Nickfromwales

Thanks for that, great bit of supporting info and clarifies things for sure I guess that was the hoo-ha over that back then, more about the multiples of (unnecessary) additional MC4 connectors then being inside the dwelling vs the optimisers themselves. 👍 Good point about the rotary isolators too, but most of these we put in the attic spaces immediately off the roof (usually some type of plant or equipment ends up in there also) and the plant rooms. I ALWAYS fit a (multi-sensor) smoke detector in any space that's got any type of equipment / plant etc in it, so that's as good / safe as it can be I guess.

I’m a mushy pea 👍. That couple were preparing the new house to accept their furniture out of long term storage. They just wanted the house ‘cold’ as they were busying about the place and in coveralls. Nothing wasted there as the 14kWp of solar / batteries > heat pump meant an average cost of heating at < 1.6p/kWh, prob less now that octopus is in the picture, so they could turn it on and off willy-nilly without pooping the bed, but now they’re moved in the heating is on at one constant temperature and comfortable 24/7 without other control or manipulation. Point being that the heat gets slowly released over a long period of time, with UFH in the insulated raft, which means the heat from the floor is pretty much undetectable. Tres bien. There are many ways to skin that poor old cat, so your method would work, of course it would, just I have done loads like that and now a load like this, and I prefer ‘this’, so do the clients and their opinion is where I base my feedback upon. We do have to self-level a lot of slabs, but MBC got the last one within 8mm over 140m2, so almost zero levelling needing doing on that one, just a double bed of tile adhesive vs bed and butter. 100% get that, and that’s why my replies are so detailed / objectionable. Trust me, it works better, and that’s my 2 cents. As above, other methodology will also skin the cat. Defo, and about spot on for what I’ve seen. The force is strong with you. But would you like to spend £10k on pumping water out of your boat, or spend £10k once getting the hole plugged permanently? Either option will cost you £10k.

Trying to ‘change the temp’ morning / evening in a decent ‘passiv level’ dwelling just doesn’t happen. A steed can react quickly because it’s heated hotter for shorter periods, but why does it have to react? Why would you tolerate the hysteresis of cool > hot > cool > hot when you can have comfort > comfort > more comfort 🫡. If you lit a fire in any one room, that room would instantly overheat and become unbearable, poor analogy in this discussion imo. In a PH you should never be void of heat, therefore you should not need more of it here or there. I turned the heating off on a Monday, on one project with a big slab like is mentioned here, and the client rang me to complain that they were still sweating their arses off on the Wednesday, (whilst cleaning, sanding and decorating etc), asking why I hadn’t done as they asked? I said go feel the HP pipes, they said “ooh, they’re stone cold!”. Yes says I, and it was turned off Monday evening when I left to go back home. Monday saw it at 20.5°, and it was 17.8° on the Wednesday, in the winter. With the MVHR running. They wanted the 15-16° that the house settled to without heating. I said you’ll have to wait another 24 hrs +. These things just don’t yo-yo heat up and down morning / evening, so having weather comp attempt to manipulate this twice or more a day just seems a waste of effort. Why not just have one happy temp per 24hrs? But you ARE saying to have a ‘heavy duty’ slab, (*150-175mm + 60mm of screed = a lot of mass*), just you suggest it should go under the Insulaton 😵‍💫 I am saying you don’t need to suffer a buffoon to over spec over size and cost you more than is actually necessary. If someone driving this is involved from the get go there’s a bunch of value engineering that can be added in, so with a machine and groundworks contractors around you it’s easy to achieve great things, if someone’s there to instruct them, and then such things can be done far more economically. If it costs more overall, but is a better outcome, then the client has time to decide that when we budget the project out at the concept/ pre-construction phase . You can drive to work in a Ferrari or a fiesta, the client decides who drives what and why. And constructional rafts don’t get covered? Only if the client specifies polished concrete is this ever a consideration or concern afaik. This had only ever been raised as a concern with my ICF guy, who asked how he was supposed to fix the shoring systems for the walls; this was usually fixed down to the slab by drilling and concrete screwing etc, something you can’t do if the UFH pipes are 30 or 40mm under TOC. We resolved this by putting timber down with shorter fixings, and fixing shoring to that. Apart from all that we’re 2 peas in a pod mate 🙂

Ah, yes, more zooming-in for me from now on lol. It wouldn’t surprise me if the threaded bar isn’t just wound into a slightly undersized pilot hole, maybe with a bit of mastic.

