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I may be wrong, but my understanding is that if you are building an extension, everything in the extension needs to comply, but the stuff in your existing house can remain undisturbed. However, if at the same time as doing the extension you decide to refurb the existing house including, for example, rewiring, then the existing house’s electrics will be caught and the BCO could require full compliance in terms of the electrics. Our extension and refurb is so extensive that the existing house is just an empty shell, no electrics, no pipes, only got floors in a couple of months ago.

Would doing something like the 7 steps at the end of this work: https://www.wcmanet.org/how-to-build-an-insulated-exterior-door/

The side door to our house is a solid hardwood timber door. Probably about 2m in height and 85cm in width and about 52mm thick. Not sure of the wood, but definitely a solid hardwood door, very dense. Google tells me the U value of a hardwood door is about 3W/m2K. Due to budgetary constraints we weren't going to replace this as part of our refurb, but I'm now starting to wonder if this is a weakness in our thermal envelope. The door is in a solid double brick wall to which we are adding 40mm of EWI (phenolic boards) plus about 6mm of render, so it will probably have a U value of about 0.54 W/m2k. The obvious answer is to replace the wooden door with something with a much better U Value. But I want something budget. Could I add insulation to the door? Maybe some of the 40mm phenolic boards, then a plyboard frame and then paint it?

My architect's first draft was silly. I walked round the newly laid out house (we have all the external shell done and internal stud walls are amost done) and made various changes to what he had suggested. But marker pen is a good idea, once the studs are done I might do this as well to make sure what I've planned is going to work.

2.32kwh/24hrs, so I need to add an extra 4.64kw. Thanks, very helpful.

For this reason I have not left it to chance and give the builder: (1) a reflected ceiling plan that shows precisely where the the light switch for each fitting goes; and (2) a floor plan which shows precisely where each socket goes. Let’s hope his electrician remembers to follow them.

Appreciate there is a fairly high degree of approximation. Will try Jeremy Harris’s spreadsheet next and see what figure that gives. How many kW extra do u need to add to one’s heating requirements for an unvented HWC? I read somewhere that the rule of thumb is to add 3kW, but that didn’tspecify what size cylinder that was for, which was odd. For 300L cylinder, how much should I add?

70W/m2 works out at only 14.2 kw for me. How much does one add to have enough to easily heat a 300L UVC? Just interested to compare how the 23.7kw figure which I got by using the online calculator compares to the 70W/m2 calculation.

The latter. @PeterW recommended that site, and it’s pretty good, though won’t be as technical as LoopCAD I imagine. I’m only doing it as I need to buy a system boiler and don’t know what size to get. The range I’m getting though has a the highest modulation range on the market (1:17 ratio) so maybe oversizing by 6kw to be safe is the way to go. Not sure. Maybe I will try loopCAD. Does it take long to do on that? Do I need to have all my drawings in CAD to be able to do it?

So I did the heat loss calculation with Delta T at 50C, putting in sizes of rooms, size and type of glazing, wall construction and approx* description of insulation and it came in at 23.7kw which is much lower than I was expecting., given this is a 3 bed 1930s semi converted into a 5 bed house. Heat requirement will be even less as it’s not factoring that I have installed 40mm EWI on all old external walls. * there weren’t really enough options for my liking.

A bit of further research brought me to this page http://www.heatweb.com/techtips/Underfloor/underfloorheating.html which suggests floor temperature is much higher, around 27C. So if water is running at 42C delta T would be 15C. I'm way out of my depth though. Not really sure what i'm doing.

I’m currently handing a £5k claim against a “damp surveyor” who conned my parents out of a lot of money to inject their walls with useless chemicals. The industry is rife with conmen.

Avoid getting an opinion from anybody that has a vested interest in selling you their services to fix it. Get an opinion from a RICS surveyor who does not sell any treatments or solutions, just diagnoses the problem and tells you how to fix it. The “damp specialists” tend only to be specialists in conning people.

Hmmm, not sure how I’m going to do this. Ground floor is 68mm screed with 16mm pipes. First and second floor are 16mm pipes imbedded in XFLO extruded polystyrene boards, under a mixed variety of laminate, tile and engineered wood. Wouldn’t the screed and extruded polystyrene be the same temperature, or is the fact that they are on different floors relevant?

The online heat loss calculator I'm using (https://starsapp.co.uk/basic-heat-loss-calculator/, recommended by @PeterW) requires the following input: Specify the Delta-T (Δ-T) of your heating system. This is the difference between the Mean Water Temperature of your system and the ambient temperature of the room. If you’re not sure then leave it at 50°C in accordance with BS EN 442 Given it's an app on a radiator site, isn't the assumed 50C only going to work for a radiator based system? What delta T figure shall I use for UFH? (My whole house is heated by water based UFH, apart from a couple of towel rads in the bathrooms, where we have UFH as well).

Actually, can't even get the Stelrad STARS app to work; regardless of what temperature I put it, there is some bug on the website that doesn't let me save and click through to the next page.

