joth

Oh and to add a smaller point, are you comparing pre or inc VAT prices? The ASHP should be 5% rated vs 20% for the oil boiler (AIUI)

The RHI compensation angle? With a ~11kW heat load expectation, you should get at least £7k - probably more - in RHi. Over 7 years.

Remind us if you're in the exorbitant SE? Did it include a large unvented cylinder and plumbing and buffer tank and stuff? For just an ASHP that's way to high but I find they tend to assume a lot more in the quotes and yes, that sort of "ball park figure" is very typical for first contact I made with 3 or 4 suppliers around here (Herts). Obviously MCS certified etc etc and obviously like every other part of a build can be undercut if you're happy/able to DIY install.

Thanks @AliG and @Russdl Sounds like if we put in the duct or grommet there's a reasonable chance they can use that if I leave the installation until late on. Snag is my electrical cupboard is not in a brilliant place to get an external duct to (in the middle of the house upstairs) so I either need to get my hands on some of their cable before/during first fix, or accept the box goes somewhere else. Either way the consumer rather than new development route sounds workable.

Key thing is what are the pipes embedded in, underneath the amtico? Assuming it's a large mass of concrete, it will have a high heat capacity you need to pump a lot of energy (warmth) it to warm it all up before you'll start to feel much coming up through the amtico. Whoever has the lowest floor flat (ground floor, or basement if there is one) will likely have slower warmup reactions and overall need to keep the UFH running longer (more total kWh spent) because the underside of the concrete will presumably be colder than all the other floors. It's possible (if unlikely) that someone actually specified the ground floor UFH a bit differently to handle a higher workload. Also a common design in larger blocks would be to put the common services & communal boiler etc into the basement, which helps offset that issue a bit.

Thanks for this! Although for us there's actually no problem about BT line, we already have one of those ? it's specifically the Virgin Media install that I'm struggling with as their two options seem to be unobtainable (New Developer Route) or unacceptable (consumer install, with a load of cables traipsed over and a holes cut into the outside of the house). This is a good option, and I might well do this anyway as we're due (they say) to get FTTP in 2-3 years. The risk I see is VM (and Openreach for that matter) seem very particular about new installs only happening via an external termination box that must be hung on the side of the building an access through the wall so would be unlikely to allow use of it. Also, VM will only route the internal signal via their own specially endorsed RG6 cable, and so if we want TV outlets in various rooms I need to get my grubby hands of a good amount of this magic cable. But that said, this all gets much simpler if I accept we'll never put wire VM cable to multiple TV sets. (I've never even subscribed to cable or satellite TV in my life, so it seems very low likelihood I'd ever want it to multiple receivers around the house).

Revisiting this old thread, can I ask when you placed the order and at what stage the installation happened? e.g. did you just complete the build them call them up to have it installed? I'm reluctant to do this later on through their normal consumer ops because their engineers will drill holes all over the exterior of the house destroying all the effort put into airtightness. But if they arrive too much before first fix I can't get them to put cable into the various points I'd like it. Ideally I would do this very early on and just have them leave a big reel of spare cable that we can put into the various rooms ourselves during first fix, and likewise we can make the airtightness fixes needed to deal with their initial install. I'm just not sure the consumer-focused engineers will do this. But if they will, I'll probably just pay for a rolling contract for 1 month, just to get the initial cable put in, which we can the bury) (I've briefly explored their New Developments process, but that seems an impossible option; only interested in large MOU not a single house renovation)

Honestly, I have difficulty convincing myself of it, but there was a lot of data thrown at me last night showing the point. (Based on survey from last month of the national average CO2 costs of acquiring pallets vs generating electricity during the heating season. Obviously any given individual's mileage will vary). I can't find the reference now of course, I will request it. Best I can get is this which backs it up (factor 7x more CO2 for ASHP) but it's well out of date.

I know it's OT for your question here, but if you're looking at a secondary heat source have you considered biomass? That would seem more complimentary as it can remove the dependence on electricity supply (or at least, on electriciry pricing), is better suited to large buildings with lower levels of insulation and rural settings, and has a lower effective CO2 cost.