All to be decided at the outset I imagine? Insulted raft is always my first choice, after that a strip foundation with passive levels of insulation in the floating infills between strips, then block & beam I guess (as long as it’s got at least 175mm of insulation and the bare b&b has been thoroughly grouted and sealed to prevent air rising up through it. Raft is very much worth the effort afaic, and they can show go down in conjunction with piles on difficult clays / trees nearby etc. 👌. Odd you think that tbh, I think they’re an excellent choice, and have many more merits. Heating a thinner screed etc, over insulation over a slab, doesn’t allow much heat to be retained so more sporadic heat needs putting in during winter. I much prefer the idea of a massive storage heater running 24/7 ‘long & low’ and the feedback from clients says a lot. The floor seems cold / cool to the touch but the whole house is a constant comfortable 19.5/20.5°C. Much harder to achieve the same with a screed tbh, as these tend to over and under shoot the stat set points.

I just don’t like the gaps, if there’s no voids then nothing can be interstitial. Foil stuck to foil of board, if you use PIR, and across the tops of the joists would be my go to. If you’re filling with mineral wool, seems to be plenty good enough and much less of a PITA, then the membrane as you show will suffice. Just seems a total ballache and a significant undertaking? No probs is you’re DIY’ing it, just your own time / effort. The membrane ‘hammock’ will be fine on its own, I doubt there’s actually any need for the OSB, if using wool or fibreboard type stuff. Just push fit it gently and you’re done, using the wool at the bottom to absorb undulations and the fixed dimension stuff up top. Or, this is belt & braces: 👌

These bad boys

Best to check if that’s the overall thickness, but yes, I’d persuade them with scores of examples of how this has been done elsewhere, successfully; the caveat is that I don’t know exactly the ground conditions at this time, so that will be key to the development of a foundation design and any further ‘argument’ here from me. If the ground is difficult or you’re going over made up ground / an infilled old swimming pool etc, then the maths all change really quickly! Yup. On the project with the thick slab I mentioned I had to work with said buffoon and his SE to change the pins / stirrups etc, eventually settling on an agreement for the client to bear the cost of cranking the pins on site. The reason for this is as you say, adding all this together, and then having to preserve adequate concrete cover over the top of the UFH pipes. On a computer screen it all looks simple and straightforward, but when you’ve done a good few of these you soon realise that overlapping mesh sheets, bars etc soon leaves you way too high up (near to TOC). I pushed on that one as the SE wanted the giant slab and then the UFH in another 75mm of dry screed on top of that!?! 😯. I said “no” to that, but the builder was clearly a bit of a bully and tried to get me thrown off the job in retaliation. The clients wife pulled me to one side and asked if she should sack the architect and SE, lol, I said no we’ll work with them and I’ll just keep pushing back where appropriate. Saved the client around £10k in unnecessary concrete volume / screed costs etc, plus having to dig further down to get TOC back to the original house datum (infill project so ridge height couldn’t change by even an inch). House got done, builder went on his merry way the second he’d fulfilled his foundation and frame / roof program and framing, and has since gone bust spectacularly. Too many people out there who can’t admit when they’re out of their depth, or, most annoyingly, are simply too set in their ways or too stubborn to ask for support / look at solutions; mostly because they see downtime as a loss and want the easiest route to the next payment. Better to do what I do, eg explain to the client that there are possibilities to explore for a better outcome / to reduce costs and time, but the time to discuss it needs to be paid for. Most agree and see the value, but some are just too worried about upsetting the apple cart and just choose to ‘accept it’. 🤷‍♂️

......🤞 indeed....

There's over 20k members on here, beware of what you ask for. The postage to you would then be around £4k

You can certainly get the stuff but it's pert not pex, and is a bit less 'hardy' IMO. Ok, less gin and more tonic needed here "Testing, testing, 1,2,3. Can you hear me at the back?" lol. The UFH pipes only emerge from the floor, for less than 1000mm in most instances, and then get made off to the manifold. There's nothing to change / fix / visit the van for here! Maintenance plumbers won't ever be changing that pipework?? For completeness, yes, don't use the same non-standard pipe for all the domestic internal plumbing of the hot & cold feeds, 15mm all the way, but NOT in the MLC as that's just overkill; and a PITA to pull in single-handed, ask me how I know. That was from a Scandinavian (IIRC) company, imported on a design / supply / install basis. I've done 16mm / 17mm / 19mm / 20mm and so on, Vogel & Noot were 17mm IIRC, so it's no matter tbf as it's going under the floor to never be seen again "Thank you, and good night" 🤗

Amen. 🙏

If you're investing time and money in a 'quality' low energy / high performance dwelling, then you need to be staying there for at least 15-20 years for the ROI. Or you write that off and hope it will serve you well for the marketability when / if you move on again.

...the whole reason people self build, me old china mug

Oi, you! Foil tape is plenty good enough here, when installed by anyone non-orangutan-like. I go over the stud first, 100mm tape centred to overlap the adjoining material, then do another 2 runs from the centre of the joist outwards left & right or up & down, so effectively tripled up where it counts. AT tape is OTT here IMHO, but it is more forgiving if the orangutan hasn't kept the different building materials all flush finished with each other. Foil is cheaper than shoplifting, so putting the 3 layers on is quick and simple without hurting the wallet.

