epsilonGreedy

Yes fair point, my foundations were dug from the diagrams produced by the architectural technician which included his guess re. the ground floor beam layout. Somewhere in the small print there was a getout clause about the final beam spec to be produced by a specialist supplier, so I suppose I was not paying him to enter into a protracted discussion re. floor structure.

I waste hours online trying to understand the array of plumbing systems available and then more hours at Screwfix.com finding converter bits between different systems and pipe sizes. I think part of my problem is working out which are legacy systems encountered by plumbers in the field v. what is applicable to a cleansheet new build. As an example here are today's challenges: I want to refit a large chunky copper compression fitting to the end of a 25mm MDPE pipe and Screwfix only offers 22mm and 28mm olives. Should such an MDPE/Copper joint have a plastic or copper or plastic pipe insert. How do I choose between 22mm or 15mm HEP20.

I decided to add a dwarf wall where the official foundation plan showed beams spanning a 5.7m x 6.5m square. I marked it up with the digger chap literally 5 minutes before he dug the dwarf wall trench. The motivation for this last minute change of plan was that the evening before my pro self build neighbour strolled over to look at my marking up and he advised against trying to handle 5.7m beams plus he mentioned the bounce issue. I wonder why the pro's who design foundations don't volunteer these options when dealing with self builders.

Where did the expense creep in? I thought one advantage of traditional/mainstream building methods is they are cheaper in the first instance though with the longer term cost of less insulation.

You should not have to seek advice on an internet forum to comprehend the design intentions of your highly paid professional. Phone him up, tell him you are not satisfied with his abnormal design presented so far and demand a substantial 1 on 1 meeting. Your current confusion with your interim classic foundation plan need not motivate a complete u-turn in foundation methodology. What are the credentials/experience of your SE?

And equally I have made a reasonable claim that there has been a 2.7 thermal improvement factor in houses built between 1975 and 2013. From that general fact I inferred there was something strange with the annual heating calculation posted by the OP. When the OP started this thread the HBB was open at the table showing annual heating of 3 generations of houses and I noted the OPs figures were strange for an improved 1970s house, ballpark maths in my head placed the OP's house half way from 2013 standards to Passiv performance levels. If I was debating with someone with less knowledge than yourself I would have posted using longer more qualified and less ambiguous sentences, I assumed incorrectly you would understand that 2.7 referred to averages across millions of houses, not every individual house built in the UK.

At a national level the main variable is frequency, changes to this figure represent a temporary imbalance between supply and demand.

Funny story for you. I once helped fit out a canal boat for a senior engineer at what was then the Central Electricity Generating Board. This engineer established folk hero status in power generation circles during a winter storm back in the 1970's . He was a duty engineer at Oldbury and as the storm progressively knocked out supplies to Bristol the whole city became dependent on the output of the nuclear power station. They set up a TV in the control room and tuned it to ITV and coronation street, he then had to anticipate the advert breaks and crank up the output in anticipation of all those kettles being switched on.

You don't have to do anything but why do you feel entitled to mock a book that attempts to produce a more accurate model? One of the most common sources of selfbuild dissatisfaction is from people who end up with thermally dysfunctional houses. Some end up buying electric panel radiators and others suffer sleepless nights in over heating properties. Selfbuilders will surely benefit from reading a book that highlights that thermal bridging could add 50% to basic calculated heat losses and incidental gains might raise the background temp of their house to 11 degrees. Your general argument that every house can be different constitutes a mockery of science. How would you regard an NHS consultant in respiratory medicine who said "everyone has unique DNA therefore I am going to ignore the evidence that smoking shortens lives".

I am now quite worried, have we seeded the national infrastructure for a spectacular cyber terrorist attack? If a software Trojan could automatically disconnect millions of homes at peak demand in the evening there would be a horrible surge of excess power on the national grid because the generators would be unable to dialback output quickly enough. Not sure what would happen next, something like the prolonged grid outage in Canada a few years ago?

Right so your house is actually so greatly improved it sits somewhere between a 2013 standard house and Passiv house on a performance scale. I still think using a single pair of oil tank level samples is a bit hit & miss though it might not matter for your purpose.

There is no average data used in these claims. The claim is based on detailed scientific thermal model that is more detailed and more useful than that offered in your own spreadsheet which by your own admission ignores that two most influential factors in house thermal modelling namely cold bridging and incidental gains. As you say mainstream builders cheat when trying to meet thermal regs but this statement does at least demonstrate there is a reference point. We can take building regulations and typical building practices of an era as a base reference point for comparison. The OP was asking for a sanity check on his calculations and I still maintain something feels wrong. The insulation improvements to his 1970's house would need to have been spectacular to outperform a smaller 2013 standard by a 30% margin.

