JohnMo

It could but I am not sure you would. The cylinder you are linking to only has a thermal power of 1.2kW, so would stand zero chance of heating much more than a very smallest of heating loads. The extra context say don't do it. The concept may be ok for hot tap water but not for heating 100m2 of floor. UFH needs good insulation standards below it. In the order of 100mm of PIR insulation or 150mm polystyrene or more ideally.

Do you need tape? A polythene sheet over the whole lot will stop any screed getting under and lifting it up.

As @TonyT says, then as you come out of the roof, leave behind another couple hundred mm of insulation. It looks very thin in the photo. Before you start looking have a watch of this video. He could have also installed a rubbish fan as shown on here

With only 140mm in the walls was assuming insulation board was being installed as well. What is your planned wall buildup?

Spray foam would not give the same u value as PIR board. It would be quicker. Frametherm 32, which is mineral wool would fully fill the studs, way easier than cut boards. Overall although theoretically not as good as cut PIR, may actually in practice give better results. Quick and easy to install, almost zero waste. Way cheaper than both options.

I put my immersion on to an external thermostat, as I could never get the cylinder hot enough, even replaced the immersion and integrated thermostat, but it made little or no difference. Max temp I could get to was about 60, even the immersion thermostat set at 75.

I do the same

Your heat usage is similar to yours, which slightly lower by month, but by hourly average, pretty similar. I am in the process of installing a 6kW machine. What you need to do is ensure at the lowest design temperature, the capacity the chosen ASHP can meet and exceed your max heating needs, so it leaves capacity for DHW heating. Previous experience and detailed monitoring of our gas consumption shows the unit to be a little over sized, but the next size down unit to be a tight fit heating capacity wise. So I would say they units mentioned by your suppliers are massively oversized.

Single zone means you don't need any room thermostats, we had then then removed them. You set different room temps you balance the flows, more flow means more heat, less flow less heat. I take it will run the manifold without mixer and pump direct from ASHP? How it's being suggested is exactly how I run my gas boiler, and soon to be commissioned ASHP.

I just went dMEV, with presence sensor. No-one in the garden room, ventilation is off. Someone in room for 90 seconds or more, fans runs for the time the person is there and an additional 30 mins. Simple cost effective, ventilates only when required. No heat recovery but hay ho. Plus points, only ventilated when needed. Fan not running 24/7 No or little ventilation heat loss when ventilation isn't needed. Very low electric consumption. Cons When someone is in room vent fan is running, with no heat recovery

You may have to initially put the unit on boost and wind the boost to max. The Titon units will not allow the normal to run faster than the boost. If you try to go past boost setting it seems like you are at max settings but you are not.

Have had quotes?

That could be why the fan speeds are high. Basically start with all vents fully open. Leave the furthest away from unit fully open. Reduce or increase fan speed via the potentiometer for normal speed to get the flow correct at the furthest away vent. Then move to the next nearest, this time do not move the pot only move the vent. Repeat. Once all vent extract done recheck and if any need adjustment, recheck all until none need moving. Repeat fro supply. Do the same for boost, but this time do not move the vents just the potentiometer. The settings you are quoting should be the normal speed not the boost. You want a supply rate of 11 l/s in a double bedroom and 5.5 in a single bedroom at normal settings. Supply and boost should be the same flow rate overall.

That a how long is a piece of string question, all depends where the services are coming from. Our gas wa a few hundred pounds, as it was really close, the electric several thousand because it wasn't close. But could be 10s of thousands of a few hundred.

Just buy one set of spare filters, do not though away the plastic frames, they just unclip from the old filter. Buy sheet filter material from RS components or similar. Then use the removed old filter material as a template and cut from new sheet filter material. Clip the frames back together. You can then have one set of filters installed and a set ready to go. Way cheaper than buying complete filters. Not sure where you have set your boost rates, should be 25% above normal rates. How have you set your flow rates? What did you do?

I think these have a pretty big hysterisis so not the best with high mass heating systems. If you are set on Valiant product, I would check out what comes with the unit it's self, that may be ok on its own. Thick floors keep it as simple as you can.

