Condensation and mould in 1930s semi

[AnotherEmma]

I have an annoying condensation and mould problem that's been going on for years and I am determined that this is year I will get it fixed.

DH and I have many talents but DIY is not one of them and I was hoping to call on mumsnet's collective wisdom for advice.

The house is a 1930s semi with external wall insulation that was installed about 5 years ago. The condensation and mould are in the two first floor rooms at the front of the house.

One room is a bathroom with 2 external walls, it gets cold. We installed an extractor fan with a humidity sensor a few years ago. DH scrubbed the ceiling with mould treatment and painted it with anti-mould paint. These two things seem to have helped a bit but the mould still grows. One problem is that we have to dry laundry in the bathroom in the winter (nowhere else to dry it) but we do run a dehumidifier in there pretty much constantly during the day (not at night because the noise disturbs me).

The other room is a bedroom with just 1 external wall with a bay window. (One wall is adjoining our neighbour's property). The bedroom had a fireplace which was blocked in by the previous owner with no ventilation. The worst mould is inside a built in wardrobe where there is obviously even less ventilation than the rest of the room.

It seems obvious that ventilation is the problem but we don't know how to fix it. DH spoke to a builder who suggested that the loft insulation might be a problem, if there isn't enough of a gap to allow air flow.

We have got a few quotes for damp surveys and we're willing to pay for one if necessary but I am wondering if there is anything obvious we are missing that we should try first.

@PigletJohn I hope you don't mind me tagging you but I have seen your posts on other threads and hoped you might be able to advise please?

Darn I think the photos in my previous post didn't load (although now I'm reposting them they will probably appear!)

I don't recognise the fan type, but it might be just an inner vent. Please have a look at the ducting and whateber you can see of the fan in the loft. photograph it too. If you have flexible ducting, it may be lying in sags, and condensation will collect in the hollows and can leak out. Rigid duct (like soil pipe) is available and much better, though it has to be cut to size which takes longer than throwing a piece of flexy down.

As you have a ducted fan, we can find you a more powerful one, which will be very quiet and very economical on electricity.

I think we will have a good solution for you.

btw when running a fan, it is important to keep the window and door shut. In your case doubly so, because the steam is blowing down towards the window and might get sucked back in.

Flat roofs on bays usually leak.

Ask around neighbours for a recommended roofer. Lead gives a very good roof, but there are also rubber-like sheet coatings. Your old one might have been zinc which corrodes away, or felt, which degrades and rots away. It also needs a gutter and downpipe that are not blocked or leaking.

I think your roof is not big enough to attract lead-thieves.

FlamingoAndJohn
We installed the external wall insulation, I wasn't keen but DH pushed for it. It was about a year after we moved in... We think the compensation/ mould was already a problem. I do think the external wall insulation might have made it worse (or certainly not better) and the fact that I can't see any ventilation at the front does make me wonder.

Mixmag
Yes, like you we only have a towel rail radiator and it's not sufficient to heat the room and dry the towels. It's also positioned in the opposite corner to the corner of external walls, which can't be ideal.
I want to redo the whole bathroom and install underfloor heating plus a dual fuel heated towel rail (so we can turn it on even when the central heating is off). I'm just nervous about getting a lovely new bathroom if the bastard mould keeps growing back

if you're thinking of a bathroom refit, this would be a good time to address ceiling insulation. Sloping ceilings are difficult to insulate from the loft, but very easy if you have a plasterer in to pull down and renew. As you have external wall insulation I'd expect the room to be well insulated in other respects.

It's a small job but would probably take two half-days so a matter of £hundreds. Better value if you have any other replastering done on the same visit.

But see what you find when you get up there with your torch.

have you got a hot-water cylinder?

PigletJohn
I salute you - you inspired me to go up to the loft for the first time in years! Usually DH goes up there - he gave me his head torch and instructions not to put a foot through the ceiling

This is the bathroom fan and ducting - what i could see of it, anyway. We dug out the order for the fan:
MANROSE MF100S MIXFLO FAN - 100MM
Photo of electrician's invoice too.

