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In my topic Modelling the "Chunk" Heating of a Passive Slab, I discussed how I used a heat flow model to predict how my MBC WarmSlab heated by UFH + Willis heater would perform. What I wanted to do in this post is to provide a “6 years on” retrospective of how the house and slab have performed as built based on actual data that I’ve logged during this period, and to provide some general conclusions. In this, I assumed 15 mm UFH pipework, but we actually used 16mm PEX-Al-PEX pipework with an internal diameter of ~13mm. At a nominal flow rate of 1 m/s, say, my three pipe loops in parallel have an aggregate flow rate of 0.4l/s or 1.4 m³/hr. At this flow, a 3kW (2.88 kW measured) heater will raise this stream temperature by 1.7 °C. However, when I commissioned the system, I found setting the Gunfoss manifold pump at a high setting (roughly equivalent to this flow rate) gave a very noticeable circulation noise in the adjacent toilet, so I tried the pump on its lower settings and found that the flow was almost inaudible on lowest one with in to return delta at the manifold still only about 5°C, so I stayed with this. The actual as measured delta for two loops of 4.9°C and the third slightly shorter loop of 4.1°C (close enough not to bother balancing the flows out). This corresponds to an actual flow nearer to 0.4 m/s or 0.56 m³/hr by volume. When scaled to adjust for this lower flow rate, the actual measured temperature profiles are pretty close to those modelled. I measured the actual Willis heater’s heat input as 2.88kW. In analysing the actual slab heating rates, I found that this raises the overall slab temperature by some 0.45 °C / hour after the initial start up. Plugging typical specific heat and density figures for the concrete, this is empirically equivalent to heating 25 tonne of concrete (Cmass = Ewillis/ΔT/SIconcrete = 2.88*3600/0.45/0.9 kg), or 10.6 m³ concrete by volume (23000/2400 m³). In the case where the Willis provides heating for the full 7 hour off-peak window (just over 20 kWh), at the end of this heating period the flow input to the slab is +9 °C above the initial slab temperature and the flow return is +4.4 °C. The temperature of the concrete immediately in contact with the pipe will follow this same gradient, with this temperature excess decaying radially away from the pipe centres. By the end of this heating window at the slab surface, there is barely a noticeable difference in the measured temperature of the floor above the out and return UFH pipe runs (perhaps 1°C). These temperatures and gradients are also comfortably within the reinforced concrete’s design parameters. As soon as the Willis is turned off, the internal temperature gradients start to flatten and any unevenness redistributed across the slab; the rebar reinforcing has a thermal conductivity 60 × that of concrete and this accelerates this, so that within an hour or so of the heating turning off, the overall slab is left about 3.1 °C warmer than at the heating start time (actually about 10% less than this, as the slab has already started to dump heat into airspace). In my original modelling topic, I mentioned that my passive slab has ~73m² of concrete 0.1m thick (~ 17½ tonne of concrete with another ~10 tonne of perimeter beams, cross bracing and steel rebar, with the UFH runs laid in 3 × ~100m long standard “doubled back” spirals (common to most UFH designs) on ~150mm centres and roughly 50 mm below the slab surface. (Actually only 75% of the slab is covered by the UFH runs, because of the need to avoid proximity to ring beams, partition walls, areas under fitted cupboard areas, etc..) Nonetheless, this empirical 25 tonne figure is still consistent with the total volumetric 27½ total estimate if we assume that the rebar is effective at spreading heat through the wider slab over this multiple hour timescale. In conclusion, based on this modelling and observation: First recall our context: our house is near passive in class with a lot of internal specific heat capacity. We only need about 1kW overall heater input in the coldest winter months to maintain overall heat balance, e.g. either by a resistive heater such as a Willis or an ASHP. IMO, there are two extreme approaches to house heating: (i) “agile” tracking of occupancy patterns so the living spaces are only heated when and where occupied; (ii) a 24×7 constant comfortable temperature everywhere within the living space. Our warm slab design is very much optimised for this second case, and our slab supplier did a good job in designing an UFH layout to match the slab characteristics to this The slab is covered in “doubled back” spirals with each loop using up a full 100m roll spaced on roughly 150 - 200 centres (and avoiding partition walls and cupboarded areas) so that each heats roughly 15 - 20 m² slab. In our case three loops were enough, and there was no advantage in trying to squeeze in a fourth. Our 3 loops will happily take up 3 kW heat input. Circulation speeds between ⅓ - 1 m/s seem to work well, with the only real difference being the slower the flow speed, the higher the delta between in and return temperatures. The slab does just as its trade name suggests: it can be treated as a huge low temperature thermal store, but because of its extremely high thermal inertia, one that is not rapidly responsive to heat input. In our case, a heat input of 3 kW input will only raise the slab temperature by 1°C over a couple of hours, and radiating 1kW will drop the slab by only 1°C over roughly six hours. In a true passive class house, one key to heating economy is the high level of thermal insulation coupled with a substantial internal heat capacity. Trying to drive such a house in an agile manner is a fruitless exercise, so forget the traditional having room-specific thermostat control; forget having traditional time-of-day heat profiles. It is far easier to treat all ground-floor rooms as a single thermal zone to be kept at a roughly constant temperature. In my view, using a resistive heating approach (such as a Wills heater) as well as an ASHP can both work well. In this second case something like the 5kW Panasonic Aquarea ASHP would be a good fit as it uses a modulated inverter compressor so it can heat the slab directly without needing a buffer tank. The choice is a trade-off between running costs vs. installation costs. In our case, switching from a Willis to this type of ASHP would save me about £600 p.a, in electricity cost, so I would really need to do the install for a net £ 3-4K to make the investment case feasible. However I would like to defer this discussion to a separate thread because there are other issues that such an approach would need to address.

