Dehumidifier Struggling to get Below 50% RH

Mortankas

Hello everyone,

I realise there is an awful lot of existing topics on dehumidifiers, and I've trawled through many posts to find an answer to my question but I cannot!

I recently bought a dehumidifier as we noticed mould starting to grow in one of our bedrooms. Many websites claim that you need to reduce relative humidity <50% to stop mould growth, ideally down to 30% in the winter season.

I bought a Duracraft DD-TEC10 dehumidifier, £150 worth of kit, awesome reviews across the board - and it really struggles to get the RH below 50, hovering around 53-55 at best when the room is fairly warm (radiator on).

The bedroom is 45m2 at the very most, not a huge size and I can't understand why the device cannot get RH below 50? I always close the bedroom door and windows before switching the device on.

Any ideas folks?

Many thanks for the time taken to read this.

Regards,

Simon.

Moss5

Try switching the radiator off. Warm air holds more moisture than cold air. After dehumidifying the cold air, turn the radiator back on. The new higher temperature air will hold less moisture than before and the RH% should drop.

macman

You still need to ventilate the room.

Moss5

macman wrote: »

You still need to ventilate the room.

Please explain Why?

TimBuckTeeth

If after several hours it is not collecting much more water then it has reached an equilibrium point as the rate that moisture is removed from the air drops as the humidity drops. There are various factors that limit the minimum achievable humidity level such as humidity level outside, temperature, power/effectiveness of the dehumidifier, sources of moisture, air flow between rooms/outside.
About 40% RH is the minimum I can get using my dehumidifier in one room with the door closed, but does vary with the weather.
If it is constantly collecting a large amount of water with the door closed then there is a source of moisture eg. a damp wall from leaking gutter.

yangptangkipperbang

Moss5 wrote: »

Please explain Why?

1. It will start to smell
2. You will get headaches from the build up of CO2
3. You will die

maninthestreet

yangptangkipperbang wrote: »

1. It will start to smell
2. You will get headaches from the build up of CO2
3. You will die

C02?? Where will that be coming from??

macman

maninthestreet wrote: »

C02?? Where will that be coming from??

Your mouth, every time you exhale!

abankerbutnotafatcat

Not sure if it's a typo but 45 sqm is a huge room.

cyclonebri1

Ventilation is essential as most here understand.
In relation to the op's question, where do you think the condensation comes from on the windows in the morning? It's actually from the breath and body of the occupants over night.

Is this a bungalow with a corner bedroom?, these suffer much worse than houses due the having cold floors and ceiling and 2 outside walls.

Dehumidifiers can help, but only after heat and ventilation have been applied. The reason to ventilate is obvious, but it is also far cheaper to change the air than treat wet air even though the dehumidifier gives out some heat.

I have waged a running battle with this issue in my bungalow for years, and have recently ripped out all fitted furniture mounted on exterior walls.

I have had 3 DH over the years, plus an industrial unit bought for a separate project. The recent 1 was a shop soiled/end of line unit bought from B&Q, (my wife has the mis-fortune to work for them).
It's a brilliant little unit and the best domestic 1 we have had.
I mention this as I have just stripped out that room, removed all insulation on the outside walls and re-insulated, boarded and replastered.
Ok the room is only 3.5 x 4.2 mtrs, but the unit drops it to 35%rh at 21/22 degs very quickly.

I'd check the unit you have in a different room, they aren't all that reliable or long lived;)

Do you mean 14.5 sq m or 4.5mtrs sq by any chance?, sounds more like it and a domestic unit should cope in those volumes.

Agree with the other poster, use the unit in a cold room, the greater the difference in temp of outside air to unit internal temp will remove most water.

Jaynne

yangptangkipperbang wrote: »

1. It will start to smell
2. You will get headaches from the build up of CO2
3. You will die

A bedroom isn't exactly sealed even with the doors and windows closed otherwise people would die if they stayed in bed all day.

Stick to something you know about.