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Building Regs do tend to be open to interpretation, but what you can lean on and discuss with your BCO if it's a problem is that in accordance with industry practice and guidance (CIBSE Domestic Heating Design Guide) for any new build, a design temperature of 21C should be used throughout the building - because of higher insulation levels and we hope, better airtightness. In this sense, adjacent rooms can be considered as a single zone: 5.21.b

The regs are quite relaxed, >150m2 only requires 2 zones, so how about one thermostat upstairs and one downstairs? BC are not going to spend the time to actually make sure they do what they think they do.

Yes, plan is insulated plasterboard on the reveals. It’s not visible but there is a solid piece of approx 50mm PIR used as a cavity closer between the inner and outer leaf at the reveals. We have the insulated plasterboard for the reveals ready to go, but that board might be useful for the head and sill. Between the builder / window installer / block layers, there wasn’t enough space left for insulated boards in the heads or sill of the windows. Those thin marmox boards might be the trick. You can plaster directly onto them?

Have you checked if there's an automatic air vent inside the heatpump that needs opening? Some come open, but I've found some which are loose but not 'open'. Also, any reason why you have an inline trap after the P of the washing machine trap? No need for the inline (waterless) one afaic.

Many ways to skin a cat, but tried and tested for 3 decades wins for me. If you're saying you stuck it down and couldn't then adjust or manipulate it, and hoped it was level, then I guess that's one reason not to use a sealant / mastic. I found this out a long time ago, where the mastic turns into a sucker cup and then it's a case of getting wood chisels or small pry bars under the edge to try and adjust it. This was with a Novellini tray, prob 15+ years ago or more, and it was clean and spotless when laid but I did notice some bounce in the centre of it, where it was thinnest at the trap, and that was it for me. Back to tile adhesive, and never looked back. Fitted 2x Mira Flight trays on a previous build, and the client commented on how solid they felt; one on the raft slab but one also on the 1st floor deck over posi's. I couldn't disagree more. Such a bond is also formed when you seal the sides of the trays to the walls, 2 or 3 sides around, and fixing trays into place firmly is of paramount importance so you don't get movement / cracks in the grout where the tiles come down to meet the tray. This is exactly what flexible tile adhesive does, the clue is in the name . The thing most people don't do is decontaminate the underside of the tray, which is often dusty and feck or has mould release agents on it. Regarding movement, these don't typically move much, if anything at all. There's a brief change in state when you turn the hot shower on, but that's about it. Even my 800x1800mm bath is stood in every day, and the grout line and silicone seal haven't shown signs of movement in a busy house with 6 people in it; I fixed a batten to the wall and set the bath down into CT1 and the same back to the 2 plaster boarded walls. Been in for around 8-10 years now with zero signs of movement. Give old Skill-boy my number, and we'll go argue it out over some beers.

The 150m² multiple zones I covered with a thermostat in hall and another in ensuite controlling a towel radiator (direct electric). Use the thermostat to trip the ASHP off, if I have the fire on in winter and for summer cooling. The rest is cover by 5.20b and 5.22a. High thermal mass buffering via thick screed floor and a thermostat in a room served by the heating circuit, in my case the hall. But I have a temperature sensor in each room, most are not generally used except for monitoring temperature. They are useful to understand what is happening, how your system performs, system balancing etc.

Madness! Do what you are planning to do. (not based on any real knowledge of building regs on this but it was fine for us)

We're planning our UFH as a single zone, open loop for the downstairs with only one thermostat. I've been round this a lot elsewhere and on this forum, but just before going ahead, our ASHP installer has mentioned that building control tend to want to see temperature control in each room. I've read the Building Regs Part L and it does mention zones, and there's a brief mention of low heat demand homes, but I'm asking here to find out what the lived experience is in dealing with approved building inspectors on this topic. Ours is very particular, and hard to get hold of to discuss questions like this (which I will try). In short - I'm wanting to know if anyone has actually encountered this issue, if they've had to argue the case, or if there's a simple way to phrase it to demonstrate it's compliant with the BR wording (screenclip of the BR section I've found on it). Thanks

Just reread what you asked and realised that you're talking about the HW temp in your HW tank?? In that case the answer is no. The heat pump runs at different temperatures when it's heating the HW tank and when it's heating the radiators. The change in temperature is done automatically but you can set the time and temperature for both the HW and central heating.

Thank you all, uninsulated until I get it up and running in case of any leaks, but system installed and closed loop. Next challenge is flushing the UFH loops (only 3x100m) and filling the system from the now connected fill hose under the expansion vessel. Also need to add the biocide and anti-corrosion. Wish me luck.

I recently saw a refurb where the newels had been beautifully overclad in oak. i would never have known, it was so well done.

More for the OP's situation tbh, as it shows full depth masonry. Yours will still be a cold cavity, even on the inside face of the PIR (if there's any kind of gap behind it). Not life or death for you, but if the opportunity exists to make things a lot better the I guess you can choose to do it to the highest standard.

Yes it does...the hotter a radiator is the more heat it gives off. The hotter you run the water leaving the heat pump the less efficient it becomes so it uses more electricity and costs you more to run. The solution to this problem is to run the heat pump cooler and have bigger radiators.

I understand its pretty good to use aircrete as the thermal break and keep them dry with a dpc. Perform pretty well for lot less £

I got 1.2 m3 hr whatever that is in ach. Masonry cavity build with dot and dab. Large coated blockwork internally

That is the hard bit. That is because I was being a bit flash to work around the charting limits in LibreOffice. I would recommend downloading the portable version as it does not install itself on a PC, just runs from a memory stick. I have some data about ground temperatures that I am looking at, so may be able to make some sense from it.