Other thing to confirm is that you have planning approval for the external unit? It can be done under permitted development, but only if it is only used for heating not cooling

Any idea why not 20% ?

Full disclosure: after a lot of back and forth we're not getting three phase, keeping with the existing single phase and a G99, so I no longer have any "skin in the game" if I've misinterpreted anything

https://www.gov.uk/government/consultations/smart-metering-equipment-technical-specifications-second-version Page 87 "Consumption shall be the sum of the cumulative Active Energy Imported on the importing measuring element(s) of its Electricity Meter less the sum of the cumulative Active Energy Exported on the exporting measuring element(s) of its Electricity Meter;" I.e. you just add up all the import ever and subtract all the export ever to calculate total consumption. There's also a YouTube video where someone got hold of a decommissioned non-smart 3ph meter and empirically tested it works the same way. However the meters are highly configurable in this (for residential Vs commercial and for different country needs). Talking to a phone support at my supplier, he couldn't vouch for how it was supposed to work, but knew for a fact they generally get it wrong first time and have to send an engineer out to fix it after the customer complains.

Just to confirm, you're planning to have a single meter for both properties? If so, AFAIK your only option is a three phase meter unless you want everything on one phase. If you're installing >4kW splitting it to multiple phases avoids the bother of G99 application, and one 3phase inverter should cost less than two single phase inverters. I'm impressed your solar supplier knows that balance of usage and generation across phases is not an issue if you have the right meter. Absolutely noneone I spoke to give a clear (cited) answer on that but in the end I found for myself it's what is specified in the SMETSv2 specification (polyphase section) so certainly the way they are intending it to work. A pound per watt installed seems pretty competitive compared to quotes I got (also black in roof, but ours is a full roof which adds some additional cost), but everything costs more in our part of the country anyway.

Blimey, I wish ukpower networks were so generous. We made a G99 application it took about 3 months for them to process, was approved for 7.6kW (and not one watt more), and had a validity of 90 days for the complete system to be installed and fully commissioned -- and whatever is commissioned at that point, they say, is all we'll ever be allowed. That 90 days expired before we could move on it. The panels take 90 days to manufacture, let alone deliver, install and commission, so I have no idea what the correct order is for making a renewed application vs placing the order.

Message sent

Doors: We had a quote for a PH certified airtight FD30 moralt door, about £2k from Latham's in Hamel Hampstead. Be sure to ask for unfinished ready to paint, otherwise they can be twice that price (!) Otherwise we thought to put 2 doors in an "airlock" configuration, one cheapest FD30 then the cheapest passive house door we could find. The FD30 may or may not remain in the long run...... (There's minimal fire risk in our garage, it's too small for a car and we don't keep any petroleum in it) There's also a local project I can point you at where they successfully certified by using a standard FD60 door with smoke seal and drop threshold, and glueing sheets of solid insulation panel to it and remedial work to get it airtight. This can only work if connecting to a non-inhabited room I'd imagine as it would fail the room comfort criteria. Finally, cheapest option maybe no internal joining door but arrange for a pair of neighbouring external doors with a small porch/link corridor over them.

Did you replace fridge/freezer with the new house? That's one of the biggest background draws

One could argue the previous time limited FiT schemes were the political tokens, set by legislation with taxpayer subsidy at unsustainable levels. In comparison the SEG rate is the politicians stepping back and letting commercial forces take their course, for better or worse... To be fair, you never ever set out to maximize the amount your system exports; quite the opposite you've designed it to minimize that exact number. Anything multiplied by a very small number will yield a very small number. With a typical 4kW system that exports 50% of its generation, I'd be expecting about £100 a year. That's still pretty crap - it will struggle to cover the MCS installation tax over its lifetime - but makes an illustration more representative of the typical ("non enthusiast") setup. As a more real world example, my parents are on an early FiT and export well over 50%. I've tried to at least get them an immersion redirect but they won't as they worry the cylinder is too old and don't trust the immersion in it or will be damaged or leak. To be fair, it must be getting on for 50years old now, but they won't consider replacing it until it finally dies and is done by the homecare cover, no doubt in yet another botched rush job. Question now is where prices go from here, can people be bothered to shop around for this in addition to price they pay for import which push up competition, or they just sit there at 5p and fail to even track inflation. And the biggest, British gas, hasnt even revealed its hand yet. Perhaps one reason the smaller players may succeed here is if they can offer deals the big ones are constrained to by legislation? E.g. AIUI big players must offer tariff to all regardless of who is the supplier, but can a small player offer special deals for people that have both import and export provided by them? Certainly looking at Social Energy website I get the feeling their model assumes they're providing both.