I've had the same one for 45 years. Still think that I am a lucky chappy. 🤣

Here is a question for all you lucky lot who have completed you projects. At what stage can you move into a new build? I am thinking that as soon as the electrics and plumbing are (mainly) in and there is a working kitchen and bathroom then we would be perfectly happy to rough it for a while while and move in. However I bet it is not as simple as that. What legal requirements and inspections need to be passed? Perhaps all fire regs met, so all plaster board in place etc. The house will have 1 bedroom, bathroom, and open plan kitchen/lounge on one floor, so everything we would need. So could we move in when all that is done then continue working to complete the upstairs?

See we wanted to tinker, learn and do father and son stuff: Made a new base plate for the Anycubic. From this: Yes this: To this: Located the PSU outside the heated enclosure etc, etc. As I don't have a middle name I was considering Faff.

😂 YOU wanted to pay virca £200 and I delivered. @Thorfun's one is twice the price. A £5k Ultimaker S5 is the mutts nuts. Dual extruder to so you could print supports in say PVA (yes PVA glue in filament form) and soak them off in water once printing is completed. Auto bed levelling is fine if you can't use feeler gauges! Honestly that Ender is a great starter printer. Cabinet? Make your own like we have:

I like "Yacht rigging" wire for an almost invisible balustrade, as long as BC are not involved.

Sure it was jtm I got them from or even eBay !

I have used these though tbh I prefer the brass version

I'm actually a 3D technician... I have an Ultimaker S5 and a Form 3 for my resin stuff. If you're going to do stuff that's in the sun then PLA will warp to sh!t as it's glass transition temperature is really low. For example a pla cup holder in your car will not be holding the cup after a summers day... you'd need to use ABS which would be nigh on impossible without an enclosure if you need to get it accurate. You could build a box over it, I did that previously with an old Ultimaker and it worked ok. Software wise I use Rhino and Fusion. Learning curve might be tough if you haven't used them before. SketchUp does work as you can export to .stl but you'll find anything round comes out basically a series of flat sides joined together.

oh wait. you mean this bit of rubber, right? sorry. it's been a long day

The link I pm'd you does it all for you. Just drag the pick points for length, width etc and it'll produce an stl file. Put that into Cura or whatever slicing program to create the G-code for the printer. Merry Christmas Mrs Pocster!

Sounds like his onlyfans site.

PLA easiest to print, the most common etc. Then PETG. ABS and ASA really need an enclosure as a tendency to warp, toxuc fumes etc. TPU if you want to print any rubber products ☺️

Wrong forum. Head over to the MIG welding forum. (I'll apologise to them beforehand). Creality Ender 3 V2 maybe would get you started. Loads of support and upgradeable. At this price just buy it...now: https://store.creality.com/uk/products/ender-3-v2-3d-printer?utm_source=googleads&gad=1&gclid=CjwKCAjwyY6pBhA9EiwAMzmfwTOrWf7HGZ8tMiYGyk5sF1qDnIEAjL4DOs4L82VLj6FjDOAvezh7sBoCKUIQAvD_BwE No you can't colour match like that. Plastic primer and paint works.

