Advice on Controlling a Condensation Mould Problem
Discussion
I've got a house-wide condensation/mould problem that I need to throw some money and time at to get it under control. I've got a few ideas but I need to know if I'm missing something effective and simple.
Its a random rubble stone construction house, so internally the external walls are often cold, hence the increased risk of condensation forming. Built in cupboards, behind pictures and above windows are often a problem. My humidity meter almost always reads around 90%, i've only ever seen 60% when I've had a dehumidifer running constantly in a small closed room.
I've read loads of advice on condensation and mould. Advice is always: reduce moisture generation (drying clothes, venting bathrooms etc), use extractor fans, heat the house and open windows. Opening windows makes the house cold, heating is increasingly expensive.
The main moisture sources in the house would be a windowless small shower room (has two 100mm extractors) and an old tumble dryer in a utility room (loose hose out of an open window). The only beneficial changes I could make here are:
- Keep the shower room door closed as much as possible, leave the two manual extractors on when the room is damp.
- Possibly replace the extractor above the shower with an in-line centrifugal fan
- Get a new vented tumble dryer, one that doesn't "leak" half its moist air out of various gaps in the unit.
- Fit an extractor fan in the utility room
- Keep the heating on more than it has been, so leaving it on for few hours in AM, few in the PM, off at night.
I did have a good desiccant dehumidifier until it recently broke, I'm looking into getting this fixed or replaced.
Where would the best place to put a single dehumidifier unit, at the source (e.g. inside the utility room or in the bedroom next to the shower room) or in the room(s) that suffer the worst effects. I wouldn't want to be running a dehumidifier every day as they are not cheap to run.
Can anyone else give some advice on controlling condensation and mould?
Its a random rubble stone construction house, so internally the external walls are often cold, hence the increased risk of condensation forming. Built in cupboards, behind pictures and above windows are often a problem. My humidity meter almost always reads around 90%, i've only ever seen 60% when I've had a dehumidifer running constantly in a small closed room.
I've read loads of advice on condensation and mould. Advice is always: reduce moisture generation (drying clothes, venting bathrooms etc), use extractor fans, heat the house and open windows. Opening windows makes the house cold, heating is increasingly expensive.
The main moisture sources in the house would be a windowless small shower room (has two 100mm extractors) and an old tumble dryer in a utility room (loose hose out of an open window). The only beneficial changes I could make here are:
- Keep the shower room door closed as much as possible, leave the two manual extractors on when the room is damp.
- Possibly replace the extractor above the shower with an in-line centrifugal fan
- Get a new vented tumble dryer, one that doesn't "leak" half its moist air out of various gaps in the unit.
- Fit an extractor fan in the utility room
- Keep the heating on more than it has been, so leaving it on for few hours in AM, few in the PM, off at night.
I did have a good desiccant dehumidifier until it recently broke, I'm looking into getting this fixed or replaced.
Where would the best place to put a single dehumidifier unit, at the source (e.g. inside the utility room or in the bedroom next to the shower room) or in the room(s) that suffer the worst effects. I wouldn't want to be running a dehumidifier every day as they are not cheap to run.
Can anyone else give some advice on controlling condensation and mould?
Edited by iamrcb on Sunday 9th October 20:24
All of what you suggest and a decent de-huumidifier. We have ours upstairs near the source of cold (windows) so that as warm air is drawn to be cooled it has thwe water extracted. No science in this! We alos use the moisture absorbing crystals intray traps on the problem wondows.
I had moisture problems in the loft which was a fan which had no ducting. I sorted the vent then ran a decently sized dehumifier for a few weeks, sorted. Since then we run the dehumidifier in the bedroom during the day and wake up to limited condensation and have had no further mould problems. We also moved furniture about so that there was a good air gap between it and the wall and that the walls near the outside had no wardrobes to trap cold damp air.
It was minimised the mouild and paint damage on our old windows. 90% sounds very high. Our is around 70% in the morning in the winter (85 for a few second after I turn it on but that is probably moisture from the tank) and it quickly drops to below 60% and I have had it down to 40%-50 which I think is where it should be? I set it at 50-55% and run it 16 hours a day at certain times.
]
I had moisture problems in the loft which was a fan which had no ducting. I sorted the vent then ran a decently sized dehumifier for a few weeks, sorted. Since then we run the dehumidifier in the bedroom during the day and wake up to limited condensation and have had no further mould problems. We also moved furniture about so that there was a good air gap between it and the wall and that the walls near the outside had no wardrobes to trap cold damp air.
It was minimised the mouild and paint damage on our old windows. 90% sounds very high. Our is around 70% in the morning in the winter (85 for a few second after I turn it on but that is probably moisture from the tank) and it quickly drops to below 60% and I have had it down to 40%-50 which I think is where it should be? I set it at 50-55% and run it 16 hours a day at certain times.
