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Which is inside a semi infinite heat sink. Sounds like you actually do a room by room calculation, but then fudge it at the end.

1,000,000% It'll be the best time/effort/money you spend (IMHO). I promote airtightness over insulation every day; with a house that has MVHR obvs.

Not really, and I've been installing for 30+ years. Just look at getting more pipe in than you will be recommended by the "knee-jerk" posse, and install at 100mm centres on an 'inverted loop' pattern. This will promote better W/m2 with the lowest possible flow temps. This takes heated water to the centre of the room quicker, vs 'serpentine'. Insulation will be the biggest issue, and the more you put in, the less heat the floor will require to do the same job.

Been there, got the no UFH T shirt. We didn't do it because our plumbers wanted an arm and a leg and I was stubbornly of the opinion that passive houses don't need heating. (Untrue, they only need very little heating) If it isn't scandalously expensive, stick in few loops of UFH to allow you to heat the house like @TerryE by banking cheap tariff electricity. Passive class houses are like those old Soviet jets, they'll run on anything. A couple of fan heaters, a stove, A2AHP, a brace of energetic children/dogs , whatever will heat the house. Don't over complicate it with zones etc. UFH mats under the tiles for the bathrooms too.

If the space between the OSB is *completely* unventilated the EPS may be doing something. If it is at all ventilated - intentionally or unintentionally - then at best the effect of the EPS may be lessened and at worst, negated. Similar applies if there is any air movement in the masonry cavity. Mineral wool may help 'still' any air movement a bit, but bonded EPS beads would be better. It would be good to do a condensation risk assessment. I don't do them, but someone on here may show you how to use Ubakus.

its hard to see exactly what he is doing in the video as his camera is not all ways on his work. But it would appear he takes a spare strand of the wire and makes up his own square section by threading the wire in as he goes along

Overall heat loss primarily, and then part O ( and common sense before it ) for overheat. TBF, it varies very differently house to house, with a live survey and some grey matter applied accordingly, and then you can get a proper handle on which 'ends/sides' of the house will need some better thought and strategizing. I dislike fudge, as installed systems are expensive to amend retrospectively. Not had to do that, yet, 🤞

Do the rooms, spaces etc, add it altogether, and utilise the average. Then look at the dwelling fabric / solar gain, and so on, and include any other known peripherals to the mix. Rooms and spaces are simply boxes within a defined global "heated and (sometimes) airtight envelope", and IMHO what happens within that divisible space is very difficult/near impossible to differentiate.

Have you done a condensation risk analysis. Generally more insulation is better, but below U = 0.1, there is not a great deal to be gained.

So how do you size the thermal emitters? And take into account differing window sizes.

I've stopped doing room by room, you just end up chasing your M&E tail tbh. Most rooms achieve an ambient, regardless, and rooms with lower temps attract heat from adjoining spaces, so seems a more pragmatic approach in most instances to just copy/paste/calculate.

Woodfiber boards don't need any membrane in some applications so the carpenters are over killing a little. Their understanding may be based on some older membrane types which demanded a ventilated layer at both sides as the weren't of sufficiently low Sd value. But for me in this situation: Rafters with insulation Woodfiber. Membrane (taped at joints) Battens Counter battens Tiles.

I would say Aerobarrier is likely to be very effective. If you use the search function on here there's a couple of people who have used it. It won't fix bad windows and doors however and if you have designed holes like badly fitted stoves it can't fix that either. I wouldn't get too caught up with ACH numbers and MVHR effectiveness, as it's largely an academic argument about energy recovery on a windy day. On a calm day it'll perform much the same in any house. You'll get the comfort and benefits regardless. The only situation I wouldn't think it's worth it is if you need to do mega destruction of a perfectly ok house to install, as the alternative of dDCV is so cheap and easy.

Depends how poor the finish is on the original concrete. you can use 25mm of polystyrene insulation on top of the concrete and below the damp proof membrane to take out any lump n bumps or sharp areas. if it’s really bad a few bags of cheap self leveling compound to take out the worst bits.

7.3N Aircrete blocks will be fine. Don't shotfire the soleplate into them.

Yes. They use a different form. https://www.gov.uk/government/publications/registered-titles-part-transfer-tp1

And as my experiments have revealed, the third best visual effect after 1) a real log fire, and 2) a spirit burner in a woodburner is 3) an iPad propped up behind the glass with a vid of a log fire burning. Still way better than the fake electric jobbies we looked at.

