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Ok many will disagree with me but here is my take on it. I did my first UFH heating system when many here were in short pants. I'm now a designer. My appoarch is pragmatic and absolutely driven by what is achievable on site, buildablity and cost driven. I honestly despair when I see folk trying to desing pipe layouts room by room! I can go on at length but it is complete bonkers! Thoery is taking over reality. To start. You are going to install pipes in a screed say and that has to be made as simple as possible. You want someone that is going to do this right, that is experienced and they will need a labourer. Take the experienced person at £300 a day and a good labourer that is going to uncoil the pipes and and not be a bit hung over, (kink them) at say at "£120.00 a day. So the labour is £420 a day. Save a day and that extra can get you more pipes.. for 50 years! Now to save labour and reduce risk its easier to make all the pipes at the same centres. Design for the nearly worst case. In real life the concrete guy turns up and may squash a pipe. You won't know. So you want some more loops as a bit of redundancy. There is a thread about how folk cock stuff up.. take my advice and avoid this scenario. Of course I'm not going to be BH angel of the month but best to be honest and give it to you straight about how things often work out on site for self builders. Yes you may think that you will be up to site checking everything.. but that is often wishfull thinking! Even then ask do you really know what you are checking.. do you have the experience / constructionknowledge to know how to argue if you find something wrong? At the end of the install you want something that has some contingency built in. But if you consider the labour saving vs the extra length of pipe it is a good balance of risk when you consider that the pipes need to last 50 years. As an SE that is used to balancing real life cost vs risk, and done UFH long before BH was even invented, I must say that much stuff you see on BH about folk trying to save a few quid is frankly complete pish! But it's not my money! My advice is to install plenty and easily buildable spare capactity in the floor and once the pipes pop up you can play with your controls to your hearts content. It's a good apporach as boiler and design technology develops.. to have spare capacity in the floor slab.. even if you don't need it right now. Put in plenty loops as a guard against the builder catching you out or say in the heat of battle you are doing the screed concrete your self.. you can easily miss a trick here. Don't think for a minute that while it looks great on paper.. on site when the concrete is coming you will likely not have the experience to say to the concrete guys,, hang on.. the may bully you and play to your wallet. So to finish.. I say to many armchair techy folk that are trying to refine UFH pipe layouts.. stop having a laugh and lets look as what happens on site and the labour cost of fannying about with different pipe spacing. Many folk on BH end up moving walls or end up with a diferent kitchen desing layout. Self building is hard enough without getting over enthused about some hot water pipes in the floor.. keep it simple and that way you'll save on labour and reduce you risk of something going wrong. That's my view in the round.

Well spotted (I know a little and am learning a lot fast) - looking at GIRA app control, but not seen what the other hardware and equipment will be. Good point, it may be very little indeed. I’ve added this to the list of things to discuss with the designer. completely agree here, just trying to make sure in making one choice I don’t *unknowingly* create a problem or challenge elsewhere (it’s fine if I’m making a conscious choice aware of the implications) - part of the reason for asking this question is to glean any experience and knowledge from others who might do things differently or recommend things that worked out well etc. I like the sound of all of this, though not all applies in our design. Added to the list to discuss. Thanks @joth

That length of loop is bonkers! But if in the floor it is what it is. Question is.. is that loop near an external wall or not and if so.. by how much and is the cold wall on the upside of the loop or the cooler side? Next is does this matter? I know many are not keen on my rough and ready approach to UFH. But they will realise 5 - 10 years down the road when they are spending hand over fist to keep it working! or maybe want to sell! Now if you look at many posts on BH there is my view on a high reliance on software.. but pretty much none on BH know how that works! they blindly trust.. they certainly don't know that FE models are and often widely wrong. As an SE Fe is subject to lots of scrutiny as it often down right dangerous! The IStructE has many papers on this.. it's a great tool if treated with caution, a very handy aid! Ah but there is an upside. The first thing is to recognise that we have not lost the skill to be able to teach ourselves. When I went to uni at 40 was in tears on my first day.. I clocked that my educators were actually teaching me how to teach myself! You can only appreciate that when you go to higher education in later life. Yes we are a bit slower.. but also faster as we have the life experience to be able to identify what we need to learn in the context of the problems we face. Mike: Is the black line your actual room temperature? If so that does not reflect real life? What room was that in?

