JohnMo

Easy enough at the build stage. Wet UFH below screed, electric above.

World heat is a different company to mitsubishi. You would need to look for World Heat. That does not sound right, 40 to 50L is nearer There shouldn't be any radiators that are too small, ask them about why there are?

Shop https://www.outsourcedenergy.co.uk/shop/

When I used the pump I was sceptical, but it's super quite, pulls next to no power. I used as a return booster (different story). But was happy with it.

Outsourced Energy That's where I got mine

I would just store at 55 to 60, with a gas boiler reheat time will be about 10 mins, your losses will be negligible. More important is suitable insulation on the pipework that will loose way more than the cylinder. Best bang for the buck is always choose a heat pump cylinder for any heat source. Fast reheats, gas boiler nearly condense all the time for added efficiency. Air in system causes corrosion of the heat exchanger, less efficient heat exchange throughout the system. Yes every instruction manual I have read (I like reading manuals) has required piping that is not air permeable and to be pressurised. I am talking heating water not fresh water.

Wife does occasionally, she used to most days in the last house, but doesn't so often in this one. May be a different feel to the house Your heating system will not have a tank in the loft, it will be pressurised to about 1 bar. So you little tank won't be there with a heat pump.

We have a 210L slimline UVC never run out of water (2 of us). Done combi boiler, unvented, really no way I would go back to unvented. Everything is hygienic all water is drinking quality with an UVC, no overhead tank, that no one looks for decades at a time, no thanks, full of stale water or worse etc. You don't want to oversize the cylinder as you need more legionella cycles. Vented I would be doing every day, unvented I never do it because we move enough water through the cylinder, so no risk. As mentioned the other option is a TS or the new cylinder from Heat Geek, requires no G3 and supplied DHW via a coil at mains pressure. It is also small in size. A thread on it on this forum and videos online. Hep2O is simple, easily available on a Sunday morning if you run out of a bit. The good thing is the reinforcing push-in piece at the joints is very thin metal so you have less flow restrictions. A manifold for hot and cold is best thing we installed, allows rooms to be commissioned one at a time without interrupting the others. UFH pipes, pert-al-pert nothing else, decent manifold. Heat pump don't buy one that is NOT able to cool also.g Your heating system will have to be pressurised, to get a start enable. We have wet UFH in wet rooms, and electric towel radiators. You need something in addition to the house heating as your house heating is likely to off house comfortable but bathroom not so comfortable.

The buble should be biased towards the lines either left or right of centre. If it's in the middle it's flat not sloped.

Possibly caused by your longish uphill suction line. The pump is starting to pull a vacuum and this causes cavitation. You need to look at on the data sheet, at the NPSH(r) or net pressure suction head (required). This is amount of upstream pressure the pump needs to stop cavitation. Ideally a neg value would be good, then the pump can pull the water in uphill and with pipe/strainer pressure losses be away from cavitation.

They wanted a 50mm ventilation air gap minimum. The way slate roofs are done in Scotland are Sarking board, breather membrane then slates attached directly to the sarking board. So for the 45 Deg roof we would need to add battens and counter battens then slates. Which need all the roof drawings redone and re approved by BC. For 12 Deg roof same thing but then I would have to add another deck to support the Sarnafil membrane.

Limits the number of start-stops, quite a bit.

+1 as @Oz07 says, that is how ours was done. You definitely need expansion gaps. T bar just straddles the gaps and makes it look pretty.

Mainly decided against it as we have some large down lights and they need 50mm depth. Didn't want to digging holes in the insulation to install. That was the design that came from Pasqual (maybe misspelt) so kept with it. We have quite big roof overhangs and didn't want to mess up the look outside. You can get deeper. I did look into blown cellulose, but was getting lots of demands from them, which made it hard to do. So dropped in the end. The company we used for assembly of the roof also do spray foam, they did all the interstitial condensation calcs and all looked good. So the same guys that did the joinery also did the spray foam. 45 Deg roof wall to ridge. 12 Deg, wall to wall.

I would membrane the lot. Have you sealed the block work? Would that also leak into the cavity? Or is that being plastered later?

We used this on the house (parge coated walls) https://passivehousesystems.co.uk/product/gerband-fortax-6400-airtight-sealant/ and this on the summer house https://novia.co.uk/tapes/airseal310-sealant Both seem to be exactly the same.

Full story Posi rafter, above was all sarking boarded, breather membrane and slates on 45 Deg roof and Sarnafil membrane on 12 Deg roof. Inside was under drawn with counter battens to increase the depth from 256mm to 356mm. Full filled with open cell spray foam. VCL double sided taped to battens, stapled and all staples and joints aluminium taped. VCL draped down walls and bonded to wall. Counter battens (50mm service cavity for lights) then plasterboard. When I battened the posi rafter, I did it to get a good thermal break. So used a small section of batten on a long section to form a 100mm Wall drape can be seen on wall. Counter battens

You could just use a simple orifice plate. Basically a plate Infront of the fan with a hole in it. An orifice plate uses upstream and downstream pressure to determine the flow rate. You need to make it with a sharp edge so thin metal may be easiest. Use something like the site below to calculate the flow. Use outside air pressure and inside building pressure as the two pressure inputs. So plate has to be outside in relation to the fan, so fan sucking through the orifice. https://toolbox.tlv.com/global/UK/calculator/air-flow-rate-through-orifice.html

Yes don't see it being an issue. Our longest are just over 7m between support. Airtightness details are super easy. We just covered the inside of the roof with airtight vcl and overlap on to the wall and then bonded to wall with airtight mastic. Then battened for plasterboard.

Sorry missed the question. Mine has an adjustable pressure switch on the accumulator which is wired in to the pump control. Think it's currently set at 2.5bar. so pump starts and stops based on accumulator pressure.

A guide to filters https://www.genvex.com/en/know-how/ventilation-filter-guide#:~:text=M5 suits most people's needs,particularly order even finer filters.

If you look at the image (previous posted) there is a raised platform at the back of the house. The wall in front of it is a structural wall. There were wall plates added to that and the rear wall to form a loft (plant room). We used something like 10 or 12 X2 timber, to form the floor and glued down tongue and groove 22mm waterproof floor panels as that is the only upstairs bit in the house.

I would be tempted to dig 4 holes (space width square and deep) get some threaded bar, chemical anchor, and postcrete. Fill holes with postcrete and level. Drill holes for flanges. Chemical anchor threaded bar in place. Tighten nuts - it's going nowhere in a hurry.

Photo from inside and outside, no bottom cord. Come ready cut to slot into place.

Other choice is posi rafter or I beam and glulam. You can also under draw with battens to get insulation depth required with further layers and just insulated with a blow in product. Plus another, which is blown mineral wool. Then an airtight vapour barrier fully taped and bonded to the wall to make airtight. If installing lights a service cavity. For others reading - Spray foam is only inappropriate when used in the wrong place or wrong kind used (close cell instead of open cell). Ok when used correctly - Sarking boards (with gaps) breather membrane above. And vapour stop below, open cell foam only.