JohnMo

The output of cooling is just the inverse of heating In simple terms if the room is 24, the floor would need to power of 63W/m² (700W /11m²), so floor temp of 24-6 (from chart below), so 18 degs floor surface temperature. As room temp gets closer to room temp output reduces eventually hitting zero.

Assume get very little solar gain through windows?

Sounds similar to us, but we have 210L cylinder. Generally heat twice per day, to a thermostat setting of 49, it actually settles to about 51 after heating. A lower set point means a larger turn over of water, as less cold dilution is needed. It adds efficiency to the boiler as you can set flow temperature lower. I keep DHW away from home assistant, I tend to keep all systems that I need simple and well detached from anything so called smart. DHW is local controller - a simple time switch between the thermostat and heat source, heating is now just weather compensation and not even a controlling thermostat, just a manual switch between cooling and heating.

Internal blinds?

Except you get into the realms of applying for dno permission at that size of unit, your cables all get bigger etc. start up current gets bigger. You would be surprised how different it makes the house feel. It's important equally for A2A. A2A is a different cooling mechanism, as air holds very little energy and next to no inertia. Sizing for peak means you can control room temperature with precision, but do you really need too?

Sorry s bit of a rant below. Cannot believe that. Our lounge is 6m tall, one end is fully glazed, to make it worse it's a bay window, even with roof overhang gets full sun from around 4pm, we control the heat with internal blinds and UFH at 300mm centres, so not even ideal for cooling. Our typical temperature trend for the lounge is below. Gets to 24.5 degs, but feels cooler due to cool floor sucking your heat away. And temp drops pretty quickly. In total we have around 50m² of glass facing south west on the front elevation of the house. A 6kW ASHP pulls about 4.5kW max. But that is not real. You have zero need to size for peak load or the way the average is done, or close to it in a house. We get peak load for a few hours per day. The other day 30 degs outside and no cloud, floor pulled 50 kWh from inside house, so an average of near 2kW. According to your calcs I need nearer 50kW cooling input - that's just bonkers. You only get solar gain when sun is actually on the window and could or should only be a a few hours per day. You will have curtains or blinds (internal or external) these slash the heat gain numbers. People aren't in the room all the time. A floor a couple of degrees cooler than the air will pull a huge amount of energy out of a room. When we are at 24 degrees we have a room air to floor delta of 6 degs over 38m². You need to take a series of average heat gains and then make an average of that, then you just trickle the cooling in 24/7. What is important here is comfort, not the actual temperature.

I would go on the heat geek website and read up on legionella and do a risk assessment. Heating to 50 is more than acceptable (do a risk assessment). Heating to 50 will just about half the heat the cylinder and piping add to the room. Storing water at 65 to 70 will release a couple of kWh of heat per day, store at 50 could reduce that to 1kWh. Which may be enough, without spending additional money.

We used Rockwool Flexi, but most products are similar except PIR which is rubbish for sound. Your insulation material needs to be thinner than the stud so neither side touches the plasterboard. Denser insulation stay in place well, but needs more careful sizing. Gaps are bad and will circumvent the insulation. We used standard 12.5mm and dry lined no issues.

Our house was originally planned for a mix of vaulted and flat in bedrooms, kitchen/diner and wet rooms. But we changed to all rooms are vaulted, way easier to make airtight, no vertical bits to insulate, construction is cheaper and easier to do. Various layer of insulation you have to be careful you don't get moisture ladden air in and it ends up with no where to go. All vaulted makes very little difference to heat loss, goes up a little, but the feeling of space trumps that every day. Assuming you are using a low temperature heating system. If you are using a high temperature heating system, you really shouldn't be anyway. Airtightness details are very easy all vaulted. Any loft space treat the same way as all other vaulted areas, the airtight layer is the roof line. You really need to do the following 1. Determine your air tightness and vapour tight layer, this should be continuous around the building. 2. Decide where your insulation layer is. Get a cross sector building - take a pencil can you draw a continuous line through insulation and only insulation, around the building without lifting the pencil? If not you need to add insulation to bridge gaps. The MVHR is building ventilation and has no bearing on your insulation layers. Condensation within the insulation is factor the temperature gradient within the insulation and control of moisture or lack of by a vapour protection layer, normally coupled with airtightness layer.