Not sure I knew you'd had those issues, Terry. That may be that you'd not shared back then, that I'd just not seen, or that my aging brain simply doesn't recall. I know I struggled physically at times with our build, so you did very well. We also downsized, or perhaps more accurately, right-sized. Though I never aimed for PH levels, our home performs incredibly well compared to our previous property. Over the first 7 years, our net energy cost averaged around -£100/pa. However, since last April, we no longer receive the RHI payments so this is the first year in which we're actually paying out for energy (albeit less than a third of what it cost us in the old house 10 years ago!) Like you, my wife's health forced early retirement (from teaching). In her case it was due to a whole bunch of complex medical issues, some of which date from birth, some that are much more recent, and (unfortunately) some that will likely have been caused by treatment she underwent in childhood. But the difference the house has made to her (and our) quality of life is absolutely priceless. I don't know how many more years we'll get, but I have no doubt it'll be more than we'd have enjoyed had we not built our bubble.

Was about making your house warm, rather than why it is not warm. https://www.bbc.co.uk/sounds/play/m002qrkc

Ah, that is a bit embarrassing. Fault lies at my end.. I should have explained in a better way. Blame is being a bit harsh on yourself. Ask and reflect. How much were you expected to know when you started? Evaluate how much you have learnt, take pride in that, and yes don't let it weigh on you. I'm making some posts that reflect my own experience. From a novice self buider to an SE / Designer that chips in here. I've made some horrible mistakes when running a contracting business! But at the time I did not know any better, I just did the best I could with the knowledge I had at the time. Now this thread is about.. hind sight and mental health to be blunt.. but also about trying to see how you get out of the woods at times when the world turns to shite. I'm chipping in as I am fortunate enough to see it from both sides.. as a past self builder myself and now on what you may call "the other side of the fence".

Already Done https://www.bbc.co.uk/programmes/b09fb6n5/episodes/player

Yes, it is. I should have split it. I have not found any controls for the pump in all the places I have looked but I am hopeful that I can squeeze that up a little further and witha complete pressure flush I can get the performance I want. Getting your head around how these things work and the perverse incentives (just the laws of physics really) they seem to have built in is fun. I have had that thought, the whole place is cold and it has a significant decrement / increment delay as you can see from the trends. I need to get the delta T down a bit more, I have 6 or so at the ends of those runs today which is re-assuring. I am hoping its just a sediment restriction in that long loop and I can get it cleared if not I am going to have to think a bit more out of the box aren't I. I was interested today to see how the heating affected the building and the slab. Going into the heating session this afternoon we had a room temperature of 16.5, at the end of the day before we had 16.9 so a drop of 0.4 deg C in 12 hours with a delta T inside to outside of 11 deg C. 6.549 kWh of electricity raised the temperature back to 16.9 deg C now. Over the three days 33kWh (£8.91) has lifted the internal temperature 5 degrees against an average delta of 10 degrees. Yes, rediscovering my inner child is real fun, I wish I still had the sponge brain I had then you can learn so much so fast its frightening now to think about how slow I am!

Thanks all, great advice.... To be continued.....(with another architect!)

