Steady does it ! : Airtightnes, floor build, rainwater reuse

The job is progressing well, tying up lots of loose ends ; the airtightness test is now scheduled which will be a moment of truth for us all. If you're not familiar the Passivhaus requirement is for 0.6 airchanges per hour when the house is pressurised to 50Pascals ( equivalent of a storm force 5 I believe). This is about 10 times the airtightness required by building regulations( which are signed off/ detailed on paper by an architect/engineer rather than field tested).

Inside we're been moving stud work to get the doors correctly positioned and the floor is now being built up with 400mm of polystyrene. When you actually see this much insulation under the floor it is quite a shock. The large rainwater tank is due tomorrow to go under the garage. Also the sections of flat roof have now been completed ( in a light grey colour) & we'll test these with a hose now shortly.

So far the self build option is going well, particularly as I did a lot of research on the field of Passivhaus before we even started & gained the PHI qualification earlier this year. The challenge with self build is that if something doesn't work, then it falls back to you, & your wallet, to rectify - rather than having a contractor who takes the hit / risk & of course charges a risk premium for that. This is particularly important for something like a certified Passivhaus which has to meet very specific performance criteria or else it fails. The old addage is that the person who has most control over the process is the person best placed to take the risk. In a PH self build this means if that you dont fully understand the required outcomes & how to get there then  this route is likely not for you. For a regular self build though - without the strict performance criteria - then this simply doesn't hold though & its is a lot less daunting. Towards the end of the job I'll do a better job of the pros & cons / ups & downs  of the route we chose.