JohnMo

I would agree adaptive heating with UFH caused my heating to go all over the place, there's to much delay in the floor.

Must agree, the site is excellent. The cylinder as standard does leak lots of heat. Loads of extra insulation has helped. Today it's sitting at 25/26, so heat loss is minimal. In the summer if it is hot it's from excess PV, it occasionally gets to 70 and the room used to be quite warm, the insulation made a dramatic difference to room temperature and also rate the cylinder heated up. Sun's out today, no real need to have the heating on, but with weather comp, the pumps are still running, so excess PV is going to the immersion and is charging the floor.

No. WC basically maintains the return temp. Target flow/return temp is increased as it colder by taking a reference from the external temperature sensor.

If the tanks are heat pump ready, tell them you are not replacing, same with the heating system. If you only need the HP replacement that's all they should be providing. Just a bunch of con artists, trying to rip everyone off

The indoor temperature is controlled in the following ways. Water flow temperature, this needs to be set so trv are not closing down flow, keep reducing flow temp until you have most the house the temperature you want, say 19-20 degrees. Some room like bedrooms may be warmer than you require so reduce the flow through the radiator or UFH loop. If a room is colder than you require up the flow. If when it gets colder the house is getting to warm your temperature curve needs making more shallow, not getting hot enough it's needs to be steeper. Think the FTC is fitted room compensation, you may need to switch that of for a couple of days while you get the target flow temps set up. WC is matter of balancing heat put into the house, with the heat escaping. Trvs set out of the way at max while you set things up. Once set up your trv should be set at a couple degrees above you normal room temp. You need to set a night time set back also a couple degrees cooler than your day temp.

Thanks for the comments, but I have say Nick the idea for the system came from you, and some of your earlier posts on here. I had to do a little refinement at the end but you always do with things that a bit different. The bit that took the most getting my head around was the heat transfer rates through a cylinder coil at very low temps is really poor. When I first started heating the house I was very confused how I could be using so much gas. Had never really come across short cycling, as all my previous House's had been heat seizes. I suppose that's why I keep banging on about, heating system design and the need to design it, to eliminate short cycling - because you can use twice the input energy you should.

Forgot to mention, took the Salus actuator off the mixer valve and it is basically closed so mixing, water just passes through. Wasn't needed.

Well in Scotland the regs say the building should be complete. Which is good enough reason for me. How do you know, for example whoever boards out, doesn't fill the airtight layer with holes for example?

So an update on the heating and hot water performance. DHW Prior to modes, May 2022 gas consumption, for domestic hot water was 260kWh, or 8kWh per day. After mods June - 105kWh or 3.5kWh a day July - 64kWh or around 2kWh a day August - 104kWh or 3.5kWh a day. Had visitors (extra 4 in house) for a long weekend. All other times we were home. So overall well worth the mods. Heating Had the heating on the whole of October, set up to use weather compensation. Flow temps through UFH start at 23 degrees, compensation curve is almost flat, max temp at -5 is 26 degs. Night set back is a 2 degree drop in flow temp. However due to the inertia of the house/floor, night set back starts at 17:30 and finishes 02:30. Floor temp is around 21degs. Room temps 19 degs. Bedrooms temp sits at about 18 degs. All rooms have UFH circulation on, as the thermostats are set at 22, so operate as a single zone. Min turndown of boiler at the flow temps is 6.7kW. But my average gas input into the UFH water is currently 0.5kWh per hour. Boiler runs for about 10 mins and is off for nearly 2 hrs. At -5 the boiler run time should run around 15 mins and off 20 mins. One observation is the gas usage is well below what Jeremy spreadsheet say I should be consuming to keep the house at this temperature. Based on last year's October gas input of 1370kWh for heating and DHW. This year I hope to consume 600kWh or so. So a reduction of about 50% overall.😁

My house was done with Knauf, the guy doing it told me to buy that, as he had used everything else and liked that best.

At the end of the day it's for sap report not you. And a box tick. Hense what the original post is asking. I couldn't get a sap report until I produced a suitable air test cert, completed at the end of the build, my tester would not issue one until the build was completed.

Got our big ones 2x1x1m from a builders merchants, but we'll also got smaller ones about 300 deep various lengths from B&Q.

Lots of builders around us are starting to slow down, cost of heat and mortgage is keeping people's money in their pockets, so may be easier now than it was a couple of months ago

Where the two bricks are length wise should that be a lintel? But generally - see above, a two year old could do a better job.

But most gas boilers are way to big in the first place. So although the modulation can be good, it's not good if too big in the first place. Why put 10kW gas boiler when you can put in 20-30kW. Which is what a lot of people have. The same mentally with heat pump can lead to a expensive to run water heater.

I did that, but also had to get a test when it was all boarded out, painted etc. for the completion.

The flue will normally have a min distance from combustibles. So you will need a double wall insulated one. I would get the installer round and what they would do. Do you need to consider airtightness?

I used 34 deg Stainless Steel Framing Nails - 50 x 2.8mm RSS. From Alpha Pneumatic Supplies. About £50 a box, used a normal nail gun, with a flat foot/shoe thing, so I didn't damage the wood.

Wow that's a2a heat pump costs?

What 6kW of head room on a max 6kW heat demand? On a house with heat/time constant of 6 days? Not sure I could agree. But I will bow out, and leave you to it.

You need to for someone to do airtightness testing. The are testing the house as a whole for air leaks. Do a Google search in your area. The is not completed until the house is finished.

You would need to find out the modulation rate, inverter heat pump do modulate. So yes you could if the figure you quoted is in the modulation range. Heat pump deliver best running long and slow. My batch charge temp was 30 degs for 7 hours. My WC flow temperature at the moment 23 deg, during the day and 21/22 at night. Floor temp is 21-21.5, room 19-19.5, thermostat are moved to 22 to limit influenced the room heating. Your issue is when the average temp drops enough to require you to put the heating on, the heat demand is really low, and the big heat pump can't cope and short cycles.

Short cycling is where the boiler/ heat pump, starts runs for short period and trips on high return temps. It is then locked out 10 mins and then repeats. Lots of energy goes into heating all the metal in the system as this sucks the heat from the water. Not energy efficient.

I did batch floor charging end last years heating season, works fine, but not always great, as the energy you put into the floor, comes out but not always the way you want it to. If you have under charged the floor the house temp drops a little more than you plan, if you overcharge it will be a little warmer than you plan. To work well you need to constantly modify the charge time, to match the average temperature outside. This was a pain, so this year I moved to WC with a small overnight setback to match the house/floor inertia (offset about 6 hours). My boiler is oversized, but I have a huge buffer (160l), so have room to try different schemes. Current input into floor is varying between 0.5 and 0.8 kWh depending on outside temp.

Some down sides Turn down issues when not at min outside temp. Steady state has a higher minimum kWh loading due to larger motors. Bigger starting in rush current to get motors turning. Bigger cables, fuses etc all adding incremental cost increases Higher minimum water flow requirements. Requiring larger diameter pipe runs, considerable cost adder. Much more likelihood of short cycling, as min flow requirements are not met. Floor hot spots, due higher than ideal water flow temps More likelihood you will need a buffer, offsetting some efficiency gains elsewhere. Big ugly unit in garden instead of a smaller ugly unit in garden. Good possibility a small unit could run on solar in the summer, no chance of the big one doing so. There may be reasons