I've had ME/CFS hovering around in my life since my first collapse in my early thirties. Luckily I spiralled out into reasonably good health over the next year and for the next 25 years, albeit with the odd post viral wobble. However, I then had a second collapse in my mid 50s and was bedridden for more than a year and had to retire early. Again 8 years of slow recovery getting to a point in my 60s where we could take on the self build. This really was a sweet spot for us: we had the time, energy and enough capital to take it on. But TBH the build was gruelling and by the time we finished, I was "running on empty" so another ME collapse, and another year+ pretty much bedridden. So doing the build extracted a toll on my health and as I stretch into my 70s I am still dogged by fatigue problems. However we've downsized from an old stone farmhouse full of character (but also high-maintenance / expensive to heat and maintain) to a cosy and cheap to maintain modern passive-class home. At the same time we freed up some capital to help our kids on the housing ladder. So yes, it was all worth it, but it did have a life cost. I couldn't do this again.

as an update, I have discovered that as we will be introducing an in roof solar panel array on south and west elevations, the possibility of a non ventilated cold roof isn't viable - https://roofingtimes.co.uk/ventilation-guidance-for-in-roof-solar-applications-glidevale-protect-can-help/ It seems my choice is now do is to select a variant of LR or HR underlay and then introduce the required ventilation strategy. It's very complicated!

I had a loom at this for my own house as wanted soemthing similar. True but what I cloked was this. @Anneker, I'm going to be a gent and say you are not as old as I. When I came back from Kenya to complete my secondary educuation Scotland was cold.. but the school really did have some real cast iron radiators. From memory the fins were about 150 mm thick and oval. The flow went in the top and out the bottom. The modern equivalent (replica) has the flow in the bottom and out also at the base. To make it work (modern column radiator) you need to fit a baffle at the inlet at the base.. which basically makes it almost work like a modern radiator. Now the baffles are not perfect hence the likely discrepancy you see. Architectural radiators need to make a compromise between performance and design look.. there is no free lunch. I would if I was you chose the thing you like, over size it a bit, say by 20%, fit a thermostatic valve. Make sure you have a good diameter flow and return pipe to it. In the round all this may cost you £100 quid more but I bet the paint on the walls is going to cost you more than that? Keep posting! Gus

Great advice I am unable to follow but wish I could. Burnt in large letters deep into the flesh of my core is the simple truth: “It’s all my fault”. Simples. That doesn’t mean it’s all doom and gloom, though it is on some days but not generally. But, if something wasn’t ordered on time, if two parts of the design don’t mesh like they should, if an operation is forgotten, etc. then I can look around all I like, I won’t find anyone else to blame. So I’ve accepted all the blame in advance and most days it doesn’t weigh on me. There’s a long list of other stuff that’s far higher priority for weighing on me, so it can go on the queue.

And that sir is the fun of it.. play away. I love this stuff. But have not taken time to really study your info. Firstly though. Your building is going to take time to stabalise.. not just the soil dumpling but the exteral walls. The moisture levels and the temperature in the dumplig below your insulation will have to settle into the new regime. Are you moving furniture about, changing rugs on the floor? Have you taken your socks off and just walked about in bare feet? Well technically yes. But in real life I've heated floor slabs by accident by a mile with flows in the pipes up to 60 -70C.. but the flooring was laid to compensate for this kind of accident as I have a gas boiler.. accidents do happen? and I'm after all a UFH philistine. Put it in.. lots of short loops for redundancy, make it buildable.. That plant room is a bit of a dream space wise.. you lucky sod! From the graph I think I can see that no flows go above 40C?

Obviously your flow rates & dt need looking, but also be very patient. I commissioned a new installation at the beginning of December that has very thick stone walls and had no heating for 3 months. Initially I thought I'd messed up the installation, but it's taken until the last week or so to find its balance. This is todays: This is what it looked like just after installation:

True but BH should be for both sexes of which there are only two biological ones. There was a Mens shed in Glasgow but funding was cut. I do think this thread is a revalation.. it's got folk talking. For all posting about the hard times you have gone through.. see if there was more of this then maybe you could have felt more supported, for many its too late but for folk starting out at least try it.. you have nothing to lose! You still have had to put in the hard graft, learn about building.. but maybe without the overstress.

It’s very unlikely the slab of the door is hollowed, it’s usually a solid slab of PIR with laminated timber either side. A smoke test will indicate where this is occurring. I do not suspect the slab but it can’t be ruled out. It’s usually down to adjustment being required as the door isn’t sealing correctly or it’s coming through the perimeter or through the glazing bead area, which is a possibility. .

