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When you find out, I need to cover some white lines near speed cameras.

A MWh cost me £52 and I sell it for £120. The simple calculations get muddied by the various tariffs/self generation etc.

Yes, a cascade is 2 or more units connected together. An advantage of a cascade in a large domestic situation is modulation as a very large single unit may not be able to modulate down low enough and therefore cause short cycling during mean temperatures. But this is entirely decided through design of the system and what your typical outdoor temperature is compared to the coldest design temperature. There are obviously other considerations to cascades v single units, but this is a big one. Some manufacturers like Nibe design their cascade systems so you can add new units onto to older ones etc. over time, or even run ASHP with GSHP and pool heating. There is more complexity in the commissioning and control of a cascade. 3 phase shouldn't really be an issue for the heat pump installer. The 3 phase units I've seen are very easy to wire up and it's really up to the electrician (I get my electrician to do all the mains connections because he's got the necessary crimping tools for the terminal connectors and testing tools etc.) including then balancing the phases.

That assumes no one else is reducing FF burning. It is quite possibly that we have reached global peak CO2e.

Any ideas how I can remove marks like this from tarmac? Not sure what it was done with but looks to me like it was spray painted on..

p.s. maybe this is the explanation, but does it not then leave the building industry up the creek? Inside Housing - News - UK certification body for construction products has accreditation suspended

Does casdade mean 2 smaller units.? Thag was the original plan. Presumably a single at 15 suits 3 phase, whereas a couple of 8s are more likely single phase. If our well respected local installer hasn't ever used 3 phase, and is tied to a supplier other than the names you suggest, then the expertise may not be forthcoming.

In my search for longer lasting battens, I called the guys above, who say those are no longer available. I also called Kedel re their plastic battens: 50 x 25 Roofing Battens, Recycled Plastic Battens ... to ask whether there's any BS5534 adherence/ certification. They'll get back to me. In the process, I looked at the BBA site. Oddly, there's this weird note (below). WTF does that mean, and who are UKAS - I mistakenly thought that BBA were the authority. To add a little spice I see on the 'myBBA' search that only Marley has a current BBA cert for their battens. ?

Respectfully, no it isn't. Fully agree we do need to decarbonise. The point here is that HMG are driving decarbonisation by trying to manage the supply side of the energy chain - not issuing licences in the North Sea. Better would be to drive it by demand side measures, e.g. a carbon tax. Then we can leave it to the oil companies to figure out how much is there and whether they can get the stuff out economically. There needs to be a cost of carbon which reflects the environmental damage it does. Dieter Helm's suggestion is that the carbon price should move inversely to the price of oil, which seems like a good idea.

Firmly disagree. Gas is going to be burned for decades. North Sea gas displaces gas from elsewhere, so is (relatively) carbon neutral. I'm fact, it could potentially produce slightly less CO2 overall due to the fact it isn't being transported halfway around the world.

Won't a standard 8 point socket fit?

Plenty of those around on 3 phase. In fact some of the larger units are only available in 3 phase (e.g Panasonic M series over 12kW), but it all depends on the system design and whether single big unit or cascade is the better way to go. You need a good designer to look at it and justify the decision.

The car, or the motorway? Best to avoid.

That totally ignores the climate change impacts though. And that is before we get involved in public health.

I shall have a look at it when I have time. We need more 'calculators' like this.

Respectfully, this is a pointless argument. Either there's still oil/gas to be economically extracted, or there isn't. The government doesn't need to get involved in figuring that out. Grant the licenses (with restrictions as mentioned by @LnPand others above), and get out of the way. If there's no long term gas, private companies will figure that out soon enough. We can deal with renewables in parallel.

A MWh of electrify will cost about £250. Do some simple calculations and see where it all stands.

Though we selected them separately, it turns out the solar heat pump people and M &E know each other, so there is trust. It was my suggestion to use 3 phase, simply based on the principle that big machines use 3 phase, and kndustry uses 3 phase, and that we have it available. Sparky has the same instinct. The heat pump will be big, around 14 or 15 output. It seems that most domestic heat pump installers don't know about 3 phase. They sell what they know. We've instructed them to try harder on this, but need whatever proof/ backup there might be... or the reverse logic if that is the case. Battery logic.... noted, thanks. In summary so far. Get it but don't oversize.

Are you leaving them fully open? I usually open a valve like this and then back it off maybe half a turn.

