joth

We did our preliminary test using a pipe though a sealed hole and then had a 1.5kW wet&dry vacuum sat outside sucking the air out the house.

Regarding the question in your xpost, I would imagine ASHP are classed as "generation" because HM Government classes them as this, by including them under the "Micro-generation certification scheme". see https://sustainablebuild.co.uk/what-microgeneration/ https://www.heatpumpsource.co.uk/blog/microgeneration/ etc

The variable missing here is what floor finishes are put onto of the slab. If the homeowner likes wood floors, or especially thick carpets, then the slab is insulated on both sides, so they will have to run the UFH flow temperature that bit hotter and longer to get the room to stay at temperature. This means the 40W of losses may well be more like 80W (for a 35ºC flow temperature) and experienced for more hours of the day. Aside from the financial impact, some users may simply not want this design due to: a) potential damage to wood floors from the higher flow temp b) the lower level of comfort achieved in having hot/cold cycling on the flooring (vs well insulated floor and a stable constant temperature) c) the CO2 cost of the energy wasted In the grand scheme of putting in an extension and UFH, £800 is not a great deal really

No, it's the opposite. Assumption 1: this question is in regards to heating season, when the outside air temperature is (much) lower than the internal temperature. Assumption 2: the building is to a high spec for insulation and airtightness An MVHR supply vent puts out air slightly colder air than the internal average air temperature. So in a steady state, and ignoring highly localised sources of heating, supply side rooms will be slightly colder than the average internal temperature, and thus extract rooms sightly warmer. Now most designs naturally arrange heating sources to compensate for this, focusing emitters in the living areas which tend to be supply side rooms. But also those rooms tend to have more glazing which further cools them. So we'd need all those details to give any sort of real estimate. Does that make sense? Hopefully that helps with the other questions

We have two CO2 sensors but they're both on mains PSU and log to a PC so would be useless in a power cut. Having one with a display and battery certainly sounds sensible. Also I've considered a small UPS for the network router and switch. Adding the MVHR onto it would actually be fairly easy as they're both in the loft.

FWIW this is exactly the route I ended up taking. I have a 1-wire thermistor in each room with wood (bamboo) finishes, sending data to loxone, and it cuts off the call-for-heat if the temperature gets too high. It also can dynamically adjust the flow temp, e.g. use a high flow temp when the screed is cold and gradually back it off as the screed warms up towards the limit. I have all the logic for that implemented, but it's pretty flaky controlling the Ecodan FTC6 via their MELcloud Wifi interface, it would be much better done over the modbus interface but unfortunately you can't have both interface modules on a single FTC6 so meh, I just don't bother with this level of flow temperature control feedback. ... if i left the ashp on 24/7 it wouldn't be interesting anyway, but the nature of overnight cheap rate (and solar PV) does make it more worthwhile to back off the temperature then blast it as hot as possible during the cheap rate window

The end for new applicants. For those already in it, it will drag on for another 7 years of paperwork to claim the ongoing payments.

I know exactly what you meant. We spent silly amounts to get Passivhaus Enerphit plus certified, but still rocking EPC D On the upside, 6 more weeks and RHI perverse incentives will be no more.

We have 2 people working from home every day, working in tech, so have quite a few PCs and laptops and monitors on most the time, which come to a couple hundred watts. The lower power modes really should be better, and I will get to looking at this again some day (we go through phases of getting it tuned to power down/sleep nicely, then the employers push SW updates and it all goes to shit again). My main home automation server needed for CCTV and running most of the house is 40W and the fridge/freezer is A+++ so base loads that are "part of the house" are not insane.

For the time being, I can sell solar at 7.5p and buy it back at 5p (Octopus Outgoing vs Octopus Go) so for the big power consumers that I can move to overnight it's really not worth buying battery. I'll keep with that as long as it lasts, hopefully by the time they discontinue it batteries will have reduced in price a bunch more. (Also, there's a lot of base load usage I can't time-shift so a battery maybe justified for them alone at some point)

+1 to this. Side comment that 600m of 240V from kiosk to house will be less efficient than the high voltage distribution to a transformer nearer the property, and you'll end up paying for most of those power losses (behind the meter) rather than WPN. Oversizing the 3ph cable from kiosk to house will minimize this, as will distributing loads across the phases. Also any solar PV that reduces import will improve the overall efficiency - so long as it's on the same phase(s) that the consumption is on.

It's changed. several success stories here (and other threads) :

it maybe worth getting yourself 3x 100A main breaker and have BG them install them after the meter. Then your electrician can hook the breakers into the CU. This makes life a bit easier if/when any changes are needed to the CU, no need to open the meter to disconnect it. - Some meters have a main shut off built in, but not sure any 3ph smart meters do - Some suppliers will automatically provision breakers after the meter, but not all will

Several folks here have got Octopus to install 3-ph meter recently, e.g.

Just to clarify, 2 ACH is still considered extremely good by UK building standards. The sort of thing you have to work hard to achieve, not something that will happen by acccident because you never put any thought into it. For a conversion, you could probably have 10 ACH and still pass building regs. So unless you're planning to set a target and hold your contractors to it, I'd get a [much] worse worst-case model done. Me, I'd set a target and intend to meet it! Less that 1 ACH is a good one to aim for. Plan in to do a preliminary air-test before 1st fix starts, and if you're way off either do remedial work, and/or adjust ASHP sizing to match.