The quotation from sunamp rep in OP said "price will be in the ballpark of their current offerings"..... So all riding on that! (I guess that means I should go ahead and get a quote for their current offering, as a baseline)

Sorry slightly OT but if you're looking at a development of 33 self builders, I bet there's plenty of things that could be coordinated to make economic that normally aren't. Ground source heat loops and rain/grey water recycling come to mind. And FTTP ? Bet there's plenty more.

A *tiny* benefit of GSHP is they can provide summer cooling without having to go through planning permission. If you're making planning application anyway I guess you include the aircon external units now anyway, which removes that benefit Installing the collector pipes is the most expensive part (doubly so if piled in, which I think they'd have to be in your plot), and I'd worry that they'd either sit there unused and forgotten after selling up, or even worse you eventually come to use them, and the installer/manufacturer refuses to use/warranty their use because they fail to meet the $random standard of the day that doesn't even exist today or something like that. So I'd either install pipes now fully intending to use them right away, or just not bother.

To be honest I know very little about this. The designer did it, the certifier agreed with it, that's all I know. From the small play I did have it didn't seem to have so much effect for us. Being a retrofit we don't have any due-south windows, and minimal opportunities to alter existing windows, which may be part of it. It was a bit disappointing the Solar PV tab in PHPP required the shading to be done all over again, and of course our solar contractor has to do it again too (for MCS and for deciding how much per-panel Optimizers will be), so it's a often repeated inaccurate science! I recall one of the PHPP books says something like "it's really hard, in fact basically impossible, to get it perfectly right, so just do the best you can" or words to that effect. Alas I can't refer to any books as they're all packed. (Moving out tomorrow!) (Even if you could get the shading perfectly right, someone can cut down a tree of put in a new one tomorrow anyway... so it's impossible to correctly model over the lifetime of the house).

My architect is doing the PHPP, she's a certified passive house designer, we're her first project, so it's a little bit of a voyage of discovery on both sides but working out really well as our respective backgrounds complement each other well (me more on electrics and, at a push, plumbing, her on the building design and fabric build up etc) I had the M&E co provide initial figures for the pipework etc I've really enjoyed having the PHPP file to use as a tool to see how it works in different scenarios and comparing ASHP performances etc, and indeed this was where I discovered the issues in plumbing figures: (i) First thing was getting the HP tab to correctly have single pump do heating + DHW -- for whatever reason, it only does this if the DHW+Distro tab has a correctly configured buffer tank. (ii) Then I needed to get the design temp down from 70ºC to 35 (update as we're no longer planning fan coil upstairs, at least initially). (ii) Then the AuxElectricity went through the roof, as for reasons I can't fathom it has a heuristic that the circulation pump power is a function of the system design temp. At 70ºC it estimates they'll draw 50W but at 35ºC it suddenly reckons they'll need 110W each. Combined with the fact we have 3 circulation pumps and it reckons they'll all run 20 hours a day, 212 days a year, and this totally dominates the PER demand (and offsetting the ASHP heating demand; a significant of the home heating is provided by the motors in the circ pumps themselves at that wattage). I just proposed an override of 40W for the pumps, as that seems more than generous enough based on examples I can find. With all that in place, this is the updated chart: generation is still a snag below the "target" dot, but our demand is much lowered making it on track for nicely inside the Plus area. Of course, achieving this in practice will be another matter.

There's a small minefield of selecting motion sensors for presence/occupancy detection vs intrusion detection. Optimize for Sensitivity vs specificity respectively. I believe there are fancy KNX ones (and perhaps other protocols) that allow sensitivity to be tuned so it can be adjusted between armed and at home use cases, but even the non-fancy KNX ones are stupid money so I gave up researching.