Depends how windy it is!

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.

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?

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.

MHVR is a good idea in all airtight beildings

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.

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.

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

you might want to look at the forum rules

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.

...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!

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.