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ok. But if I want all 3 bedrooms cold. So I have to go around turning them all off then. And I also want my kitchen, bathroom, sittingroom cold too. Ok. So I turn those off too. And all back on am. That's fine. But far easier do this very setting, all in one go, by selecting that you don't want any rads on overnight! (& which is totally logical). I'm now starting to go barking mad. Is it a full moon or something? We're all going potty I think.

@ProDave I said I'd certainly use -Rick's- list of points to ask the engineer on Monday. I'm actually not asking you. I'm not asking anyone. I've stated from the start I didn't expect the HP to heat here. I just got it for the cylinder. I then said how cold the cottage is. But I was -not- implying the HP was to blame, no. I was simply blaming the structure. My choice to buy it. A cheap cottage, that will have it's caveats (tho 20sqM of knotweed, vile hateful folks all around me, cold ingress in, & the damp -vicinity/ not my house- atmosphere I physically had to adjust to for 2 months of serious chest ache.. are collectively a bit much more than I bargained for). But at this juncture, it was assumed you see I think, that I WAS blaming the HP. And the suggestions & info & explanations came flooding in. I wasn't at all. I moaned about it's breaking down so often, the complexity of it, & the noise issue battle with Vaillant.. which like a boss, I won. I tried repeatedly to remind folks that I didn't expect the HP to warm this house. That I think it can't. That the calculations folks concur that it won't. But this opinion was rejected outright, by everyone, who for some reason (which I can't still understand) say opposingly that the HP -can- & should heat it. (Eh? No, it can't & this is a pro's opinion, not mine per se). And this is how it works & this is how you can make it work you all kindly state (by spending £700 a month? I'm still unclear about this figure's relevance). All very kindly & patiently.. but the opinion by now, was lost. Cast aside. This is why I am admant it can't work here. Not me just being obdurate, but because this is what was said to likely happen by pros who dod their sums about this cold storage structure I call home, & this is what I find, too. I'll absolutely try my best on Monday, but rads on overnight.. just ain't happening! Ok?

It’s meant well if you are lost on the roads sat nav will get you home - but if you ignore it and decide you know better you can end up lost. the contributions here regarding zoots ASHP are well meaning so think of it as sat nav directions…,.. zoot can chose to ignore it……

I may have to take you outside and thrash the information out of you. Wales vs Scotland it is..... 🙄😆

I'm trying to see the good in that........ My late dad once told me (probably many, many times) if I had nothing productive to say......... I'm not a wet blanket btw, just a mod on a popular forum where everyone's welcome. Let's allow Monday to happen, and have a day of rest here.

It means literally - want a warm house in the day you need to allow it to trickle heat in 24/7 Want a cold bedroom - turn the bloody rad off overnight and back on in the morning

Sat nav works for roads....... ASHP not so much

Ok but when you say run it 24/7, like someone else pointed to with the word 'ENABLED' I seem to recall.. does this literally mean 24/7-? I have a suspicion, that it doesn't mean it literally. I'm not having any rads on overnight- that is a definite. So if this doesn't fit your suggestion, then I just can't accept this "24/7" settings way. I have no comprehension why anyone wants rads on overnight. Perplexing & absurd, to me. Maybe I just grew up in a cold house, compared to you guys. We never had rads on overnight. They came alive at 7am, to mean a warm room at 8am. That's just basic stuff. You just can't veer away from such a fundamental morning heating setting, in whichever syatem you have, gas CH, a HP whatever, to me anyway. Unless you have stacks of money to burn unnecessarily, &/or like hot bedrooms at night. I very much do not like this.

The man's a little lost. ..........why he's come here, to try and get a grasp of WTF to do. @zoothorn is a tough nut to crack, but I doubt that is by choice people. Let's take this off the boil and let Monday happen, and then old Zoot can come back with some of what was discussed. For anyone running out of patience, lift your hands off the keyboard and go do something else. Other forums operate boxing rings, we do not.

Exactly........................................