It's impossible to set this into someones brain. You're in for a treat, I assure you. I have to do it for every single client and it just never gets old (speaking to them after they've moved in and how they'd NEVER consider any other type of home ever again) "RESULT!".

What times supper, I'm starved?

Might be a good idea to get the plumber to T off those and kick the pipes back to the wall, terminating them in 2x isolation valves, even if you don't use them. Means not having to drain the whole system down for the sake of £60 worth of bits, and you'd need the isolations in the downstream install if you did proceed anyways, for service and maintenance or repair etc.

I'd invest in less invasive and more passive mitigation tbh, like the inline units, but I don't know the finite details of your build, or you, so cannot really add much more here Running redundant stuff is wise, that should cover your arse just in case

Depends on the remit from the client, as no two instances are ever the same. Further depends on whether there's a very good cold mains water supply, with plenty of l/p/m dynamic flow rate. As I've said elsewhere, I design and install to the requirement. I've always done a pipe / valve to each single feed to each outlet / appliance, as that's just how I prefer to do these things, as this is defo the better solution for equal flow / pressure to every outlet (comes mostly into play when multiples of outlets are being used simultaneously). One client wanted to have 4 people showering in different en suites, all at the same time, and also said there's a likelihood that will be happening whilst the kitchen sink or cloak WC was also possibly going to be used by other occupants, so I went 'nuts' on that one. Most UK homes have a scabby pair of 15mm hot and cold pipes run right through the house with all the outlets T'd off willy-nilly. They seem to manage so best to take with a pinch of salt sometimes, but also know it is fine to dial this back if it's just unnecessarily adding to cost with no real benefit.

Yes, I noted that, and I use Pex - Al with the aluminium liner as part of the MLC construction, hard as nails, you really have to pretty much maliciously damage it tbh, but still stops one from sleeping well in the hotel bed if done 'that way'. Done a couple, and it went well, but I insisted on being there and also having the pressure up to around 4bar for those ones. Conversely, on others, I rarely pressure test as the pipe is just too good. MBC don't test iirc, and they're putting this stuff in by the multiples of km's per month. I've heard of only one failure since 2016!! That client isolated one loop, and then all was fine (ish), and then said they couldn't really notice it wasn't heated for that part of the slab The joy of a passive raft and a well insulated, airtight house with MVHR!!

I did one that had a massively over-engineered slab (I think I talked the buffoon in charge down from nearly 300mm with a screed for the UFH down to 230 with the heating pipes inboard of the raft). Bonkers. This was a 1.5 storey ICF build, timber floors. The client has a 7kW heat-pump running UFH with 120mm c's; the idea of the tighter laid pipe loops is so that they can use the additional water volume and additional cross sectional area of pipe > concrete (surface contact area) to quickly chunk heat into the slab during pockets of cheap electricity, but more importantly to allow cooling to be done at a higher temp (to stay WELL away from the dewpoint). Is in and working well, but it's a huge thing to get to a set temp. Once it's there, it's very comfortable, just needs the stat to have the aforementioned tight hysteresis to prevent unwanted under / over shoot. Seriously consider the extra volume of pipe & water as it can reduce or negate the buffer tank

Nice job. I very much like the idea (simplicity) of installing the mesh atop the UFH pipes, as the UFH goes down very quickly and simply, just it pains me to trust the groundworkers to not damage the pipes during the steel installation.... If one company is doing the lot then it's managed and there should be some quality control and robustness of their procedures, but if left to Tom > Dick > Harry then I'll always prefer leaving the meat get off site and then I install over the top before the concrete goes down.

I have to say, the Illbruck FM330 stuff is very good, a totally different beast to the regular build-shed foams. I've had the pain benefit of being around some very elongated full new builds from day 1 to day Z (thanks to Covid) and have used this stuff for many different applications, from fixing things, general sealing, through to airtightness work and more; I've used it thick & thin! I've then been around it for anywhere up to a year, sometimes more at the plant rooms etc, after it was first squirted in, and I cannot recall any notable shrinkage with this stuff. I do make a point of spraying a mist of water, if adverse I'll do a 50/50 water/PVA mix, and this does help the curing process no end. It's also massively hardier than regular foam, when poked / scraped / cut into etc. Yup, I install the PIR with angled cuts, so there is friction for fitting, and a gap to get some foam into. Gaps aren't the killer here though, addressing airflow up between the boards is, hence me saying to foil tape over the tops of the joists from PIR board to PIR board (foil backed obvs) as the VCL.

Great, IF it's a 1 bedroom house yes? Factor in some redundant space for one, install cables and plumbing in abeyance, then add it later if needed?