A DIY approach could UFH gypsum boards attached to wall, fit pipe and plaster finish. Floor finish can be carpet etc.

Or an alternative to UFH and fan coils https://www.variotherm.com/en/products/modular-wall-heatingcooling/technical-information.html

A link https://www.solray.co.uk/effective-and-efficient-cooling/ https://www.variotherm.com/en/products/modular-wall-heatingcooling/technical-information.html

A link https://www.solray.co.uk/effective-and-efficient-cooling/

Almost any breathable membrane will be fine, use what's on your drawings. We used Proctor. Would you be better to use sarking boards instead of osb, once installed these will shrink a little and give lots of small slots to let moisture ladden air out.

Only thing to add about fan coils is the heat pump NEEDS to be sized correctly, if it's too big the heat pump will cycle, sized correctly with decent modulation, iit will just tick away all day. The fan coil will switch on off in response to heat pump cycling. We have that issue with the summer house and our oversized with limited modulation heat pump, so we end up getting a 2 deg swing in temperature, on all but the hottest days. Once we get to 30 heat pump will run for several hours at a time.

I would concur with that, why dick about with two systems. If you wanted cheaper DHW you could do a heat pump cylinder.

UFH throughout (single storey) does heat and cool. Cooling isn't the be all, end all of cooling, but with none of the blowing air of Aircon (which I started to hate after living in Asia). But does make house more comfortable for zero additional equipment and zero costs, house doesn't have the extreme of heat and cools down before bed time. But we have huge amounts of solar gain, once outside is as cool or cooler than inside we purge ventilate as well.

Your missing the point. You will have a battery - all your available DC power can go direct to battery charging. The battery inverter is basically pegged at 3.6kW. So can give 3.6kW to the house or the grid if battery is full. If you want a bigger inverter get a G99 etc. With 11kW on the roof, you are going to be exporting or wasting a bucket loads of energy in the summer. You will.not know to put the energy after lunch most days

All my room temps are in an app, all the rooms have a thermostat, but the boiler output isn't connected. Anyone could change any set point but it doesn't actually do anything. It's just a monitoring tool.

It called overclocking. Big array and smaller inverter. In full sun PV production is great, but 95% of the time we don't have that. So in 5% your panels produce loads but the inverter clips output to only output 3.6kW max. The rest of the time you are still limited to the inverter capacity of 3.6kW but you are more likely to actually produce that. Not all inverter like overclocking. Quite a few hybrid inverters do.

I paid too much using a gas boiler ASHP hybrid, just because of the gas standing charge. So gas meter had to go.

Possibly why the app says estimated below the graph.

I am a 4G meter, but that sends data direct to DCC and everything gets read from there. But strangely I have consumption data from prior to the 4G hub being installed. So the smart meter must store a period of data as well. Communication was established last Friday, but I can see 30 mins data back to 15 June on the octopus app. I am also using an octopus mini, which connects to your meter wirelessly, so that my be reading directly from the smart meter and utilising the app to display data?

If you reduce the bedroom flow rate the mean flow temperature for that loop reduces only. It adds less heat, so over the 6 hours will add just enough to get that room to the temperature without any need for a thermostat. But if only this room is using a thermostat to limit room temperature rather than call for it, you just don't need the buffer, especially if batch charging the floor. I just used a single window for batch heating floor, but used a 0.1 hysterisis thermostat to stop overshoot. Could do the same for boiler and ASHP. Both would run a single cycle (so start at start of time and run continuously until the end), only ASHP having to defrost when required. Once outside the running window the thermostat was set a couple of degrees below actually room temp. But don't bother with any thermostats any more.

Or Sunsynk are supposed be good