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We have a modern detached house with bags of insulation but humidity hovers around 75% which is apparently too high and could be making it feel cold. All advice is to open windows but the humidity is usually at least that outside so useless. Has anyone any experience of running a continuous dehumidifier to reduce humidity levels and does it help?
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Modern houses are so well insulated that they don't ventilate moisture as much as old houses, so humidity is a bit higher. If you improve ventilation you should be able to get humidity lower than outdoors - they won't equalize completely as houses are sheltered from rain and have dry floors rather than wet ground.


I would check that rooms generating moisture (bathroom, kitchen, laundry drying area) are well ventilated. Open trickle vents on bathroom/kitchen windows or put windows on latch if it allows slight opening. Open bedroom window trickle vents at night. Maybe even remove draftproofing if you don't have vents in the most humid rooms. If you have ceiling extractor fans you can upgrade to more powerful ones or change the timer so they keep running for at least 10-20 mins after light is turned out. Running central heating will also help as it dries out damp bathrooms quicker.


Sorry, can't advise on dehumidifiers as I don't have one, but it shouldn't be necessary unless you have a damp problem that can't be fixed easily.


also check you don't have overflowing gutters wetting outside walls.

75% is far too high. You should be in the 40s-50s%. I have bad humidity and am happy if my dehumidifiers get humidity down into the 50s%. I don't run dehumidifier all the time, although I needed to initially in the sitting room for a few days when it was 70%. Now I put one on in sitting room/bedroom if monitor goes into the 60s%. A dehumidifier can be helpful. I bought one for my mother who has a problem at her home and she is amazed by the amount of water it collects. She also uses it with a humidity monitor.


The outside levels of humidity don't help and various issues can affect humidity within the home. Central heating can help a bit and good ventilation is vital.


See: http://www.telegraph.co.uk/finance/property/advice/9614700/What-is-the-recommended-humidity-for-a-home.html and have a google.

Everyone advises opening windows, fresh air etc but this morning humidity outside is 85% which I guess is pretty normal for winter. Letting fresh air in will therefore only make matters worse as our house is 75%.

I think that mancity68 is right~ a dehumidifier is the answer!

  • 1 month later...

Hello,


We recently had a damp problem and got Abbey Property Maintenance round to assess. After getting one or two more quotes we gave them the job. They were clean, fast and good fun. Father son team, nice chaps and fairly priced, would definitely use again without hesitation. They?ll sort your damp out. Give them a call for a quote on;


0781 869 8249

  • 1 year later...

Hi Apbremer,


There is a flaw in your logic regarding relative humidity inside and outside.

I assume that the air outside is colder than inside your house.


Cold air can contain less moisture than warm air - hence condensation when moist, warm air meets a cold window.


It is probable that cold air outside at 85% humidity contains less water than warm air inside at 75% humidity.


The cold air enters your house, you warm it up with heating and it becomes less humid.



Graham


Edits -

I put some figures into a calculator on this web page :- https://www.aqua-calc.com/calculate/humidity


I assumed inside temp is 20 Centigrade and outside is 10 Centigrade.


Actual water contents given in grams per Kilogram of air -

85% relative humidity at 10 C -- 6.5 g/Kg

75% relative humidity at 20 C -- 11.0 g/Kg


If the outside air is warmed up to 20 C the relative humidity drops to 45% and therefore feels dryer.


Further edit... oops... just noticed how old this thread is ... more wasted time.

Bob Buzzard Wrote:

-------------------------------------------------------

> I live in a 5-bed Victorian double fronter, so I

> don?t have any humidity problems associated with

> modern construction techniques.


Hows the roof looking Bob ? Replaces all those 1890 era sash windows yet?!

  • 2 years later...

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