No hot water tank. Previous owner installed a (crappy) combi boiler. Plans for extension include replacing the boiler with a megaflow.

So just to summarise action points as I understand them:

• get roofer to check flat roof and guttering above bay window for leaks and blockages
• get plasterer to rip out sloped ceilings and install insulation before replastering
• possibly replace bathroom fan and/or ducting

Do you think we also need to put some ventilation in the old fireplace in the bedroom?

I'm not a fan of Manrose, but the MF100S is plenty powerful enough, assuming it is working and the ducts are not blocked or crushed. I was going to have recommended something similar.

It might be that it has not been running long enough or often enough.

Look for the sensor or adjuster he mentions in the ceiling. It will probably be a Manrose 1361 Remote Humidistat. I'm not familiar with them.

I should think you will hear the fan when it starts.

Adjust it so it is permanently on, and leave it on for a week.

It has enough power to suck out all humidity from a steamy shower or wet washing. It will be cheaper to run that your dehumidifier. It is pretty quiet, unless the motor bearings are worn.

If it doesn't, there is something else wrong.

Have your neighbours got same problem? If don't want to ask... Are their windows continuously open upstairs gives a clue 🤔... Purely so you can tell if likely to be your changes or if a general problem in area.
Our previous 30s semi had this issue (less so) and we had to put back in air bricks that seemed to have disappeared.. Plus ventilation and a dryer/clothes dryer rail in garage.

If you get a megaflo or similar, and if you have a suitable airing cupboard next to the boiler, you can get the installer to plumb it so that the towel rail and/or radiator is heated whenever the cylinder is heated. Typically this will be during or after running a bath or shower, which IMO is the ideal time.

You may want another radiator that comes on with the central heating. It is less common to have one that does both, and only very superior people have one.

PigletJohn
Yes that's the exact one Here's a photo.
It definitely works, it's quiet but we can hear it running, and it kicks in when we have a shower etc. So I just need to run it constantly then?
When drying washing we have the extractor and the humidifier on at the same time - can't be very energy efficient can it

happy
Good idea, I hadn't thought to ask the neighbours (doh).
We don't have a garage, hence wanting to include a decent utility when we extend.

"only very superior people have one"

here we are

the ad for the fan says "it goes without saying that the anti-backdraught shutter must be installed the right way round" (!)

If you hold a piece of paper near the ceiling vent when the fan is running, it should suck the paper up and hold it against the vent

run it for a week and see the difference in room dampness.

then you can adjust it to a level where it comes on quickly, and goes off only when the room is really, really dry. If you can't get the humidstat to do the job (I don't rate them) you can get a timed runon instead.

Envirovent have good products, pick is good. Ventilation in roof space is also necessary and worth checking.

PIV good not pic

ah, I see the controller has a run-on timer.

Adjust the humidity sensor anticlockwise to very low humidity first; then adjust the timer clockwise for run-on time max.

You can ease off the settings, if necessary, once you are sure it has cured the condensation problem. 20 minutes run on after a shower may be sufficient.

There should be no need to use the dehumidifier.

Earlier you said the fan should be running constantly, but now you've seen the controller, you think we should set it to kick in at the minimum humidity level (40) with the maximum run-on (60)? Have i understood that correctly? And should it be sufficient to dry laundry in there?

I'm just concerned there must be another problem (maybe to do with the loft insulation and/or ventilation?) because we run the fan and the humidifier a lot and as you can still we've still got a lot of mould.

It would explain why we have it in the bedroom too despite obviously generating less moisture in there.

as you can still see

I have enquired with the local Envirovent person, free survey and quote so I figure it couldn't do any harm (despite what everyone has said about the free surveys just being an excuse to sell you stuff you don't need!)

PS I forgot to say, the bathroom vent passed the paper test!

I'm not an expert at all, but what is your external wall insulation made of? I was told that 1930's houses need to 'breathe'