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Education Humidity

Discussion in 'General' started by Corky42, 30 Jan 2017.

  1. Corky42

    Corky42 Where's walle?

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    So I've been trying to find an answer to this for a while, what's the normal humidity level for a UK home?

    I got a cheap temperature/humidity meter ages ago and the lowest I've ever seen it is around 60% but normally it's around 70% is that bad as I've read bellow 50% is better, do any BT folks have a humidity meters and if so what's your average, should i be doing something to lower humidity?
     
  2. Parge

    Parge the worst Super Moderator

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    Yes, that is bad.

    Most houses in the UK should be 50-55% humidity.

    You need to get a dehumidifier for starters, and then investigate the cause of the humidity.
     
  3. Corky42

    Corky42 Where's walle?

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    I did look at getting a dehumidifier but most seem stupidly expensive and i was concerned about noise and running cost as it would probably need to be running 24/7 due to living in a single bed flat, that means having to dry washing indoors and the lack of a window in the bathroom.

    Basically removing the cause seems a bit of non-starter so i guess the only option is a £200+ dehumidifier and higher electricity bills. :(
     
  4. mrlongbeard

    mrlongbeard Well-Known Member

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    Open a window a bit
     
  5. Corky42

    Corky42 Where's walle?

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    Isn't that a bit self defeating when humidity outside is 100%
     
  6. ElThomsono

    ElThomsono Well-Known Member

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    I've got a cheap humidity meter and it never agrees with the Nest; take yours into the office or to a mate's house to make sure it's not reading permanently high.

    If you do go down the dehumidifier route, look into desiccant dehumidifiers, they're quieter and far more effective in colder environments.

    And how can it be so humid outside? Venting the place with the heating on is probably the best way to drive out moisture.
     
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  7. Corky42

    Corky42 Where's walle?

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    I don't even understand humidity, i mean if it's 100% wouldn't we be drowning. :p

    Thanks for the tip on the desiccant dehumidifiers, not that i know what they are ATM. :D
     
  8. Gareth Halfacree

    Gareth Halfacree WIIGII! Staff Administrator Super Moderator Moderator

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    It's about the moisture capacity of the air. Swap 'air' for 'water' and 'humidity' for 'salt concentration', then start putting salt in a cup of water. Eventually, you'll reach maximum capacity: at 100% any more salt you add to the water won't form a solution but just drop to the bottom in solid crystals and stay there, 'cos the water can't take any more salt.

    Humidity is exactly like that: at 100% humidity, the air can't take any more water. If you put a wet towel on your clothesline when it's 100% humidity out, it'll be almost exactly as wet when you bring it in - regardless of how long you leave it out there.

    Obviously, 100% humidity doesn't mean that the air is 100% water - or, like you say, we'd be drowning - just that the air holds 100% of its capacity for water and can't take any more.
    Y'know those sachets of silica gel you get in new shoes and electronics and things? That's a dessicant: a substance capable of pulling moisture out of the air and locking it away. Trouble is, dessicants - like air - have a maximum capacity. After a while, your silica gel will have absorbed all the moisture it can absorb and it'll stop working.

    A traditional dehumidifier works by chilling a surface using the exact same technology as a fridge, then the moisture in the air condenses on the cold surface and drips down into the container at the bottom. This works brilliantly, but - like a fridge - is noisy when it's running and completely fails if the room temperature is below freezing, 'cos then you either get frozen water stuck to the cold surface or the 'cold' surface remains warmer than the surrounding room's surfaces and you don't get condensation at all. (Some models have a 'defrost' function which periodically warms the surface to melt any ice that has formed.)

    A dessicant dehumidifier does away with all that in favour of a big box filled with a chemical dessicant not entirely unlike silica gel. When the dessicant reaches its maximum capacity for water, the dehumidifier begins heating it in order to extract the moisture - you can do the same thing with 'full' silica gel in a microwave or oven, except that then puts the reclaimed moisture back in your room while the dehumidifier sticks it in a container as liquid water. This, typically, uses less energy and is quieter than a traditional dehumidifier, with the added bonus of working at almost any temperature.

    They do have their drawbacks, though. Most dessicant dehumidifiers run their fans continuously while a traditional dehumidifier usually switches on and off as it needs to, so while peak volume may be lower overall noise levels are higher. The dessicant material also has a very distinctive smell that never really goes away.

    Either work, or there's the electricity-free option of a chemical dehumidifer like a Unibond Aero 360. They're entirely silent - apart from some dripping noises as the block deliquesces - and require no electricity, but when the moisture-absorbing block is finished you flush the water down the toilet and have to buy another block at about £2.50 a piece (each one lasting about a month, give or take, depending on moisture levels and room size.)

