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1970's build Mould/condensation problem

  • 07-02-2022 10:35pm
    Registered Users Posts: 1,472 ✭✭✭

    Hi all. Looking for some help on cost effective way to remedy mould and condensation issue on a 1970's detached 2 storey house I bought in 2020.

    The house has seen some insulation works but we have been having mould issue and condensation issue in main bedroom/bathroom and utility. I've noticed that there is no ventilation at all in the house. As vents. Barring presumably trickle vents in windows.

    Its a weird one as the house is a c2 and would not be air tight. So I imagine air is circulating but the mould would suggest not.

    The initial plan is installing mechanical fan in bathroom which should solve that issue. But for bedroom etc. Would coring a hole for ventilation help? Worried about noise then. And the place being freezing.

    Any advice appreciated.


  • Registered Users Posts: 1,540 ✭✭✭Dudda

    If you can afford it look at demand controlled ventilation. Slightly more expensive that what you're looking at.

  • Moderators, Home & Garden Moderators Posts: 10,133 Mod ✭✭✭✭BryanF

    ‘cost effective’ solution:

    Open the windows when cooking

    dont dry clothes in the house

    open window at night in rooms people are sleeping in

    open windows in bathroom for a hour or two after using shower.

    clean mould with vinegar and baking soda .

  • Registered Users Posts: 1,472 ✭✭✭Pepp1989

    I hear you but the house is on a main road so opening windows increases the noise.

    What should I be looking at if I wanted a more permanent solution. Does the house need to be airtight for these mechanical systems to work?

    Is there little to no value in boring holes for vents these days? I have seen evidence of cavity beads. Attic is insulated. I'm changing back door and one old window. Rest are double glazed, although not the newest. Front door will be done too at some point.

    I'm trying to make the best decision for dealing with the mould. The bedroom window is soaked in the morning.

  • Registered Users Posts: 88 ✭✭Calvin001

    You could look at vents and installing acoustic T90 vents or similar.

    There are a few PIV options, Nuaire have a drimaster (self assembly) or vent axia have pozidry pro. You could review these and others to se if they would work. Ventilation is key

  • Moderators, Home & Garden Moderators Posts: 10,133 Mod ✭✭✭✭BryanF

    I have demand control extract. If I was doing it again I’d go with mhvr it kind of depends on the house layout and disruption etc

    re air-tightness, you can make certain improvements, the level of air-tightness will dictate the efficiency of mvhr.

    mold issues suggest you’ve poor ventilation and separately /maybe you have cold surfaces where moisture will tend to condense, insulation and air-tightness measure might be tackled together.

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  • Registered Users Posts: 1,472 ✭✭✭Pepp1989

    Thanks for all the comments. Where would you go to get someone out to advise on this and maybe survey the property?

    Im in Cork. Any recommendations?

    I don't know where to start.

  • Registered Users Posts: 1,261 ✭✭✭Gant21

    The house needs fresh air. As said previously open windows.

  • Registered Users Posts: 567 ✭✭✭kuro2k

    I've seen Rebel Energy mentioned on old Boards threads, a search might help. I haven't used them myself

  • Registered Users Posts: 26,907 ✭✭✭✭GreeBo

    If you only have an issue during the winter, you could just get a dehumidifier.

    I got the Meaco DD8L Zambeezi and its pulling out 4-6L/day from my 200sqm house at the moment.

    Was ~€300 and all my windows are bone dry now in the morning.

    1930s solid wall, detached house with no room vents and very old/leaky windows.

    They are also local to you :)

  • Registered Users Posts: 25,880 ✭✭✭✭noodler

    I bought the low energy 20L Meaco one, takes about 6 litres out every day and a half. Also about 300e

    Condensation on non bedroom windows is down.

    Bedroom is a trickier one. I find I need to very gently crack the window and also not completely cover the window (blind not all the way down and curtains not all the way drawn in order to reduce the condensation).

    I try to open nearly all windows for an hour every day though and for longer in the warmer months to give the dehumidifier a break.

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  • Registered Users Posts: 7,784 ✭✭✭munchkin_utd

    As I said above.... quick proper measured airing works !

  • Registered Users Posts: 757 ✭✭✭C. Eastwood

    S - ( I + V) = C

    This is a simple way to explain Condensation. 

    S. Steam (and moisture)

    I. Insulation 

    V. Ventilation 

    C. Condensation 

    You state that your house has some insulation- you probably need more.

    Your house is 1970’s. Insulation was first used in Irish houses in late 70’s. But only 25 mm of Styrofoam was installed in the cavities then.

    Insulation in ground floors in Ireland was introduced in the early 80’s.

    Trickle vents are perfect - provided there is enough ventilation area in the vents. You probably need more ventilation.

    The 2002 Technical Guidance Document L - required a Vent high up in the wall or a trickle vent of 6,500 mm2.

    Note:- a 100 mm dia pvc pipe in the wall would give approx 7,800 mm2.

    Then there is the problem is Steam and Moisture created within the home.

    This Steam /Moisture is caused by the following:-

    1. People breathing
    2. Drying clothes on rads
    3. Steam from boiling water, boiling vegs, cooking, etc
    4. Baths
    5. Showers
    6. Tumble Dryer 
    7. etc sources of moisture

    Clothes should not be dried in the house.

    Tumble Dryers must be exhausted to the external atmosphere 

    During cooking- extract steam to the external atmosphere and have the Kitchen door closed to prevent any steam escaping in to other parts of the house.

    When finished having a Bath / Shower, open the Bathroom window / switch on a Mechanical Extractor and shut the door of the Bathroom on leaving. 

    Also seal all draughts to prevent heat loss by Convection.

    Walls with dark olive green mould should be washed down with 3 parts water to 1 part household bleach.

    To try to stop / reduce the mould from occurring on the walls/ ceilings again - coat same with Zinsser paint in accordance with manufacturer instructions.