This might sound a bit daft, but given the recent news that OfWat is apparently allowing water companies to hike bills, I started to wonder whether instead of getting a mains connection which is around 3.5k, I instead pay the monies now and get a bore hole installed. Yes, it's an expensive initial outlay, but you could say exactly the same about solar panels. The wife is notorious for high water usage and no matter how much nagging, she's not going to change. At least with a borehole, you are not at the mercy of the PLC water company.

A doctor I know who worked in Africa told me the locals there could not believe that in England we sh1t in drinking water 🙄

Methane? What do your drawings state? Is you house wrap certified for roofing applications? Suspect the joiners are wrong.

I'm pretty sure they're just on/off style (and it takes a minute say to switch from one state to the other). That is, heat the wax, or don't heat the wax. https://en.wikipedia.org/wiki/Wax_motor https://waxmotor.com/blogs/introduction-to-thermal-actuator

Have you thermally modelled your new build. If not, now is the time to do it. You need to do a room by room analysis, not just an overall loss calculation. Also remember that, via conduction, thermal energy can travel downwards/sideways though the floor, so you need bare that in mind.

Yes, I think this is probably the extent of the information which Thames Water have. It was the same for me so I got a CCTV drain survey done to find out exactly what I had on my plot. It was only £250 + VAT and they provided a written report with a map showing where the drains are and the CCTV files. It's been invaluable information. Good value, maybe because they expect to get remedial work from what they find - their assessment of what they found was quite pessimistic.

If you have choice of finding spaces for radiators or everything hidden, I would go everything hidden. Plus lower flow temperature for better efficiency. Wet UFH everywhere, plus you could add electric (in addition) in ensuite and bathroom, if you want if hot underfoot, and for off season heating. Add electric towel rads for bathrooms either way. You don't need much piping in the floor for UFH to work (if well insulated), we are on a loose 300mm pipe centre and it works fine

Wet UFH everytime Worst case is you don't need it, but it's relatively cheap to install the pipes anyway during build vs virtually impossible to add them when you find out you should have done later. This logic holds regardless of sap, phpp etc.

Stand down; I've found a local fabricator who'll make the bracket for £200 with angles/measurements. If anyone's interested, it's Toomers in Salisbury.

You might be. How are you going to deal with waste? I pay £2.0714/m2 for water, plus £0.197/day for water £3.3206/m3 x .95, plus £0.167/day for waste.

Use a rainwater collection system for flushing toilets and watering garden. That'll slash you mains water usage. A borehole will have annual operating costs, and you take 100% of the risk if something goes wrong. It really is crazy the amount of effort that goes into treating water, for 90% not to be used for potable purposes.

We went for borehole for various reasons. We pay way less than normal water. Think we paid about £140 for the annual service. The steriliser is just a light in a tube, bulb gets replaced as part of the service once per yearq. Our council tax water element of the charges is £500 plus waste water of £560.

The cost of keeping the borehole / pumps / sterilizing will outweigh any water bill.

Again... keep you head up and stick with it... more often than not things suddenly get resolved. BC have a "process" and "holidays". Post when you feel able and all the best. Offer of PM ing me still stands.

Your design team should be able to sort this out. Cut them a bit of slack as dealing with BC can be like chasing cats. Some BC's don't work to the same professional standards that can be expected in normal professional life.

Well said GP. Man doth not live by U value alone.

What has happened to romance! Too many folk thinking about cost and practicalities of stuff on BH and maybe not seeing the whole picture. You can't beat a real fire / stove. A home is not a home without compromise between needs and wants. Now I bet a lot of folk have an expensive car outside that is depreciating fast.. cf with making a home with a bit of comfort and luxury. We are not building a sanitised office! We have a wood burning stove in a room and sometimes I shut the door, settle my self down in front of it with a large kebab.. that stinks, watch telly and.. be selfish. Yes I know the flue cause probelms with air tightness but in the morning the air is purged.. I'm forgiven. Self building is about compromise.

No wonder, that is a big but not unexpected list of comments. However at times a game is played at your expense. BC folk get holidays and are adept at kicking the can down the road. It can be fearful for the public! I do this as a day job..make submission to BC.. lets leave it at that. Don't throw in the towel at the moment. From experience a lot of these things can often be resolvedvery easily. Your Architect should know how to navigate this common problem. If you feel you want a second and broad opinion then post all of the info and drawings you have on BH but sanitise it so you can't be identified. By all I MEAN all as there are folk that will dedicate time to helping you, some of us do this as a day job so you'll get probono professional advice. Now once you resubmit there is a way of wording your response where you can back BC into a corner where they need to talk to you face to face or on the phone. You turn the tables on them.. again this is part of the game. Keep you head up and forget about giving in. If you get stuck PM me, I can spend 15 min on the phone with you if you need a bit of probono advice and hopefully lift you spirits.