]
Edited by Cogcog on Monday 10th October 08:46
elanfan said:
How about an electrically heated towel rail in the shower room - local heating should keep the costs down and will dry out your towels too!
But where's the water vapour going to go?To the OP, if you have radiator heating have a look at where the radiators are. If they are on internal walls they will be contributing to your problem.
I've decided that I'm going to insulate the back of a fitted-wardrobe with 50mm of Celotex as this is the area with the worst mould problem. The back wall of the cupboard (external, north facing) is always cold. This is a £100 job. Even without the condensation problem it'll still do some good.
I'm getting my dehumidifier repaired as the heating element has broken. This is a £70 fix, but cheaper than a new unit.
I'll also put some foam strips on the door shuts of the utility room and the bedroom next to the shower room so that the moisture is taken out by the fans or window rather than back into the house. A cheap and simple job.
Must remember to open windows more. I leave the shower room fans running for a good while after getting out.
The heating is back on so I'm monitoring the mould situation to see where I need to tackle next. Future jobs could be a replacement shower fan is another £100 job, a less leaky vented tumble dryer is £150+ and a utilitiy room extractor linked to the light is £50-ish.
My humidity meter read almost 90% almost all the time. I can only get it around 60% when I've had the dehumidifier on for hours. Even if I get the source/ventilation issue improved then I'm still concerned about the house in general as another source of moisture. The house has two blocked up chimneys (one each side of the house) and the south facing gable end has some penetrating damp in one upstairs room, nothing severe, just a patch. The loft has a huge condensation problem when the outside temperature drops to freezing (rarely). The loft is well insulated, has six roof tile vents but no ventilation as the eaves at all due to the construction of the roof and eaves. The roof membrane is about 12 years old and not breathable.
The house-wide mould problem has only happend in the last few weeks, so it was relatively manageable before.
I'm getting my dehumidifier repaired as the heating element has broken. This is a £70 fix, but cheaper than a new unit.
I'll also put some foam strips on the door shuts of the utility room and the bedroom next to the shower room so that the moisture is taken out by the fans or window rather than back into the house. A cheap and simple job.
Must remember to open windows more. I leave the shower room fans running for a good while after getting out.
The heating is back on so I'm monitoring the mould situation to see where I need to tackle next. Future jobs could be a replacement shower fan is another £100 job, a less leaky vented tumble dryer is £150+ and a utilitiy room extractor linked to the light is £50-ish.
My humidity meter read almost 90% almost all the time. I can only get it around 60% when I've had the dehumidifier on for hours. Even if I get the source/ventilation issue improved then I'm still concerned about the house in general as another source of moisture. The house has two blocked up chimneys (one each side of the house) and the south facing gable end has some penetrating damp in one upstairs room, nothing severe, just a patch. The loft has a huge condensation problem when the outside temperature drops to freezing (rarely). The loft is well insulated, has six roof tile vents but no ventilation as the eaves at all due to the construction of the roof and eaves. The roof membrane is about 12 years old and not breathable.
The house-wide mould problem has only happend in the last few weeks, so it was relatively manageable before.
Edited by iamrcb on Monday 10th October 21:09
rather embarrasingly I seem to have sorted this problem by simply opening the windows and switching the heating on more. Relative humidity dropped from 90%+ to 65%.
I bought an infrared thermometer and it seems that a few walls that I get mould on are 6 to 10 degrees colder than anywhere else in the room; even the windows!. It may be worth internally insulating these.
I bought an infrared thermometer and it seems that a few walls that I get mould on are 6 to 10 degrees colder than anywhere else in the room; even the windows!. It may be worth internally insulating these.
Edited by iamrcb on Saturday 22 October 21:09
Bill said:
How thick are your walls? Our surveyor reckoned random stone walls needed to be 45cm thick to be impermeable.
I was thinking that too - both rising and penetrating damp could be contributing significantly.MHRV systems alledgedly work well even in non-sealed houses but they can be difficult to install in existing property.
OP, I contend the more you understand condensation the easier it is to control. You have taken the time to do this and it seems to be paying off.
Just a couple of things to add. From a moisture creation point of view, research by the BRE shows that rising & penetrating damp, including damp floors, are a negligible source of moisture vapour when compared to other sources.
If you have mould growth to a wall, that wall does not suffer from rising damp. The ground salts will prevent mould growth.
Just a couple of things to add. From a moisture creation point of view, research by the BRE shows that rising & penetrating damp, including damp floors, are a negligible source of moisture vapour when compared to other sources.
If you have mould growth to a wall, that wall does not suffer from rising damp. The ground salts will prevent mould growth.
Our house suffered condensation problems for years, and its a 70's built cavity wall house.
