can't get house humidity below 65%

moneypit9

hello there:j

My house's relative humidity reads at around 78% more or less consistently. is this unusual in UK?? We are relatively nearby a river.

i can run the (powerful dem10) dehumidifier 24/7 and it will bring the humidity down from around 78% to 65% but no lower. it will fill the 2l bucket in a day. but the air will then be very, very dry at 65% (the humidistats do work)... which i find strange because it seems that most people shoot for around 45% which would be like a desert in comparison. I turn the dehumidifier off and it will shoot back up to 70-odd within a few hours.

When i open the windows to change the air every morning it will shoot up to 89% (muggy, rainy outside), i close the windows and it's back at 78 after an hour.

We've had problems with damp and condensation and muggy indoor air obviously, which has been manageable since purchasing the dehumidifier 2 years ago. but i don't understand why inside the RH reads so high consistently.

the humidistats (sp) work accurately enough and i have a few. It's a 50s brick ex-council terrace. Floated wooden floors. Air bricks to subfloor are clear. Air bricks to walls are open to the cavity (want to sleeve them but hope that doesn't prevent any drying out in the walls). Double glazing- UPVC, and metal frames to rear (which need replacing= condensation). Guttering has been done recently with great results. Cook with lids on, close kitchen/bathroom door when in use. Extractors used. As far as i have seen, there is no water leaks. outdoor ground level at least 2 bricks under DPC at the rear, 4 at the front. Needs lowering more at the back i know.
Any opinions or advice much appreciated!:beer:

savemoney

Mine in dining room is currently 59% and room is warm @ 23.9c I have woodburner on which obviously increase temperature in room and thus can absorb more water vapour

We dont yet use the dehumidifier in house we have two though. My daughter had the dem10 and it was nothing but trouble she had a replacement and both broke

upstairs in bathroom is 17.9c and 83% humidity its a little higher than normal but we have had no showers this evening

moneypit9

thanks savemoney that's really helpful to know. indoor temp is around 18/19 deg mostly. i don't like to put the central heating on yet as it feels so warm indoors...

savemoney

Its quite a damp miserable night where I am pi**ing down and fog which will probably increase humidity. Roll on Spring

DRP

I also have a bit of a problematic house, being a terrace but with only one air brick at the rear (plenty at the front)

my hall is currently at 77%/20degC

my lounge is 70%/22degC

Doesn't actually cause any issues though.

changed_username

Maybe a dehumidifier with a stronger extraction would work.

Generally speaking compressor dehumidifiers (which the DEM 10 is) and desiccant dehumidifiers are equal in efficiency at around 20C which is about which your temperatures seem to be.

The problem with compressor models is that extraction rates are typically tested in environments of 30C and 80% RH so your actual extraction rate would be far lower.

As far as the Dem 10 goes it rates well with wattage and noise (for a compressor model which are generally louder and heavier than desiccant models) but I wonder if you'd get a better result with a larger compressor model or am ore efficient desiccant model.

How many rooms are ye trying to control at once?

benjus

I've just bought a desiccant dehumidifier, mainly for drying laundry indoors over the winter. According to the instructions the recommended humidity levels for human habitation are 40%-60%, so your 65% isn't too wide of the mark.

I'm impressed with the desiccant model so far - it's relatively small and quiet, but has already accumulated a good amount of water (and we don't have issues with damp or condensation where we live).

If you're having to empty the tank very frequently you might want to look for one with a continuous drainage pipe so it can drain into a sink or similar.

stator

Humidity meters vary greatly in their readings. I have three in the same room, one of them might read 40%, another 60%, but if the humidity goes up they all go up.
If you don't get any condensation then I would say it's working.
Buy another meter.

Terry98

I have got a similar problem to the OP and cannot get the average RH below 70%

We moved into our present house over a year ago and suffered from bad condensation and mold. In the summer I fitted a Nuaire Drimaster and the condensation and mold has now gone completely but the average RH stays between 70-75%

I am not exactly sure how this works http://www.dpcalc.org but is increasing the temperature the only way of lowering the RH because most of the family do not want the heating on at night?