This is a great point, I'm surprised also as insulated plasterboard is not tested for this, in fact many bodies have realised that this does not work!

Yep, I have 100s of meters of the stuff in my store and it's very good. If I'm doing large installation work, MLCP and the fittings are what I pick up in preference of both push-fit plastic and copper. However, if I'm having to run new CH pipework through existing floors and joists, plastic layflat push-fit pipe is my choice as it's easier to work in these kinds of situations than MLCP. But in other situations it's not as good because it expands much more at high temperatures and the clipping distances are silly short - like 300mm on the horizontal - and it doesn't self support, so it sags. With MLCP clipping distances are over 1m and it has inherent stiffness and memory so when you bend it, it stays bent. Plastic doesn't stay bent but has a very annoying memory (even the layflat PB type) The big disadvantage with MLCP is that you typically need an expensive press-fit tool along with expensive jaws for each size of pipe you use. But you can now get manual press tools that are a lot cheaper and some manufacturers now have compression fittings available - I've even seen a German manufacturer with a push-fit fitting for MLCP but no sign of it over here. With MLCP you can also get pre-insulated pipes which save time and effort where you need insulated runs for the installation. Your other advantage with both plastic and mlcp is that you can run continuous lengths and minimise joints throughout the installation. Copper is very expensive now, requires lots of joints, and if you have runs in existing floors, it's just a pain. Even if it is pretty when first installed and polished, this tarnishes over time. Overall, with the brands I use, MLCP actually comes in at better value than plastic, believe it or not, and it has slightly reduced installation time overall even in retrofit jobs. What's also nice about MLCP is that you can dry fit all your joints without fixing them and then when you're ready go through it all with the press tool. Another small thing, that can sometimes be really important is that the sealing of MLCP is on the inside of the pipe. On plastic, it's on the outside, so you have to be careful you haven't damaged the surface of the pipe. With MLCP this isn't a problem. Since I've used MLCP I haven't had a single leak on an installation. That's more than I can say for copper and solder! And there's no hot works or stinky soldering!!!

185m loop is very long, it will dominate the system pressure drop I removed glycol a year or so ago, system flow jumped from 18 to 22L/min. Add inhibitor and biocide to system, use only one manufacturer for both - do not mix as you may have chemical incompatibility issues.

@Jammy5 Three story building, advised fire rated cavity closers on all openings. Are they really required or will normal insulated cavity closers suffice? I'm going to have a go at this at a basic SE/ practical level which might help folk, no matter where you live in the UK, to get their head round this stuff a bit. I'll start with masonry cavity wall construction. Timber frame is much more complex and I've not covered it here. Please excuse my spelling / grammer as it's at the end of the day. But to start: 1/ One of the key concepts for fire design is that it can be split into two stages.. and that is where many folk on BH find it hard to get their head round things when looking at the regs. The following is just a rough summary, but for the newcomer I hope it gives you a bit of an insight. Stage one: (a) We give warning to the occupants of smoke, flame / heat..these are your smoke and heat detectors, this indicates you need to get out the house. (b) On taller houses we need to recognise that there may be disabled people, so we need things like protected stairs / floors. (c) All that happens, occupants are safe and the insurer's pick up the tab. Stage two: The fire service attend. They first ask.. is everyone out? Their next job is to not to protect your property, (as of course you are insured) it's to assess whether your burning house is going to set fire to the rest of the street and put other folks lives at risk. The regs are founded on the fire of London in 1666, I kid you not! https://www.london-fire.gov.uk/museum/london-fire-brigade-history-and-stories/fires-and-incidents-that-changed-history/the-great-fire-of-london/ Now the fire service then need to assess how close they can get to your house without it suddenly collapsing on them. And this is where the regs have in interest. A 3 story masonry house ( 2 floors + an attic often relies on the fact that the floors stabalise the higher walls for example. Now you may legitimately ask.. but there are many town houses like this.. why do I need to close my cavities..ok this is supposed to be fun so and humour is welcome! The fundamental difference is that on Victorian or earlier houses the walls were often solid. In the latter day with cavity masonry the cavities were closed off by returning the inner masonry leaf with a DPC against the outer leaf. But now we are wanting to stop that thermal bridge so the cavity is open at the window reveals and over the head. @Jammy5, now you could ask.. why can't I do this.. leave the cavity exposed as I'm filling the wall with insulation. Well the insulation could not be that fire proof. If it is you are going to have to prove that it is equivalent to a closed cavity with a proper and tested material. You'll struggle to to this and you'll also need a fire engineer.. they will likely tell you.. don't waste your money! You ask.. it seems ok to me. But to reinforce my point. Any cavity acts as a chimney and draws.. this excacerbates the development of fire. That fire can shoot up the cavity and compromise the floors etc that are providing lateral stability to the walls. If that happens the walls can fall on the fire brigade. Things like posi joists are designed to hold day to day working loads with some basic fire protection only, unless specifically detailed = money. Solid timbers are bit more forgiving.. provided the connections hold up. Now in the old days folk had few furnishings, there was no plastic, kids toys and appliances say. In a modern house what we call the "fire load" is much increased.. that is the stuff that maintains not just the duration of the fire but also it's intensity at times. In summary you can see why BC and designers are saying.. you need fire rated cavity closing.. and as a benchmark lets use / set that against the traditional way of closing off a cavity wall by returning the masonry. So hopefully that has given you all and understanding about what we are trying to do and it will let you see behind the curtain when looking at the regs in your particular part of the UK.

