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Bad condensation in attic

  • 30-12-2014 12:33pm
    #1
    Registered Users Posts: 116 ✭✭ gorgo


    Hi,

    I seem to have very bad condensation in my attic. 1st year in the house.
    Its dripping down from the felt onto the bedroom ceilings!! In the summer I upgraded the insulation to 100mm rigid foam. I imagine the warm moist air is getting into the attic.

    We have 8x 70mm soffit vents dotted around house.

    Is this enough ventilation?

    All help appreciated,

    Regards.
    G


Comments

  • Registered Users Posts: 243 ✭✭ baby fish


    If its a new house it might be still drying out but it seems like this house is at least a few years old and dry?

    The new insulation has probably made your house warmer but your attic is now colder and you may have blocked the vents when installing the new insulation?

    First look at reducing amount of moisture making its way into the attic :
    Are you removing as much of the moist air as possible at source? is the extractor fan on when cooking? do you use an extractor fan when showering and then leave it run for maybe 15-20min afterwards to ensure all moisture is removed? how do you dry your clothes - in your house on a clothes horse?

    So it doesn't matter how many vents are in the soffit if the are covered by insulation. Make sure there is a free air space (at least 50mm between insulation and felt)for the air to flow in to/and out of the attic, and its also important to have vents at both sides of the house to ensure cross ventilation : the air will flow in through one side and out the other.

    Your 8 vents doesn't seem like much , that's 4 on either side. The regulation for vents as far as I can remember is a 10mm opening the entire length of the building or equivalent, so if you cut 8x70mm vents into 10mm strips, would get enough to run the length of both soffits?

    Start by making sure you haven't blocked the airflow from the vents into the attic, if they are clear then add more vents where required.

    Google : Irish technical guidance documents, scroll down, find the one that deals with ventilation - PART F. you'll find details about ventilation here.


  • Registered Users Posts: 116 ✭✭ gorgo


    Thanks for the reply babyfish.

    House is 20 yrs old.

    I have vents spread on 3 sides of the house. 3 back, 3 side & 2 front. We dry the clothes in the house in the spare room.

    We have no extraction fan in the bathroom! We just open the window wide open. Always use the extractor fan when cooking but may need to check its working right.

    Need to read the regs you pointed out but based on your 10mm whole way round the house, my vents equate to about 5.6m which would only cover one side of the house!

    G


  • Registered Users Posts: 243 ✭✭ baby fish


    20 yrs old - so it not a from e.g. new plaster drying out and its been a fairly mild year so far, if it gets really cold you are going to have even more condensation.

    I hope you have trickle vents open in all rooms? I've a feeling there mightn't be any:eek:

    get an extractor fan for the bathroom, get a good one with a timer, when you turn it off it will run itself for 15 or 20min, its a good idea to have this even if you are not having condensation problems in your attic. Vortice are a good brand, im sure there are others too.

    there isn't a lot of options but drying clothes in your house is not a good idea, it usually leads to mould growth in your house. the cost of running a condensing tumble dryer or the normal one ducted to the outside in my opinion is better than having mould growth from drying clothes in your house

    if you do install new soffit vents don't forget to make sure there is clear space over them into the attic for the air to move through or else it is a waste of time.

    it wont happen overnight but sort it out before your roof rots and you get mould in your house .. good luck!!


  • Registered Users Posts: 116 ✭✭ gorgo


    No trickle vents on any windows!!

    We have mould starting in the bedroom. I'm starting to get the picture here. Gonna go read them regs.

    Cheers for the help.

    G


  • Closed Accounts Posts: 9,088 ✭✭✭ SpaceTime


    There's nothing venting into the attic by any chance?
    I've seen situations where bathroom fans or cooker hoods were venting straight into the attic either accidentally due to broken ducts or deliberately due to shoddy builders.


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  • Registered Users Posts: 116 ✭✭ gorgo


    Kitchen extractor goes straight out the exterior wall through vent. Need to put an extractor in the main bathroom.


  • Registered Users Posts: 243 ✭✭ baby fish


    gorgo wrote: »
    No trickle vents on any windows!!

    We have mould starting in the bedroom. I'm starting to get the picture here. Gonna go read them regs.

    Cheers for the help.

    G

    trickle vents can be in the walls too, a 100mm pipe in the wall with a hit n miss cover over it. These are probably more common than the window trickle vents. make sure they aren't blocked on the inside if you have them. If you have nothing you should consider installing some or maybe DCV


    that's a good point made by spacetime, when you do install a fan in the bathroom don't vent it straight into the attic, i.e. just to the other side if the ceiling . it will be ok for a year or so but you will soon notice mould growing on the ceiling in the bathroom as the exhausted air will just condense around the fan duct in the attic. straight out through the wall is best

    Preventing mould is not all about extracting, in your house you need
    1. the walls and ceilings insulated properly- to keep the cold out and inner surfaces warm i.e. above the dew point.
    2. Heating on during the heating period( heat will allow the air to hold more moisture, it will also heat the surface of e.g. walls, surfaces need to be kept above the dew point).... so turning off a rad in a room that is not used is not a great idea
    3. extraction/reduction of water vapour at source
    4. fresh air supply in to house through ventilation to carry away all that moisture that has not been extracted at source. e.g. the moisture in the air you exhale, boil kettle, steam iron

    if any of the above are missing then the chances of mould forming will increase

    you are probably aware with all the ventilation and extraction your heating bills will go up, so its a decision if you want to live in a house with mould or one with higher heating bills.

