TerryE

I call our build passive-class or low energy rather than passiveHaus complaint. For me, IanR hit the spot with his above comment. BTW, we use resistive heating only, and on current Octopus Agile tariff pricing our monthly energy bill varies from about £75 or so in the warm season to maybe £200 for the coldest months. It's hard to put a precise value for the bill as we take all of the price variation risk on the Agile tariff. However, looking at the potential monthly savings in going from a CoP of 1 to an ASHP-based 4, say, for the heating element of these costs; These savings are significantly less than amortised cost for the installation, maintenance and depreciation costs of adding an ASHP, so unless something changes radically in our case we won't be installing an ASHP.

I am 182 cm tall, and a couple of our internal doors were about 181 !! I'd just duck slightly automatically, but about twice a year (especially is some spoke to me from behind) I'd forget and clip my bonce. Ouch. 🤣

In our previous ~2-300 year old Cotswold stone farmhouse we put it a silicon DPC back in the mid 80s and completely repointed over the next 10-20 years the infill showly turned from damp loam to bone dry dust and grain husk. The effective U-value slowly improved down to around 1½ W/m2K. The main problem was that the house leaked air terribly and the floor slab was uninsulated. Our current house has a U-value for exterior walls, roof, floor in the range 0.12-0.15 W/m2K and an an ACH of around 0.4, plus MVHR. Just no comparison in terms of winter comfort. When the kids were young, they ran around naked in doors in the winter but then again gas was dirt cheap in the 90s so the boiler was going flat out when we were in the house.

Actually the code and graph were mine; the context was a passive house twinwall (high insulation with decent thermal capacity) with an outer stone skin. This is a world away from the thermal characteristics of you stone cottage (which is of similar construction to my previous house). The U-values you get from a solid stone wall are terrible as stone is an awful insulator compared to a passive profile (the U-values are typically 10-20× greater). Yes there is little temperature variation inside as the walls are just always cold in the winter. You can really only mitigate this by adding something like an inner aerogel backed plasterboard liner to the exterior walls. As heat just wicks away through every external surface, you just need to input a lot of heat to get a comfortable room temperature.

That being said, I believe most ASHPs can be programmed to have a few time slots each day when the ASHP outputs at the higher temperature setting and a Y-plan valve switches between the UCV and the manifold loop, so the CoP is 4, say, when doing the heating, but 2½ say when heating the water. This assumes of course that you using that you are using low temp rads or UFH. But this all adds complexity. @JohnMo or @ProDave will tell us if I am talking rubbish. 🙂

The LCoE for new solar and wind is about £30 / MWh, that's 3× less. The revenue starts to come into on about a year after the mean investment point, that 10-15× less. It is just really hard to make new nuclear numbers economically competitive, even SMR technology. We can get up to ~90% renewable with investment in grid-scale battery and maybe pumped hydro, whilst running our existing gas peaker stock until EoL. By then other options will be available.

Octopus are quite transparent about how they set their Agile price: 2W+P where W is the half-hourly EU wholesale price which is fixed for the day-ahead each Midnight CET. The 2 is a markup of 100%; P is another uplift of 14p/kWh from 4-7pm GMT -- a time limited markup to discourage peak use. The two markups combine to cover their distribution and service costs. This 2+ markup may seem a bit steep but it is less than the others charge. This total price also capped to 100p / kWh inc VAT as per current UK legislation, but other than this, consumers on the Agile tariff don't have to pay a premium for buying future prices, so whilst they take the pricing risk, the expected price is less overall. If I we doing this, I'd have had the markup 2 for W>0 and 1 otherwise, but I am not going to make this suggestion. 🤣

Yes. there's an excess of energy being generated -- such is the variable nature of renewables.

The 20A Power Relay and the 25A Contactor are pretty much identical in form factor. The contact is far more robust and only about 20% more expensive. I'll just buy 10 1N4007s and make up my own flyback straps.

Mike, it's nice to give back on this one. ESPhome does now support the Pico W. See ESPhome - Raspberry Pico W. The ESPhome environment is layered over RTOS, so I assumes this is just a port of their RTOS build. The standard ESPHome dev environment typically runs in a docker container -- either via the Home Assistant add-on or a standard docker container from the Docker Library running under Docker. This is just a builder WebUI using a load of Python scripts to wrap around the make environment. I find it easy to use. I like it. You configure the particular device using a YAML file which can include C encoded actions using the "lamba" nodes. It's all pretty straightforward once you are past the initial learning curve. Update is normally via OTA, so if you need to tweak a config, then you just edit the YAML file and hit deploy. The build and update takes less than a minute. If you want to discuss further then why not spin off a specific ESPhome (on Pico) topic? PS. The Pi Hut 8-relay board that you linked to has a similar form factor to the ESP one that I suggested, but you would need to mod the case slightly to take the external Wifi antenna. Pi Hut also sells a 4 relay version. It's a pity that I can't find a proper 24VDC relay driver board / hat for the Pico or ESP32. I see that some designs use PWM relay drivers with RC smoothing and flyback protection. The idea here is that you set the op to 100% for 50 mSec for force contact close then drop the PWM to 50% dropping the smoothed voltage to ~ 12V which is enough to keep the contactor closed but only a ¼ of the power loss in the relay and if you don't need sharp one, then drop the PWM ratio to 0 over 100 mSec, say, which pretty much dissipates the coil energy before open. Anyone know of / recommend such a off-the-shelf board? PPS. ESPhome can be configured to act as I/O subsystem for HA or work independent of HA using MQTT as its command interface.