For anyone browsing this in the future these BG electric ones are fantastic. Really thick and nice, not many holes. Highly recommended. At £2 ish each also not much more over the plastic junk. I should have never really been put in this position let alone having to cut all these out, but at least these are a nice solution

Good first go. A few comments: 1/ Your cavity tray is only one course above finished ground. BC will and I will pull you up on that. 2/ The insulation shown as a triangle just below the cavity tray is unbuildable as detailed . You are concentrating on the technicalities rather than balancing this with what is buildable, the cost and how you are going to make sure that what you are paying for actually happens on site. Don't blame yourself.. as unless you do this as a day job and have a feeling of build cost there is no way of you knowing this. 3/ You have a wide cavity. Why not thicken the perimeter insulation up to 100 or more thickness. Have a look at how MBC do an insulated raft slab and pinch their ideas. Then you can omit the Marmox block unless you want to spend money. You could be pragmatic and use the same money in a better way and in the round still achieve what you are looking to do.

Watch this like a hawk. You TA is probably in a loss position. Double check if you have any fire protection and if any changes alter the design intent. Check if you are changing the exposure rating and make sure this is ok in terms of your detailng and wind driven rain. Go back and just have a look at what you have done so far. You have learnt a lot. Don't bury you head in the sand and hope it will be ok. If it turns out you have dropped a bollock then now is the time to address.

Could someone tell me: I have the HW temp set to 46*C. Does this temperature have any bearing on the temperature the rads emit? Thx Zoot

I'm very impressed from what I could see. It took you two hours!.. well you are sharp as a tack. No way could I have churned that out in two hours.. even the small bit I can see. You're probably a bit like me.. as an SE / desinger I spend most of my time thinking and how I'm going to communicate the information so everyone can understand it, lots of folk are reluctant to pay for that. I know I have to produce structural calculations.. which after a while are not that envigorating when doing day to day stuff. I like maths but up to a point and get excited when I have to design whacky stuff. You are more adapt and nimble at high level maths than I. Far all. The idea is that you do the thinking, plan out how you are going to set up the calculation pack do the supporting drawings, bite the bullet and just get on with it. Then you have to check your sums and design philosophy is still valid. Is there any way you can make it idiot proof at my end so I can open it in excel? The reason for me pressing is this. When I joined BH it was as a result of a prompt. At the time Jeremy Harris (JH) was someone that floated my boat, he popped up again a while back but then went back into retirement. His thermal loss spreadsheet must have been used by many thousands of folk. Life has moved on but your spreadsheet has, from what I can see has potential. It's something that I would want to interrogate, see where the limits are, the best way to use it. I design insulated raft slabs for example, done it for years. But I can see there is potential for tweaking the perimeter insulation to extend down towards the foundation. This can make a big difference if the site conditions are ameniable. The actual type of soil under an insulated slab and around the underbuilding can have a huge impact as does the mobility of any ground water. @saveasteading is probably the best exponent of this practical art on BH as he has actually built hundreds if not more. At the end of the day the key to designing for self builders is to keep it as simple as possible, even if everything is not prefect. This allows for example a local builder with limited knwoledge, who does not have access to specialist trades to compete for and have a chance of delivering what you are paying for. @SteamyTeaYour absolutely right to highlight the form factor for example.. that is one bit I could see. I tried to track you formulae but the references are not familiar to me. But in the round my feeling is that you are introducing the next generation spreadsheet. call it Jeremy mark two?

I'm never going to understand the basics of the difference between this ON setting that I thought was being suggested, & this timer setting that I thought wasn't being suggested. I've tried today to read BB's link he sent me, but it's for the black controller vrc720, furthermore I'm lost immediately on the most seemingly simple stuff. Basic settings. I think the only way forward, is saying maybe what I don't want. And seeing if something fits around this. So what I don't want, is the heating on overnight. I don't want the heat, the wasted cost, nor any mechanical noise (absolutely fumdamental is no machinery "wakes up" kicking into gear at 3am, no murmerings/ nothing/ not even outside cos some noise transmits via pipes, into bedrooms, the very rooms you least want mechanical noise entering at 3am). Thanks, Zoot

A ground bearing slab means the inner leaf is built directly off the foundations.

It's fine. I've got back to the TA regarding the blocks and he is liaising with the company who did the SAP calcs to find out whether a medium density block will result in the target 0.18 value.

Hi BB, no the VRC700 is not in a hot tiny enclosure with the cylinder.. I don't think any installer would be -that- inept. It's where it was, in the small bedroom on a wall outside the cylinder enclosure (this thin wall is never ever, even barely warm). This bedroom is gonna be the warmest, cos it's the smallest, cos it's got the cylinder in the corner enclosure... but it's still a feckin freezing cold room compared to yours! It's got cold loft air behind the plasterboard walls, no insulation bar loft fluff above, & a cold sittingroom below it. Only way I can move the thermostat is buying 30m of cable & running it thru an attic, drill hole in ceiling, run cable down to kitchen/ thermostat there. But this room is SOO damn cold, 2nd coldest (one reason is bc there's no convenient wall to put anything but a single small double rad on: a mini fan heater is FAR better at heating this mostly ininsulated room, than this small rad ever does, or could ever do I reckon). I don't think this is a sensible place to put it myself, as surely just --too-- cold?? Anyway point is I can't afford to buy new wireless thermostat/ transmitter- receivers. Nor can I afford a plumber to reposition this vrc700. Nor will V likely send me a vrc720. So it's me do the job, if a freezing cold room is a sensible place for it.. rather than merely a cold room. Thanks, Zoot