ProDave

If you have treated mains water into an unvented tank. there should be no bacteria in the incoming water and no way for any to get in, so several people have concluded it is pointless to heat it hotter once a week. Private water or vented cylinder, yes you do need to do it.

Option 2, pictured in your first post, is the standard way of fitting windows in brick / block / stone clad timber frame houses in Scotland.

Devil's advocate: Converting that garage will turn your semi detached house to mid terrace and may devalue it.

Are you normally in at the rogue time? If so keep an eye on the power usage and when you see the spike, start turning circuits off one at a time at the consumer unit to see which one it is.

If your immersion has a local isolating switch, turn that off and see if the rogue power stops.

I am sure it is doable, but strongly suspect with those rafters it is roof completely off and start again so may not be cost effective.

OV10 vent in place of or on top of very bottom tile batten https://www.roofingventilation.co.uk/Over-Fascia-Vent-10mm-x-1m-Harcon-OV10

I have said for ages that is a load of tosh. Thankfully people are recognising that. I look forward to the announcement that DRAX is finally closing.

Another point about Jeremys spreadsheet. The last part, where he inputs OAT data and predicts monthly heating requirement is flawed. If I look at the figures I have, which still has the OAT data for where Jeremy lives which is a lot milder than here, it gives me monthly values way higher that reality. In particular I find OAT of 10 degrees is a tipping point for us. 10 degrees or more and we don't need any heating at all. Yet Jeremy's spreadsheed is still calculating a June / July / August heat loss where nobody will be using any heating.

I have said before we have a WBS because we have wood. If I did not have my own stove the wood would be waste, it is not good enough to make anything with, so it would either go to someone else to burn in a stove or worse still get burned outside.

It sounds like a ploy to put lots of non Chinese production plants out of business. So this could be a relatively short over production, as capacity will reduce and the lower prices will increase demand. Keep an eye on the market and catch the sweet spot.

It seems somewhat illogical that you have a EA permit for foul water disposal, and are now struggling with rainwater disposal. I would not have thought rainwater soaking into the ground would be a bother even in protection zone 1. Have you actually submitted a design to the EA and had it refused?

Air change less than 3 in Scotland triggers the need for MVHR, so the mass builders will aim for just under 5 to pass without it.

My ASHP is on a south facing wall. In winter on a still day here, the front of the house that does not get any sun can stay cold and frosty all day long. The south that gets any sun going, warms up and the frost melts. I cannot believe being on the warmer side of the house has no positive effect on the ASHP performance.

I have one in my boat as well, they work well for a small space but as above make sure they are installed properly.

We were talking about this earlier. Over the last perhaps 10 years, around us all public buildings like schools, leisure centres have moved over to wood pellet boilers for their heating. So now the Scottish Government have banned such things, will we see these now replaced with heat pumps?

It is possible, I wired a whole house where the owner wanted OSB as the wall finish everywhere. The builder found a clear coating that was acceptable to building control, but sorry I don't know what it was.

The suppliers make it hard for themselves (and us) The only thing that separates THTC from E7/10 is the second meter that meters the 24/7 cheap rate. In it's simplest form, to convert from THCT to E7 they just need to remove the second meter, leaving the existing dual rate meter and time switch, and connect the feed to the heating circuits to the normal rate feed with a henley block. An electrician can't do that as we are not allowed to touch the metering. I don't know why the suppliers cannot just offer that as a simple option. That still leaves the radio teleswitch that will need replacing some day whether or not you change to E7 or stay with THCT, that is a problem yet to solve. As I understand it, in the absence of a radio signal it becomes a dumb timer so on / off periods may creep a litte depending how accurate it is. Not sure how it handles a power cut. As a temporary measure they could always fit a mechanical timer, remember the old Sangmo Weston timers that were clockwork with spring backup for a power cut?

You (or at least your electrician) can replace the meter tails with longer ones. However another issue coming down the tracks is the future of THTC. It is an old SSE system with the USP of offering cheap rate 24/7 for heating appliances. I hear nothing but complaints now as not many suppliers other than SSE will take it on, and it has become expensive. A long term future perhaps is converting to standard E7 or E10. While it is possible to do that just by reconfiguring the existing consumer units, it might be time if doing that to replace with new CU's one for peak one for off peak all correctly wired so all the issues go away.

I have a really really low opinion of BT / Open Reach. For years and years, we had to put up with very poor "end of the line" ADSL as our only option. Then OR started laying fibre up the trunk network that passed the end of out road. They missed, or rather could not be bothered to put a cabinet there and give us all FTTC broadband. It would have still used copper for the last 300 metres but would have been a vast improvement for relatively little upheaval. Of course they did nothing. Later a local company installed a wireless network covering our village and we now get 100mbps from them. Of course that now means OR won't install fibre down our road as I don't think there is a single BT customer left here. That's probably good because I would not allow OR to drill through my air tight walls to shove a fibre through.

There is an even simpler way I did not bother looking up the OAT data for my location so I only filled in the spreadsheet down as far as row 70 so row 70 column H shows me with a delta t of 30 degrees (20 degrees inside, -10 outside) the calculated heat loss is 2310 watts. So on the coldest day in winter my heating needs to put 2310W of heat into the building. Why make it any more complicated?

An Ecodan plus FTC6 is probably one of the simplest ASHP's to install from the electricians viewpoint. The FTC6 connects to the HP just with a 2 core cable and all the user control connections are in the house in the FTC6. In it's simplest form there is just a pair of contacts for "call for heat" which is just about exactly what you get from say an UFH system with a standard UFH manifold controller. Any electrician that cannot look at a manual and connect that is not competent imho. The MCS companies not wanting do do non MCS work, it probably just a thinly veiled way of saying why would they want to work at normal labour rates when they can do as much MCS work at inflated MCS prices as they want to.

The other "trust the theory" thing, is from the experience of others, I believed my house would be well insulated enough not to need any heating upstairs. So I didn't for any in the bedrooms. Instead I fitted an electric point on the wall of each bedroom for a panel heater if they proved to be too cold. I have never needed to fit those panel heaters and the points for them remain unused.

It is not difficult. I put all the details of my house into Jeremy's heat loss spreadsheet, and it told me at +20 inside and -10 outside my house needed a little over 2kW of heat input. That was not exactly difficult therefore to specify a 5kW ASHP, about the smallest generally available. And it is working fine. Before actually buying the ASHP I ran a convector heater for a week, plotting inside and outside temperature and that confirmed the heat loss was in line with the calculations.

An ASHP is NOT rocket science. All you need is a plumber, to him is is just about like a system boiler driving a heating system (hopefully under floor heating) and a hot water tank. He just needs to be able to read a manual, and be prepared NOT to use a 3 port mid position valve. And the electrics, it is close to a system boiler, but every ASHP is different in the way you connect it, and the way it interfaces to the rest of the system. It will all be detailed in the installation manual, so all you are looking for is an electrician that is literate so can read and digest the manual, and be prepared to do something new to him following the manual. It does annoy me when they say "I can't do that" Also agree £600 per day for the plumber is too high, but that might be the going rate, one of the reasons I left the south, everything was just too expensive.