Dehumidifying issues

[danlightbulb]

Not sure which section to put this.

We have a 1930s house, solid brick walls.

I am struggling to control the humidity and mould. We have a dehumidifier, on almost all the time and removing 5+ litres of water a day.

Yet the humidity gauge won't get below 60-70%

I don't understand what is happening.

Nothing is wet to the touch, but we get mould in some corners of rooms. We also get condensation on the bedroom windows on cold mornings, unless the dehumidifier is in the room with us.

We open windows when it's dry outside to let air in, we keep the trickle vents open, we open windows and use extractor when showering and cooking, and there are airbricks in all three bedrooms upstairs and in the kitchen downstairs which are not blocked.

There's only two of us here plus dog. We don't dry washing inside unless it's wet outside, and we're using the dehumidifier almost 24/7.

 

[Murdochcat]

You need to ventilate your bedrooms every night. We humans release moisture when we breathe and this settles on cold surfaces.

 

[danlightbulb]

You need to ventilate your bedrooms every night. We humans release moisture when we breathe and this settles on cold surfaces.

As I said, there are airbricks already in the bedrooms. We also open the windows regularly, and I have an electrical dehumidifier running continually.

It doesn't make sense why I can't get the humidity down.

 

[Murdochcat]

There maybe air bricks but do they let air in and out ?

 

[lostinthelight]

If you have lots of fresh air your moisture meter will be measuring a constant supply of what could be moister air from outside, also your dehumidifier will be trying to dry that air which us constantly being replaced which is why its advisable to close windows and doors when one is running .

 

[danlightbulb]

If you have lots of fresh air your moisture meter will be measuring a constant supply of what could be moister air from outside, also your dehumidifier will be trying to dry that air which us constantly being replaced which is why its advisable to close windows and doors when one is running .

I do try and do that but it's a losing battle continually.

If the dehumidifier is downstairs then the upstairs humidity rises, and vice versa.

Do I need to be sealing up the house more if using the dehumidifier? All the airbricks, trickle vents etc?

 

[lostinthelight]

I do try and do that but it's a losing battle continually.

If the dehumidifier is downstairs then the upstairs humidity rises, and vice versa.

Do I need to be sealing up the house more if using the dehumidifier? All the airbricks, trickle vents etc?

I do temporary seal, try an experiment by sealing all entry points, noting the humidity levels, run dehumidifier until the levels start to drop and then unseal the vents...if they rise again, you have your answer.
My meters, including the display on the dehumidifier are so sensitive that if its been running in one room, if I open the door into another they will rise in seconds

 

[foxhole]

You won’t get humidity levels down this time of year , ( not sure why you are concerned) just need ventilation, dehumidifier is just a waste of money.Ventilation prevents mould spores settling .As soon as you open a window you let in lots of humidity as the level outside are higher than those inside.
So you are trying to solve a problem that doesn’t exist , so fail.

 

[Old Salt]

What is your heating/temperature like. We have a dehumidifier normally used in the kitchen to dry clothes in this weather. Runs for approximately 7-9 hours for a normal sort of wash (4 litres). Tried it this week in the garage and it ran for about 15 hours (6 litres) and the clothes still weren't dry enough to iron. The only difference is the garage isn't heated so we are back to drying in the kitchen. Dried 2 loads today in 8 hours.

 

[lostinthelight]

What is your heating/temperature like. We have a dehumidifier normally used in the kitchen to dry clothes in this weather. Runs for approximately 7-9 hours for a normal sort of wash (4 litres). Tried it this week in the garage and it ran for about 15 hours (6 litres) and the clothes still weren't dry enough to iron. The only difference is the garage isn't heated so we are back to drying in the kitchen. Dried 2 loads today in 8 hours.

And maybe garage not so airtight so pulling damp air from outside

 

[danlightbulb]

What is your heating/temperature like. We have a dehumidifier normally used in the kitchen to dry clothes in this weather. Runs for approximately 7-9 hours for a normal sort of wash (4 litres). Tried it this week in the garage and it ran for about 15 hours (6 litres) and the clothes still weren't dry enough to iron. The only difference is the garage isn't heated so we are back to drying in the kitchen. Dried 2 loads today in 8 hours.

I have the heating on normally, circa 20 degrees target in the winter. In the summer its not on at all, but I was still seeing humiditiy above 70% alot of the time, which I just am really struggling to reduce.

I understand air will be coming in from outside, so is the solution to completely seal up everything as much as possible? Aim for fully draught proof, then run the dehumidifier?

You won’t get humidity levels down this time of year , ( not sure why you are concerned) just need ventilation, dehumidifier is just a waste of money.Ventilation prevents mould spores settling .As soon as you open a window you let in lots of humidity as the level outside are higher than those inside.
So you are trying to solve a problem that doesn’t exist , so fail.

Im concerned because there is mould settling in some areas, despite having windows open and running the dehumidifier when windows closed. Obviously I see that there is no point simply dehumidifying if moist air is coming straight back in from outside. If the house is left for even a couple of days with noone here, its musty when we get back, so there is a problem somewhere.

As I said above, even in the summer the humidity levels were above 70% alot of the time, which can't be right.

 

[foxhole]

I have the heating on normally, circa 20 degrees target in the winter. In the summer its not on at all, but I was still seeing humiditiy above 70% alot of the time, which I just am really struggling to reduce.

I understand air will be coming in from outside, so is the solution to completely seal up everything as much as possible? Aim for fully draught proof, then run the dehumidifier?


Im concerned because there is mould settling in some areas, despite having windows open and running the dehumidifier when windows closed. Obviously I see that there is no point simply dehumidifying if moist air is coming straight back in from outside. If the house is left for even a couple of days with noone here, its musty when we get back, so there is a problem somewhere.

As I said above, even in the summer the humidity levels were above 70% alot of the time, which can't be right.

Mould is prevented by ventilation which prevents spores settling .

 

[danlightbulb]

Mould is prevented by ventilation which prevents spores settling .

And mustyness?

Are you saying its ok if my humidity meter reads 70-80%, if i am still ventilating the house as much as I can? That doesn't feel right, the healthy range is meant to be 40-60%.

 

[Old Salt]

I have my heating on at about 20 degrees at the moment, humidity this morning 54%, windows opened and it rose to 58%. Bear in mind the storm that has just passed through but its generally within the range you quoted. Sorry not sure what else you can do apart from trying the advice given by lostinlight post #7.

 

[danlightbulb]

We've had the windows open all day today in the whole house. Humidity outside was about 59%, I put the meter outside to check.

It's now 9pm and the windows have all been shut for a couple hours now and the meter is reading now 63% inside.