ProDave

Fit a proper air tight membrane over the inside of the rafters with all joints taped, and taped to the air tight layer on the walls.

That's a big house but you don't have a separate living room, just the one big living / dining / kitchen space. Are you SURE you are happy with that? Have you lived in such a room? I do not like it, we just use our large room as a kitchen / diner and have the living room separate. During the build we did use the kitchen / diner as a living space for a while and it drove me nuts trying to relax in peace and quiet with the Fridge Freezer and / or the dishwasher spoiling the peace and quiet.

I have had a self build insurance from the start, that's ended now we are Complete and now on normal house insurance. Oddly when we contracted a builder just to lay the foundations and build and erect the shell, they asked to see my insurance, particularly the "contractors liability" bit as we were the prime contractor. We lived on site in a static caravan for much of the build then moved into the unfinished house and building it around as as even an unfinished house was more spacious and comfortable than a caravan. There were no issues then as we did not have anyone working for us, it was just ourselves completing the internals of the house.

Borrow the regs from your library, if your local library does not have it they should get it on an inter library loan.

The well known "re boot the computer" I have gone as far as install a time switch that turns the power off for 15 minutes each morning just before the scheduled heating time to automatically reset any errors that might leave the heating not working if we were away.

The 2 main things are run the heating at the lowest temperature that it will deliver enough heat, and heat your hot water only to about 48 degrees. You can also play around with temperature compensation curves, but best first to find the minimum heating temperature that delivers enough heat in the very coldest weather without compensation first.

And if you are going to run a big load on an extension reel, then FULLY UNWIND the reel first or it will turn to a melted mass of plastic on the drum.

When the heating is off I am willing to bet it is the return pipe getting hot first on the radiator. Ask the installer he piped it with a common return. That is the work of the devil and should be avoided, always fit a separate return for radiators and hot water.

I am confused from the picture. What is the big black tank if it is not your HW tank? The things on the wall are expansion vessels they can move much higher to make more space. Is that picture new as in work in progress or what you have had for some time? Plenty of room in that cupboard if it was laid out properly.

What are these THREE buffer cylinders? That seems to be the issue if you are short on space?

Positioning needs to be accurate. e.g. of you have rows of downlights thena badly positioned smoke alarm stands out like a sore thumb.

We are just getting confused with symantics. When I say eaves height at the lowest point, I mean the point of the building that gives the lowest eaves height measurement. That of course is at the bit of ground that is the highest, as in highest above sea level. Sorry if I confused.

That is standard for the design SAP. When you get the house built and an air test done, they will update it to an as built SAP with the actual figures.

Plenty of cases where a neighbour has complained about a shed or something built on sloping land and complained the eaves height is too high, and the ruling has come back eaves height is measured at lowest point and no action is being taken.

Mine was 1.4 which I was disappointed with, I wanted under 1, but they guy doing the testing nearly wet himself with excitement proclaiming how good it was.

Very easy. Just make sure the floor and shower former are clean and dry before starting. It sticks like the proverbial so get it lined up right before you start peeling the backing off and smooth out any air bubbles as you go. Then keep it clean and avoid walking on it much until you tile.

That's what I used. Are you fitting the Impey WaterGuard tanking system as well?

The spread sheet makes no allowance for incidental heat, e.g. from cooking, showering and just people being in the house, and solar gain through windows. So when you get to the months that fon't show as needing much heat, the reality is none at all. Typically I find once the outside temperature gets to about 12 degrees we need no heating at all. An 8kW ASHP would struggle, it would have to be running 24/7 doing heating. The reality is it has to stop heating the house to do DHW heating from time to time so it would not manage. 12kW might be closer to the mark. I have a 5kW ASHP and it runs 6AM to 10PM and meets our max 2.5kW demand. Now is the time to experiment and see what you can do to improve some of the U values to reduce the heating requirement.

4.1kW is the heat input, i.e. run two 2kW electric heaters continually and it will maintain the desired temperature. so that tells you the size of the heat source you require. So 4.1kW over a 24 hour period is 98.4kWh Note the h for hour, Killo Watt Hours. That is the amount you will be metered and charged in a 24 hour period. In rough figures a heat pump consumes about 1/3 the electricity than it outputs in heat, so a typical heat pump delivering 98.4kWh would consume about 32.8kWh of electricity in a day. You don't say under what conditions that is taken, i.e. is that the coldest day? Our house (half the size of yours) needs about 2.5kW to heat it on the coldest day, +20 inside, -10 outside.

There appears to be a recent change in the new Scottish law that allows radio linked 10 year life battery alarms. That makes my job a lot easier in some cases. I am sure the first version of the law when I looked over a year ago did not allow that.

Ouch. That will test his building / self build insurance policy.

I changed my pump from a cheap one to a grundfoss, way quieter. Wilo are also pretty quiet pumps, I put those on the UFH manifolds to quieten those down as well.

No my tiler friend did that at mates rates. He has a better tile cutter than me.

Most heat pumps demand a high flow rate. Be thankful it works. Had you installed an LG like mine it would have refused to run if the inbuilt flow switch was not satisfied, forcing me to add the second pump. I doubt it will affect efficiency. More likely with a lower flow rate, it will limit the amount of power through the heat exchanger so the heat pump might never run at it's maximum power, which if anything might make it more efficient.

What is the context? New install? Old install? Has it ever worked properly before suspecting a 3 port valve issue?