JohnMo

So minimum is going to be 28mm piping. Ideally in copper, Hep2O should be ok, 22mm the pressure drops will be too high. Depending on heat pump you may need to add a boost pump. MLCP in 32mm I would check the cost of pipe insulation - min wall thickness 19mm it could cost quite a bit.

Not sure that helps, I tried a flat curve, to see what happens and it got a lot worse. The heat loss reduces, so still throws the controller out. That sounds like too much intervention and faff. I would be setting to manage coldest outside and then have a thermostat, used in an energy limit mode. So basically a permission for boiler to run, but cut out when curve doesn't exactly match house needs and house starts to get a higher temperature than target.

This is ours heated via 3kW immersion. 210L slimline cylinder. Temp messing about 1/3 up from bottom. Basically 1hr or 3kWh to heat.

I have a very similar issue with my heat pump and working through it, I think I know what causes it. Mine occurs when the heat pump hasn't really got any work to do or on an upward outside temperature change, with a warm house. The controller wants to keep the heat pump running but it not getting the return temperature doing what it expects. It's trying to pull return temp down, but the floor isn't willing to change quickly. In our situation the floor is saturated with heat and return temperature is very stable. So the logic starts to loose control - acts like a spoilt child. Not willing to switch off, but really has nothing to do. The control logic, being to manage a dT and upper flow temp (with an over temp hysteresis). So return is stable, dT cannot be maintained with reducing target flow temperature, so controller starts to work, counter intuitively and it's normal programming isn't working. Here is a plot over 50 mins. The previous hour to this outside temp rose a couple of degrees, plus the sun was starting come through from dark and below zero. I have set up a simple thermostat to kill the heat pump, when house hits a given level, about 0.2 above target room temperature. This limits this behaviour quite well. Your radiator system could be doing exactly the same thing, it just cannot shed the heat, so return temperature stays stable. You boiler control system isn't setup by Viessmann to cover this situation? The same as my Hiaer one isn't. This is a problem 99.9% of users will never notice, I monitor mine to death, so see everything, so do you.

I found it in there somewhere, but did the design 6 years ago now, so no longer have to hand. May not even be in the latest edition.

We have our cold water pipes embedded in the concrete sub floor. Scottish building regs say the pipes need to be replaceable. So used 20mm flex conduit, tie wrapped to the rebar. Good thing we always have nice cold water, summer and winter. DHW pipes could have gone in the insulation but they are run elsewhere. But no joints below ground.

Why not heating, what will you use? If you have a heat pump use it. 2+kW means you need heat. Not been on buildhub for a few days. Our Haier 4kW will kick out over 6kW, even though the datasheet doesn't state it does. So will easily heat a big cylinder. But we use the immersion.

Watch this, lots of reasons to dump the glycol - plus are you managing it's condition and any acidity build up. https://youtu.be/gHHrQzoX7C0?si=GtEdv9g732mCe_xK

Official you need a certified flow meter with current certificate, to support you flow rate settings

Can you, do they take offence?

Bit like the OP then

I just simplified all this. We have a 15mm pipe from cylinder to a manifold, then one pipe to each wet room, again in 15mm. The 15mm is branched out once in wet room to each hot water outlet. Our ensuite is about 20m from cylinder so it has a hot water return. Run the same size pipe, in our case 15mm, back to the return pump and then to cylinder. Ideally you want the thermostat on the return pump and a timer.

Simple, you find the GSE tray sizes and then choose a PV panel that fits. Doing it the other way around doesn't really work.

Not in your imagination - you are living in a nearly unheated space, it isn't a healthy place to be. Heat the place never let it drop below 16 degs (yes even at night). Bet your chest issues go away.

Yep, I installed an electric pulley, single handed MVHR install through loft hatch into plant room, same for the 210L cylinder.

Just a single dMEV fan in the utility - Greenwood CV2 can be picked up on eBay for about £30. Pulls a few Watts.

Yep. We had rain for nearly month, mostly at or near 100% humidity, (in fact the year we have high humidity outside) house stays at 40% humidity, not by magic, because its heated.

But won't cut it, on pissed angle then

The membrane does two things, stops thin fluid screeds from going under the insulation. But second stops a chemical reaction between the aluminium skin on the PIR and the cement in the dry or wet screed forming hydrogen gas.

The person that put the UFH drawing together, has assumed you will be having a fully zoned system, so each space will have a thermostat including the hall. That is why they bunch all the pipes together when transitioning through an area. This where the design comes in not making pretty images. You need to understand the heat output and space heat demand. Areas like the utility can be overheated very easily with so many pipes going through area. You need the so called designer to factor this in to the design - LoopCad will do this for you automatically. LopCad is a free to download and a month or so free to use. A weekend messing with is will have a good design done.

There me thinking people that needed dehumidifiers, really needed to sort out the ventilation - maybe they do? If we dry clothes on an air dryer in the utility, they dry fine, humidity levels bearly change in the house, certainly nothing noticeable.

Just done a search "This has potentially increased since the COVID-19 pandemic (Young et al., 2024), with many people working-from-home in environments with poor mechanical air-ventilation (Naz- aroff, 2021). The proportion of time spent in indoor, CO2 enriched environments could also contribute to the changes in blood chemistry noted in the NHANES data and is an important consideration in interpreting changes over time, and forecasts for the future.

Dehumidifier - not sure it would make our house comfortable at all, it never much above 40% in winter. Stripping more humidity would not make sense. Think a heat pump dryer pulls 3-400W.

But could it equally be increases in house airtightness, coupled with poor ventilation, kids playing less outside, spending too much time inside etc.

Not sure how, neither condenser dryer nor heat pump dryer have an air outlet. Older ones are supposed to have air vent routed outside