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  1.  
    Very good, all the more reason to suspect that Greenfish's test result is perfectly acceptable and doesn't warrant spending a significant amount trying to improve it.

    Any idea at what level of airtightness it ceases to be a heat loss issue and turns into a comfort issue?
    • CommentAuthortony
    • CommentTimeSep 11th 2014
     
    Depends how windy it is!
    • CommentAuthorPeterStarck
    • CommentTimeSep 11th 2014 edited
     
    Apparently high levels of airtightness affect the level of moisture in the wall more than heat loss. I asked this question on the AECB Forum.

    http://www.aecb.net/forum/index.php/topic,3928.0.html
    • CommentAuthorGreenfish
    • CommentTimeSep 13th 2014
     
    Posted By: djhSadly perhaps, the reason quoted for such a tight airtightness level in PH isn't to do with the energy or cash saved directly. The point as I understand it is to avoid drafts and to maintain internal surface temperature everywhere. That in turn allows you to reduce the internal air temperature by a degree or two whilst maintaining the same level of comfort, and that is what saves the energy and cash.

    Have already noticed this effect. New build at 17C with the plaster still damp, felt more comfortable and warm than our old leaky house heated to 20C. Was flitting between them and old house just felt so chilly despite having heating going especially on windy days. Looking forward to living in new build this winter.
    •  
      CommentAuthordjh
    • CommentTimeSep 13th 2014 edited
     
    Posted By: GreenfishNew build at 17C with the plaster still damp

    Our new build is currently at 18.2°C and 101% humidity according to my cheap Chinese meter :bigsmile:

    Well, actually it's now at 100% humidity since I put a fan in there to stir the air around.

    edit: I should say that we've just applied some internal plaster, I suppose. Doh.
    • CommentAuthorGreenfish
    • CommentTimeSep 13th 2014
     
    I should have said that my comfort of air tightness experience was in Feb when we had just finished applying the internal plaster, gently raised the new build temp to 17C (while it was 9C outside and blowing a gale) and prefered staying there in middle of the mess to our furnished home at 20C in the sheltered city.

    djh - 100% humidity, open a window maybe?
    • CommentAuthorEd Davies
    • CommentTimeSep 13th 2014 edited
     
    RHs greater than 100% are quite possible. 101% would be typical of the air just below a cumulus cloud. If all the walls are saturated I wouldn't be terribly surprised if it could happen in a house. In extreme cases, under special laboratory conditions with very clean air, you can get up to 300%.
    •  
      CommentAuthordjh
    • CommentTimeSep 13th 2014
     
    Posted By: Greenfishdjh - 100% humidity, open a window maybe?

    Windows are sealed (a) for the duration to keep plaster particles and other dust out of the seals and mechanisms and (b) at the moment because the protective film stops them opening in any case.

    I'll see what happens over the next day or so and maybe use some forced ventilation to get it down. One of the wall terminals that will connect to the MVHR is open and so is the front door so I can probably jury rig a fan.
    • CommentAuthorborpin
    • CommentTimeSep 18th 2014
     
    I had massive problems with condensation on a very air tight build to the extent that one of the door locks rusted and failed completely! I thought I had a water leak round the velux windows - again condensation but somewhere inside that I could not see it actually forming. This with a dehumidifier running constantly! Of course, the condensation did not appear on any internal surface or the windows :)
    • CommentAuthortony
    • CommentTimeSep 18th 2014
     
    MHVR is a good idea in all airtight beildings
    • CommentAuthorGreenfish
    • CommentTimeSep 19th 2014
     
    Here's hoping Borpin is talking about the initial drying phase like djh. My build was dripping with condensation when first plastered and gently heated, and too wet outside to open the windows much. Dehumidifier eventually got on top of it, and getting the windows open once the rain stopped. Did not put the MVHR on, too much dust around would have damaged the filters etc.
    •  
      CommentAuthordjh
    • CommentTimeSep 19th 2014
     
    I haven't seen any sign of condensation so far. The humidity just sticks at between 97% and 100%, which I suppose is what I might expect whilst the plaster dries. And the smell is just wet plaster and fresh straw.

    We have cracked open one window to get a bit more air circulation; hopefully with the plasterer offsite at the moment we won't see too much dust. I've also got a couple of fans and a low-powered heater in there. The lime plaster does seem to be getting slowly stiffer.

