epsilonGreedy

I agree with this. The OP's question can only be answered properly in relation to the overall style of the whole house. Perhaps a modern take on the Georgian front door would work i.e. a segmented square fan light above the door & side windows with a simpler flat roof porch?

I have paid a personal pilgrimage to this holiest of shrines to self-build centralized manifoldness. It is a wondrous sight though at the time I could only comment on the colour of the floor tiles.

Is that because the output temp of an ASHP is close to the ideal input circulation temp of UFH pipes?

Ok though I am struggling to picture this drawing off process probably because I know nothing about mixing valves. EDIT: I just reread the @PeterWpost 3 above... starting to make sense. When the buffer tank is at 60(c), the house and slab are at ideal temp and the outside temp is 8 degrees, the there will be little draw from the buffer tank. I need the Janet & John book on how UFH works. This FAQ is useful for a beginner: https://www.underfloorheatingsystems.co.uk/technical-information/questions-and-answers/

Think you mean 100 m2?

Ah ha, reading that led to a major realization. I thought the buffer tank just bulked up the total water volume flowing around the UFH pipes at whatever temperature is right for a particular slab and house heat loss rate. Given the 30 degree operating range of the buffer tank, somewhere there must a device that somehow leaches heat energy from the buffer tank to the circulating UFH water until the buffer tank drops to the base target circulating temperature, about 35(c) in your example. Thinking some more about this, even when short cycling is happening in the absence of a buffer tank, the operating temp of the circulating water in the UFH pipes must be a bit of thermal roller coaster.

Is a buffer tank usually sized as a ratio of the water volume in the UFH pipes or is the tank size calculated to give the boiler a long working burn at its minimum modulated rate?

You answered a future question of mine. I noted that some boilers in the Valilant range had a feature quoted as 1:10 modulation. In other threads UFH experts here had warned that poor modulation leads to excess heating cycles hence a gas boiler can wear out prematurely when coupled to UFH. Will a combi boiler with a 1:10 modulation range cope with UFH?

This is interesting, I have been looking at boilers and wondered how the same boiler chassis/model could be sold with a rated output from 25kw to 38kw. I wonder if they obtain the higher outputs with more finely channeled galleries? https://www.vaillant.co.uk/homeowners/products/ecotec-plus-combi-832.html

I think you have found the sweet spot, with replacement every 10 to 15 years. I reckon the nightmare for many starts with a succession of bills in the £100 to £300 range, not enough money to spring £2000 on a new install hence they get locked into a £250 per year maintenance contract. Having thought about the situation today I reckon the sensible midway DIY path is to learn everything to do with central heating maintenance outside of the legal restrictions on the boiler. Keep a spare pump and diverter valve on hand for quick DIY replacement. Do routine filter and inhibitor treatments on a diy basis and then intermittent servicing visits from a pro. Having witnessed one service at my house I think I am capable of looking at the flame burn once a year and just like the visiting CORGI pro, saying "yup nice consistent clean blue fame burn there".

It is a keep it running type contract not matter how many visits and parts. Your < £360 p/a figure based on a replacement cycle indirectly validates that these other contracts are within the realms of reasonable.

The £250 is for a comprehensive warranty that British Gas will keep your boiler and central heating running no matter how many bits fail.

I was thinking more about installation features that would persuade a pro to lower his regular service fee because a self builder's central heating installation was very easy to work on.

Agreed about the sillyness. The £250 is for a first-year fix any number of problem at zero cost contract with British Gas. Apparently annual increments often push this up to £400 as the computer algorithm gets to know how wonky your central heating system is. Cases mentioned in the papers cite £700 annual renewal premiums which I assume is BG's way of saying, we have had enough time to fit a new boiler. The £250 level figure is justified in the marketing on the basis that an annual service is going to cost £90 regardless and this is included with the £250 annual cover.

Ok but I was thinking of a more specific case. If a householder ignores a central heating boiler for 25 years and never arranges a maintenance inspection by a qualified pro would that constitute an offense?

Another thread today got me thinking about the long-term cost of maintaining a gas central heating system which led me to investigate annual contracts to keep a whole central heating system working. £250 to £400 p/a seems like a sensible medium range to base calculations on when assuming £0 per fix excess. Using pension annuity rate tables I reckon for me that would require £15k placed in an annuity to generate a life long indexed linked income to fund comprehensive gas central heating maintenance cover = ouch. I can already hear some well known forumites saying "design out gas". I would counter by saying the long-term maintenance costs of ASHP are an unknown. At this point I can see the whole lifecycle cost advantage of inline electric heaters, running on E7 charging up the heat capacity of a UFH slab, when in stalled in a near passiv standard home i.e. little heating outside the E7 time band. Plus a very cheap install cost. But back to designing a gas central heating system to keep the £££ hungry GasSafe wolves outside the front door. What can be done to aid DIY monitoring, servicing and fixed of gas central heating? @JSHarrismentioned cleaning and swapping inline filters in the water circulation. Another post described a clear glass view port to eyeball clarity of the water. Isolators on all rads. Isolators on all the swappable bits such as the pump and direction valve in the airingcupboard. How about some extra plumbing to make a complete system drain/flush a doddle. What can be done to legally make it simple to conduct an annual pressure test on the gas supply? And finally thinking of extreme measures how about buying a duplicate boiler from the start. This would guarantee the simplest swap out of a boiler at 10 or 15 years and hopefully a cheap quote from a pro for the job. In my experience the maintenance costs mount up beyond 8 years as each component failure requires two visits, one to diagnose and another to replace. Such a bill is typically £150 for labour plus £100 for the part.