See page 2:

The Hep2o tap connector is what I use on these, and the spare / alternative ‘square’ washer goes in the bin. Sorry to be late to the party, just crazy busy atm.

A pretty good rule of thumb. Passivhaus heating specs are designed around around heating via the MVHR system. The 10W per m2 value, specified for the max heating requirement, is the maximum value of heat transfer you can provide to the house when the the MVHR is providing 0.3 ACH. Any more than that the air smells burnt. So if you want to provide 60W per m2, you will need a minimum air flow of 6 x 0.3 or 1.8 ACH, based on your house volume. So 93m2 X 2.4 X 1.8, so 400m3/h. If you want to provide 10kW you are looking at the best part of 800m3/h or around 3.6 ACH. That's a lot of air blowing around.

No it’s tapered the wrong way, it should be tapered inside not outside

I have some Sonos stuff. The amp gets very hot, so I suspect uses a fair bit of juice. Startup from power on is painfully slow. They also lose signal every now and then and don't always group properly, even though they all have CAT5 wiring. I don't rate it and was really annoyed when they wrote to suggest they were retiring some models. Bet they will be wanting a subscription next. I have an Arcam amp and it is still good 20 years on.

Just looked into this and even gave Lithe a call (very helpful) The bluetooth versions of these look absolutely perfect for me! Thanks @crispy_wafer

I see a lot of raised floor systems sat on adjustable metal feet like this. Instead of being screwed down they bond the feet to the concrete floors with a "puddle" of adhesive: https://www.accessflooringshop.co.uk/products/mfh-007-steel-adjustable-pedestal-support-psa-90-mm-140-mm.html?gclid=EAIaIQobChMIkJzm2ProgQMVV9XtCh3MywAzEAQYAyABEgLpofD_BwE https://www.accessflooringshop.co.uk/products/pedestal-adhesive-voc-free-single-part-9kg-mpa-003.html

i don't really remember! i'm pretty sure i bought as and when i needed it from SF. i found them the cheapest on hep2o stuff and i have one just over 5 minutes from my house. so i am constantly popping there when i've forgotten something. for long rolls of hep2o it's often collect next day so you do need some kind of planning. i have purchased some bits from JTM on @Pocster's recommendation but have since looked after they were bought out by PlumbingSuperstore and their prices seem not as competitive now. Plus, a local Screwfix will take parts back for a refund with no questions asked and that's very beneficial when you don't know what you're doing and buy every part you think you might need just in case! 🤣

if it was mine i would use slurry primer on the copings. As for fixings we have done dozens of these as per spec drilled through the DPC and never had a problem. A small squirt of silicone may help.

This is true. It's like so many things it is easier and quicker to do it correctly. I knew it was wrong but when you are standing there arguing with a tradesman who does this day in day out it infuriates me. It cost them about 3 hrs to rectify this one and the other house hadn't got the joists fitted but still cost them a couple of hours to alter. It would have taken them 10 minutes to get the ply cut and drilled before placing it behind the timbers. Thanks everyone for your input. My floors are complete and we power on with the next lift of brickwork.

Fair enough reason . Personally I hate any pipe work anywhere visible .

and here's a Pegler Tectite version https://www.toolstation.com/pegler-yorkshire-tectite-sprint-wallplate-elbow/p26550 afaik, Pegler are a quality push fit copper manufacturer and i have a Toolstation 5 minutes from my house. could pick some up on my way home from work.

think i'm going to have to do a lot more research on the difference between flat and tapered as i'm confused and can't tell the difference.

Pretty sure they used to do a brass version, as I was looking the other week. I'm not sure I have too much confidence in anything that has plastic threads. As much as we don't want too many hidden connections I think I'll do the same and convert to copper.

these https://www.screwfix.com/p/hep2o-plastic-push-fit-adapting-male-coupler-22mm-x-3-4/5653f and then a reducer down to 15mm https://www.screwfix.com/p/hep2o-plastic-push-fit-stem-coupler-f-15mm-x-m-22mm/8401f

Mortar under the dpc, mortar above the dpc. A 20kg coping stone isn't going anywhere.