I started playing with the new heat pump on Sunday, first day I had since commissioning. Thought it would be fun to run it and heat up the slab so just set it going, I had not done any tuning or fiddling about so this is the out of the box operation and in the context of a very cold slab! So we are setting out to raise 70T of concrete 8 or so degrees. (Spoiler alert we still are not there yet.) Here is the first day as observed by the EMON heat meter system. Clearly a number of issues, two main ones - of course the experts I hope will see more. Firstly the delta T is huge 11-12 deg C for the most part, and really does not improve across the day. Secondly the flow rate is quite low - which may explain the high delta. So I did fiddle with the flow meters at lunch time but put them back to where they were as 5l/m was the design flow - rightly or wrongly and it didn't improve the delta T massively although, as you can see it did close to between 10-11. I checked the pump settings and it has a few of them PUMPf. PWM.OUT PE and PUMPf.PWM.IN.PE the former was at 5% and the latter at 15%. (PWM being Pulse Width Modulation and 50% being the duty cycle of the pulse so the motor could be wound up to 100% from there if needed. The room temperature is climbing and carries on doing so after turn off as the slab continues to give up heat to the space. (15.2 at turn off tops out at 16). That was Sunday, I turned it off at 23:00, remotely via the Huilian app, because I was worried about over heating the slab. COP across the day 4.3. I had the set point at 28 degrees, but as we shall see that was a very daft idea as it goes way beyond that, or so I thought! So by the end of Sunday I knew I had a flow problem but was not sure where that was coming from given that the pump appeared to be running at 5% PWM, the flow meters were all, just the three of them, showing 5l/m flows and the calibrated heat meter flow was showing just around 9l/m actually flowing. Something wrong somewhere. So it could be a flow restriction or a pump setting or something I was not understanding. Monday I just started it up again but this time I played with things a lot more in the AM. I spoke to the Heat Pump manufacturer just really confirmed what I already knew. I fitted a slab temperature sensor to give me some comfort I was not going to crack the slab, I had fitted the pockets at the slab pour so now I just stuffed the DS18B20 down the pipe 10m or so and connected to my data logger. (Turns out I could have connected it to the EMON heat meter system had I wished) So I now knew what my slab temperature was mid slab. (I could get the surface temperature via the IR camera.) As you can see the playing did not reveal much I cleaned the filter, tiny amount of clag in it, replaced it no improvement in flow and I adjusted the set point down to try and control the max temperature, as you can see it had no effect - I was obviously not controlling the set point I thought I was. The pulses you can see in the AM are me playing, observing, stopping, making an adjustment and restarting - nothing worked so I set everything back as it was. I looked at the Carell controller settings didn't find much. My setpoint was there but was not affecting anything. The Huilian App has loads more settings, you just have to find the one you want, or think you might want! Lunch time and I thought I would just work through all the settings on the Huilian app and see what was there. I found one which set either 'control on out' or 'control on in' it was set to 'in' I thought that cannot be right for my setup, I suppose you might do that in industrial situations but surely not here, I need to control on flow (out) as I want to limit the temperature of the water entering the slab, don't I? - so I toggled it. Now it looked like I could limit the flow temperature but as a tweaked that down all the happened was that the heat pump shut down hence the pulses after