By chance I just got an email from GBS saying they now offer installations nationwide: https://www.greenbuildingstore.co.uk/services/mvhr-installation/ We used Enhabit - now part of GBS - for design supply and install, and they did a pretty OK job. We did have to get them back in once to fix a bunch of stuff it was all done without too much drama.

I would say that plays absolutely no part in it. Again, to clarify: this is likely true when using direct electrical heating (immersion heater) only Anyone attempting to charge it from an ASHP would do well to have an installer that understands how to get the two to work together.

Personally I'd use type 100 cable, I liked the Webro WF100 but e.g. https://www.cef.co.uk/catalogue/products/488397-pf100-satellite-cable-black-100m is CAI certified . If you're going to the effort of installing coax at all, the extra 16p per meter for quality low-loss WF/PF100 cable seems peanuts Some rambling info on the differences on these pages https://www.webro.com/rg6-sdu-cable-cai-approval/ http://www.stevelarkins.freeuk.com/digital-coaxial-cable.htm https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=60442#:~:text=The real difference is the,and fits F connectors properly.

It's not just that the external outlet will defeat all your airtightness work, but you need a balanced flue of somesort, or some other hole in the house to allow a corresponding inward airflow. Wherever you send the dirty expelled air to, you need to think about the return route for replacement air to makes its way back around and into the intake side of the vent. Really in an airtight house I think option 2 is your only bet. Perhaps you can combine it with Option 1 to a degree - vent it out over the top of the units, and also through to behind the fridge. Or vent it out over the units and also put a concealed hole above the units into the ceiling, and be prepared to cut another ceiling void outlet grill somewhere if needed? On level 3 your hood is about the same as our Bora Pure X max (548 m3/h) and we have that venting out via about 8m long x 10mm tall gap around the island and it doesn't make any noticeable noise -- just aware of it from the cool draft on bare toes. Remember this is only an issue when the hood itself is on full whack, which is not silent by any stretch, and you probably have something fierce boiling/frying at that time too, so it's not exactly going to risk disturbing an otherwise library-like atmosphere.

I wouldn't hold this against SunAmp: a standard UVC hot water cylinder and even an electrical house battery require the same compromise/ trade off to charging strategy The other key issue discussed at length (but only indirectly mentioned in the OP) is heating from an indirect heat source, esp ASHP with the lower output temperatures, has some technical challenges. This has been partly solved by them introducing various new PCM types, but last I looked into it a much larger issue was SunAmp had to individually test & qualify each and every ASHP controller to ensure compatibility, and in many cases they needed to physically ship out a different SunAmp controller board depending what ASHP you wanted to hook it up to. Has this situation changed at all? It seems a crazy and unsustainable business practice. Obviously not an issue for anyone keeping with direct electrical Sunamp charging only.

This is what my MVHR control looks like (sensor.mvhr_boost_request is set true when the Hob is on, the showers are running, or a triple click on a bathroom light-switch indicates a big one has dropped)

Octopus have just increased their fixed rate SEG export price to 7.5p/kWh which moves the needle a little bit in making battery even less economically justified for me, and also flips the self consumption incentive: it's better for me to minimise my PV self consumption and maximize export at 7.5p and then buy it back at the overnight 5p rate. "We’re increasing your export prices from 5.5p / kWh to 7.5p / kWh, a total increase of 36%."

The RHI application is extremely vague on this point, during sign up it has a warning that if you make changes to the house that may impact the EPC you may be required to get a new one done, but no indication as to what could actually trigger that or when. And as Ian said above, even if it were triggered I could get a fresh EPC done today but absolutely nothing (except pride) obliges me to provide the assessor with our actual insulation or airtightness numbers thus the up to date EPC would still payout higher RHI than if a fully informed EPC were done. The only reason I persevered through the ridiculous green home Grant application to limit impact of these RHI vagaries. At the end of the day anyone thinking of gaming the system by getting a crap EPC for RHI then renovating to passivhaus standard will end up paying of order 10x in VAT on their eco measures than they score back through the delta in RHI, so with both the government coffers and the environment benefiting from this devious intent, it doesn't smell like the moral crime of the century.

EPC F I guess? So long as it says no improvements (loft or cavity insulation) are needed. It's a function of heating demand, so the bigger the house and the worse it is insulated, the higher the payments. Against that, having a low design flow temperature on the MCS certificate also increases payments, and a bad EPC is going to lead to a high flow temperature needed, so maybe in practice there's a sweet spot around EPC D somewhere but it'll vary on the specifics of the build.

If you have an AOV that probably makes sense, but with a glazed window I thought you'd want it in the loft to get the benefit of the light and solar gain in winter. AOV aren't much on my radar as it's hard to get airtight / high U value, passive house certified ones? But makes sense on a non-certified project. Displacement ventilation sounds another way of saying stack ventilation? Either way it's using the chimney effect ?