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6100 - ASHP usage of 2650 is 3450 Electric used by other appliances so that's a little over the average but then so are we at around 3600 (2 people in 4 bed house with a reasonable level of tech/convenience) The scop is good too!!!

CoP sounds good, but heat generated how does that compare to your design energy usage? If 12,000kWh is correct all good. But I thought your house was near Passivhaus standards, so maybe high depending on house size and hot water usage.

Just check the datasheet to ensure chosen heat pump does it, then never mention it again to the installer or umbrella company - it's just a can of worms that very few understand or want too. When I was looking at heat pumps I looked at the scheme by CoolEnergy, but their heat pump offerings weren't really suitable size wise for us, either a little too small or oversized. So read the datasheets before committing.

That's better.

As it happens our total electricity use since the board was made live is exactly 6100 kWh as of 2 hours ago. This includes the couple of months prior to us actually moving in full time. so there will be a little consumption not accounted for elsewhere. Small amount, i dont think it changes the figures enough to care.

If you implement the planning you will be liable for the S106 payment. Once you get the paperwork your solicitor should be able to advise. That is a fair chunk for a replacement dwelling and you may be able to reduce this.

OK guys i get what you mean. Apologies. So, that 2650 kWh is what the Vaillant app records as energy consumed. For a generated 12119. so a SCOP of 4.56

Update I had a nice chat with the woman at the VAT reclaim office. She said wardrobes are notoriously difficult to get a successful claim on. The fact that they have to have no back on them (you must see to the wall) and only one rail and one shelf. Ditto with hobs with built in extraction. She said HMRC had taken legal advice on hobs and they consider that as the hobs main use is for cooking and not extraction they are disallowed. I suggested they updated their information as it seems very outdated (no extraction hobs are mentioned and they have been around a while now). I didn't resubmit these two invoices and put it down to experience. Won't be self building another property EVER again! Good luck all with your builds.

Yeah i thought about white, but thought it may be a bit too 'in your face' to look at from the street side, so I stuck with a grey similar to my window frames. I've got plenty of thermal images of my windows from the various heat waves this year, so will try and collect some next year (if we have any, probably won't now i've made these!) and upload them to compare. I don't currently have any ceiling fans, only portable ones which I can move about, but the noise tends to keep me awake. I do have an evaporative cooler which i get out when its rediculous hot, which when filled with ice packs knocks about 1C per hour off the bedroom temperature with the door closed, with the downside of adding a lot of humidity, but again, i don't have it on all night, usually set a timer for 1hr when i climb in bed, and a good 75% of the time i don't hear it switch off, but the ice packs only last an hour when its really hot

I think @Post and beam was declaring the electric consumption of the heat pump rather than the heat generated (which would work out as a cop of 1) @Post and beam if you are pulling usage data out of Octopus it can be a bit flakey - I've reverted to the old consumption page because it doesn't have missing data as often as the current consumption data extract

It suggests a CoP of 1. Cost me about half that on E7, storage heaters and an immersion heater.

All good. I worry a bit that I'm coming across a bit negative. I do like your design. This is all a matter of choosing where you want to spend your money (or otherwise control the cost) and as long as you consider that things you like might cost more that's fine (so long as you have the money). Sure. I was saying that more just in case you were concerned about losing space. I think if you have extra space it should go more to the bedroom areas. Equally, you could go overall shorter if the building is a bit wider. Good points. Wider does potentially have undesirable consequences vs longer. Extra length is easier/cheaper but maybe doesn't help with layout as much. True. You can get some very 'stair like' loft stairs that should be easier to climb. But if you are planning for everything to be fully accessible then it's not the way to go. Again if the building is 1m wider you could move some plant to cupboards along the corridor. If longer, could be cupboards against the kitchen wall around the door way.

I asked the Marsh rep what cable we needed and he said "Generally, a 2.5mm 3 core armoured cable will need to be ducting out to the tank." He also attached the installation manual which says "A single run of 1.5mm (or greater dependent on distance/voltage drop considerations) 3 core SWA cable". and "Cable protection via 10amp MCB/RCD or RCBO, rated 230V AC and tripping current 30mA." The length of cable will be about 25m from fuse board to tank. I don't know what power the pump draws to make air bubbles but I seem to recall it is under 100W. It's only worth about £15 difference in cable. But put it another way and it is 20% and wouldn't that be nice through the whole job. Plus the skinnier one will be easier to manipulate. And does it really need a duct? I was planning to put it in the drain trench. Electricians' advice welcomed.

