JohnMo

So are you just heating the thermal store, the UFH flow coming off the thermal store? Or are you heating the thermal store and the UFH flow is separate?

To make it work you need somewhere to dump heat that is useful. A thermal store would normally be scorned on here. But install a large one, 500 to 1000 lts. Use a plate heat exchanger for domestic hot water take off, size the heat exchanger to work with 50 degC water. Heat TS to 50 degC. Take central heating direct from thermal store. That should give the ASHP plenty to work against and no short cycling. Make sure you site the TS where lost heat is useful.

You are making life complicated for yourself. Keep it simple. Not sure I would do a SA with a heat pump, just use an UVC. Take heating and cooling flow from heat pump via a buffer cylinder. Feed to mixer valve /pump at manifold (low temp). Run downstairs as a single zone. Run DHW cylinder at 46-48 degC UFH flow should be circa 26-30. Don't limit yourself to one pump manufacturers heat pump. Valiant heat pumps use propane, so limits your placement of the outdoor unit. Also I believe Vaillant unit is only reversible with a £300 (should be £1) resister in a plug.

People usually avoid PIR in blockwork walls because it's difficult to get gap free insulation. Every gap is a heat leak, mineral wool cavity batts would be more forgiving and possibly better performing in real life. Or as mentioned EPS beads.

A gas combi boiler uses a pressurised heating loop, as described. The alternative is your existing header tank.

We have UFH in bedrooms, wouldn't do it again, slow to heat up, slow to cool down, never the right temperature really. Towel rads either electric only or dual fuel (electric/water). Just do something like this for bedrooms, for heat and cooling. https://coolenergyshop.com/collections/radiators-fan-coils

Issues 1. With a combi tank the thermal store header/expansion would be below the level of the upstairs rads meaning they'd need to be decommissioned. Could you run from coil in cylinder, then no issue supplying upstairs rads, just run a pressurised heating system?

Wow £3k, mine about £150, including the tube heater and half sheet of 25mm PIR on the door and hinges and bolt.

Pallets, insulation, VCL, cladding boards, sarking boards, breather paper, all left overs from build. Only added roof sheeting. Needed a shed to hold water borehole filters and pump control. And log store X2. So build this.

I have a wooden garage with steel roof. Mine is surprisingly cool inside, full sun most of the day. So metal roof, breather fabric, sarking board on roof rafter, 100mm accoustic mineral wool between ceiling joists, 25mm PIR below, fully taped. Walls similar, but without the 25mm PIR, just used silver bubble wrap.

But you need at least 6 of the solar collectors linked to give 70% saving in DHW in July. So realistically you could have 9 or 10, so are over £1k just for panels, which is in the 30 evacuated tube price range.

If your leakage rate is greater than 3m3/m2 @50Pa, keep your money in your pocket. As cost to run v savings made will not be a benefit to you. I would instead (irrespective of your leakage rate), look at a demand based MEV or dMEV, more cost effective to purchase, simpler to install, run and maintain and only ventilates at the rate required.

All my 50mm battens are fixed with 90mm nails, unless they are screwed to woodcrete. I have all the ceiling battens and the second layer of external battens (for vertical cladding) all nailed with 90mm

I looked at those and for a house need quite a few, which ended up being quite expensive.

This how I did mine. Nail into the side of the rafter, so the nails have to shear, rather than just fall out. The center section were skewed nails.

Your boiler has weather comp built-in. Go on to heat geek website and have a read up on weather comp.

Confused, what's not condensing? Condensing with natural gas starts with a return temp of 54 degC and lower. The lower the return temp the more condensing that occurs. The more efficient the boiler becomes. With UFH there is no point heating water up, to then mix it down to a cooler temp.

Ours was £4k with slate hearth, the flue, air supply pipe, full labour and Heta Scanline 8 full soapstone. Costs don't stop at just the fire.

If it's UFH, why are your flow rates to high? Seem high temps.

Don't buy a big sand hill. Views great, but landscaping costs are huge. Less glass, or Aircon from day one. More solar. More insulation. No more than one thermostat in the whole house. I had loads caused loads of issues with the heating and short cycling of the boiler.

12 degrees makes it a normal roof, less than that it's a flat roof. But the third person today that wants to miss a designing it correctly stage and make up as they go along.

Insulate

Why are you doing building work without proper structural engineering input. Flat bar will do nothing for you structurally. Primer does not provide rust resistance, it is porous to provide a key to finishing coats. It will rust in no time at all.

We have almost stopped using the recirc extract, just put the MVHR on boost job done. Only really use for smelly cooking.

Can't understand why you would build and not have a structural engineered design and then follow it. I like the Scottish rules, no structural design certificate, no warrant, no build. Keeps everybody right.