Wumpus

This is the key. You will likely do well in heating season, through the winter, but does this hold out in the summer, when presumably your heat pump is working a lot less hard? You can shift some/most hot water to off-peak tariffs anyway, so perhaps not so much saved there? I suggest looking at how your electricity demand varies month by month and see how many months of the year you would get 13.5kWh of benefits. That might extend your payback calculation a lot?

This sounds great. Can you recommend the company?

This could be tricky, the bigger return on investment is on DHW. Our UFH flow temperature is 35 degrees, but that wouldn’t make a dent in the hot water?

I like this idea. I would need my plumber back as I certainly don’t trust my abilities in that direction, but the rest is very possible. There is intello fabric on the wall where our MVHR ducting exits, so I guess just adjacent to that and good taping to keep everything airtight. Thanks

Fair challenge and this may be the path we go for. I was trying to reduce our CO2 footprint and perhaps enhance value if we sell in the future. Of course we could remortgage as well.

Hello Buildhub, I need your experience please. Theres a bit of a story to go with this, so bear with me. We completed our house last year and have been living here for over 18 months. The house is built to Passivhaus principles - air tightness tested at 0.38, insulation is great with floor 0.09, roof 0.1 and walls 0.13. Triple glazed throughout (Norrsken, very happy), MVHR at 86%, thermal bridges minimised. We did not complete a PHPP but do have detailed heat loss calculations for each room. As funds got a bit tight, we didn’t put in the ASHP we planned, and instead put in an electric flow boiler which feeds our lower floor UFH, and we have a direct electric cylinder. Maybe this was a mistake, no point go in back over it. The house is performing exceptionally well. We batch heat the lower floor slab overnight in Intelligent Octopus GO hours, and typically the requirement is 10-15kWh a day. We don’t really top it up during the day except when very cold outside, which is not very often in Devon. The internal temperature loss is around 1 to 1.5 degrees a day and we maintain the lower floor between 20 and 22 degrees (heat to 21.5 overnight). All of our heat for the last 12 months (2600 kWh) cost us £191, which I think is pretty good. Hot water (4100 kWh) about £340 a year, again overnight. All this points to an ASHP being of marginal value, we won’t save much on £530 a year and need to add in annual servicing. At a COP of 3, we might save £350 a year on the electricity? This would all be “case closed” if it were not for our mortgage, which is with Ecology (who are fantastic). Ecology offer a discount for achieving a B or higher SAP on the as-built building. Our SAP as designed was A101, our as-built is C79. The only difference is the change from ASHP to electric boiler, everything on the SAP certificate is “very good” except for heating and hot water, which are “very poor”. Our insulation levels exceed the as-designed SAP numbers. We could spend some time discussing how SAP does not do a great job for houses like ours, but again not much value here. So, I had an MCS certified contractor around to look at replacing the electric boiler. He pretty much understood that we have a house with very low heat loss, but old me that he had to install heat emitters in every habitable room. We don’t have UFH or radiators on the upper floor, and adding them would add a lot of cost and make quite a mess of the house. Any advice or experience from anyone on whether it’s is an MCS requirement to have heat emitters in every room, or any other thoughts on how to proceed? The mortgage discount is worth doing if the costs are less than £2500 including the government grant. Thanks all

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.