mould issues, mass concrete council house

jmBuildExt · 21-01-2022 3:23pm #1

Not sure what the traffic is like here these days...dont drop in as much myself anymore...but hopefully someone can offer some advice.

Have one of those typical 2 bed mass concrete council houses built from the ~50s onwards in dublin (Cabra, Crumlin etc).

Small house (80sqm max) incl small kitchen extension.

Ground floor : small hall and stairs, front parlour room, sitting room at the back and double doors out to kitchen extension.

Upstairs: 1 front bedroom, back bedroom, bathroom.

There's no insulation apart from some rock wool rock wool in the attic.

Have had mould issues, particularly on front bedroom external wall upstairs.

Added 100mm vents to front parlour room, kitchen extension, front bedroom, back bedroom and bathroom.

This has little or no affect on the issue.

In this room there is a gas boiler and HWT in a press over the stairs. Boiler vents out same front (cold) wall as the one with mould issue.

Anyone had similar problems in these types of houses?

I'm reluctant to bang up some insulation on the wall and hope for the best, without understanding it more.

Thanks

mike_2009 · 21-01-2022 6:31pm

Is the attic dry, cold and suitably vented? You can easily top up the attic insulation yourself but it's below that where the fun starts! Is is brick or render outside the front external wall? There is a product called Stormdry that can help prevent excess damp penetrating the wall - try youtube skillbuilder channel "How to Stop Damp Penetrating Brickwork" and have a think along with other options people come back with here. Caveat: not in trade, definitely not an expert!

It's unlikely to be a cavity wall you can pump based on date but worth getting a look into those vents to see what the wall build up is? Doing internal insulation well is tricky as it can make things worse. External insulation would be best once you understand the problem and why its happening.

Is the damp issue worse in Winter?

You could try a de-humidifier in that room to help keep ahead and a humidity monitor would also be a good idea. There are two types of those units, check out youtube "the ev puzzle" and his comparison of two types for an idea.

Mods - sorry if calling out products / YT channels I've referred to not allowed but hoping it helps here.

MicktheMan · 21-01-2022 6:50pm

The cause of the mould issue is likely a combination of excessive moisture available condensing on surfaces under or close to the dew point temperature of the air.

Are the worst effected rooms on the North or East side?

The excessive moisture is likely caused by inadequate ventilation and/or under-heated internal space.

The longterm solution is multifaceted and might not completely eliminate the issue entirely if the external walls are not sufficiently and appropriately insulated:

Reduce as much as possible the moisture generation... stop breathing (joking!). Try not to dry clothing inside. Do you have a lot of potted plants or other moisture releasing items in the house? An average family of 5 can easily produce up to 20 litres of water in a 24hr period.
Increase the internal temperatures primarily by reducing the heat losses and having the heating on for longer.
Your "hole in the wall" vents are inadequate in our temperate climate and therefore should not be part of a ventilation solution. You need to consider some type of continuous system that is ventilating your home 24/7 regardless of what the weather is doing. This is only a heating season issue (not needed in the summer). you need to consider a centralised mechanical extract ventilation system (cMEV) or a demand control ventilation system (DCV).
Do not install insulation internally without careful consideration and analysis of moisture movement and interstitial condensation. Proper detailed external insulation is the proper way to insulate these walls if possible.

Hope this helps somewhat. Fyi, you can have surveys done which can hone in on which of the above aspects are dominant and how to address.

jmBuildExt · 24-01-2022 1:34pm

Thanks for the replies.

Just to answer some of the things raised there and give a little more info.

The house is mass concrete (prob about 200-300mm thick) with pebble dash finish, painted. Don't think its damp coming through the wall as such.

I've a friend living in the house (i.e. its rented) I've been there on several occasions, and from knowing them personally, I know it is well heated all the time. (too hot for me)

I know there is a clothes horse kept in the kitchen for when it is raining (and possibly used when its not raining) - and there would be pots boiling away in the kitchen most days for dinner etc. Extractor fan does not go out an external wall (i.e. recirculating). So kitchen would be main source of moisture.

House faces north west. And outside of affected wall is facing north west.

I will get some humidity sensors and possibly a dehumidifier. Hopefully help them understand when the issue will occur and what is the source. They can observe the patterns and try to anticipate the problem and alleviate by opening windows or switching on the dehumidifier.

Will look into smart mech ventilation and EWI as a longer term solution

beggars_bush · 24-01-2022 10:14pm

https://www.boards.ie/discussion/comment/118525175#Comment_118525175

whats the point of an extractor fan if it doesn't go out a wall? might as well just open a few windows

clothes horse - get wet clothes out of the house and into a drying shed or something

jmBuildExt · 25-01-2022 10:04am

https://www.boards.ie/discussion/comment/118528017#Comment_118528017

Thanks for that.

Extractor fan has a filter for trapping grease and what not.... better than nothing in a situation where its not feasible to go out the wall.

mould issues, mass concrete council house

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