Gone West

I built a PH with an Isoquick insulated raft foundation which had 300mm of EPS under the concrete slab. Obviously not something you can do but I would want at least 150mm PIR insulation under a concrete slab. It would mean digging out probably below the foundations which would mean getting advice from a structural engineer. An alternative would be to use an air to air ASHP which would mean you would only have to carry out repairs to the floor. There are people who are very happy with their A2A systems and The Green Building Forum has contributors who have given details.

I would have thought it would depend on the type of construction. We had our TF first tested after windows and doors were fitted and plasterboarding done, but then we didn't use airtightness membranes or tapes. We got 0.5ACH but the tester wouldn't accept it for SAP until the house was more complete. The final test was done after all second fix plumbing was done and he did a final SAP test which averaged 0.47ACH.

I wouldn't fit insulation unless the building was weathertight.

You should consider whether UFH is the best way to deliver heat to the rooms in an old house. Unless you're putting 300mm+ under the slab you will be spending a lot to heat the ground under the house. Even with 300mm EPS you will be losing around 8% of the heat to the ground.

I don't think it makes much difference if you've got airflow behind the counter battens. The only reason we staggered them was because the counter battens held the insulation against the racking.

IIRC they tore the tape which is why I thought it was a type of gaffer tape. Don't know if you can tear butyl.

It was done by the TF company but I think it was a type of gaffer tape but it had a metalised, (if that's a word), surface. It never came off until the protective layer was removed.

Don't know if you've seen the similar thread here.

They're fitted in the middle of the 400mm of insulation.

The cladding was fixed with hidden pins so the staggered battens didn't affect it. The counter battens were sloped slightly to the side so if any moisture got behind the membrane it would run off onto the lower counter batten.

One of the problems with cycling on and off is that as the level of solids builds up so there is more back pressure each time you restart the pump. This causes premature failure of the diaphragms in the pump. There is a thread on here somewhere where this was discussed in the past and Jeremy designed a pressure sensor which would warn when the pressure was too high.

Horizontal cladding seemed straightforward with horizontal battens and vertical counter battens holding the EWI in place. For vertical cladding areas in order for air movement and possible water drainage I staggered the counter battens and had a very slight slope on them.

I didn't use any silicone but did check the surfaces were flat and smooth. IIRC I used silicone grease on the outlet compression fitting.

I used McAlpine Hi-Flow shower wastes at our last place. No leaks. https://mcalpineplumbing.com/traps/shower-traps-accessories/st90cp10-hp2c-112-90mm-hi-flow-shower-trap https://www.screwfix.com/c/heating-plumbing/traps/cat831610?trapapplication=shower#category=cat831610&brand=mcalpine&trapapplication=shower

I borrowed one from the Icynene installers. Amazon had one, but no longer in stock. https://www.amazon.co.uk/Spray-Foam-Insulation-Saw-29/dp/B00G2G0XT4 Sorry a quick search but couldn't find any.