JohnMo

If you have MVHR the air change per house is 0.3 to 0.5. But this has about 80 to 90% heat recovery. An air test of building tightness of 10ACH would give you around 0.5ACH natural infiltration. If you looking at a grant, the MCS spreadsheet has pre added ACH figures. You want them to move on the numbers you need an airtightness test result and then argue the point.

Bit confused by this Can you draw what you mean?

Although the outer part of the frame isn't structural, would have thought it needs to be supported, not just floated. Pre insulated planks seems complications. If you have to do suspended floor why not block and beam? Add allowance in heights for insulation and screed etc. Just do it thermal bridge free. The 140mm structural bit sounds over kill.

Think you are mixing up heating and ventilation. The heating on will be making matters better rather than worse. You either need to fix the ventilation, to keep humidity in check but way more importantly the CO2 levels are going to be at an unhealthy level most likely. Or implement a purge routine. Purge routine is pretty simple, you open windows doors for 10 mins, and then close. It replaces the air, but reheats really quickly once the windows are closed again. Air contains very little energy, the fabric of the building reheats the air. A dehumidifier may remove moisture from the air, but does nothing to help the CO2.

All heat pumps are a bit steep, £7500 of free money makes that occur, everyone a piece.

Sorry looks a bit naff The window should straddle the insulation otherwise you get a big cold bridge. So sitting on the brickwork and a ventilated cavity is not good. Without careful design of you chimney it will leak heat.

As I said above min output is 17kW. 5 UFH controlled zones, it will be zero seconds cycle time.

2020/21. £670m² fully installed. All made 4 miles away. Includes 5 doors all with side glazing panels each side, a big wall of glass (12 windows) and 6 other windows, all wooden frame, nearly all 3G, except 4 glass doors which are 2G Krypton filled.

Sorry not a lover Looks good, but from a practical point of view why not just do wooden cills? And sit the window on compacfoam? Looks loads of work, for little or no gain

And 5kW for £3500

But is that because closed the UFH mixer right down to get away from 70 Deg flow temperature?

Good luck getting that to run without a big buffer. Lowest boiler output is 17kW on any of the boilers in the range. And the lowest circulation pump flow rate is 15l/min. All 5 UFH loops will not support that flow rate on there own or all together. There is usually a good reason why boiler manufacturers don't want you trying to run lots of zones direct from their boilers, because they cannot modulate to small enough outputs.

Back to my original post? Flow needed for UFH on its own is small with a mixer. In flow terms your trying to push an elephant through your front door. You are likely going to need to flow radiators and UFH at the same time. Or put your UFH on a secondary loop via a close coupled tee.

Best you get your pens and paper out, or a computer version. Or pay additional.

Shows the need for detailed drawings and a clear airtightness strategy. Don't you have room in roof and cathedral ceilings? If so do you need tonytrays? Again back to a clear drawn out strategy.

So maybe good reason it only does 3 zones. Otherwise lots of short cycling unless you are buffering to a big buffer or thermal store, which as you are S plan out most likely are not.

Lots of boilers don't use volt free. So nothing unusual there. Add it then? Think you are missing a trick, not using weather compensation and priority demand hot water.

Install manual has about 10 pages of connection options, including the dip switches options. Trouble is the boiler is quite smart, looks to do PDHW out the box and WC, but normal UK install does S plan, why?

First need to identify a location for cylinder. Suitable cylinder should in most circumstances be available. Worst case a night in B&B or hotel or trip to local sports centre or swimming pool for a shower, while cylinder installed to run immersion only.

So basically sometime one of these, but with a feed loop being reheated by the heat pump. Instead of water going down drain https://www.powrmatic.co.uk/products/air-conditioning/powrmatic-vision-h20/

Been there bought expensive. Paid 4x more for a kitchen in the 90s than I did in 2021. One in 2021 no better or worse. They are all MDF with a plastic cover at best. A good design is way more important, with parts available in the uk, for when the installer messes up.

All cylinders have immersion heaters. Combi boilers, different set of issues. But heat pump connected a small cylinder heating coil isn't going to be great either, could well dominate what the heat pump is doing, with very long reheat times. The plug in unit only fixes heating, but so does a £50 electric heater or two. Less faffing about also, do the calcs, fit once not twice. Heating on in 5 mins of arrival.

Just get a basic immersion timer then, Screwfix, Toolstation etc all sell them

Then you end up with a garage that isn't and cannot be garage when you come to sell the house at any point in the future. Or when you get older you may want it to become a garage. So irrespective of insulation it's going to get cold in there. If you want it to be a less cold garage floor, get some old (or new) carpet.

Have you read searched on here, lots of information already available.