Mould/condensation problem

[EricNorthmansFangbanger]

We have always had a slight problem with mould growth/condensation on the walls in some bedrooms since we made the switch from single to double glazed windows a few years ago. We appeared to have the problem under control recently and found no new growth.

We are currently having external wall insulation applied to the house. The problem is that there now seems to be an increase of mould growth and condensation again. Each bedroom has a vent in, but these have been covered over by the external wall insulation, as has our bathroom extractor fan. I enquired about them putting the vents back in to the external wall insulation and was told that we don't need them anymore. They are going to put the bathroom extractor fan back in for us.

Surely this new mould growth/condensation problem is caused by the vents being covered over externally? They have only just put the first layer of plaster/mesh over the big foam block things, so aren't anywhere near finished. Should I contact the site manager again and insist that they put the vents back in? The problem is worst in our daughters bedroom so I'm eager to get this sorted ASAP.

Thank you for any advice.

Hiya,
How old is your house?

We have always had condensation problems due to living in a victorian property with original sash windows. We got some of the windows (at the back of the property) replaced with uPVC double glazed and they never have condensation. However, the original old sashes do, and mould spots appear on the wall in bedrooms (where walls and ceiling meet).

A few years ago we took up the government grant scheme of having cavity wall insulation...biggest mistake we ever made! Apparently older properties are not really designed to have such treatments. The company that did it never installed or advised us we'd need additional ventilation systems in place to cope with the retained heat. We have had terrible condensation issues in our loftspace, where the beams are just sodden in winter and causes mould in the upstairs bedrooms.

We have since had independent builders visit, who have put in extra air bricks, some special vent tiles in the roof, which has improved the problem somewhat. Our loft space still gets very condensated in winter, and the mould does still sometimes appear in the bedrooms, but we treat the bedrooms with bleached-water, and the condensation in the loft is much less since the additional vents were put in place.

So, after that long rambling post, no huge words of advice other than do keep pushing to retain ventilation where you think it should be, as I'm sure condensation problems will only become worse as insulation is added.

1950's -ish house. It's an ex council house and we were offered the external wall insulation as when the company came to do cavity wall insulation we were told the house was unsuitable.

We've really noticed a difference in the warmth of the house, but I think you're right that we definitely need to retain ventilation.

Mould is caused by a lack of ventilation as you rightly allude to. The inhabitants & white goods etc in a property generate a lot of moisture which needs to be extracted.

Getting the bathroom extractor re-instated is very sensible. If the vents in the living accommodation remain covered up the mould will persist or even get worse.

As i mentioned on another thread, you could use a de-humidifier but oviously there is the initial out;ay & running costs to consider although the savings on you heating bill might compensate.

Personally, i think the vents should also be reinstated as keeping the windows open all winter is not really an option!

sorry for typos!

bathroom and kitchen ventilation, and preferably an extractor, is absolutely essential.

Some airbricks are put in to insulate the cavity to the outside air only, and do not open into the room. You do not need these any more. They are no longer used anyway, and if you are having external cladding then rain will no longer be making the outside bricks wet.

However if you had air bricks ventilating the rooms (these are usually found in bedrooms, pantries and rooms with gas fires or stoves) then they may still be needed. Many modern windows have trickle vents which should be left open at all times to give slight ventilation. Do you have these?

With the new insulation, your walls will be warmer, so moisture in the air will be less liable to condense on them, and will be more visible when it condenses on windows instead. Also, as the walls warm up, the water they already contain will evaporate out. this will only happen once.

A very bad source of condensation, damop and mould in UK houses is wet washing draped around or hung on radiators.

Your house is a similar age and probably construction to mine. These houses are designed to be ventilated. Our condensation problems started when we replaced the back boiler, which actively sucked air through the house in the same way a fire would and kept the core of the house warm. We live on the Northeast Coast, where the air is often very damp, anyhow, so we've invested in dehumidifiers for upstairs and down.

And definitely avoid drying washing on airers or radiators in the house, if you can. Tumble dryers aren't cheap to run, but they're cheaper than constantly fixing condensation damage and replacing mouldy stuff.

The vents go from the inside of the bedroom to the outside of the house. It's pretty much like a hole in the wall just with vent covers at each side if that makes sense?

There was physical water drops on the slanted bit on the ceiling where it meets the wall in the girls bedroom. There is mould patches here also. I think we will most likely have to get that part of the ceiling replaced eventually to be permanently rid of the mould there, as even though it was cleaned away it has come back.

The windows do not have the trickle vents on. They were fitted in 2009/2010..ish. It was done through a government scheme, so we paid around £3000 to them. The company that did them was meant to give us a guarantee that never came through the post. They folded a few months later and someone new took over. They refused to give us a guarantee as it wasn't their problem.

if your air bricks go right through the wall into the room, yes, they should be opened on the outside. I expect the builders thought it would be extra work and cost to fit external vent covers for them.

You probably have a white plastic hit and miss vent on the inside. People usually close these complaining of the fresh air. As you have a condensation problem, open yours.

If you have a sloping section of ceiling, it is very likely there is no loft insulation above it, which would attract condensation. It is possible to poke insulation down between the timbers from the loft, but not easy. It is also possible to insulate the inside surface of the ceiling, but there is not usually room to put much thickness. Otherwise, either the plasterboard ceiling has to come down to insulate it, or it can be done if the roof is being renewed or repaired. A plasterer might charge a few hundred pounds per room

Window Trickle Vents are just holes with an ornamental plastic trim. They can be drilled by someone familiar with plastic windows. There is sure to be at least one local firm in your town that specialises in plastic window and door repairs.

Tell us about the extractor fans and wet washing.

We've always had the vents kept open, as we know how much it helps.

Thank you for the advice about the ceiling. I remember someone mentioning putting insulation board above the slopping part in the loft when they came to assess for cavity wall. Would that work? Other than that I'm assuming it would be better to just fully replace.

We have a bathroom extractor fan, which we used all the time before they covered it over. They will reinstate that but they've not done it yet. We have an extractor fan in the kitchen but it doesn't lead to the outside as the boiler is in the way, so it just has filters in that have to be replaced. The washing goes in the tumble drier, which is self condensing. Other than that I wipe away any condensation that forms and open the windows to try and air out the house. We only get mould problems upstairs really.

loft insulation is usually between 100mm and 300mm thick, and you will probably not be able to put anywhere near that on the inside of the ceiling. If you can get it packed between the roof timbers it will be reasonably thick. If the ceiling is being replaced you can get bonded insulating plasterboard that will help a bit.

A recirculating cooker hood is no use.

I just leave the windows open a crack and open bathroom windows after a shower/bath. You need to close the door though, to let the steam out and keep the cold air from making the rest of the house cold.

We have a similar problem with mould developing on windows and on an area of non-insulated wall. Seems particularly bad at the moment! We did have to do a big clean up last year too.

We are wondering about a heat-recovery ventilation system. Anyone any experience of these? I am already confused about how they do the whole house...

I once had a single-room heat-recovery ventilation unit in a kitchen.

For that it was not much good. it balances air in and air out, so there is no suction, so the cooking smells drift around the house.

I am not convinced there is anything that gives such a good cost performance as an extractor.