JohnMo

Is putting the modules on the walls an option. You get better winter output, your electricity delivery curve becomes flatter, instead great in summer rubbish in winter.

There are issues with oversizing. The modulation range of the heat of pump, usually about 2.5:1 This is not an issue when at the lowest temperature outdoors, but becomes apparent when the outside air temp is in the 5 to 10 degC range. At 11 degC outside your heat demand is half your design case, so about 3kW. If your heat pump cannot modulate to that level, you then need a buffer added to the system.

Where's does the 12 or even 16k come from, the original post said 6 and 8kW. Sounds a big heat pump for an ICF new build. Unless the house is huge. My house, 190m2 single storey, lots of glazing and a 70m perimeter, but at -5 I have a heat demand just over 3kW. What does your SAP EPC, say your heat demand is?

To comply with MCS regs he has to do a proper heat loss calculation. This is a contractual document. He cannot put his interpretation on things, he should not use rules of thumb etc. I believe to comply with MCS installer rules he is to quote you before and work commences and get the bus grant If he's a lone contractor tell him what you want or he is off the job. If he's from a bigger company, get his boss to site and ask him to show you where in his installation regs it states you can apply rules of thumb and "what if" to heat loss calculations.

The other way to look at the heat loss. Say you have an airtightness of 2m3/m2 at 50Pa., Your infiltration rate is 0.1358. So inputting that in to a ventilation heat loss calculation Qv = 0.33 × n × V × ΔT watts. So say your volume is 300m3 0.33 x 0.1358 x 300 x 22 = 295W So at an airtightness of 2 if your house has a volume of 300m3 your ventilation heat loss without MVHR is 300W. If your house is is bigger small just change the 300 figure. Rules of thumb do not apply

If your MVHR fails on the coldest day your heat demand would go down not up. You are in a nearly airtight house otherwise you wouldn't have MVHR. Think logically, MVHR provides the ventilation, it recovers heat from the outgoing air and transfers to incoming air with some losses. If there is no outgoing or incoming air, because your MVHR has failed, then there is no losses, so heat demand reduces. Your installer is less than dim, possibly has no real idea what an airtight house is, or what the MVHR does

I think the oil companies and power generators are taking us for fools. And politicians just useless. Wind, tidal, solar, hydro, biofuel and nuclear cost no more to produce electricity than they did a couple of years ago. Neither does the oil and gas produced in the UK cost any more to get out of the ground and onshore. In Scotland the gross renewables is now equal to 97% of electrical demand. https://www.scottishrenewables.com/our-industry/statistics Gas only accounts for about 10% installed capacity. Buts it's cost dominates the overall cost of electricity. Cost to us has gone up hugely, and the profits of oil/gas producers just ridiculous. Its all stupid

You need to look at the options in person, what looks great in photo, may not really be that great on your project when you look at it or possibly see the price. We did the round and round in circles. In the end went to local saw mill, they showed us a few samples and we just plumped for one, by this time the wife had lost the will to live. We went with vertical Scottish larch grown just down the road.

Install up/down lights at top of wall. Have no lights in the ceiling. They are usually too far from you to be much use anyway. Sorted, make life easy not difficult. No fretting about roof life expectancy.

Fixed price deals for gas are stupid expensive, want 16p kWh, Vs 7.33p paying now

Just fixed my electric with British gas, at 38.3p kWh and 44.3p per day. 1 year deal, so ok to end June next year.

Another thought is maintainability of vaulted ceiling lights, can you get to them once the house is furnished, without a scaffold?

So to clear you have vaulted ceiling, so head height not an issue. The insulation is not in the joists, but between the rafters . Assuming the insulated plasterboard has not been delivered, change the buildup. If the 100mm PIR not fitted. Insulation between rafter dense mineral wool, use whole sheets of 100mm PIR under the rafter. Tape all joints or install vapour control layer. Underdraw with 50mm battens, this will give you space for wiring, slim led down-lights and the control module. Then plasterboard. No holes required other than in plasterboard. The above is way easier to fit well, our between rafters is a pain and not easy to do well.

I think like me https://forum.buildhub.org.uk/profile/8-prodave/ is a self install, so no payment for export.

My Solic200 cost £144. I am displacing gas consumption, and have around 2 to 3 year payback. Not sure why you are paying £500, get the basics, does what it says on the tin, nothing more or less.

Don't think it likely to work on any night cold or hot, as PV needs sunlight.

Top it back up to 1.2 and monitor. Green marks are likely to be areas where the pipe has go wet. Wrap some toilet paper around those areas, go back and look at the paper in a hour or so or overnight. If slightly damp or wet you have the leak.

So what is your CoP?

Took me a weekend to do 190m2, 7 loops at 300mm centres. Had never done it before, used a home made decoiler. Had assistant for one day. Mine was stapled to PIR with my thumb.

Our drive is circa 70m and rises 7 to 8. We hard cored and used crush lime stone. Seems great for cars doesn't move around too much and is pretty quiet.

Unless there a gale blowing the generation is best of nothing, if there's a gale blowing they shut themselves down. Big one are ok, small domestic ones not much use. And still the SAP assessors insist on putting as a recommendation on their reports.

The timer will use 3kW per hour no matter what you PV output is. So if your generating 1kW, you will be paying for 2kWh. The diverter only sends any excess to the immersion. So if your generating 1kW and using 800W, only 200W will go to you immersion.

The actuators are on/off devises, so flow would be either on or off, so each fan coil would be in its own zone, which is not what you want with a heat pump. Your generating a lot is small zones which will lead to the heat pump short cycling. You would use the flow valve to control flow and ideally tune the flow to give the heat output required.

Standard UFH pipes is 16mm o/d. Not sure why you need to run 22mm, unless the fan coil is rated over 3kW?

NE Scotland, 3.1kW with optimisers, 45 degs and SSW direction. Have seen a little over 3kW being generated a couple of weeks ago. But I don't monitor all the time, just happened to at the inverter so took a look