JohnMo

Your drawings state by specialist contractor. So are only indicative. My roof worked like this Approach company to build roof, they used specialist roofing fabricators, specialist company design and provide drawings Contractor approved or modified as appropriate. Full drawing and calculation package sent to structural engineer for approval. Again any modification made to enable structural approval. This aspect becomes part of the overall structural certification. Same will be true for you pozi joists.

If you used a different tariff would the saving be better?

There area few variables there. Mean flow temp sets the energy being input into the floor. As below Simple heat output graph for floor heating, you will have extend some of the number scales downwards. Just draw across from mean flow temp to pipe spacing to get W/m². Room temp is just an output of kW input, kW consumed and how long you apply the energy for. But a heat pump is unlikely to run 24/7 even if you wanted it to. It will manage its self and cycle when energy demands is lower that energy output. With a floor heating system you don't need a buffer. Parts needed are manifold, pipe clips for pipe, eurocones for pipe to manifold coupling and a couple of isolation valves. You don't need mixers or pumps, do all direct from the heat pump. You don't need actuators you don't need a buffer. I spent less than £1k on UFH parts for a 192m² floor. Running a single zone system, you get whatever room temps you want. By adjusting flow rates and how much pipe you bury in the floor. Set weather compensation up you don't need a thermostat, running a time of use tariff just use a 0.1 Deg thermostat to stop and start the heating, the 0.1 will limit under and over swings on temperature.

2-3. Bleeding air out the rads will lower the pressure slightly, so you needed add water which you have. When you first run the system micro air bubbles come out of suspension - which is all pretty normal. The condenser gets cold this time of year and will often freeze up and defrost, so getting wet is normal. But if getting a pathway wet, then the flow/drips should have be diverted to a soak away by the installer.

You should have been given a commissioning certificate, this should show the room by room flow rates - if they haven't handed over ask for it now. When commissioning was taking place, did the person go around the supply and extract terminals (room by room) to set flow rates, they should have used a certified flow meter - if they didn't the unit wasn't commissioned correctly. Test for you to do - In the bathrooms, utility and kitchen, tear off a 2 square strip of toilet roll and place it over the extract terminal - it should stay in place. If it doesn't and falls off the flow rate is just too low.

2 general reasons for fire doors, to stop fire spread and provide safe means or route of escape. Adding an additional floor level (loft conversion), brings in a whole load of extra rules. Not sure removing doors will help, either speak to your architect or building control.

My advice - review design about a 100 times, whiles it's all on paper or in a computer. Go to the beach draw it in the sand walk around inside, does it flow etc. Tweek design as required. Ask questions while you are doing so. Think about construction method, insulation for walls, roof, floor, air tightness, ventilation and heating, ask questions as needed. Build a plan of action, know in your head how you will build. Have exactly where you want sockets, switches and lights planned. Once fully clarified and you have committed to design, don't look at sites like this again, until you have finished. Just build as per design you are committed to. Be prepared for for a 101 questions you never expected from trades. If you do come sites like this mid way through build - and ask questions, you get 300 different answers, go down rabbit holes, make costly changes, waste endless time going round in circles. That would be my advice and is pretty much what I did. Building is a compromise they are never perfect for everyone, you may want something, your partner may hate it, you do something different that you can both live with. At the start of the whole process, write down your goals and always refer back I to them, check you aren't going on a costly diversion. Fine if you are so long as you know why. The really important bits and they cannot be changed later easily Insulation, building it airtight, ventilation. All cost very little during the build and will save you money every day after you finish.

Good luck,we had a property with no water, no bathroom, no kitchen and it took us 7 months and we had to pay for an engineer to inspect, basically in the not wanting to go there basket for the council - they want the money. By the time everything was sorted then house had been fully refurbished.

What happens with wiring for lights and plumbing etc? Really see zero advantage to block and beam for anything especially for first or mid floors.

Would think you are making life difficult and possibly way more expensive. You will have a structural oak frame AND a structural ICF doing nothing more than window dressing. I make a decision on ICF or oak frame and go from there. Not sure I would mix. Oak is flexible and will move about initially or will in the green state, the ICF is concrete there is no flex.

That's the issue doing UFH, the floor can suck the heat away really quickly, this means return temp stays low, as heat pump wants to manage dT first, target temperature second. So if you try to run UFH for short periods, you never achieve a stable operating point. This means UFH can happily absorb most heat given to it, and big flows of return water keeping the return temperature low, never achieving target flow temperature. Run UFH long a long time the return temp increases, smaller quantities of hot water are taken into the mixer, more water is recycled within the mixer. Return temp increases because, more flow is routed to radiators and less to UFH. Heat pump achieves target.