On Monday the internal structural walls are up to the top of the ICF walls and are tied in to the ICF walls. The windows and doorways have extra bracing ready for the pour. Nobody on site on Tuesday it rains all day and no more prep is needed before the pour. Wednesday starts with the last minute checks ready for the pour. The concrete pump arrives on site at 12pm it takes 30 minutes to set up before the first concrete pours out. We have 4 builders onsite plus the concrete pump operator. The concrete is poured into the ICF on all four walls in stages twice round and its up-to window cill height, the ICF cills are pushed into the wet concrete and the wood boards replaced so that the pour can continue higher. A poker is used to vibrate the concrete to ensure the concrete fills the ICF without any voids. At 4pm the pour is finished and the cleanup can start. The pump driver tests out our hammer head turn which was required by BC as we are so far from the road and Fire Engines are not allowed to reverse more than 20m. I think this proves our access works and it’s all down to the driver of the vehicles, the pump driver is great if only all delivery drivers are like this. The gables will be completed later so the concrete has rebar inserted, the other two walls are trowelled level. By the end of the week one gable is braced and poured. Total man days of labour week 6 is 17 days.

We put half our UFH in the concrete slab and tbh this was far less of a pain to do than the other half we decided to lay on top of the slab and screed over. Our slab was 200mm and had two layers of rebar mesh (actually four, two at the bottom of the slab and two at the top), I tied the UFH pipes to the bottom layers of mesh then put the top rebar layers on, separated by rebar deckchairs. I did this all myself so could make absolutely sure no pipes were damaged. Seems to have worked well.

So at that thickness you will have most likely two layers of rebar. They are usually 50mm of more below the surface. So zip tie at 200mm centres to rebar. Nothing will float up. You have two opinions with UFH pipes fill with air or water glycol, water glycol less likely to float. Plenty of examples on the UFH section on here.

Yes. Just timber and ply box a bit bigger than your intended shower tray. Need to carefully plan these things now. Will the floated concrete floor be your finished floor? If not, it's a simple matter of bringing the sewer pipe up to where the water trap will be and shuttering off a big enough area to fit the trap. A fall, if needed, can be done via tiling. Unless of course the concrete will be your finished floor, in which case all of the above is a complete pain.

Think it's more likely the ground workers will be wearing wellies during the pour. How thick is your raft concrete? Confused by the comment on wet rooms?

But as he says, until air losses are tested MCS will only use spreadsheets values equal to a very leaky house. Needs his air test certificate in hand first.

There has been recent publicity about a hot water unit that really would fit inside a large kitchen cupboard. See But it's very much untested in real domestic settings, so far.

UFH as a single zone on ground floor and any upstairs bedrooms. Consider fan coils if you need cooling upstairs. Other provision for electric panel heater in bedrooms (don't buy until after you know you need them). Electric towel rads in wet rooms. Make sure you have decent heat loss calculations before going any further. Ideally do them yourself so you know what's what. You don't want the sun shining on the ASHP, ignore any advice that says otherwise. Sun will mess up the heat sensor reading. Indoor controls depends on unit being installed. Many will have an internal thermostat so really needs to in the living space not in a cupboard. They are just like a thermostat. Only consider a monobloc ASHP so everything is outside except a small controller. Don't do any 3rd party controls. Single zone means no thermostats other than the one in your controller, no actuators on the manifold, no need for a mixer or pump on the UFH manifold. Most likely no need need for a buffer or volumiser. Using a Government Grant for the free £7500. I didn't bother was too expensive, so just bought it all myself. Installers just want to rip you off.

Final update Been faffing about in the background, to get the house heating and summer house heating to work together, one is high inertia (thick screed UFH) and one very low inertia (low volume fan coil). Final solution is, have dumped WC altogether and now flow set to a fixed demand temp of 35. That suits the fan coil in the garden room and a slow batch charge of the floor. Observation the heat demand of 35, the discharge temp from the heat pump never actually gets to 35 for the 10 to 12 hrs it runs, at the moment. Most days it gets to about 33 by the end of the heating cycle. Zero cycling occurs, except for defrosts. There are two thermostats, one in house and one in the garden room. The house thermostat can call for heat and changes set point of an electronic UFH mixing valve, the garden room thermostat can call for heat. The electronic mixer valve in the house, is selectable to two different adjustable set points, currently set to either 35 Degs or 27 Degs. The 35 Deg set point ensures mixer is fully open and zero mixing occurs. The system volume isn't large enough to support the heat pump driving a single fan coil on its own, so the house floor is always available to act as buffer via the 27 set point on the mixer valve. Batch charging is simply controlled by a single room thermostat, with a hysterisis set to 0.1 - at 00:30 it is set to 20.5 (starts heating if at or below 20.4), at 07:30 it is set to 20 (switches heating off when above 20.1) and at 12:00 it is set 19.5, makes sure heating doesn't restart. DHW heating is timed to allow heating any time between 1pm and midnight.