I'm doing the calculation now. It asks me to insert the outside air temperature. What shall I put in? Below are the average winter high and low temperatures in my area: December 8° / 2° January 7° / 2° February 8° / 2°

I made this exact point to them on the phone last night. In response, they said "nobody would complain about a rendered wall" and I replied "this is very subjective, I don't like render which is why I applied for permission to have brick, whereas you don't like brick, whose to say what everyone else with a view of my wall will think". They just didn't understand this. They are luddites. Honestly, some of the objections we had from other neighbours were so far fetched that god only knows what someone might complain about. Well as it happens, this same neighbour has various leylandii in their garden growing to about 14m (I'm not exaggerating, their leylandii are taller than our house) and I could ask them to get rid of them. But... having researched the position I'm fairly confident I can force them to cut down their leylandii to 2m tall, as two leylandii growing next too each other along a boundary are caught by the definition of a "high hedge" in Part 8 of the Anti Social Behaviour Act 2003, and so I could just write to them separately about that and if they don't cut them down complain to the council. So my current inclination is not to ask for that as a quid pro quo, but maybe I should. I don't know...

This made me laugh. But more seriously, I think they'd have a reasonable argument that "reinstate" means to put back or establish again as it was before. So as it was a wooden fence, I'd probably have to reinstate a wooden fence.

All very helpful advice. Thanks everyone - helps reassure me that they are indeed mad and it is not me. I think what has happened is I have given an inch and they have tried to take a mile. A similar situation happened when I agreed to pause my works for half a day as my neighbour apparently needed to rest before some medical exam and this got interpreted as their unfettered right to demand when my builder should take his lunch break - on an ongoing basis. Anyway, that's another story. But back to this lost inch: Shortly after we got the party wall agreement (PWA) sorted, I realised that the 2 weeks that we were allowed under the PWA to take down the fence and come onto their land for the purposes of building our extension was not going to be nearly enough time. To clarify my extension is entirely on my land but within 2cm of their land as it goes right up to, but not on, the boundary. So to point the bricks I would need to access their land. By that point in time, things were already incredibly difficult with our neighbour as we were making lots of noise, they were complaining several times a day and also failing to understand: (i) how the party wall system works and what they had signed up to; and (ii) people are lawfully entitled to make noise to build their extensions. I was concerned that the party wall award required me to reinstate the fence, and doing so might prevent my extension wall from breathing, in that the fence would have to go right up against it. Maybe this concern was misconceived, in that I think I could just reinstate the fence without a gravel board so that the portion of the wall below the DPC can breathe. I also thought that the fence itself might not be able to breathe and would rot more quickly in that position, and as I'm responsible for the fence they would bug me more often than they do already to replace it more regularly. So I suggested that perhaps instead of reinstating the fence as strictly required by the PWA, I could get their agreement to start the fence from where my extension finishes and instead affix some trellis to my extension wall so that they could have a couple of non-invasive creeping plants along my wall. Nothing was decided but they liked this idea and we agreed we would revisit the position once the extension was finished. I guess they had assumed the wall would be rendered, without actually studying the details of my plans as approved by the council (and as provided to them originally in 2018 which also showed they were to be exposed brick). They now consider that point in time has come (although it hasn't really, as we're not finished yet, but I guess most of the externals are done). So I need to decide what to do about the fence, as they could insist I reinstate it along the wall since this is their right under the PWA, or I could negotiate a different agreement. But rendering the wall is madness, even if they do offer to pay for it, because any other neighbour could complain that the wall is not in keeping with the plans and the Council are mad enough that they might uphold that complaint. Basically, everyone is mad.

Three years ago I knocked on my neighbour’s door to explain that I would be filing a planning application, but before doing so I would welcome any views he had in case he didn’t like anything we were ptoposing, so that we could address any of his concerns prior to filing, in the hope that this would avoid him objecting. He refused to engage (whereas my other neighbour on the other side politely told me they wouldn’t object). Over the next two years they proceeded to object to everything we tried to get approved, including by lying. Eventually we got approval. Today, same neighbour calls me and asks me to render over my brickwork on the part of my extension facing their house because it doesn’t match their house. I tried to politely explain that I had got planning permission for bricks even though most houses in the neighbourhood are rendered with pebbledash and that I wasn’t about to breach my own planning permission to suit my neighbour’s tastes. They were genuinely gobsmacked and started lecturing me that I wasn’t doing the neighbourly thing. Some people are just incredible. The stupidity of the situation is that I can’t see most of the wall that they are complaining about and that if they had taken me up on my offer of consultation at the outset, they could have explained their concern and I could have built it out of blocks rather than facing bricks and then rendered it. In actual fact, none of their objections were about this issue. It was always about the proximity of our first floor extension (which ironically is rendered) to their house. Madness. Knowing my neighbour, they will just keep asking for this.

+1

How are you going to soften the water? If with salt, I hope nobody in your household suffers from high blood pressure.

Why are you even bothering with UFH then. Install radiators.

I think that timing is optimistic. To do it properly will take longer.