We had exact same issue with an island unit 1800x1200, also with quartz worktop. No nails was my friend, to fix the plastic legs to the floor. The island hasn’t moved. Frankly it was heavy enough that it probably wouldn’t have moved anyway. Your peninsular will additionally be braced by the the worktop. if still worried other option would be to construct a timber underneath, no nailed to floor and bottom of cabinets. no nailed legs will be fine though unless your units / legs are poor quality/wobbly.

A neighbour was advised by the company that fitted his Composite Front Door not to have a dark colour as the front of the house gets full sun for most of the morning....due to fading of colour and heat expansion. However he chose to ignore the advice at his own risk....the door does stick in the frame during high temperatures and after 4 or 5 years the dark grey colour (almost black) is beginning to fade a little. From memory I think the door make was:- Door-Stop International. A friend had an Endurance composite door fiited as the brochure/website spec seemed to suggest it was less likely to warp than the similar Solidor composite door due to the different method of construction. It has not warped out of tolerance so far but the outer shell cracked after 2 years for no reason, the company that installed it had gone out of business but Endurance did eventually agree to replace it under their warranty.

“The reason for the two washers is to cover all types of tap tails, some have a square end (flat washer) others have a tapered internal bore (tapered washer).”

Overall (average between all windows/doors), no. You have to take it in context. What is the PHPP saying, what is your heating demand, what is you air exchange etc. A window is tested at 1230w x 1480h to obtain the results in the certificate, smaller windows are generally a higher Uw than that tested, larger will generally be lower (more glass than frame, is better than more frame less glass). I wouldn't say they are useless, as there are so many other factors to consider.

@FuerteStu, with this type of house, yes you can put a manual thermostat on the wall, but don't connect it to anything! Let's say your better half is feeling a bit chilly and cranks the stat up by 5° just before going to bed. Well at ½°C / hr, it will be hours before you even notice any difference; by the time you do, the slab will be too hot and the rooms will carry getting warmer for hours, and there will be nothing that you can do about it short of throwing windows and doors open. An analogy: think of a canal boat vs. a little skiff with outboard. The first is far more fuel efficient per tonne of payload carried, whilst the second is "agile"; however, canal boat can't respond to the tiller the same way that the skiff does. We just set our house a to 22.4 °C average setpoint. Because our heating is done overnight, there is a time-of-day ripple of ±½°C on this: never too hot and never too cold, so always comfortable. Last winter I dropped this to 21 °C to do my bit on fuel economy, but I also bought a cheap free-standing oil-filled radiator and put it in our living room. 20 mins on a low setting when we felt cold was enough to turn the room toasty. Having something like this would give your wife the control that she likes over her sitting space.

@SteamyTea Nick, the more I think about your comment, the more I like it. 🤩 Just think of a warm slab as a 20 tonne (or whatever yours is) storage heater under your feet. Don't worry out the internals; it just works. You can stick 1,2,3, ... kW into it, and it will soak up the energy, and then slowly radiate the heat back into the internal airspace. I feel another modelling exercise and post coming on.

I'll offer the contrary view that a short-term imbalance won't harm anything, and cooking may well be excess heat that then causes the rest of the house to overwarm. We've two normal extract points at the "cooking" end of the kitchen area and these deal with day-to-day moisture and odours. But I also have a sizeable extractor over the cooker which can separately deal with the big heat, smell, and grease from rapid wok cooking. At other times it's sealed off by a gravity flap in the duct.

No I don't know. Cheap seats / skip diver here.

It actually looks like really good kit, I did see it on BPCs website but dismissed it was it was similarly priced to the Zehnder and Airflow stuff which are more recognised. I spend hours procrastinating over things like only to fit it and never give it a second thought once it’s in.

With your budget it's got to be a Bambu Lab X1. Super fast.

what rubber?!

do i undo and take off the Loctite 55 tape? don't want @joe90 to accuse me of being a bodge again. 🤣

Hmmm...I fitted Pegler ball valve isolators either side of my mag filter on the boiler. One or both are letting by.

@crispy_wafer even cheaper at B&Q! https://www.diy.com/departments/pegler-yorkshire-tectite-push-fit-90-wallplate-pipe-elbow-dia-15mm-dia-12-7mm-15mm/5022050670687_BQ.prd

that's just old age

Probably not, just smacks of “bodge” to me

nope. not finished yet. maybe one day though ask me again in about 6 months. 🤣

I live alone, so put up with the ripples. I suspect if I had my own wife, I would be warm with rage most of the time. Someone else's wife, warm with passion maybe.