joth

BUS requires that the installed system supplies "all" the space heating needs. You need to establish that the ground floor UFH is sufficient to meet the whole house peak heating demand. Increase density of pipes in the GF if needed to increase the W/m2 (rarely necessary in a passivehaus). (Also if you have underfloor electric matting or towel rads in FF bathrooms be clear that is for luxury comfort only and not needed to meet the building's heat demand) End of day if this installer won't give what you want, take your money elsewhere.

In my experience if the ASHP has failed it's likely to be supply failure (trip) or something foobar in its controller (or cloud portal there of). Either these would take out its backup heater too. That said, it'd likely also take out control of the circulation pumps and manifold actuators etc. One of several reasons I'm slowly moving my systems to have the ASHP just heat (cool) the buffer when told to and have Loxone manage everything downstream of that.

If this a heat pump with glycol? If so any pressure release overflow should technically be captured into a separate vessel to be reused or safely disposed rather than flushed into the public sewer. The MCS approved bucket to capture it is like £100 though ... For something you don't intend to ever use it is a bit OTT

This was with respect to the solaredge battery. Batteries in general don't work well in the cold, reduces capacity and can't work them as hard. Or battery ended up with inverter in the garage which is outside temperature, more or less. So poor place for storing energy in winter (mostly for time shifting to make use of overnight cheaprate electric)

Good example of ASHP and plumbing internal gubbins. Solar PV won't add much onto that, but ideally goes somewhere that stays cool in summer. (indoors may well be the best you can do there. Ours is in garage) If you add a house battery that's a lot more space. Ideally indoors, ours is in garage - does not perform well in winter. The MVHR takes a about half as much as the HW tank shown there. Best Location depends on the routing of all the ducts to every room - ours is on the loft.

Full citation https://www.ribaj.com/buildings/regional-awards-2023-rsua-northern-ireland-studio-idir-ballyhackamore-house-belfast I do think it looks marginally better from the inside looking out. Still not to my taste though. Happily being at the back of the house not many have to stare at it. /me aware our retrofit RIBA gong was also won not for its visual attraction

Does your ASHP have any kind of monitoring or logging support? What you want to know is how much energy it pushed out each day and how many kWh it consumed, rather than how much money you poured into electricity in total in the day. This will then give a first clue if the house is leaking energy, if the ASHP is poorly setup, or if it is in fact some else entirely. (Or combo of all three). Most MCS installs had the option of advanced monitoring package, you could ask the installer about adding this as it's not performing to your expectations

Out of curiosity, how did they enforce it was only showers and panel heaters on the 24/7 cheap rate output? Seems an invitation for abuse (intentionally or not)

Cavity walls are a nightmare for airtightness. This is why we put airtight layer on the inside of our retrofit walls. If doing external airtightness retrofit over a cavity wall, I think filling the cavity with a airtight foam (that happens to also be an insulator) is the best hope. Else the air can enter the cavity anywhere at all internally and work down through and under the foundations. In fact seen this happen on another retrofits even though they used internal airtight layer. How expensive a specialist are you talking to remove batt insulation? Demolishing the entire house to remove it sounds a fairly extreme alternative.

I expect you mean you'll have 19kWh of batteries. I.e. energy capacity is 19kWh, enough for 1.9 hours of showers at 10kW. However batteries have a max discharge current that typically limit them to 5kW output power. This is only half what you need for aforementioned electric boiler hence the other half would likely come from grid.

Yes well done on what you have achieved so far. We did an enerphit (certified), but did it in one big hit rather than piecemeal. So here's my experience and thoughts. Financially ours was borderline (mostly due to the VAT saving if we'd rebuilt) but the process would have taken longer (probably another 2 years in planning alone, based on average for modern rebuilds I know in our area) and we wanted to live in the completed house, not the wreck we had bought, which was the real decider. Plus of course the lifetime CO2 savings of retrofitting. We never worried about hitting airtightness as we were paying an experienced team to do it all in one go (achieved 0.5ach 👌). For you it seems you're living in it while DIYing the work. So the time and logistical hit to go to a rebuild will be bigger as you'll have to move out for a year+ (more if you plan to slow build it yourself). How many in the house and how will they all handle that disturbance to their lives? And you have to find somewhere secure to store all the components you'd like to reusue. If it's just the risk on airtightness giving you doubts then consider how much you need the certification. "Good enough" airtightness may well be good enough even if you miss the goal. Play in PHPP and see what happens if it's 1.5 or 2. I'd only think of rebuilding if it's what I was emotionally heart set on. Not just because one box may not be ticked on the approach you're already on. There's absolutely no question the rebuild can be better quality outcome. Unfortunately you've undermined several of VAT savings by reusing MVHR, windows, kitchens and bathrooms. The VAT on those often helps swing the decision. Instead you'll be paying VAT on storing them for a couple years

The issue is when generating the drop is in the other direction (as that's the direction of power flow) so the garage voltage will rise 1.5% above the grid voltage. This is an issue if you're somewhere with already high grid voltage as it can cause the inverter to cut out if it sees to high a voltage at the output. Which means you loose the benefit of having PV especially on days when lots of people are generating This is a bigger problem in UK than in EU as we tend to use the same kit but grid voltage tends to be higher.