I'm more familiar with it being a version of a portal frame too. But it both came to mind and your images came up in response to searching 'space frame buildhub'. I could easily be wrong about what @Gus Potter is thinking of here. In any case, I can see your type of build being a good way to build something like this (with the exception of the big windows on the long wall being a difficulty)

Thank you very much for your advice - and I am also in white PVC camp. Windows ordered, now it's just a small task of fitting them before winter really kicks off. The suspended wooden flooring plan is pretty much what you described. I suspect you don't recommend running any services through the floor void? There's a lot of brick walls in the original cottage (incl internal separator walls), which would have to be chased for the re-plumbed heating. Will read up on ventilation. Anyway, I've discovered a section of the external wall where I fixed a blocked overflowing gutter. The paint in this place seems to be coming off in sheets - there's a very obvious gap between the brickwork and the paint layer (composed of some (potential) remains of very thin old rendering + at least 2 generations of external wall paint). What's the best approach here? Heat gun this section of the wall to brickwork, then cover with masonry paint? I've got a bucket of Fortress Smooth White masonry paint ready to go. Product description says "breathable".🤔 Also, is there a way to figure out what mortar I should be using to repair & fill gaps in the wall (e.g. from an old removed pipe where workies didn't bother filling the hole they created in the external leaf because it was behind some tall grass?) It's definitely a cavity brick wall, but given the age (early 1950s), can I just use modern cement-based mortar as opposed to lime-based stuff?

I've never heard of my type of house construction being called space frame. I always called it a timber I-beam portal frame. IIRC the idea was later used by a company called PH15. A space frame to me is the type of frame used in old, light weight, racing car construction, but I could easily be wrong.

Yes because only they can get you the grant so they must do the design or sign off on yours, I put together a design pack for them to pick the bones out of to check and transpose the things they needed for the MCS form and no it did not really limit our choices. They would have been happy, I think, just to get the professional fees for the design and commissioning. I liked the look of their tiny ASHP so I purchased that and a stack of other components from them, sadly their cylinder was not suitable for our space but they rolled our Telford cylinder choice into the design even though we purchased it direct from Telford.

https://www.dualchas.com/our-journal/dualchas-video

Why? Heating & hot water. I cut the cooling fraction out.

I should say that ETC has agreed to have a look at my plans and give me their thoughts. So I'm going to wait and see what they say before I change anything else. I still really value all the feedback I've received in here so far though.

1 - I think the fact that the factory is literally on the doorstep makes me want to properly consider the hemp option. I've been in touch with them and although they have made no promises yet, I am hoping that a deal can be done for direct supply. It doesn't seem that expensive when bought retail though. They've given me some samples and it's a lot stiffer than mineral/rockwool which I like. It doesn't seem like it's going to be prone to slumping, which is what I've found in a lot of the houses I've renovated that have mineral wool insulation. I'm still at an early stage with all this and I am not going to knuckleheadedly insist on anything at this stage. I'm just exploring possibilities, but my preference is definitely for the hemp if possible. 2 - I did have a straight wall with overhang in an earlier version of the plans but I cranked it later as I was worried about the north end of it catching the prevailing wind and introducing a lot of wind-load stress onto the structure. Also the SW corner of the living space wasn't doing much, so it felt ok to sacrifice a bit. I completely get what you are saying re angles being tricky and the need to avoid introducing unnecessary complexity, but I do really, really like the slanted overhang. I also like the way the roofline stays as a rectangle and it's just that end gable wall that angles. 3 - I guess the building doesn't seem like it needs to be wider though - I don't think the living/dining need more space. My living room in my current flat is 8x4m and it's just ridiculous. The kitchen/diner next door is the same size and feels perfect, but that much space for the living room is actually a bit impractical. I actually did first put the plant room etc in the exact area you mentioned ie where the armchairs are in my current drawing but moved it away later on as I couldn't find a decent place to put the telly without it blocking the view! In Old Holloway the living room is where I have my kitchen and that's an option for it, but it felt a bit too small there, mostly because of the central door to the bedrooms. It's a good point re airtightness detailing for the lean-to though. Another point is that a steeper roof is better for winter solar generation - the time when you really need it most. The payoff of less generation in summer should be ok as it's not as critical then. If I go wider I would need to go higher with the ceilings/roofline to keep the same roof pitch and both are fairly optimised at 40 degrees (though I have taken on board what @ProDave said about 45 degrees being more practical to build and intend to raise that with Gus later). 4 - I can see what you mean. It would make use of space I don't really need up there, but I do worry that it would mean getting the ladder out every time I want to change a filter or re-boot something. Everything is a compromise though, and maybe that's the lesser one in this case. It doesn't seem very 'old age' friendly though (I'm 55).

Ok. Thanks

Used to be true, rules were changed recently. (Last year or so)

Not sure it is related, but I did reach out to a company about the grant ... and as soon as I mentioned cooling mode. Their response was "You are unable to get the grant approved if you are including cooling mode"

A cob horse and a few partridges and pheasants who live in the field behind. Thankfully, no people.