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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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    • CommentAuthormalakoffee
    • CommentTimeFeb 23rd 2020 edited
    Posted By: bxmanHave a look at :-

    Thank you for this video. Very useful.
    1) I think I'm doing everything right w.r.t. Lifestyle.
    2) I strongly suspect that the high RH is related to being built low on the land. Damp air is able to pass up, from the underfloor, into the living space. Although the floor is insulated between the joists, there is no vapour barrier/blocker membrane.
    3) Even if I get the RH down, I suspect I will always have a condensation problem on the big bay windows, because I now have to seal them off with heavy curtains due to nuisance outdoor lighting ( from more than one source ).

    Posted By: bxmanDo you have a water meter? . . . if so turn everything off and check the meter stops dead.

    No problem there, I replaced all the pipework from the street main & all internal house pipework .

    Posted By: bxman" the oversite concrete shows some dark damp patches after heavy rain " . . . . .Is that area within the house itself ?

    Yes, within the house.
    Prior to my major works mentioned above, there were damp patches on the oversite concrete close to the external walls AND at points far away from the external walls within the house.
    That was years ago and I no longer have a view to these area because the between-joist-insulation is in the way.

    Posted By: bxman"The existing wall cavities are filled with some sort of paper-fluff " . .. .
    and how damp is that ? . . . . Get some out and if it is not bone dry think about having it removed .

    The installation of the cavity fill was before my ownership.It appears that the installers had tried to keep the fill material above the DPC. Inevitably, some had fallen into the bottom of the cavities. That lot was soaking wet when I hooked it out . All cavity bottoms cleaned, as best possible, before fitting the numerous telescope vents.
    • CommentAuthorbxman
    • CommentTimeFeb 24th 2020
    I replaced all the pipework from the street main & all internal house pipework .

    even new pipes can develop leaks

    can you put an outside shutter on to keep out the offending light ?

    is the sub floor below the joists with their insulation damp?

    are you certain the telescope vents are not letting water into the crawl space.?
    there has to be something wrong . you have got to get it dry down there
    you can not rely on a vapour barrier

    maybe you should dig a sump and have a pump to automatically move any water away to the bottom of the garden
    • CommentAuthorphiledge
    • CommentTimeFeb 25th 2020
    If you got a wall with its DPC above internal floor level, that wall is likely to be damp and giving off as much moisture as having a basket of wet laundry sat in the room continuously. If youve got wet ground under a ventilated suspended floor but no air tight seal between the underfloor and the habitable space then youll likely have cold and damp air moving into the house. Id get both those issues sorted out before doing anything else.

    Once youve got obvious damp ingress sorted, Id replace one of the window DG units with a modern low E unit and see what diffference that makes. In our utility room the external window has Pilkington K glass from 2001 and the external door has standard DG from the same era. If theres washing drying and its cold outside the window will be dry and the door dripping wet- same temp/humidity but the K glass stays so much warmer.

    You mention mould growth to the sides of the windows which likely due to the cavity being closed with brick so youve effectively got sections of uninsulated solid wall to the sides of the windows. It could also be missing insulation when it was blown in. As part of some insulation upgrade work we did last year we found some pretty large areas of cavity with nothing in them. It might be worth getting an inspection done to be sure the cavity is fully filled.
    • CommentAuthorGreenPaddy
    • CommentTimeFeb 25th 2020
    There's a lot of speculation going on about huge amounts of damp coming from the ground. This "could" lead to costly, unnecessary works, which is the furthest thing from green building possible. So let's just make sure we're clear what the problem is, before chasing solutions.

    The main statement from Malakoffee about the moisture levels in the house is that he has at some point measured 80%RH at 13oC. That is not excessively damp. As I suggested earlier, if that air were warmed to 21oC, the RH would be 50%. Most nice, warm dry houses would have an RH of 80% if you let it cool to 13oC. So I don't see anything that implies there is any moisture source worse than any normal house, ie. generated from within. You can only confirm that by warming the house, and see if more moisture continues to be drawn, and the RH stays high, at that warmer air temp.

    The DG windows will currently be much colder on the internal face, than in a house where the internal room temp is 21oC, so of course the moisture will condense on those (and all the other bits of structure not being kept warm).

    If you want to stop/reduce condensation on the DG, and keep the house at 13oC, the absolute humidity has to be reduced. That will drive down the due point of the room air below the temp of the internal face of the DG. If the DG internal face is say 6oC, you'd need to get the RH@13oC down to about 60%. At 21oC, that would have an RH of about 35%.

    Very easy test is to warm the house to 20oC for a few days, and see what happens. Not suggesting you should maintain it at that temperature. Get back to 13oC, but for a very small cost, you will have proven, one way or the other, if you have a damp ingress problem, or just a natural consequence of the behaviour of air, and internally liberated moisture.

    Once that is confirmed, then we can all start up with the solution ideas. Just sayin' :bigsmile:
    • CommentAuthorgyrogear
    • CommentTimeFeb 25th 2020
    Sounds good to me !


    • CommentAuthorMike1
    • CommentTimeFeb 25th 2020
    Another +1 for GreenPaddy's suggestion. Maintain an even temperature throughout the house and measure the result.
    • CommentAuthormalakoffee
    • CommentTimeFeb 25th 2020
    Thanks all.

    First things first . . . information.
    I'll try some higher temperature tests first.

    A rather more expensive hygrometer will be delivered soon, which I can cross-check with the cheapo ones.
    I'll record the results.
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