ProDave

DON'T employ this plumber: 40mm waste coming up from the floor, is the outflow from a macerator about 4 metres away that goes down, along under the floor, then back up here. Small waste into the top is the condensing boilers condensate drain. The middle of the tee branches off sideways into a strap on boss on the soil stack. Even I know this is not going to work as planned.........

If the flow and return to the HW cylinder is "the same" then something is wrong, like the HW is already up to temperature and the system should have turned off. You have got a proper "heat pump" HW cylinder with a large area input coil?

This is a new build. Take the chance to insulate it properly, detail it well to make it air tight, fit mvhr, so you will end up with a house that does not need much heat input. Heat the whole house with UFH so it only needs to run at a low temperature, and then an ASHP will admirably heat the house well. Fit solar PV as well and that will gain you SAP points and reduce your real running costs.

Before the build started I dug three 2M deep trial pits for the structural engineer to asses the ground conditions. I left one of them open just covered with a board. I frequently looked down this hole over the winter and found anything from a 2M deep empty hole, to a hole full of water within 6 inches of the surface.

The requirement to concrete it in is dependant on your ground water levels. You don't want the empty tank (when it is pumped out) floating up out of the ground because the water table is high. Check with each of the manufacturers, some make risers to allow the unit to be buried deeper in the ground.

The I would seriously consider External insulation above the rafters, turning it into a warm roof, rather than the extra insulation under the rafters. The External insulation will double as a sarking board. Then you can full fill the gap between the rafters without need to consider any ventilation. Over the external insulation you need a "non tenting" breathable membrane and the gap between that and the tiles needs ventilating with eaves vents and a vented ridge. I found Frametherm 35 was a good option. A lot more solid than the yellow fluffy loft insulation and a lot less nasty to handle. It is stiff enough to cut slightly over width and it will push in between the rafters and stay there.

I have mvhr. I do have an ASHP that will do cooling and might one day incorporate a couple of fan coil units to give proper cooling on the few occasions it would be useful. It was originally going to be wood fibre EWI with wood fibre beads filling the frame, until i worked out Frametherm 35 gave just about the same insulation and decrement delay for half the price and was a DIY job to fit whereas the wood fibre beads would need to be blown in.

My concern is the bottleneck is the pressure reducing valve on the UVC and an accumulator in front of that won't help.

Yes. Our house has 100mm thick external wood fibre insulation board, and then Frametherm 35 filing the timber frame. The combination has worked out very well indeed, the house has a very slow thermal time constant meaning it takes a long time to warm up and a long time to cool down. If it gets hot in summer, the time constant is such it does not heat up much in the day, and a night time purge with windows open to cool it down keeps it all in check.

This could well be a case of "be careful what you ask for" You complaint seems to be all the parked cars make the road dangerous, so you want a ban on further development in that road to stop adding traffic so it does not get any worse. I could see that backfiring and the "solution" being to ban parking on perhaps one side of the road as it is clearly a dangerous situation. Where would that leave you and the rest of the residents if half the on street parking disappeared?

Is this an existing building built like this or something you are planning to do?

Some stoves only duct one of the air supplies. Choose carefully to find one that takes both primary and secondary air from the external duct and has no inlet grilles on the stove itself. e,g, our Mendip Churchill stove.

A normal house supply is typically rated at 18kVA which translates to 80Amps at 230 Volts. Your 100kVA transformer will comfortably supply 6 or more houses, usually a lot more when you allow for diversity. We currently have 8 houses sharing a 100kVA transformer here. If you really have bi phase, then you could get up to a total of 44KVA from that, but bi phase is not common in the UK. What is your business doing that you think it is going to need anything like that much?

Another one that is 2 weeks early?

No that wasn't me, but I could well have written that.

I just stumbled upon this https://www.theguardian.com/environment/2021/mar/16/first-microwave-powered-home-boiler-could-help-cut-emissions I would love to know how anyone can think that using a microwave device to transfer heat from electricity into water can possibly be more efficient than resistance heating? That's why I think it is an April fool that got published too early?

Can you post a copy of your spreadsheet here? the 25kWh you quoted, is that per day? It's certainly not per year as you stated? 3500L of oil per year would equate to 36,225kWh of heat total. Lets guess 30,000kWh of that is for heating, the rest is DHW. Assuming you heat the house half of the year, that will be using 164kWh per day on average for heating. Lets assume on the coldest of days you will need twice that (and obviously less when it's mild) so a worst case of 328kWh in a day. assuming 20 hours a day heating, that's 16.4kW average. So I would say the larger units you have been quoted are only just adequate and a 5kW unit would be woefully inadequate. Also how is the heat conveyed to the house? radiators or under floor heating or both? If radiators I would definitely say don't swap to an ASHP.

I think the logic is the road crossing is always ducted so a cable can be replaced without digging up the road, but a cable in the verge is normally buried bare so it is easier to connect into in the future.

They usually put the section under the road in a duct but SSE up here normally bury other sections direct. You would need to check their requirements.

The contestable work can be done by any contractor with a minor streetworks permit. It would be worth talking to an independant contractor to see if they can make both road crossings in one dig, and lay a water pipe and a red 150mm duct all the way under the road crossing and along under the verge to your plot, with a drawstring in it.. If you get a good price for that, then re negotiate with SP energy on the basis of them just pulling a cable through a duct and connecting it. SP networks may prefer the cable to be buried outwith a duct, you would need their agreement and in that case they would have to supply the cable before your contractor started. You would also need to ensure the contractor satisfied Scottish Waters needs. I bet it is a similar story with water, the present arrangement is inadequate to join another house onto.

If that is the case, that row of 5 houses is all fed from one 35mm cable, That is not something they would do now and no wonder they don't want to just join another house onto the end of an already potentially overloaded run. Hence a new cable needed over a longer route,

Is this a new build or loft conversion?

Can you mark your plot on the plan. Replacement of the house already there or a new plot?

A for me. I see the vertical section in B detailed incredably poorly very often. With A you have the potential of warm eaves storage.

Please show a photo of the transformer, that is presumably up a pole or more likely a pair of poles.