Unlikely as an ASHP normally will supply a minimum of 25 Deg in heating mode. Then at deltaT 4, plus restart hysterisis for the heat pump, you need the floor temp to drop below 20. If that's the case your floor would provide zero heat to the house. Tried that with mine (25 Deg flow) it ran fine, but never restarted, floor just never cooled enough to allow ASHP to restart. Thermostat you need a hysterisis of 0.1 or less if you can one. It has to be on/off not TPI. I have 100mm concrete with UFH pipes at the bottom - I am also 300mm pipe centres, response is slow. But if you are prepared it's something you can use to an advantage. But don't expect setbacks to work, they won't. WC works fine. If you use a tou tariff, get a bigger heat pump and batch charge the floor storage heater mode. I am at a out 3kW at -9 and have a 6kW ASHP, will run without stopping buffering into the floor if I want it to. If your heat loss is 2kW, you need 48kWh of heat, if you only have 7 hours to heat you need 7kW of heat input, plus it may need defrost or modulate down to manage dT, so even 8kW would be fine.

Both are correct, over 30 Deg flow it's 7dT, while under that is 5dT.

Think that's half your issues, running more like a boiler than a low and slow heat pump. You have a mad blast to heat in short bursts, Trying to stuff loads of hours of heat in 3 hrs just doesn't work, may do with a boiler but not a heat pump. That would indicate your flow temps are way to high.

We heat with a fan coil, but it only really gets secondary heat from the house UFH, ASHP circulation pump runs 24/7. So we generally have a min of 16, but it can get as high as 20 (currently) due to solar gain.

Just do wireless thermostat, easy, battery lasts a couple of years. You can also move it about. We are running WC but use a thermostat to trigger a second operating point, basically WC plus 2 degrees. Use the thermostat to force the heat pump to run hotter during cheap rates period and also shelly relay across the terminals of the receiver to drive the heat pump hotter during excess solar production periods. Converted 3kWh of excess solar in to 11.5kWh of heat today for free.

dMEV fan install now and then forever more let it run 24/7. Cost about £1 a year to run. Set to min speed, buy a Greenwood CV2 from eBay pretty cheap. This last year's humidity of our garden room

You are just scared mongering now. So now you are worried about a lots of steel plates that are insulated inside an insulated box freezing. If that is the only concern, remove insulation, wrap with 12v heat trace, re insulate, and use simple relay to switch the heat trace on in event of power outage when heat exchanger drops to 3 degs.

UFH needs plenty of insulation to be efficient, otherwise you heat the flat under you - they will like it - you won't like the energy bills! Or you will heat the worms under your flat if on ground level. Really wouldn't bother.

Did you do the print out? It should give you model for your design and build regs design so you can compare. What did you put in for airtightness at 50 Pa? What did it give you as an infiltration rate? Would compare target house with your inputs, check your inputs are not strange. Would also add another 50mm insulation to the floor. Check MVHR inputs, different duct types can make a big difference in efficiency etc. Heating controls make difference, can you select pure weather compensation?

Mostly, longest is 12 hrs, some we don't even notice because the battery hides them, which is good

Questions to ask yourself 1. How often do I get a power cut? 2. How long do they last? 3. How long to totally freeze a pipe? 4. Do I have a generator and or battery? My answers are (we have insulated buried pipes) 1. 4 to 6 times a year 2. Up to 12 hrs 3. With no circulation I think to freeze a pipe or the parts inside the heat pump, when tested was about 18 to 24 hrs at -20 (in freezer) when tested. 4. Yes and yes I have NO, antifreeze valve or glycol. In normal use the ASHP circulation pump runs 24/7, even if off the antifreeze running protection in the heat pump will look after the unit and pipe. Observations My outside cold water pipes have never frozen they start from cold (not warm) they aren't insulated and are buried to a similar depth. We have had -9 for several days over the last couple of winters. You need to get extreme cold and power outage for a prolonged period at the same time. External oil boilers don't use antifreeze etc. Have read here https://renewableheatinghub.co.uk/do-air-source-heat-pumps-really-need-glycol

Just occurred to me, you just paid an arm and leg to get this system installed, get the installer back to rectify. You have an MCS performance guarantee.

Then you need internet to get your heating to work - not good Something like this, which an RF relay not WiFi. https://mainsswitch.co.uk/ You can get them for £43 on eBay

I used CV2, super cheap on eBay. No app, do you need an app? Set and forget