Hi there A couple of things, your stored water temp will be around 47 degs, so 200l capacity will need to be looked at bearing that in mind. Your cylinder does not power the UFH, your heat pump does, it basically supplies two temperatures via a diverter valve either to UFH or cylinder. To get CoP (lowest running costs) from the heat pump it needs to be run at as lower temperature possible. Hense running two temperatures. You possibly need to do quite a bit of reading in the heat pump sections on here and UFH so you do that correctly also.

Trickle vents in the wall instead of window trickles? MEV, dMEV all require vents in the rooms. You don't need trickle vents in the rooms with the vent fan, but in this case you need vents in the dry room. PIV would require vents in all rooms. You can install humidity activated trickle vents.

I just did underground duct, used 28mm Hep2O pipe, 25mm thick black insulation, which I wrapped in aluminium tape, and inserted each length in 110mm flexible twin wall duct. Made 2 x 4m lengths. Terminated the duct at both as they went in to our out of ground. Used stainless steel mesh spray foamed in place at each end of the duct to stop rodents making their way into to duct. The pipe was taken the through wall about 300mm above ground at both ends, into house and into shed the other end. Exposed pipe will be wrapped UV stable insulation.

Didn't notice anything on resolution

Just had a proper look at the MCS version I have 3.0 Sizing the Heat Pump 3.1. General Getting the design and installation right Sizing the heat pump correctly is of paramount importance. Various field trials seem to indicate that accurate sizing is important in order to maintain efficient running of the system Heat pumps should be selected as closely as possible to the design heat demands. MCS Standard MIS 3005, requires the unit to achieve 100% of the duty at an external temperature condition exceeded for 99.6% of the year, if reasonably practicable...

If you are heating the whole contents of a 300l cylinder from 15 to 48, that's about 12kWh. So from cold to hot about 2 hours (7kW unit). But that should only happen once the rest of the time you only be heating about half the water or less, so about an hour. Assuming you have a big coil in the cylinder. If you're well insulated your floor temp will only be a couple of degrees warmer than the room. So the floor temp will be around 22-23. With weather comp you set a curve based on outside temperature, the colder it is the warmer the flow, thermostat is only there to help stop overheating so set a couple of degrees hotter than target. Ours flow temps vary from 25 to 32. On UFH based on our house I can operate in two ways 1. Run WC and let it look after itself, set the thermostat slightly higher than target temp. This works best for us on a gas boiler when consistently cold. 2. A variation of the above is set WC curve a degree or so higher than needed, use a thermostat (0.1 degree hysteresis) with a combination of time temp targets to force heating on when house temp drops and off again just below target temp. This basically batch charges the floor overnight based on outside weather. The heating is off for about 14 to 16 hours. This works best at start and end of heating season, when there is plenty of solar gain in the day, our heating hasn't come on for about 10 days now. Note we have 300mm loop spacing and 100mm screed, floor response time is slow. Someone will chip in if I'm talking rubbish.

All depends on how you live in your house. Some want UFH to operate like rads, because they are out all day, so thin is better. Steady room temp or batch charging floor, thick is better.

Are you putting in any secondary heating like a stove, if so that what takes you down to the lower temperature. No way would you size for -20. Valiant are talking out of their a*** Using MCS guidance you would size for the 99.7 (think that's the right number) likelihood lowest temp. So the -9 and -10 temps would not be included. So you are likely to be sizing or -3 or 4. So if you use the 16.6W/m2 fig you will not be far off. Then you need to allow time for cyl reheating also in your daily allowance then divide by 24. Allow some time for defrosts, although not that likely at the lowest temperature. Most the time your conditions will be warmer than the design case, so an oversized unit will be struggling with turndown. I would be going the smaller unit no buffer and run weather compensation. Or run weather comp, a degree or so hotter than needed to allow your floor to batch charge, with the thermostat tripping the ASHP off at 0.5 degree below your ideal temp. Not sure I agree with the thermostat on buffer as by default you will never run at the lowest temperature possible, so CoP will always take a hit.

Keep it simple don't put them in the ceiling. Use coanda effect nozzles and put them in the wall. The coanda effect will cause the air to travel across the room.