We have Baumit SilikonTop and it attracts dirt very easily and is a pain to clean: anything abrasive takes off more render than it takes off dirt. Can't comment on the dirt proof upsell but it does sound rather like sofa salesman tactics. If doing it again I'd definitely try and find out what the alternative options are. (we have pavatherm insulation system and they strongly recommend the Baumit)

Yes, I mean a thing that increases the system volume in that circuit. Buffer / tank / cylinder/ volumizer/ etc

I buffer can be useful with FCU as a volumizer as usage patterns may differ to an UFH only design. Our house is fairly typical with large open plan area downstairs and several smaller well sealed rooms upstairs. In heating season UFH throughout downstairs is used as one zone and needs no buffer. But in cooling season often only one bedroom needs the cooling during the night and without a buffer the ASHP short-cycles terribly. For another property I'm planning to specify UFH piped to bypass the buffer (T into it as a LLH for hydronic separation) but the FCU flows to pass through the buffer so it increases system volume if only one zone is in use and thus avoid short cycling, but with minimal impact to ufh efficiency. I'd be interested if anyone has done something similar?

In my book (white male, <50 years old), you have this the wrong way around. Wired switches are always going to be more reliable and long lasting than wireless, however something digital ("smart") will allow a pair of wires to each switch to have infinite uses, and be software reprogrammable if needs change, without need for a wire per light Like others here I use Loxone, but other options like Rako exist. All that said Lutron have gone wireless only and it is the trend with other tech (ZigBee Zwave Bluetooth and Matter) so maybe I'm the luddite. I just hate wireless tech when a wired option is possible

Zero VAT is only on supply+install. If you purchase and diy install then you'll pay full VAT. (Same with ASHP.) Only trick is to get a friendly installer that lets you do a lot of the grunt work yourself and will give a discount for that.

Can you clarify what you mean by "needing" to be able to export so much - where does the requirement come from? (it's not technical or financial, so... ecological? which is fine. just confirming )

Victron Quattro is very powerful for a fully off grid or seamless grid failover, however it's complicated to use this for grid-tie operation as you also need to conform to the various standards around anti-islanding etc. Some info on the page below, but sounds like you need the MultiPlus rather than Quatro variant? https://www.victronenergy.com/media/pg/Energy_Storage_System/en/system-design.html#UUID-7c21d64c-8be3-5162-abc8-027577d36a7a Will you have a backup second AC source (generator?). This seems to be where the quattro really comes into its own. Controlling the inverter to only export (some amount) at peak times is highly inverter dependent, but of all manufacturers I'm sure with Victron there's some way to do it in local config (i.e. without involving a cloud portal being online, SolarEdge looking at you). As others say, you won't get paid ££ for your efforts, due to the MCS cartel. Anyway good luck keep us updated sounds a great project.

Because you originally had 14 x 300W panels, i.e. 4.2kWp so a 3.68kW inverter was a fairly sensible choice and avoided G99 admin, but when you added the 7x 390W panels this started to look a worse idea. In the thread I linked before I asked you why such an undersized inverter and you said you were too tight to replace it. A cookie for whoever can be arsed to dig out the citation - I can't 🤣 Looking through photos it seems the SE is also setup for export limitation, which presumably is in the case PW is exporting (would it ever be?) it shuts off SE to keep the sum within $whatever limit it was set to.

Depends how it is configured, but the default is maximize self use which would be yes. Up to 5kW PV generation, above that you hit the charge limit of the energy bank (it will only charge or discharge at 5kW) so your 7kW array could have 2kW spare that would go via the inverter and off to AC and hence to the PW, if it needs it. Also, LOL at your PV installer getting kW vs kWh wrong on both the batteries. They're a match for you made in heaven. There really is no hope.

OK @pocster is too lazy find his prior post asking exact same question, so I did it for you. The schematic was eventually beaten out of him on page 6, here: The answer is your PV inverter is an SE3680H so can output 3.68kW MAXIMUM (sum across internal use, AC coupled battery charging and grid export). So if the AC coupled Tesla powerwall is charging at 3.68kW that will consume all of your PV generation and none will go to grid or other AC loads. As you were.

I'm just installing a second fan coil unit for bedroom & office cooling. It was salvaged from a restaurant refit, so is already absolutely caked in grease 🤮 but fortunately the air runs very clean through it. Anyway the inlet filter got lost at some point so I've ordered a roll of this stuff to try as a filter https://www.ebay.co.uk/itm/202978181622 it claims G4, I'm sceptical but thought it worth a punt and better than nothing. Back to the MVHR extract vents I bought some of the no-name ones linked previously, again at 15gbp for 20 I thought it worth a punt. As Mr Tea says, they maybe straight off the same manufacture line as the genuine article. I'm very surprised our installer didn't put these in to start with. If it works OK I'll put them on the bathrooms too.

I keep meaning to get some of these ordered. I notice there's less than one-third priced copies available from china on eBay: e.g. https://www.ebay.co.uk/itm/374385197240 Anyone tried them?

I seemed to have been a wally. I ended up forgetting this thread, buying the upgrade anyway 6 months later, sitting on it for 12 months, and now struggle to install it as it has no thermostat pocket, exactly as you predicted. Emailed oso to try and get some clarification 😬