lunch. So I could control the upper limit but not close the delta T gap as if I tried it tripped. At about 15:00 I tried another trick asked the machine to heat the hot water. Let's see what 28mm pipe all the way did to the flow rate. You can see the result below: 19l/m so no restriction in that pat of the system, if that was the problem. So I had a cup of coffee at 3:15 (how very civilised) and took stock over the last M&S chocolate digestive! I thought, OK, the flow must be restricted or the pump settings are wrong. Let's remove all restriction in the UFH system by opening the flow meters to full bore. This did have an effect on the flow rate immediately. I could just about see the outer two flow meters in the bottom of the sight glass and the middle one is maxed out at 5l/m. We now have 12.2 l/m flow and control of the setpoint so the last few runs were done tweaking down the setpoint and I got to a delta T of 6.6 deg C which I thought was OK to head home with. Tuesday (today) could wait but there were still some thoughts to be had. We cannot open the flow any more, but there may be a restriction in the central loop, this is the longest at 185m, as I cannot get the flow meter float into the bottom of the glass, possibly air in there somewhere. The pump looks like it is just ticking over so I needed to know more about the pump and its control but my search on Monday had not revealed any setting for the pumps 'aggression' level! SO I decide that first thing tomorrow I would fit the pressure transducer to the UFH flow line and see just how hard the pump was actually working. Today dawned another day and I had some proper work to do for chunks of it so I left the heat pump off after fitting the pressure transducer. At Midday I started it all going and you can see the results below. First things first the pressure transducer revealed that the pump pressure was about 62 kPa (9 psi ). The pump has a max output of about 88 kPa (12.8psi) so there is some headroom in there to increase output somewhat if it wanted to, or could be forced to. So here, above, are the runs up to around 15:00 from 12:00 today. Looks like its making sense 2 defrosts and one 'breather' maybe not a short cycle because the pump stays running. But at the end you can see what looks like something else! here it is: Two short cycles and defrost over a couple of hours - should I like this - I think not. So where to next. My plan is to pressure flush the UFH loops again, remove all the Glycol (I know I didn't tell you about that but hey you would just have been putting everything down to that if I had told you earlier - didn't want to put it in but felt I needed to for cover over the XMAS break when the system was not running.) and pressure flush the rest of the system and fill it with one of the sludge removing chemicals in case there is any residue in the UFH loops, they have been filled with the previous Glycol since 2018 after all). Anyway if you have been reading this far and have any thoughts, observations, advice or even distain you might like to share I would love to hear it. The playground should you want any further voyeuristic opportunity!

I've also noticed that CIRC state that a 4 column 760x1310 has an output of 2400W; where as their 3 column 745x1310 has an output of 2403W. A smaller section with one less column having a greater(albeit slightly) output surely cannot be correct or am I missing something?

Adds a bit more context that the Cast iron radiator centre are claiming that their 745mm high 3 column section has greater output than the Stelrad 760mm high 4 column section. It just doesn't seem likely to me. The thing is that CIRC seem to be a lot less expensive than all other suppliers, even if in reality you need to size up from their performance tables. I just want to make sure I get genuine performance figures from them.

Mobile Self Build Shed with sarnies by @SteamyTea MBSS with @SteamyTea's sarnies.