-50%.
nukhelenc,
Aug 17, 2:14am
My place 18Deg & 52%
johotech,
Aug 17, 2:20am
My place is 20deg & 38%. 7deg outside and probably over 95% humidity (drizzle).
So you can pretty much see how RH works. I have roughly 3 times the temperature inside and 1/3rd the RH = Exactly the same total moisture content in the air.
nukhelenc,
Aug 17, 4:20am
Now 21.5 & 47%
pogram0,
Aug 17, 4:30am
Well, after all that, I am now thoroughly confused!
ianab,
Aug 17, 7:28am
I have my DH set to 60% and that seems about right to keep the mould etc down. Still get some condensation on the windows in the cold weather, but that's hard to avoid completely without going overboard.
Without the DH it's more like 70%, and that starts giving issues.
Increasing the humidity is pretty easy. Cook dinner, have a shower or just breathe for a while.
johotech,
Aug 17, 7:32am
That information is meaningless without knowing what temperature it is inside the house.
ianab,
Aug 17, 7:47am
Changing the temperature does certainly change the relative humidity for a given sample of air. But assuming it's a normal house being kept at 16-20C, the difference is not great.
Put it this way I don't go and readjust the DH unit from hour to hour. It's set at 60%. If the house warms up a bit more in the day, the RH drops to ~55%, and the DH turns off. House cools off in the evening, humidity starts going up, and the DH starts up again.
OP was wanting a simple answer. We could drag out the calculations for absolute humidity, temperature etc and how they relate. But I don't think that will help them much.
58% @ 20deg is fine, if it is 58% and 20deg outside.
If it is 10deg outside and 80-90% humidity, then that means your relative humidity inside is higher than outside. Inside should be around 40-45% @ 20deg.
If inside has reached 58% @ 20deg because there are 10 people living in one room, or because the missus has been cooking up a storm, then you have a moisture problem.
A "normal" house, the RH inside will be comparable with outside (in relative terms), not significantly (relatively) higher.
rojill,
Aug 17, 9:48am
+2. In the South Island, expect the humidity to be lower than the Northern areas, ie, 35 -45 %. Just make sure your outdoor temp and humidity sensors are protected from sun and rain, ie hang in a hedge where the leaves prevent the suns rays from warming up the sensor. To do this place the sensor inside a plastic 2 litre milk container. Cut the bottom off the container and cut holes in the sides, thus allowing the air to pass through it. (The sensors need to sample the true values of the ambient surrounding air.) Tie a fine wire or thin string to the sensor. Remove the cap, thread the loose end of the wire/string up through the top of the container and and screw the cap back on, trapping the wire/string in the threads of the cap/container ( if fine wire or thin string is used this will be no problem ) Whilst screwing on cap adjust the length of wire so that the sensor hangs down inside and clear of the sides of the container so that the sensor is protected from rain. The other loose end of the wire/string is then used to hang the container from a suitable branch in the centre of the hedge so that the sun cannot strike the container as the sun traverses during the day.
nukhelenc,
Aug 17, 1:06pm
23.2 Deg 41%
tweake,
Oct 24, 5:49pm
just don't go putting it in a hedge or near trees. they put out a lot of moisture, humidity around trees etc is higher.
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