Precisely. And the answer is no, not at the moment 😱 but I should have a freewheeling diode across the control contacts of each. Do the math and Finder relay coil stores about 0.6mJ of energy when closed and as soon as the Sonder relay opens this coil field collapses creating a flyback voltage in the kV range at its contacts which will rapidly degrade the relay. Probably don't need an RC snubber with a freewheeling diode (something like the 1N4007 which are orderable in 5 off quantities from Farnell etc. for pence). What I hate about this was that I really wanted to avoid customise tweaks. I really wanted a compute off-the -shelf module. I have found a for ~£200 from an AliExpress supplier I've used before but it has 32 channels and is really overkill. No the 22.20s are power relays really designed for straight AC1 resistive loads like the immersion heaters. The 22.32s have sensible AC7a rating but the profile is slightly different so I need to check that they fit in my enclosure. If anyone have setter advice then I am more than willing to listen.

A quick update. The system has been working well (subject to the caveats below) for over 3 months now. I've stripped out and refined the Node-RED application, and am reasonably happy with it, but a few lessons learnt: I have now retired all of my custom ESP code. I use ESPhome for my Wemos D1 mini based temperature loggers using One-Wire DS18B20s controlled by the ESP8266 chip. ESPhome just proved the easiest way to configure these and the pre-built environment is available as a Home Assistant add-in. The relay controller uses Tasmota, though I am considering switching to ESPHome, but am not sure whether this is worth the hassle. The UVC heating algorithm works really well: once a day I use the average cylinder temperature (from the top and bottom DS18B20s) to heat it to target. The CH system then schedules this top-up at the cheapest time slots. The relays are powered off early if the top/bottom is at target temperature. For example, today's top-up was 1.3 kWh at a price of~ (-3p) credit. The Finder coils are about 0.5H inductance, so the relay contact opens are particularly hard on the little Songle relays on the ESP32 relay board. Even though they have a nominal electrical life of 100K cycles, the one controlling the circulation pump failed the other day. I think that I really need to add RC snubbers across the finder coil contacts to get a decent operating life. Doing the math, the capacitor needs to be ~ 0.3μF and the resistor 1.3 kΩ. Most pre-made snubbers seem to be designed for 230VAC rather than 24DC. I killed one finder relay myself as a typo on a small change I was testing. I accidentally set the relay in blink mode (where it was cycling every second). Unfortunately, Jan interrupted this with a demand that we leave to go out for the day and I didn't get back and discover this cock-up some 10 hours later. In the meantime the relay was buzzing like a chainsaw, and by the time I realised I'd worn the poor thing out. Scratch one power relay. The Finder 22 Series relays do not handle AC7b loads well even a 30W. I am currently cycling my pump 48 times a day or ~1.5K times a month. 5K cycles at this load has already knackered the power relay controlling it. I really need to move to a contactor which might increase the snubbing requirement or back to an SSR for controlling this pump.

We've got an MBC twinwall with a blow cellulose filler. We were impressed with the choice and its implementation. I found the thermal characteristics great: a good balance of low conductivity and good specific heat which gives a very stable environment with low decrement delays through the walls. It is pretty solid with no voids. It is essentially a product made from recycled newspapers, etc. with some added fire retardants and insect repellants. I liked the idea of using a recycled product with low environmental impact. It is a plant-based rather than mineral product, so it does need additives, but this isn't a potential health issue for the occupants -- so long as your build includes a proper vapour barrier inside the fill. The fill process is a bit disgusting for those doing it. TBH I felt that our MBC crews were a little sloppy IMO when it came to things like personal HSE, and only used them when necessary rather than on a precautionary basis. However, the blowing process was notable in that they were fully kitted in masks, respirators and dust suits for this. Definitely not something to do DIY, IMO. So they have their pros and cons, with cellulose winning on eco credentials and slightly on thermal performance, but less suitable for DIY installation.

This being said, my control system does cycle the UFH loops for 6 min every 30 min for two reasons: (i) to spread any solar heating from windows across the entire slab, and (ii) so that I can use the return flow temp as a proxy for the slab temp. My Grundfos pump has just failed. 🙃

I suppose you are right: we have been living in "cloud cuckoo land" for 7 years now. And very comfortable it is. 😱 🤣🤣 Models are tools with limits and uses. What you seem to forget in this polemic is that many of us live in builds that were the designed were tuned using such tools, and they worked for us.