MikeSharp01

....and on out into the pine forests, across the glen, glancing off the mountains and onward to the Lochs and thence the sea - bucolic or what...

Get a good inverter controlled unit and you can control the output quite finely and, if you get reversible one and add some control valves / pumps etc, you can cool the slab in the summer.

That makes sense, but as @PeterStarck says the 100l might be a bit high, so I think that means you get: Worst case day ASHPKw = (174 * 30) + (n * 2) Average case day ASHPKw = (174 * 10) + ( n * 2) Where n = number of people at home Substituting n = 2 Worst Case is: 9.2Kw (Where temp delta is 30) Average Case: 5.7Kw (Where temp delta is 10 as is roughly the average case for the UK across the year, so might differ in your actual location - Cornwall for you!) You can assume that there will be very few days in a decade when in most parts of the UK where the temp difference will be 30 degrees, and even fewer for your location, so you already have a good safety factor. This all means that for 2 people a 10Kw ASHP should be enough for even the worst case and on a normal day it will be working at about 62% of its max capacity. If you want to get to 50% you need to somewhat heed @SteamyTea's thinking about where you are as critical.

Don't forget to add a bit if you have a young family or anybody else who takes loads of showers / baths as DHW will be a key factor over and and above heating the building.

Welcome to THE forum for self builders and like minded individuals.

Welcome to THE forum for self builders and like minded individuals ask away and there will be advice a plenty.

That is a relatively low SAP rating for a new build and will demand quite a big ASHP. What dies it need to do, UFH / Rads... DHW.

Eeeeeek scream, funny feeling in the gonads........?

Welcome to THE forum for self builders. Self building is not for everyone but it is a very broad spectrum from cheque book self builders who pay others to do all the work to the person doing most / all the work themselves and everything in between. Where you are is about finance and inclination.

Is there heat anywhere in any of those pipes?

If you are having an ASHP connect it direct to the UFH - if you get a reversible one you can cool the floors in the summer! You dont' need a battery or a buffer tank, although some have them but you do need to modulate the ASHP output so you need an inverter controlled one or you wont be able to tune for optimum COP.

We were concerned about commercial matters getting mixed up with the not for profit forum. I will dig out the thread and see what we said.

We have looked at this but it soon spiralled into quite a complex admin system. Given that each of us, 4000 members, is spending a couple of hundred K we are a big market.

Yes but grip the lower section above the tube with mole grips so you don't twist the pipe / damage the joint if the screws are very tight.

Welcome to THE forum.

I notice that the larger diggers now have rails round the engine housing so you can clamber over them in safety without a fall arrestor. Also worth noting that although it all feels like something of a pain the injury and death rates on construction sites is massively less per 100,000 workers than in the states so it must be doing some good. Wonder if this difference will figure in trade negotiations?

Interesting post. Taking the big picture view and using your 90% efficiency there are two issues. 1. The environment - everything we can do to conserve energy is going to be a help and if we pay directly now or indirectly later is common on both sides of the equation (and you can improve the 'now' situation using standard accounting approaches). @SteamyTea can probably do ths sums on the energy required to manufacture the MVHR but your solution has a tec solution as well for the most part again creating a common factor albeit perhaps of different quantums. 2. While I appreciate your view that you don't save much it is clear that this is probably due to more factors than your air tightness and, I hope we can agree that air tighness is not, draftproofing but also the amount of the losses due to the difference between the two and the effects of cold bridges etc taking heat you pay for and giving it to the environment for free. Heat which never sees the MVHR. I am confident that a few minutes with a package like Therm and section drawings of your property will show you how the heat is leaving the house without reference to the MVHR. All this said you may be right although I feel it is situation specific.

Do we need to make it longer?

Size of overal plot in our case. I guess it might make sense to use the build m2 but there are costs to the landscaping etc. Doing it on build size for our build and we get £700 ish / m2

Just worked out our plots land cost - in Whitstable at around £400 per m2.

Land we assume?

Looking great - bit away for us inspiring none the less.

I did all mine, 12mm, with a manual pipe bender and a new 120mm former. Not a problem to bend or to cut with long handle cutters and or the grinderette.

If you can keep it dry - you are right everything is in the detailing, and you don't set fire to it then it should last 100 years plus. Timber buildings can last 100s of years and many have.

Mean Trump or Johnson Nope = "stubbornly refusing to change one's opinion or course of action" I was using the latter meaning in that it, natural wood, can absolutely be relied upon to warp / twist / shrink / bend constantly until you get it in a controlled environment. You have to admire chippy types who understand the nature of wood to such an extent that they can cope with this as I find it frustrating.