Avoiding mould without putting the heating on?

tara747

If you have the heating on every day, even just for a while, you should not have mould. Hope some of the other suggestions help. Sorry for assuming you didn't put it on at all.

mandylee216

Or maybe just turn on your heater at a certain time of the day for just a few hours. Then have your windows opened on other times.

David_Aldred

Hi,
Playing around with the heating will shift the dew point (the temperature at which condensation occurs) which is dependant upon the relative humidity (RH) within the rooms, the air temperature within the rooms and the surface temperatures.

If the room air temp was say 18 deg C when you have the heating on at at 65%RH the dew point would be 12 deg C. That is to say any surface at or below 12 deg C would have condensation form upon it. If the air temp falls to 13 deg C at the same RH then then the dew point will shift to 6 deg C.

Conversely if the room air temp is 18 deg and you cause the RH to shift and rise to 75%RH the dew point will shift to 14 deg C and if you cause the RH to fall to 45%RH then at 18 deg C the dew point will drop to 6 deg C so I hope you see how the heating is only a part of the three components for when condensation with associated mould growth will occur and if you shift the air temp, or the RH, or the surface temps then they all interact with each other as a consequence.

In winter a building without heating on overnight is going to have cold surface temps and only banging the heating on in short bursts during the day may raise the room temp whilst the heaing is on but the surface temps will usually lag considerably.

You might not see condensation upon surfaces and think everything is okay but you could get considerable condensation within the fabric of the building itself and if over time this creates a significant moisture resevoir it will sustain dampness / decay / mould even during more favourable weather.

You can have cold air temps within rooms and cold surface temps within those rooms yet still not hit the dewpoint if you reduced the RH to an appropriate level.

There is a balance to be met between what you deem comfortable for you, what you can afford by way of heating and what you are prepared to put up with by way of condensation. The products of significant mould growth will however make your health worse not better.

Kindest regards, David Aldred Independent damp and timber surveyor

newleaf

Very good explanation, thanks David.
We were starting to get a problem with black mould in our shower room (which is fully tiled), despite flinging the window open at every opportunity. The steam from the shower just condenses on the cold tiles and streams down the walls onto the tiled floor. The towels were not drying because the heated towel rail is part of the CH system, which isn't on yet (set to come on at 14 degrees). The wet weather hasn't helped as opening the window just imported more damp air from outside and was adding to the problem.
We bought a dehumidifier yesterday and it has made a huge difference already, we have already emptied several litres of water out of it! Also, I hadn't realised that it would heat the air by a degree or two before expelling it, so it has made the house feel warmer as well as drier, and that horrid dank, mouldy smell has gone - and as an added bonus, the towels are dry too :T
I don't know how much the dehumidifier will cost to run, it's 180watts. It will just have to be factored into the budget though.

David_Aldred

Hi - glad you're getting sorted and from the above you will see that the application of the shower raises the RH to a level that for the temp of the surfaces is at or below the dew point. Opening the window may be inadeqaute to remove the moisture laden air if there is no cross ventilation of the room but always cook and bathe with these doors to other rooms closed so as to prevent warm moist air from these wet areas moving to colder surfaces elsewhere in the house and condensing out. Kindest regards, David Aldred Independent damp and timber surveyor.

missychrissy

I must be lucky! I never get any mould occurring in my house when I don't switch heating on for days. I hang my wet washing on an airer in the utility room and just leave it till dries naturally. I hang sheets, quilt covers etc over the banister at the top of the stairs as well. I have a modern house that I can only assume must be well ventilated because I never open windows. I don't believe in heating outdoors or bringing the lower temp outside indoors.

27col

Exactly my thoughts and situation missychrissy. At least there are a few of us who agree.

David_Aldred

Hi 27col & Misschrissy,
We have four kids plus my wife childminds and there are baths and showers running all the time, we hang clothes over rads and cook / bathe with the doors open and never get any mould / significant condensation that lasts more than a few minutes - we have open coal fireplaces in this cottage I built myself and so I quite agree you can get away with these things if you are lucky enough to be in a property which will cope but it really does depend upon the property you live in, its construction, exposure, heating and ventilation regimes regimes, insulation and how you manage the issues - all the very best David Aldred Independent damp and timber surveyor

roswell

Humidistat extraction fans. Like these

http://www.screwfix.com/prods/45360/Heating-Cooling/Extractor-Fans/Xpelair-CF20-Centrifugal-34W-Bathroom-Fan

Like a de humidifier minues the need to empty and its cleverer than you at knowing when it needs to be on.

out of interest have you done the usual maintenace of your heating system get get it serviced / bleed the radiators, block any outside gaps (except air bricks) with silicone ?

bilibala

I've been living in my house for 27yrs now, we have some condensation on the windows in the 2 front bedrooms and some mould on the sides of the windows.
A few months ago (August) I was cleaning out one of the rooms and noticed black mould on one of the wall behind some boxes and behind a wardrobe. This is the first time I seen mould on the walls of my house. Could this be because
we had our loft insulated November last year? I now open my windows as often as I can but don't think I'll be able to do this when the weather gets colder.