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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthortony
    • CommentTimeJan 25th 2020
     
    If it was mine I would remove that horrid plastic layer on top of the insulation now.

    In many lofts condensation does form both on the underside of the sarking and in droplets on the very top of the insulation

    This is why it is important to to ventilate lofts and yours looks OK assuming not tightly sealed slating as the covering

    I would keep loft trap shut, draught strip it and don't look up there too often , most people rarely if ever look in their lofts
  1.  
    Posted By: denianceI’ve also noticed that since the air sealing and insulation that mould has started to build up below the coving in my bedroom and the other bedroom, but the bathroom that is the wettest has zero mould around the ceiling!

    Probably because the bit below the coving is now the cold spot (relatively speaking) so that is where any condensation will settle - and mould grow. Is the coving plaster or EPS? If its is EPS then this will be warmer than the wall beneath. Do you have EWI and is it joined to the loft insulation? If not then again the wall will be the cold bit.
    I had mould at the top of the wall after better insulating the loft - it stopped after putting on the EWI
    • CommentAuthordeniance
    • CommentTimeJan 26th 2020
     
    Thanks Tony, I’ll give it another search today, see if I can get the fan on and see what’s leaking air
    • CommentAuthordeniance
    • CommentTimeJan 26th 2020
     
    <blockquote><cite>Posted By: Peter_in_Hungary</cite><blockquote><cite>Posted By: deniance</cite>I’ve also noticed that since the air sealing and insulation that mould has started to build up below the coving in my bedroom and the other bedroom, but the bathroom that is the wettest has zero mould around the ceiling!</blockquote>
    Probably because the bit below the coving is now the cold spot (relatively speaking) so that is where any condensation will settle - and mould grow. Is the coving plaster or EPS? If its is EPS then this will be warmer than the wall beneath. Do you have EWI and is it joined to the loft insulation? If not then again the wall will be the cold bit.
    I had mould at the top of the wall after better insulating the loft - it stopped after putting on the EWI</blockquote>

    Yeah I get that bit, it’s plasterboard coving too, just wondering why bedroom 1 and 2 have mould but bathroom doesn’t?
    You would think a well used steamy bathroom would be mouldy but nothing and it’s the same build up as the other rooms, external walls solid stone no ewi, plasterboard ceiling etc maybe it’s because we are breathing out in the bedrooms each night? And this causes mould?
    • CommentAuthorbxman
    • CommentTimeJan 26th 2020
     
    I had exactly the same problem

    I solved it by adding vents to the soffit boards and just as importantly fitting ducts to every bay above the insulation at the eaves to facilitate fresh air penetration .

    Although I used plastic pipes I now believe I would have been better using short lengths of corrugated plastic roofing material to separate the insulation from the roofing felt (there are commercial products available.)
  2.  
    Posted By: denianceYeah I get that bit, it’s plasterboard coving too, just wondering why bedroom 1 and 2 have mould but bathroom doesn’t?
    You would think a well used steamy bathroom would be mouldy but nothing and it’s the same build up as the other rooms, external walls solid stone no ewi, plasterboard ceiling etc maybe it’s because we are breathing out in the bedrooms each night? And this causes mould?

    But you do say that the bathroom has good powered ventilation so this may prevent problems also house orientation may be a factor. I will leave comments about heavy breathing all night in the bedrooms to others :devil:

    Oh - and if you click the Html button below the comments block then quotes come out in blue. It just makes posts easier to read.
    • CommentAuthorphiledge
    • CommentTimeJan 26th 2020
     
    Its likely the bedrooms will be cooler than the bathroom so more likely to get condensation. If you havent got trickle vents in the bedrooms it may be witth cracking open the windows during the day to get some fresh air in. Dont forget to crack a window on the opposite side of the house to get s through draft.

    For your roof ventilation I think the felt vents you have will be way less than the normal ventilation requirement which I think is the equivalent of a 10mm continuous eaves gap along opposite sides of the roof. Whilst you may see the cobwebs blowing near the felt vents if its windy, there may not be much air movement when its not blowing much, especially if the roof covering is well sealed as Tony mentioned.
    • CommentAuthorgoodevans
    • CommentTimeJan 26th 2020
     
    It strikes me from the photo that the outside air coming in between the felt is dry enough to prevent condensation (not all the time probably but alot of the time). My thought would be that increased ventilation in the loft would be what is required - in particular ensuring any eaves ventilation that may be present has not been blocked by the insulation. (The insulation at the eaves seems to be piled up here).

    This is a tricky area - you want lots of insulation here, and it's tricky to reach, but any eaves vents need to supply plenty of fresh air from outside - with plenty of ceiling level insulation a draughty loft is what you are looking for. As the insulation levels increase this becomes more important as you haven't got heat from the house keeping the loft warm.

    On clear winter nights the roof will be colder than the ambient air and condensation is inevitable - the trick is to create conditions during the following day to dry it all out asap. I agree with Tony in that the plastic needs removing from the insulation - moisture in the form of water drops will be able to get in faster than vapour will be able to get out and so overtime could become waterlogged.
    • CommentAuthordeniance
    • CommentTimeJan 26th 2020
     
    Thanks for all the help guys!

    I’ve been up there most of the day!
    I found a few more holes and cracks but nothing drastic , filled them up , checked insulation.

    It’s a little bit dryer up there already, there are dry patches around the vents.

    I did find quite a big hole near the bathroom door, whacked some foam in it, so maybe this will help!

    Had the FLIR camera out , the loft hatch is leaking heat as if it’s not there , so gonna make a nice lid for it!
    • CommentAuthordeniance
    • CommentTimeFeb 8th 2020
     
    Managed to get a bit more done!
      65BD7555-4057-4F77-B3A5-535587C270E6.jpeg
    • CommentAuthortony
    • CommentTimeFeb 8th 2020
     
    If there is a difference in the partial vapour pressure between that in the air in the house and it in the loft, water vapour will move from the house into the loft, straight through paint and plaster, wood and vapour open insulation.

    If is cold in the loft this vapour will condense wherever it finds a surface which is below dew point.

    For me this surface will be the underside of the shiny layer on the cold side of the insulation. 🙁
    • CommentAuthordeniance
    • CommentTimeFeb 10th 2020
     
    Posted By: tonyIf there is a difference in the partial vapour pressure between that in the air in the house and it in the loft, water vapour will move from the house into the loft, straight through paint and plaster, wood and vapour open insulation.

    If is cold in the loft this vapour will condense wherever it finds a surface which is below dew point.

    For me this surface will be the underside of the shiny layer on the cold side of the insulation. 🙁



    The underside of the insulation is plastic so any vapour coming up from below cannot get into it, only the top silver piece is perforated , but having said that been up there this evening and did find a few cold edges when I was moving insulation , made a hole with finger and yes bits of the insulation were damp!! But don’t know if this is what you said or is it from when the condensation was dripping down on it last week?
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