MOULD everywhere!

As a non expert foreigner, it's my perception that the overall humidity in Ireland is generally very high, which combined with annual low average temp of 10 C, makes mould a near inevitability. Opening windows seems to be the Irish solution, which I have always felt isn't likely to be very helpful, given the outside humidity is usually ideal for mould:

For mould to grow on a surface it generally needs moisture to be present. This can arise through condensation from the air, so it's likely all surfaces in your house are cold enough on average that moisture is condensing on them. The solutions seem to be to make the surfaces warm enough that condensation doesn't occur and/or reduce the level of humidity in the air.

Unfortunately, both require energy, in terms of increased heating or running a large capacity de-humidifier. the latter is likely to require far less energy and cost. De-humidifying to below outside ambient levels, like heating, requres some degree of airtightness to the house.

I have a dehumidifier in my house and that can pull 4-5 litres of water from the air per day. When the external humidity is high, I don't open windows and air, as that just raises the humidity inside. (I am aware that taking in 90% humid air that's 10°C and heating it to 20 will result in a lower humidity) Sorry, I understand the cost of buying and running a de-humidifier may be too much for you, but i don't think there is any low-cost solution.

Use vinegar to wipe mouldy surfaces as that kills most types, with bleach killing the types vinegar doesn't.

OP,

when did you buy the house?

was it occupied or vacant for a time before buying?

when did you move into the house?

how is the house heated?

does it hold its heat well?

how many in the household?

when was the house built?

Working backwards, mould is a living organism and needs moisture to thrive. Unless there are active water leaks or water ingress from outside, this moisture comes from internal moisture producing activities (breathing, cooking, washing etc). This internal moisture needs to be exhausted from the building and if not then there will be a build up of moisture resulting in what you are seeing. Three things govern how efficient the moisture is exhausted; Ventilation, Heating and Moisture load. This is generally a problem seen only during the heating season.

To tackle this adequately you need to

1. ventilate properly, little and often is better than large and infrequently. Maybe consider a low energy continually running background centralised whole house extraction system for the wet rooms via the attic space
2. Use the heating more to maintain a higher internal temperature
3. Stop breathing inside the house - only kidding. Avoid adding extra moisture such as drying clothes inside, excessive potted plants etc

If the house has an open attic and no rooms upstairs it could be relatively easy to fit a MHRV system which would solve your ventilation problem! You're probably still talking about 3 to 4k though

Similar situation here I didn't know who to ask. 70's bungalow with mould in ever room except for the hall. Its mainly on the windows - glass + frame (20yr old double glazed) and the walls beside the windows, there was also an issue with clothes in a wardrobe that is rarely used.

There are hole in the wall vents in every room. There is an extractor in the bathroom linked to the light switch and the cooker hood extracts outside. Insulation in the attic is patch near the sides, I am getting someone to look at this. Overall the house isn't great at keeping the heat in.

Cillit Bang Mould Remover spray is way way way better than white vinegar.

Sodium Hypochlorite in a drum is the same chemical but you need to dilute it very much with water. Needs extreme caution but is very handy to have if you have large areas to clean.

For clothes:

Clean washing machine door/seals/detergent drawer with Cillit bang/bleach.

Wash everything @60ºC minimum. Add vinegar to rinse cycle.

Run washing machine on 90ºC cycles often and leave door open when washes are finished.

Clean the dryer (if you have one) with bleach/mould remover, run on hot to clean that, and then dry all clothing/furnishing in that to as hot as you can.

Make sure your clothes are as dry as you can get them, and consider using vacuum bags to store clothes in for the time being.

If the spores are in the house they're in the house. You have to be methodical and set aside time to clean the whole house top to bottom, doing this with windows wide open, and not doing it piecemeal.

Every surface in the house should be treated, repeatedly most likely, and definitely treated before painting.

If you can't bleach or wash something, consider getting rid.

Things like fibreboard/MDF/Cardboard backed wardrobes can be disastrous to hold spores and can be nigh on impossible to clean. I'd get rid of as much stuff as possible that was in the house when you bought it, in terms of furniture/lino etc

Move all furniture away from walls. Turn up the heating and conversely ventilate the house more. Consider using additional heaters and dehumidifiers. Creating air movement in areas you can't open a window in is helped by getting a pedestal fan.

Get someone to check that there isn't water coming in under window sills etc. Make sure there are no blockages in your guttering/loose guttering. Check for any issue with water tank in attic like a broken stopcock causing an overflow, or overflow pipe directed to the wrong place.

If you have insulated plasterboard on interior walls, it might be worth inspecting behind that if the problem persists, because in older houses that can be a breeding ground for mould that you won't see.

I hope you get to the bottom of it, it's stressful to have mould in a home, best of luck with it

The fact that it's a draughty house you say should have been a help with ventilation I'd have thought!

Have you been doing anything to contribute to it like drying clothes indoors on clothes horse type thing? It's not a terribly old house, my own is only a few years younger with original windows and I have nothing like that at all, my house is fine and draughty coming from a converted attic which is an advantage in it's own way!

It's puzzling to have that level of a problem unless it got very bad in the few months it was empty, if that was the cause then it could be a case of get rid of a lot of soft furnishings etc that can't be cleaned successfully. Although couches etc can be professionally cleaned and if you were sure of a bout of fine weather you could put them outside to dry fully.

Hi Op, I was the one who mentioned the temperature drop. Warm air holds more moisture and if the temperature drops suddenly then you can get condensation on any cold surfaces - windows, cold floors, leather furniture, etc. It is best to keep the temperature stable if possible, but I managed the dampness in a house once by wiping the windows every morning and wringing out the cloth in the sink.

Your last post sounds like you might have more problems than ambient moisture though. If there is mould on the skirting boards, is there any discolouration to the paint on the walls? How is the drainage outside the house? Does rainwater puddle near the walls? Are any of the gutters leaking? Do you know if a damp barrier was ever installed when the house was constructed? Can you lift a small bit of the lino in an unobtrusive spot to see if there is black mould on the concrete underneath or if concrete feels wet?

You could Google damp proofing or damp treatment and see if there are any useful guides. If you could find out more about the house, it might help too. Some builders used to mix beach sand in the concrete and the salt ends up transfering moisture through the walls. There are moisture meters and humidity meters, although I wouldn't know much about them myself. Newer dehumidifiers come with inbuilt humidity displays.

Lindsay

When you are ventilating the house, an open window in a room with the room door closed will not provide through ventilation.

Open room windows and internal doors to provide purge ventilation, to remove the damp air from the house. The more often you do this will help to reduce the mould growth.