ProDave

If payback was the only thing, I would not have spent £200K building a really nice house, I would have stayed in the static caravan and the £200K would have paid the very high heating bills of the static caravan for the rest of my life.

My question is, is the house detached or joined to another. Like others the double tacked and plywood braced construction does sound like it is for racking strength. Is the house masonry or timber framed?

0.14 is quite respectable, it's what our house is. Another decision is what insulation material are they using to achieve that. Something like PIR or PUR (solid foam) has a short decrement delay. Things like glass wool and celulose and even wood fibre have a much longer decrement delay. So you can have 2 different walls with the same U value, but one will cool down quicker than the other. So a more important decision is select the TF manufacturer on what type of insulation they are proposing.

Some VERY rough sums. Assuming you use all of that 1800 litres in winter, or 182 days, that will be 9.8 litres per day Kerosene has about 10kWh of heat per litre, so your roughly 10 litres per day will be producing about 100kWh of heat per day. As a very rough estimate, the coldest day in winter is likely to consume twice the average for the whole winter, so a peak perhaps of 20 litres of Kerosene or 200kWh of heat on the coldest day. So if your heat pump in this cold spell had produced 200kWh to replicate the previous oil heating, it would be likely to have consumed perhaps 66kWh of electricity per day. You say it is costing £29 per day, and with electricity at about 28.5p per kWh that would mean it has consumed about 100kWh in a day. That does suggest it is using the resistance heating for some or all of the heat.

Have a look at this blog, he build a small house as a holiday let to comply with the "caravan" definition. If you have not already seen it, this is how the Highland Council interpret the definition of a "caravan" build it within that definition and it won't need building regs https://www.highland.gov.uk/downloads/file/1346/bst_018_caravans_and_mobile_homes You will need building regs for the installation of a treatment plant, unless you do something like a composting toilet.

How much OIL did you burn in a year with the old boiler?

Look into your drainage. Any running water e.g. rainwater, will wash away any non hard surface.

Another vote for multipanel. Used them for several bathrooms and not had a problem.

If you desperately want to design it yourself without being troubled by buildling regs, it is possible to build a building that falls within the legal definition of a caravan while being very well insulated and very well built. The downside of doing that is you won't be able to reclaim the VAT and resale value / mortgagability might be a lot worse.

If you buy a bare croft, I think it is pretty much a given that you will be allowed to build a house, and usually a portion of the land is decrofted for that. There are usually several for sale.

ASHP, heat pump unvented hot water tank, heated to 48 degrees. What challenges are you thinking of?

That is a small outside space in my book.

Yes, the big orange DIY store is well known for this, even when you specifically ask for a "VAT receipt" you still just get a till roll. I just sent o covering letter explaining the situation that all receipts from this company, that is the best they would provide and all were accepted.

How thick is the timber frame? That wall insulation is pretty poor, I am surprised it even met building regs? Where abouts are you so we know which regs it should have complied with? Make yourself a DIY blower door, using an old office fan or car radiator fan. It will let you find where all the air is leaking in and out. Most of the leaks will be lack of detail, there is no mention of an air tight layer so assume there is not one. If you really want to improve it it would be very intrusive, get back to the bare frame, overlay more insulation inside the frame, proper air tight layer, service void, then plasterboard. Something that is oh so simple and not very expensive when building, which is why it annoys me so much that the mass market builders don't do it. I bet your service void is already a plasterboard tent not least with cable penetrations up into the loft. When you next get a windy day, unscrew one of the switches or sockets and I bet you are greeted with a blast of icy cold air coming out of the socket hole.

The immediate thing that stands out for me, was the tile size was chosen to be exactly 2 tiles fit the height of the stove, and then the stove was set into the wall at exactly the right height to make the top of the stove 4 tiles above the floor. A lot of forward planning before you start anything.

I am not sure it is really an electricians job, but at least someone is looking at it.

That is the issue. I have an old desktop with an old monitor and it has a really sharp image. I was given a larger Samsung monitor so thought I would try it. The larger monitor has higher resolution, but I found everything was blurred and no way as sharp as my old monitor. I concluded it was because the native resolution of the monitor would not match any of the native resolutions available on my video card, so the monitor was rescaling to fit making the blurred image. I am still using my trusty old sharp as a pin monitor.

Don't forget legislation coming down the tracks that will demand a minimum EPC on rental properties. Now might be the time to think about upgrading the fabric of the building. I think the eventual target is all rental properties to be a minimum EPC C EDIT: Ignore that, I see the property is in Portugal.

I made a small recess, to house the power sockets and give space for cables etc. That allows you to mount the tv closer to the wall than if you just had surface sockets etc, but the tv is still in front of the wall and covers the recess. This was discussed before and the external dimensions of tv's are not standard so in x years when this one dies or you just want to change it, the next one won't fit the mm perfect recess.

Not understanding what you have. I was expecting a modem and router supplied by your BB supplier (may both be in one box) and the router would have some RJ45 network sockets, and you would connect a cable from there to a wifi access point at the back of the house. Are you trying a solution that receives the wifi from the suppliers kit and relays it?

An un used roof tile vent. I bet the builders miss calculated how many and where the vents needed to go and fitted one too many. That decision needs making early in the build as the roof goes on. Then perhaps later there was a change in the plumbing, perhaps the soil stack did not need a vent but an AAV was sufficient. In the short term I would create a little platform under that and put a bucket there to catch the drips.

Unless you can get the price down I would be going off grid. Solar PV and batteries for small loads and lighting, Diesel generator for large loads, should only be needed occasionally, welder etc. Wood fired hot tub. It would be interesting to see the quote.

The contractor that did ours wanted to see the planning permission and then took my word for it that we had not yet got completion. then they zero rated the work.

At the top of picture 2, where two wires terminate in yellow crimp connectors, to the left and right of that are red dots in the middle of those black blocks. Push those with a screwdriver to see if they push in and go click.

New 3.68kW panels will be 2 strings and will be the max your inverter can take. Then put the original panels on a separate inverter that does not need to be as big. And don't forget to ask permission from your DNO first to have more than 3.68kW