    Alternatives to intermittent extraction with trickle vents (this is what you will have) are
    1. MHRV (this is not an option for you, your house is not airtight enough)
    2 DCV will work but as to how much it will reduce your heating bill I don't know for sure.


  • Registered Users Posts: 1,882 ✭✭✭ Robbie.G


    If this is the type of vent used they are supposed to be fitted at 200mm centres to achieve the equivalent to a 10mm continuos vent


  • Closed Accounts Posts: 2,008 scudo2


    Heating pipe overflowing/venting into the small heating tank in the attic will cause condensation.

    Are the tanks covered ?
    Is the small tank warm when heating is on?


  • Registered Users Posts: 116 ✭✭ gorgo


    Robbie.G wrote: »
    If this is the type of vent used they are supposed to be fitted at 200mm centres to achieve the equivalent to a 10mm continuos vent

    That's the vent yeah. I have 8 of them dotted around.


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  • Registered Users Posts: 116 ✭✭ gorgo


    scudo2 wrote: »
    Heating pipe overflowing/venting into the small heating tank in the attic will cause condensation.

    Are the tanks covered ?
    Is the small tank warm when heating is on?

    Big tank is covered not the central heating tank. Checked to see if the central heating tank overflow pipe was warm but nothing just tepid.


  • Registered Users Posts: 116 ✭✭ gorgo


    Update:
    I checked the vent in the bathroom. It looks like it's just two holes behind the vent, in the plasterboard and external wall. I can feel the insulation and a gap. I think when we're showering the steam is going up through the gap to the attic.

    Bought a new extractor fan with timer and humity sensor for bathroom with duct n louvre gravity outer vent. Gonna fit that and add some more 70mm soffit vents around the house. Maybe cover the small water tank in the attic too.


  • Closed Accounts Posts: 2,008 scudo2


    gorgo wrote: »
    Big tank is covered not the central heating tank. Checked to see if the central heating tank overflow pipe was warm but nothing just tepid.

    Should be cold.
    Is there any sign of green corrosion on the tip of the pipe that loops over the top of the tank ?
    This would indicate that heating is blowing / pitching water up it from time to time.
    If so, vent pipe has to be extended up higher and then redirected back to tank, water wont pump up greater hight.

    Is it oil, gas or a stove ?


  • Registered Users Posts: 116 ✭✭ gorgo


    scudo2 wrote: »
    Should be cold.
    Is there any sign of green corrosion on the tip of the pipe that loops over the top of the tank ?
    This would indicate that heating is blowing / pitching water up it from time to time.
    If so, vent pipe has to be extended up higher and then redirected back to tank, water wont pump up greater hight.

    Is it oil, gas or a stove ?

    We have oil. There is green corrosion there, like it was leaking at some stage. Was there when we moved in a few months back.

    That overflow comes up from the hot press to the start of the pitch in the roof. There's no room left for a 90 degree bend.

    Would it be better to put a 'n' shape bend where there is room for a higher bend or

    Cut the pipe where it meets the pitch in the roof and run a pipe parallel to the pitch and then directly down into the small tank? Will post some pictures


  • Registered Users Posts: 116 ✭✭ gorgo


    gorgo wrote: »
    We have oil. There is green corrosion there, like it was leaking at some stage. Was there when we moved in a few months back.

    That overflow comes up from the hot press to the start of the pitch in the roof. There's no room left for a 90 degree bend.

    Would it be better to put a 'n' shape bend where there is room for a higher bend or

    Cut the pipe where it meets the pitch in the roof and run a pipe parallel to the pitch and then directly down into the small tank? Will post some pictures

    Below are pictures of the gap between the wall just behind the vent. The Green corrosion on the overflow. The overflow running along to the small tank and the 90 bend on the overflow close to the pitch in the roof


  • Registered Users Posts: 1,793 ✭✭✭ whizbang


    Bought a new extractor fan with timer and humity sensor for bathroom with duct n louvre gravity outer vent.
    This is the answer.

    The warm moist air is travelling up behind the plasterboard, into the attic. Needs to be ducted straight outside. Pack around the duct with spare bits of polystyrene foam, the main thing is to prevent the bathroom air from getting behind the plasterboard.

    you really should do this in all your vents too.


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