Wumpus

We used compacfoam to form the upstand. Robust and insulated.

It might be possible to create a couple of terraces and use the dig-out from the lower level to backfill the upper level behind some kind of gravity structure like gabions. Cartaway will be expensive so best avoided, especially as your access looks difficult. It will need some kind of excavator I would think, not something you would want to do by hand. another option might be a criblock system which can look softer than gabions.

I think this will be more of a building control question rather than planning. There are rules about how close to a building the treatment plant can be, from memory more than 15m. I think planning is only concerned with demonstrating a viable scheme, so once that is achieved, any alternative location would work. Any scheme would need to be approved by your building control officer, so I would start there. I’m pretty sure you could substitute for any alternative treatment plant. A lot of people dislike the bio disc units because of the moving parts and greater mechanical complexity.

Yes, potentially helpful for a PV installation. You would be allowed 16amps export on each phase, if you can get that much on your roof, without requiring special permission from the DNO, so more than 10kWp. If you install your PV on a single phase, any exports net off against any imports on the other 2 phases at the time. Same standing charges etc. as single phase.

Agree it would be better to deal with the water behind the wall than try to hide it. Is it too late to put in a land drain behind? Some form of waterproofing membrane on the back face would give the best result.

Costs may not be as much as you think, it would be worth getting a quote from the DNO, but as you say, it may depend on available capacity on the line you’re connected to. Off-peak tariffs are available on 3-phase. We have Octopus Go on our 3-phase supply and it all works as expected, the meter just adds together the 3 lines to give a total kWh consumed.

Just my take, without understanding how it looks from the outside, but I would centre all three on the same line - front door, French doors and glazed doors? Centre on the dining room/table so you can see through the side windows front to back.

Bit slow to respond on this. I did my own KNX installation, along with our electrician who ran the bus cables and radial 240v cabling to two KNX cabinets. It’s all very possible and is absolutely solid. No complaints at all, everything works as it should every time. If you have questions let me know. ETS takes some getting used to, but once you get the concepts it is all very logical.

If it’s any help at all, our contractors use about 10kWh per day for everything, including the site office heating, kettle, power for tools etc. They are pretty good about switching stuff off when not in use and I am OK to pay for it. This is for a team of 2-6 depending on the day. It was a lot less in the summer of course.

I have to endorse the comments on wet underfloor pipes. We have a Passive build and our contractor suggested we wouldn’t need much heat and panel heaters would do the trick. I am so pleased we initiated on underfloor heating pipes. Experience has shown that 3 hours overnight on Octopus Go tarring does everything we need for the next 24 hours. We put in an inexpensive electric flow boiler rather than Willis, but the idea is the same (long story about our plumber not really liking the Willis and this was a compromise). The savings with a heat pump didn’t add up for us, we spend about £1 a night on heating and with a COP of 3 that would save 66p a day which takes a super long time to recover the costs of a heat pump. We can add one later if needed. The concrete acts as a great heat store and I don’t think we would have got there just heating the air.

Always learning. We bought the Mixergy and are happy, but I like to understand alternatives if we ever do another build (not for a while, we still have the scars)… I get how the overnight can work well with our 4 hours of Octopus Go, but less clear how the day works? We use a “maintain at max 20%” strategy on the Mixergy, which uses a small amount of daytime power. If we don’t top up, we run out for washing up and hands in bathrooms etc., but it uses very little electricity to get to 20%. How does that work with a twin immersion strategy? Genuine question, looking to understand. thanks

I really like our 300l Mixergy tank, it has many positives. We heat overnight to 80% and then maintain at 20% for the rest of the day after showers first thing. Just be aware that it’s quite slow to heat on direct electric at 3Kw. 4 hours overnight takes ours from 20% to 80%. Although what is produced is available quickly, large volumes of hot water take time. The max temperature is 65 degrees. it works for us, but it’s not anything like instant.

I have a couple of thoughts, and I hope they come over the right way. First, undertaking any project like this is hard so do cut yourself some slack. It’s a long slog and will be a lot easier with a trusted contractor, but mistakes happen on all sides. It sounds like he’s well intentioned, and that is worth a lot. Second thought is that you can’t be on site every day, so you need him to care about the details as if it were his own house. Getting to good airtightness takes a lot of attention, minimising thermal bridges does not happen by accident and if he’s not checking the subbies and there every day, how can he be confident you will get the results you need? The electric bill seems to be a small symptom of a bigger oversight question?

Fair point. If the oversight isn’t enough things will get missed that are more significant and in a Passive construction that’s not going to be a good thing. Would a “disappointed not angry” approach work? The suggestion to add a timer might work? …or if they really don’t care they will override it somehow?

…to add, I think this is the key point. A good working relationship with someone you trust is worth an awful lot more than some electricity?