I can see two different interpretations of that, the worst is that knowingly never inspecting or servicing a gas boiler that was installed and certificated correctly eventually constitutes criminal behaviour. Is that the case?

I have called in two recent years, both of whom I would rate high in terms of competence and trust. The problem is their financial expectations which is £150+ as they step though the front door. It is a market distorted by government policy and incompetence. Even though I will be fitting an LPG boiler I intend to design gas fitters out of the rest of my life so that no GasSafe person will ever be let into my property. Looking at the going rate for comprehensive central heating maintenance cover we are talking about £250 to £400 per year. Many examples in the press quote £700+. At my age that would require about £15k being placed in an annuity to fund index linked central heating maintenance cover for the rest of my life.

Condensation resulting from the recent change in weather as we switch into autumn? Has something blocked ventilation of the attic space? Or change in householder habits, e.g. air drying of cloths in the room below.

Is gas boiler servicing economically rational? My point is not technical, I am observing that in the UK a competent GasSafe person is such a rare commodity the cost of their time is bizarre in relation to the task performed. The last GasSafe person I employed was complaining about the cost of horse feed and the £22k invested in the 2 acre paddock to keep his wife and daughter saddled up. My one and only boiler service seemed to precipitate failures. It was 12 years ago but I do not recall a check of the quality of the circulating water and has @JSHarrisillustrates this is definitely within the scope of DIY heating system maintenance checks equivalent to looking at a car dipstick on a Sunday morning three times a year.

You might have detected I have a downer on the whole Gasafe/Corgi industry and view the extraordinary fees charged as a symptom of longterm of failed Government policy that for 30 years has produced legions of unemployed Business Studies graduates with £50k of loan debt and a shortage of qualified trades because of the willful destruction of vocational education. The net result is that an enterprising GasSafe fitter will retire with a greater networth than an NHS brain surgeon.

I have always been suspicious of the concept of servicing a gas boiler, it is not like a car with things that require regular topping up or tweaking. The boiler in my new build house ran without any care or attention for 7 years at which point I got it serviced mainly due to peer pressure from others at work. I watched the service, it was observational looking for negatives then the clot, who had complained to me about his bad back and the cost of his individual CORGI registration rammed the case back on and clipped a case ventilation fan vane. For the next 7 years the boiler sounded like a jet engine and then started to regularly break down, year 8 it was a circuit board, next a valve deep inside the boiler then the main circulation pump. I appreciate that the jet engines on a commercial airliner warrant routine observational maintenance checks but I doubt "boiler servicing" will spot pending failures or extend the working life.

Update: Flowery emotive prose is ok. I visited the planning office and got some good advice. The duty planning officer at the public walk-in desk was helpful, his main interest was not to assess the merits of the NMA details but to advise on whether my changes fell within the scope of an NMA. Because I am in a conservation area he said that if my garage had direct frontage to the public road it would require a full application but in my case an NMA is ok because the view from a public road is partially obscured across the back garden of another property. He advised that I drop the brick bond change from the NMA because it is subject to another approved condition and that change requires a different form. As to flowery prose presented as an addendum to the NMA, he said why no, no harm. His view is planning is all about the art of persuasion and anything that helps explain motive or the applicant's justification will help the planning officers or other bodies such as a parish council.

Looking at the responses you seem to be getting feedback on two different types of laser. The most common laser used outside on a building site is a rotating laser that does not paint a visible line and has a range +15m. These are cube in shape and about 10" across. Builders typically set them up in a fixed position on a tripod for most of the working day and then use a receiver on a staff to get levels. The old model I used just gave an audio sound and an lcd up/down display to indicator high or low. This is a single handed operation. Typical cost £400 to £600. A much cheaper type of laser paints visible lines. At night on site my dewalt can cast a line to at least 25m but I only use it up to 10m. This is really an indoor laser hence I use it outside near sunset, in practice I only have 40 minutes between it first casting a legible line and the whole site getting too dark to stumble around looking at levels. Mine cost £135. I would like to own both and serious outside building pros use the expensive rotating cube lasers. In practice I have got a lot of use from my indoor line laser outside. I check my blockwork heights every few courses and check how vertical a blockwork door aperture is. I have also learned how to check levels of things like poured concrete, drainage gradients and the level consistency of my block & beam floor. This requires using a 2x1 batten of wood, marking the position of the laser line on the wooden staff at a reference point and then wondering around site looking to see if the line is high or low against the reference mark. This again is a sunset operation. One downside of using a visible line laser for obtaining heights across a site is the limited angle of projection of the line, I would guess it is not much over 90 degrees.

I thought your foundation costs were much higher and you had adjusted your absolute m2 build cost downwards to a lower headline figure because your plot cost was discounted in view of the problems? Perhaps the better question for comparison is total project spend including design, surveys, engineering, site access prep, historical digs, newt hunting, services, crane hire, spoil disposal and actual construction to get to dpc.