My last attempt. Just TRY running it 24/7 for a week to see if it CAN heat your house properly, and if so see how much it actually costs for that week. Then and only then can you decide if you can afford it and if it is worth it or you would rather be cold but rich. Without actually trying SOMETHING different to what you are doing (spending almost nothing and freezing) then anything we suggest is wasted because you are ruling it out without even trying. If you won't try anything then why are you bothering to ask us?

Eh? I'm even more loster. I thought this £700 figure, was what you expected me to be paying each month. Youe sentence here above.. I honestly cannot understand one word of. Each word isn't joined to the next in my brain. I'm that far from understanding all this stuff. Tbh honest chaps I really can't cope. I haven't a clue what is being said now. It's a shame as I can see how much effort you guys are expending on my behalf. I just feel panicked now reading yet another reply I can't make head nor tail of sense out of. That I can't possibly formulate a reply to. It's starting to seem like I'm reading a foreign language. I have to massively simplify. Strip everything right back. Forget this £700 mystery figure. Cop whatnots. U calculations. TRV's/ dual thermostats. I just need to ask the man a few basic Q's. Get him to set it. I can't do anymore than that. Thanks, Zoot

Setback is the minimum temp you want the house to be kept at, ie, overnight if you are running a timer schedule. Rad temperature. 46C is lower than I was guessing based on your description of the rads being hot. Your system should be relatively efficient with rad temp of 46C. So a COP of >4 rather than the 2.5-3 I'd previously guessed. This is good. Though rad temperature and setback temperature are two different things so maybe he was talking about multiple things and the two got jumbled? Different to HW temp. Ideally HW temp should be a bit hotter. 55C maybe 46C is a fine temperature for your situation, I wouldn't worry about changing it but if you want to then ask the engineer on Monday.

The £700 is an approximate maximum amount of energy your heatpump could use in 1 month if running flat out 24x7. It is not what you need to spend to warm your house. That your bills are so low is a sign that your heatpump has been working much below it's maximum capacity and with some changes could provide much more heat. @Big Jimbo's question is a good one. Would appreciate your thoughts on that.

A separate question. When my new HP installer was here, asking how I wanted it set up ("what do you want for your seback temp at?" he asked, & I replied "my what?")... he said the following. Pointing at the big fan unit box thing outside, he said "you could run that at 45, maybe even 40 for maximum efficiency due to the settings you want" (my lowly settings of 16*C required temp I set the thermostat to). Question. What was he referring to, specifically, when he said I could run that at 45, maybe even 40? The hot water twmperature? The rads twmperature? Are these the -same- anyway? I mean you have hot water in the rads. So there must be a temp at which you can choose, for the water within them, to be running at. But I see no obvious place to set this rad water temp. Surely their temperature, is fundamental, to how warm the rooms get. Is this the same as the HW temp I wonder ( was he even rferring to 45 or 40 degrees even? I've no idea). I mean I can see where to change the HW temp. That's straightforward (& fwiw I set mine to 46*C). But doing this HW setting of the temperature to 46*C.. am I concurrently also & kinda unwittingly, setting the hot water that runs around the rads temperature, to 46*C too-? What is this he was pointing to, to set it? What could he have been referring to? I mean he must have been pointing to/ indicating towards, some specific aspect within the outside fan unit box. Anyone hazard a guess? Thanks, Zoot

@sharpener thanks for your post today. It'll take me a week to go through it though. Ive read it twice & can only understand the bare minimum. Alot of the trouble is I just find it too complicated to understand. TRV's added on, & I'm -really- up against it. Two thermostats. And I need two brains. I can't possibly understand the Cop stuff. --- As for the £700 a month thing, I mean I'm absolutely bewildered. If I had all of my 5 cold rooms, built to the same standard as my 2 warmish new-build ones, my heating bill wouldn't be affected. It'd still be £70 pcm. Conceivably likely a bit less. So of that was the case here, I'd have my 7 new-build rooms, at reasonable warmth, with the rads on during the day doing the on-off dipping thing, none on overnight as I prefer.. for £70 pcm. So where on earth is this ten times a much figure coming from as some form of reference figure-?? I'm so lost & getting loster too. Zoot

Couple of things to add: 1. The only time a 9kw heatpump would need to work flat out continuously in zoots property is during the few super cold days of the year, if that. The rest of the time it would work a lot less. 2. The electricity bill is averaged over the year, so even if you spend £600 in the worst month, the amount you pay monthly will be a lot less than that. 3. @S2D2's calcs assume a COP of 3. That's the measure of efficiency of the install. A COP of 3 is a good guess for zoot's current setup (maybe less) but with some changes the COP of 4.5 or even higher is possible. If that was done the amount of electricity used to produce the heat goes down a lot. Instead of needing 3kw of electricity it needs 2kw. So £446 running flat out vs £669.