    We haven't fitted any of the door hardware yet so it can't rust (well at least not from the plaster curing!) and tradesmen or visitors can't open windows! MVHR is indeed a good idea in all airtight buildings, but it's an extremely bad idea to use it in an unfinished building because of dust etc, especially one that isn't even at first fix stage so has no proper power or drainage.
    • CommentAuthortony
    • CommentTimeSep 19th 2014
     
    you can be pretty sure that mould will start growing there soon! open the windows 24/7 if possible if not all dat at lease, out door humidity is almost never as as it is in your building even when misty or raining.
    • CommentAuthorGreenfish
    • CommentTimeSep 20th 2014
     
    Oh yes had mould too. The MDF window ledges were like a magnet for it, bad choice in a wet finish build or should not have plastered them into the reveal in the traditional way. I could have wept at the worst point, but all is well now I am glad to say.
    •  
      CommentAuthordjh
    • CommentTimeSep 20th 2014
     
    Posted By: GreenfishOh yes had mould too. The MDF window ledges were like a magnet for it, bad choice in a wet finish build or should not have plastered them into the reveal in the traditional way.

    Thanks for that tip. I'll keep an eye on them.
    •  
      CommentAuthordjh
    • CommentTimeSep 21st 2014
     
    The RH has come down to 83% today and the plaster feels a bit harder. No sign of mould anywhere. I'm beginning to believe in all this lime and straw stuff :bigsmile:
    • CommentAuthorandysadler
    • CommentTimeNov 23rd 2017
     
    I notice some of the comments above and would love to recommend our company for your air testing. We have had it said to us many times that air testers turn up, test and walk away with little help or advice on site. We work differently and spend time on site, showing you any leakage paths during the test so that they can be remedied and the test re-run, in hope to achieve a pass result first time. Have a look at our website below to find out more.

    https://www.sadlerenergy.co.uk/services/air-tightness-testing
    • CommentAuthorjfb
    • CommentTimeNov 23rd 2017
     
    you might want to look at the forum rules
  2.  
    Can anyone recommend a basic DIY setup for finding leaks rather than calculating a number?

    I was thinking a car fan in a piece of ply and take out a window pane...

    Run at full speed and chase round with a vape pen as mentioned. Sound okay?
    •  
      CommentAuthordjh
    • CommentTimeNov 23rd 2017
     
    Posted By: VictorianecoCan anyone recommend a basic DIY setup for finding leaks rather than calculating a number?

    I was thinking a car fan in a piece of ply and take out a window pane...

    Run at full speed and chase round with a vape pen as mentioned. Sound okay?

    Yes, that will work, as long as you're airtight enough that the fan can blow enough air through the cracks you're looking to find. You may find you don't need to take out a window pane but just open a window and tape the ply in place.
    • CommentAuthorsnyggapa
    • CommentTimeNov 23rd 2017
     
    when I had my test done years ago the engineer said leaks were easier to find with the fan extracting air from the building and a damp hand to feel the air movement as it rushes in .

    Walk around the usual suspect places and stuck your hand near it, you can feel the air moving in through the cracks

    I guess a smoke pencil will also have the same effect
    • CommentAuthorDarylP
    • CommentTimeNov 23rd 2017
     
    ...suck the air out of the dwelling, use a smoke match or smoke pellets from plumber's merchants... the effect is startling, and a little depressing sometimes!:wink:
    • CommentAuthorneilu
    • CommentTimeNov 26th 2017
     
    Ideally you want to get enough air flow so that if you opened a trickle vent it would feels like someone is blowing in with a hairdryer from the outside.
    Try to position your fan in a central room or hallway and close all the internal doors. Then when the fan is running just open the door to the particular room you are looking for leaks in. That will concentrate the air flow to that particular room.
    • CommentAuthorGreenfish
    • CommentTimeNov 27th 2017
     
    Located in an exposed site (hill top 4 miles fro the sea in most directions), I found gales pretty good at helping to locate leaks. Nature provides pressures that well exceed the test fans! Good airtightness means that any tiny leaks seem to whistle, and you can feel air with your hand (assuming it is an accessible leak of course).

    My few leaks were all related to external doors. All but one I have adjusted and no longer leak, the last still has issues when 60mph wind is directly at it and is really fiddly to adjust (I have to remove it from the hinges to do some of it). But I will crack it in the end!

    I now think there are good arguments for outward opening windows and doors on exposed sites, I wish someone had suggested it. OK, front door it would be silly to hit vistors in the face with the door, but backdoors and French doors etc. the inward opening ones have been far less of a propbelm than the outward ones.
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