MikeSharp01

Sounds like a great project in a truly wonderful place - building in a national park must add some small costs but is neutral in most dimensions assuming labour can be locally sourced. Are there any caveats around affordable housing etc for the build - are they for local people or will the wealthy coves from Edinburgh and Glasgow rush in a snaffle them up for holiday homes? If they are able to do that it would raise the base price, and hence your headroom, albeit at some disadvantage to the local people.

Sorry I perhaps was not clear. The reason we will have an ASHP is more nuanced than the AECB approach (was a member for about 5 years but have let that lapse.) On our original plan, 2018, we had a gas boiler - no problem getting PH requirements. We decided we didn't want gas for all the reasons we now understand so well. As I was quite taken with the work @TerryE had done with the Willis heaters that was, until late last year, our plan. However, when you go direct electric heating everything else needs tightening up to meet the energy limitations for the house which we did but now as we are further into the build the room for maneuver is limited. Then we noticed that the EPC system trips in and you cannot get a good EPC, see discussion elsewhere on this forum, with direct electric heating! So although we could get PH certification, just, the EPC would have been rubbish and as we feel the need for both we will adopt an ASHP to make it all hang together again - PH certification possible and a, hopefully, better that 100 EPC. For us the spin off will be very low heating bills and a warm airtight home that matches our personal 'machine for living in' requirments - certificate or no certificate. So no different to anybody else really. SO I will now jump down from the head of this pin. Is that the annual cost?

Tend to agree, although, it rings a bit hollow having spent yesterday at a graduation ceremony for 600 Engineering and Science students all of whom got a certificate telling other people what the students and the staff already know so sometimes it is for other peoples consumption and holding it has a personal value. I also happen to think that the Passive House standard is now getting better understood and much more widely talked about so we may well be heading the way of more acceptability of the certificates value among buyers.

We did set out to build a certified Passive House (PH) and we are very close now to doing it although we may not certify as we now have other priorities. For us the lower impact on the planet, in the long term, was/is the key driver. I do tend to agree with: while I think any impact is worth while and we will use a lot less of the local generation than many in our all electric house. Can't see how it could be done any other way really. The costs are higher and the challenge more technical, my life partner - wife says she might have thought twice had she known just how technical is has become, because you are working with a bigger number of constraints which often result in difficult compromises. For instance - we, our situation, cannot now get PH certification without an ASHP in the mix - so we will fit one. As a self builder, who did not employ a PH professional at the design stage or an experienced PH Architect there were additional challenges. Instead I did a course on PH and the PH Planning Package (PHPP), read loads, worked with our architect and structural engineer to take their outline designs through the PHPP and make sure it would pass and once the design was finalised we have stuck to keeping the PHPP model up to date and building as close to as designed as we could. I feel that the Cold bridging element is the toughest aspect because the PH certified standard needs evidence of any cold bridges being worked through which we did twice because we changed the windows system during the build. (Went from Rationel to Norrsken) So things have changed a little. We also dropped the gas boiler idea early and changed the insulation from frametherm to blown cellulose which made the overall balance go a little awry, the insulation's U value goes from .35 - .38, but we brought it back by adjustments elsewhere. This, incremental change approach, is quite hard once the house is under way hence the ASHP became a requirement to get us down into the energy demand zone.

Welcome to THE forum for people like us - but you already knew that.

So in this context size, or perhaps volume / form factor, is everything.

Very true the problems though seem to come from the Engineering rather that the physics so the machine is more complex, has more things that can go wrong and so costs more and therefore has a longer payback in pure £. Not sure on the embodied carbon side of the equation, or the availability of; support - ASHP's don't have much good support and reliable installers. We chose not to have one because of space.

When I think about it the CCC report just assumes we are trying to get to net zero - something we agreed to a long time ago. So all they are doing is looking at the road map and assessing our progress. We also might conjecture that switching over to renewable is sensible anyway, we will need them eventually unless Einstein was wrong, because we will run out eventually after all.

If it fires when you push it against the target woodwork then the thing is basically working. It maybe that the the depth setting is at max and this is making it hard to push down to trigger point.

So is there another owner with the land surrounded bt the red / blue portions ?

I am sure I don't know. Isn't that what the trick membranes are for in the modern era?

This whole topic is frightening - only thing that let's me sleep nights is the wufi analysis we paid for. All technical membranes high / low vapour permeable materials makes my head spin.

Great work Bob.

Yes we did blow it in ourselves and there were not any voids when we did it for 8 months, then we had heat wave and I noticed the bulges getting worse and found the voids at the top. So we added the intermediate battens - chamfered the edges to avoid damage the membrane and then refilled the voids. No problems since.

We used intello plus as it has strengthening strands for exactly that - but it didn't work as expected we had bulging much more than expected on the first pumping. We put additional supporting vertical battens under the horizontal battens that hold the plasterboard, at 300mm centers to keep it in check. (Main studs are 600mm. This bulging gets worse when it gets really warm as the plastic stretches and we got some slumping on the tall.columns. So I let it slump and them filled any gaps with more cellulose when I found the voids with an IR camera / strong torch- if you put a bright LED against the membrane you can see holes. Attached is a pick of a roof section the 300 centers.