Nothing particularly wrong with multifoil, but it needs to be used correctly and have the correct airspace either side of it, which is often not built-in. I wouldn't use in isolation, but with other insulation. But when you take into account the correct air spaces either side, it doesn't save any space, compared to mineral wool

Others have covered this, but just to be clear: 9kW heat output / CoP of 3 = 3kW electric import 3kW * 24 hours = 72kWh per day 72kWh * price cap unit rate of somewhere below 30p = £21.60/day £21.60 * 31 days in the month = £669.60 6696kWh of heat per month. The heat pump can keep your house above "seeing your breath" temperature. The real issue is, you don't want to spend £700 a month on heating, which is absolutely fair enough. But it also has absolutely nothing to do with whether the heat pump can heat your property. Now let's back out what you're actually putting in. £70 monthly might equate to around £60 a month on heating in the winter. Don't focus on that number, it's an estimate and we're just concerned with order of magnitude at this stage. £60 per month / £0.30/kWh = 200kWh electricity import 200kWh * CoP of 3 = 600kWh of heat per month About 9% of the rated heat pump output. Of course the house is going to be cold. For reference, I have a moderately insulated house and in the last 30 days it required 2508kWh of heat to hold its temperature. You've input 24% of that into your uninsulated property. Only you can decide how much you value warmth. You have a very wide range to play with for the coldest month of the year, £60 to £600.

Is the cell padded with this YBS stuff? If so at least it will be warm. 😉

It’s the endless ‘just’ jobs that trash hours each day. It’s the face in your hands frustration of struggling with an awkward task and being asked by those watching ‘why can’t you just?’ I’ve decided to classify ‘just’ as a swear word. It can join ‘should’ on the banned list.

Probably a fictitious house that never actually existed, and you posting from a padded cell (like me).

"Simply" any better? Just........an alternative suggestion lol. Just saying.

Hi thanks for the replies but as I said I'm not really interested in the standard sizes, which I know are inadequate for what I want to do, but in the actual method of how the sizes/clearances are worked out so I can figure out something custom. I should probably have described the general plans to illustrate why: externally the garage will be clad in rigid insulation(probably high density rockwool or rigid wood fibre) then rendered, internally I will be building a "room-within-room" stud wall arrangement with a small air gap between it and the existing single block skin with a vapour control membrane on the back wall-facing side and flexible medium density rockwool between the studs on which will be fixed a double layer of 18mm ply for the interior face; the existing flat roof will be replaced with a timber framed pitched roof(primarily to carry solar panels) clad externally with PIR/aluminium composite panels and partially filled internally with more medium rockwool and lined with acoustic plasterboard with dampened washers. It will have a mini MVHR system with maze vents and I also intend to damp seal and insulate the concrete floor. There will be no glazing anywhere. I want to have a workshop for wood and metal work I can use year-round in comfort, all day and into the evening if I want, and without disturbing my neighbours(one elderly lady, one family with a young girl, and two doors down a nursery) hence all the effort to reduce noise - ignoring the door with my planned buildup you could stand a couple of metres away from a box with someone inside using a metal saw to cut steel and struggle to hear anything at all. A standard door whether just steel skinned or composite foam panel would make most of that effort pointless, I need to be aiming for something more like 100mm thick with significant mass and layers of different materials to improve its ability to absorb different frequencies of sound plus a frame that allows for a double or triple seal. If the maths of it isn't widely known I guess I'll just have to make little mockups and experiment.

They are uPVC systems 😉