We did all the right things, but still suffered at anything above an RH of 55%.
Ultimately we managed to get it under control with a mixure of better extraction, less drying clothes on radiators, and having the cavity walls insulated.
Obviously the latter is not an option for you, so you need to bring down the RH. The simple thing is more heat, and windows open (as you've done) but this is just throwing heat out.
The best long term solution is a fan heat recovery system, these will pump fresh air in, and damp air out, but they recover the heat from the outgoing air. You could drive this from an RH sensor so that its not running all the time.
We did all the right things, but still suffered at anything above an RH of 55%.
Ultimately we managed to get it under control with a mixure of better extraction, less drying clothes on radiators, and having the cavity walls insulated.
Obviously the latter is not an option for you, so you need to bring down the RH. The simple thing is more heat, and windows open (as you've done) but this is just throwing heat out.
The best long term solution is a fan heat recovery system, these will pump fresh air in, and damp air out, but they recover the heat from the outgoing air. You could drive this from an RH sensor so that its not running all the time.
I had a problem in my bathroom, I too 'kind of' solved it by leaving the window open very slightly, and opening up the radiator in that room a bit more.
I also used anti-mould paint which helped.
Another factor was using the bath more than the shower, as the shower creates a fine mist in the air that then attracts to the cold walls.
In the room below we had the washing machine and tumble, after a bit of testing, I found that the hose from the tumble did the square root of feck all, and that the moisture simply leaked out of every orrifice on the tumble other than the hose.
I solved that one by moving the tumble and washing machine into the garage and putting a vent directly behind the tumble.
If that hadn't cured it, I was going to go down the route of getting one of these, which I saw at a trade show
http://www.homeventilation.co.uk/products.php
I also used anti-mould paint which helped.
Another factor was using the bath more than the shower, as the shower creates a fine mist in the air that then attracts to the cold walls.
In the room below we had the washing machine and tumble, after a bit of testing, I found that the hose from the tumble did the square root of feck all, and that the moisture simply leaked out of every orrifice on the tumble other than the hose.
I solved that one by moving the tumble and washing machine into the garage and putting a vent directly behind the tumble.
If that hadn't cured it, I was going to go down the route of getting one of these, which I saw at a trade show
http://www.homeventilation.co.uk/products.php
Riknos said:
I'm no expert on the matter, but I got some bad damp and mould on some of my exterior walls, which are very cold. I've been told you can buy some paint to put on the outside of said walls / inside to stop this happening, is this true or is it a load of rubbish?
We use this http://www.homebase.co.uk/webapp/wcs/stores/servle... stuff on out bathroom ceiling and in window reveals. You can paper over it too.I suppose whether it would stop it completely depends on how bad the problem is, and the damp may well just find another cold surface to go to.
The house I own now must have had a similar problem years ago as it is fitted with a low volume fan in the attic which blows into the landing via a large square vent. It was fitted when the houses had the old style steel window frames. The house is a cavity wall type built by the council in th 50s.
Why not swap the shower room extractors for a heat recovery extractor. About £300 but should negate the continuous venting and heating in that room. Could also fit one in the utility room along with getting a self condensing dryer.
Are the walls smooth? If they are you could try Sempatap or Wallrock insulating wall paper systems.
Are the walls smooth? If they are you could try Sempatap or Wallrock insulating wall paper systems.
Dear oh dear. Have you recently had double glazed upvc windows put in?
Random rubble houses can be more airtight than people think. This is what is causing your condensation problem. Try opening the trickle vents on the windows if you have them.
You need to sort your ventilation out. The best way to do it as said before is "tempered air" ie ducts to bring fresh air into the living areas and out of the kitchen and bathrooms at the very least. The tempered bit is the heat exhanger between the inlet and outlet.
If done right it will cut your heating bill and wont feel drafty because the incoming air is warmed by the outgoing and it wont be noisy. It will probably be mean quite alot of upheaval though and will cost a good few grand once all is said and done.
Anyway, this is very likely to cure your problems unless you have a hole in your roof of gutters that are leaking water into your house.
HTH
Random rubble houses can be more airtight than people think. This is what is causing your condensation problem. Try opening the trickle vents on the windows if you have them.
You need to sort your ventilation out. The best way to do it as said before is "tempered air" ie ducts to bring fresh air into the living areas and out of the kitchen and bathrooms at the very least. The tempered bit is the heat exhanger between the inlet and outlet.
If done right it will cut your heating bill and wont feel drafty because the incoming air is warmed by the outgoing and it wont be noisy. It will probably be mean quite alot of upheaval though and will cost a good few grand once all is said and done.
Anyway, this is very likely to cure your problems unless you have a hole in your roof of gutters that are leaking water into your house.
HTH
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