Last year when I mentioned here that my new site connection had a smart meter this seemed to make @ProDave angry, I forgot to follow up and ask why. Now I understand there is a near political issue at play.

@jsharris your post and graphs offer nothing to disprove the assertion that a 2013 standard house is 2.7 times more thermally efficient than a 1975 house. My "flawed" source is the House Builder's Bible with a table of detailed thermal calcs that show a more detailed assessment than your spreadsheet offers. The relative difference of typical U-values between 1975 and 2013 for roof, walls and floors were x4.4, x6.8 and x3.8. Given the massive relative improvements in standard insulation practices I am not sure what prompts you to deride my 2.7 times improvement that I lifted from the book?

Not sure what else to call the process, you claimed you "got very anal about this" and entered into an iterative adjustment process that few new houses would benefit from.

@jsharris Those are all factors but at the end of the day it is odd that a 1970's house with some unspecified improvements requires 30% less heating than a 2013 standard house that is 30% smaller and also an efficient rectangular box. A 2013 house is 2.7 times more thermally efficient than an unimproved 1975 house The explanation is most likely an arithmetic error by the OP or some human factor such as the OP being happy living in a house at 16 degrees or the upgrades to the house were more like a complete renovation and insulation upgrade.

Until this week I was not aware that thermal bridging was such a major factor. The HBB model house calcs estimate that thermal bridging accounts for 30% of heat loss in both the 2013 and Passiv standard versions of the model house. Starting with a basic 2013 design the HBB shows the relative heat losses are: 32% Thermal Bridging 27% Air leaks & ventilation. 16% Doors and windows 14% Walls 5% Roof 5% Floor

That is cheap, I had assumed the going rate for one of those was £150.

True but am I correct in thinking the quoted manufacturer radiance power should have been measured at an ambient 20 degree? So looking at the following you tuned your way to 80% of the Stelrad rated power and 60% of the AEL.

I had a quick look last year and was daunted by its size, having looked at it this morning I now realize the mandatory data input in white spreadsheet cells is much less. Re. the spreadsheet's overall scope am I correct in thinking that thermal bridges are not part of the calculation?

Nope for 2 reasons. The annual KwH consumption figures for a 160 sqm model house built to 1975, 2013 and Passive standards are 56,000, 18,000 and 5,000 for space heating and hot water. Given the mixed thermal heritage of your larger house 13,200 looks like an underestimate. I lived in a 2500 sq ft house for 3 years, it was built in 1900 and extended in the 80's and 90's. We consumed 3000l of oil annually.

I have not yet worked this out for my house design, so far I am using the House Builder's Bible model house 160 sqm which is a no frills rectangle. My house is 139 sqm in an L-shape and for the moment I am working with heating/thermal losses at the 2013 regs standard. The HBB model house sheds 6 Kw of heat at a 20 degree delta and 3Kw in Passive house form. Once incidental gains are included the space heating demands are 4.7kw and 1.7kw respectively (bit of guesswork here because the table showing incidental gains is an annual KwH/Cost table.). Looking at the elements of heat losses for the HBB model house built to 2013 regs I hope to improve in a few areas: If I can half the 2013/Passive performance gap for air leakage and ventilation that would equate to a 20% improvement. Thermal bridging accounts for another 39% of the remaining heat loss but he does not break this figure down so I am not sure what improvement I can make in this aspect of my brick & block build. The model house also has fairly pedestrian U values of 0.18/0.22/0.18 for attic/walls/floor. So all in all I hope for a 30% improvement on the 2013 standard = 3.3 Kw space heating demand at a 20 degree delta. Edit: Maybe not a 30% saving because the HBB 2013 house does not have UFH and using the @JSHarrisspreadsheet my UFH floor at 25 degrees with 150mm of insulation will loose 5.8% of its heat downwards. My hunch is a small towel radiator in each bathroom upstairs and a radiator in the master bedroom in my less than passiv house which will be 2 to 3 times more thermally leaky than yours.

Interesting... while looking at official radiator power ratings I had concluded just 3 mid sized radiators and no UFH would be enough to heat a 1600 sq ft house built to just 2013 thermal regs in all but the coldest snaps. This intuitively feels wrong. Given your best CH tuning endeavors could only achieve 60% of the rated input/output temperature drop maybe I should assume a similar real world performance factor.

Radiator manufacturers quote the "power" of different size radiators in BTU's and Watts. Does the industry use a defined setting at which the power rating is achieved e.g. room temp of 20 degrees and water circulating at say 60 degrees? I ask because I am trying to calculate how many wet radiators I will need in addition to UFH and I am reassured to read that a middle size double panel radiator is rated at 1.5 Kw.

I wanted to do the same but the electrician said it would not be possible in a standard size meter cabinet sized to fit within a cavity wall.