Had DHW heating and cooling running in the summer, once commissioned, no issues. So thought when I installed the UVC there would be no issues when heating instead of cooling. But this hasn't been the case. It looked like the DHW heating cycle finished and the heat pump didn't start on house heating again. First couple of times I just shutdown the heat pump at the isolation switch and all reset and worked fine. However yesterday I actually watched at the heat pump, to see what was happening. The heat pump was trying to start in heating mode, after a very brief off period when it completed DHW heating. But during the restart it was overshooting the set temperature point by quite a margin, and then seemed to be locking itself out. So issues with my install, the heat pump is around 14 to 15m from the cylinder, so although the temperature in pipes drops fairly quickly, at the end of the heating cycle, there was still enough heat being carried that adding a small amount of extra heat was enough to overshoot. So have implemented a few changes 1. Found in the controller the PI regulator integral time, was set to 255 seconds (max setting). This setting apparently is good for large flow rates and large volumes. So ok on a big heat pump, not ideal on not a small one. I reduced this figure to 60. You actually hear the difference it makes as the compressor starts, as it rains in the temperature rise very quickly. 2. I added a forced 10 minute break, in the underfloor heating timer of 10 mins after the DHW heating period. 3. Increased the shut down hysterisis from 0.2 to 0.4. This allows the heat pump to run at a slightly higher temp than set point. 4. Increased the UFH flow rates to the previous ones. Now UFH resumes around 30 mins after DHW, which fine. But the run time of the heat pump has increased significantly. Previously it would do an on off cycle once per hour, now it seems to run for around 3 to 4 hrs straight. This has allowed me to reduce the flow temp slightly.

Ola. Have you worked out how much more ( additional ) heat you actually need up there to get it to an acceptable level? Could adding skirting heating get you there? Would save a bunch of extra work. If you migrate to rads then could just ditch everything back to the 2x 22mm flow and return and connect the rads directly using only TRV's on each rad for control. If you wish to retain the UFH controller and stats ( do you have 1 stat per room / space up there? ) then you'd simply ditch the TMV on the manifold and install a TRV on each rad. Yes, that's correct. The TRV's would still open up fully to get to their respective set points, and only reduce the flow rate as the room / space is arriving at / has achieved the set temp. Just pipe each rad back to each respective manifold port and then job done.

OK did a little more research: As per Approved Documents Cover Page, these documents contain: * general guidance on the performance expected of materials and building work in order to comply with the building regulations * practical examples and solutions on how to achieve compliance for some of the more common building situations So indeed they are not legally binding. Instead the actual law - Schedule 1 - Requirements item M4: Access to and use of dwellings, Category 1- visitable dwelling M4(1). Reasonable provision must be made for people to— (a) gain access to; and (b) use, the dwelling and its facilities It is abundantly clear that it's unreasonable to expect every single socket (especially those in effectively fixed use) should be accessible. Instead, a reasonable amount of sockets and switches should be at that height between 450 and 1200mm.

I have always understood dedicated function accessories can be at any height, like high up sockets for a wall mounted tv. I have never known BC question this as long as most are at the correct height. If they did, they would get replaced with a blank plate, and put back after completion......

If you want that level of performance go for MVHR. Use the shower light fitting as the MVHR extract in the bathroom if you want to keep the light fitting.

With a dual stat setup and an oil boiler, you’d struggle to not get DHW almost on demand tbh. A TS is a beast for producing DHW, and the heat goes almost directly in / out. With an oil boiler you can size the TS smaller and it will then recover faster, but if ST and / or PV are present on an install you’ll typically want to size a TS significantly bigger to harvest that ‘free’ energy. A TS will give a diminishing output vs an UVC, so needs careful thought and consideration, but if @Gone West has oil as a parachute, they’ll never ever be stuck for DHW with a TS. A 15-20 minute burn from the oil, from cold, and you’ll be able to jump in the shower, assuming a 200L TS vs 21-26kW boiler. To maximise the performance, I always specify a 28mm high recovery DHW coil with my TS installs. Trevor at Cylinders2go can get pretty much whatever you want specc’d / made to order.