I recently changed my view on this - I used to argue you might as well wait, because the cost to buy the battery was coming down fast enough to balance out the usage savings. Right now though the balance has tipped with battery prices look more uncertain and export tariffs making it more cost effective to use your own stored energy. An ancillary benefit of installing now is that it should improve your as built SAP rating by a couple of points.

I agree you need to protect against this financial risk and I wonder if it's a sign the seller really means subject to a scheme they like being approved. The biggest benefit of buying both plots is only realised if you're going to develop at the same time - sharing costs for prelims, groundworks, services, having same trades on both at similar times, less material waste etc so I'd focus on just getting the most out of the plot that works best for you.

This is a great contribution to self build and wider market @SimonD. It strikes me as taking the work @Jeremy Harris did way back and moving it up to a whole new level by both allowing the heat loss work to be undertaken and moving it through to the design of the accompanying heating system. It is also great that you chose to share it with us.

Preach.

I'm actually not sure where the best place is to post this but as it's primarily about heat pump system design, I'll put it here. @marshian and @mads ,and maybe @MikeSharp01? you've expressed your interest so mentioning you here too. I hope the admins don't mind me putting this up here, but maybe if it is found to be useful, could be pinned to help so many of the people who come here struggling with poor heat loss calcs and designs and want to complete their own. I've finally deployed the tool I've been working on for initial public use. It's available free and open source, so repository on GitHub if anyone wants to host locally. It's currently in a bit of a test mode so I can get some feedback and bug reports to refine it and add further important functions. Just bear in mind I've been developing this myself along with everything else in life and it's been quite a major piece of work since last summer. It is now based on the CIBSE 2026 Domestic Heating Design Guide implementation of BS EN 12831:2017 and BS EN12831:2017 so complies with MCS design requirements. I have been using this tool for MCS heat pump projects in house that I'm doing. It's at https://openheatloss.com Important user notes: At the moment when you arrive, you can complete a whole project anonymously without logging in but this persists only for 48 hours or until you close the browser. The save a project, just register using name and email, nothing else. If you want to remain largely anonymous, you can just add the post code prefix to the installation address to set outdoor design temperature and Typical reference temperature. No need to put in loads of personal information. The workflow design is to work you way from left to right across the app tabs. Current limitations: I have not populated the database with standard wall build-ups and U-values. If you're a self-builder or doing major diy hopefully you'll have this info already for your project, otherwise you'll need to look it up manually. There is, however, a comprehensive floor u-value calculator and a simplified one in the room elements input too, so these can be calculated for you. Same thing with radiators - no standard sizes or outputs in a global database yet. I will do a scrape at some point. All outputs entered should be the Delta T 50 catalogue values and if you want system volume calcs, also input the radiator water volume. The UFH sizing calculates volume automatically based on your set pipe diameter, spacing and room area. Text based design - I've tried some of the design tools that are trying to be like cad design software, so you've got do draw your project. Having used cad software, I didn't warm to any of them because they're not proper cad software but in house bespoke design. As I also found out they have limitations so you have to fudge some shapes - roofs in particular. Text based means you can input elements more flexibly according to your needs. Well, I hope so anyway. What you will find different if you've used other tools, although I'm sure they'll either be doing it already or soon, is that the tool provides 2 different heat load figures. is for the heat generator which calculates the whole house fabric and normal ventilation includes a full fabric air infiltration calculation and is usually higher than the generator load To explain this, the new heat loss calculation methods according to BS EN 12931:2017 and specifically those implemented in CIBSE 2026, with wind load under certain conditions, parts of the building and rooms may require higher heat outputs, whilst other parts may need less. This 'total' value comes to a higher result than the generator. In my own test projects that I've run through the new software, I can attest to this working quite well. For example, in one design and installation project of mine, one particular room in the house was designed for 23C but over the winter, whilst never cold, the room never managed more than 21C. I had thought it was a balancing issue, but no. When I ran this project through the new software it predicted that I would need larger radiators in this particular room, base on the new ventilation infiltration calculation, so that is what I will be installing before next winter. Anyway, please have a go and let me know what you think, and ask any questions you have here, or email me at the tool - heatloss@openheatloss.com Does anyone need a user guide to the design workflow and inputs? Let me know..

The battery would be VAT free during the build and maybe VAT free after. They became VAT free (outside of a new build) a couple of years ago and for sure that gift will be removed at some stage in the future. Definitely get the battery when you’re building, they change the game entirely compared to just solar PV. It’s costing us naff all to run this house (and hybrid car) the battery and off peak tariff is a large part of what makes that possible.