    EDIT:
    Oh, I forgot a key point: air's capacity for moisture is directly related to the temperature of the air. When air's warm, it can hold more water than when it's cold; this is why you get condensation on cold surfaces. So, you were asking about opening a window being a good idea when it's 100% humidity out: the answer is 'maybe,' depending on the difference in temperatures. Using illustrative figures pulled out of you-know-where, if your house is 60% humidity at 21°C and outside it's 100% humidity at 3°C then opening your window a bit will reduce the level of moisture in your house 'cos 100% at 3°C represents less moisture than 60% at 21°C.
     
    Last edited: 30 Jan 2017
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  9. teamtd11

    teamtd11 *Custom User Title*

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    I use a few of these around the home. We had some issues because of drying clothes inside so swapped from hanging clothes on the radiator to a condensing dryer.
    Next issue that remains is I need a extractor fan in the bathroom, so the wife is under instruction to take showers with the window open :)

    That aside these work great. at first they filled up once a month but now it is taking a few after recent changes.
     
  10. Corky42

    Corky42 Where's walle?

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    Thanks for taking the time to explain that Mr H, it makes much more sense now and I'm feeling a lot more confident about dehumidifiers, at least i know what the reviews are talking about and what to look for when shopping for one. :)
     
  11. asura

    asura jack of all trades

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    What's your bathroom extractor fan like, do you leave it on for long enough and/or does it have a timed off?

    And (now this sounds bad) does it actually go to the outside - I've seen some horror's before now where the extracted air was just left hanging in the wall, or piped up but only as far as the ceiling... It's unlikely, but not impossible.

    Were you told of a designated drying area indoors and outdoors as in Scotland they're required and England isn't normally very far behind us?

    England has regs' too, just not my patch... and they read like legalease...
     
  12. VipersGratitude

    VipersGratitude Well-Known Member

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    I literally bought a dehumidifier yesterday, and was about to explain everything but gareth beat me to it. Oh, and right now it's sitting at 54%, and usually sits around 48%.
     
  13. Corky42

    Corky42 Where's walle?

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    @asura, The bathroom extractor fan was all but useless, not only was it noisy as hell it went nowhere other than the ceiling space (like you suspected :)), cowboy builders are cowboys i guess and it's just to much work to run a pipe through the ceiling space of an adjoining room just to vent a noisy extractor fan.

    I'd never heard of designated drying areas, you people up north are way more advanced than us, can't you send someone down hear to sort out the mess England's in. :D ;)

    @VipersGratitude, Was it a desiccant dehumidifier? What one was it as I've got my eye on the Meaco DD8L Zambezi but it seems a bit pricy and maybe overkill.
     
  14. wuyanxu

    wuyanxu still wants Homeworld 3

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    Heatyour space more?

    I've got a Tado smart thermostat, which gives humidity reading. I've found when heating the house via central heating, humidity level drops. When I was on holiday all December, humidity level in my house goes up to 55-60%. When we are living in the house, with cloth drying in the same room as the thermostat, but heating to 20c, humidity level stays at around 50%.
     
    Last edited: 30 Jan 2017
  15. legoman

    legoman breaker of things

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    I always thought this.

    Humidity in the office is about 50% at home its a little more but, if its recently rained etc it goes up.
     
  16. play_boy_2000

    play_boy_2000 It was funny when I was 12

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    The only thing Gareth missed is humidity is generally stated as relative humidity. The warmer the air, the more moisture it can hold. The dew point is literally the point at which the temperature has to drop for moisture to condense out of the air (as dew or frost). Although it might be 100% humidity outside, if the air is only 5C, once you heat it up, to 21C, it might be fine (I'd imagine there's a formula that can be googled).
     
  17. Comrade Woody

    Comrade Woody Obsolete

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    I've had a problem with condensation and mould in my flat lately and need to pick up a dehumidifier (or ask my landlord to). For the price I might try the UniBond first before getting something bulky and noisy.

    I was going to send some rep your way Gareth but apparently you're the last person I gave rep to so it won't let me. I'll just say thanks instead for the excellent reply above :thumb:
     
  18. Gareth Halfacree

    Gareth Halfacree WIIGII! Staff Administrator Super Moderator Moderator

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    No, Gareth didn't - read to the bottom of the post :p ;)
     
  19. Corky42

    Corky42 Where's walle?

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    This maybe a dumb question but does dry air more readily accept moisture than humid air, in other words does air with low humidity take up moisture from it surroundings quicker than air with a high humidity, or is the evaporation of water entirely dependent on temperature?
     
  20. theshadow2001

    theshadow2001 [DELETE] means [DELETE]

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    I would say dry air is like a dry sponge and vice versa. Obviously the temperature of the room will come into play here as well. The warmer the air the greater the capacity and the more readily water will evaporate.
     
    Last edited: 30 Jan 2017

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