joth

Haha so literally, the architect omitted about the need for plant room space, but when you suggested your ideas for heating he rubbished those plans and asserted the need for something else that requires more plant room space? Smh There's a really awkward circular dependency you need to pick your way around. Ideally you get the eventual installer in before tender pack is created, as heatpump installers are trained (and obliged to provide) design services as part of their industry certificated supply and install package. But obviously you can't tender the work until you have a tender pack. And if you're going for a single principal contractor to run the whole build (this sounds like custom build rather than self build so i very much assume you will), many principal contractors have their own tame subbies they much rather work with and will slap a hefty P&A surcharge on dealing with anyone else you foist on them. (And/or use it to play the finger pointing game when issues occur). My own suggestion would be to specify the thing that's cheapest in professional fees that you could definitely live with if the install price is right, e.g. UFH everywhere, and be very upfront during tendering that you're open to engage in constructive value engineering on anything that is adding undue build cost, and flag that as one such candidates. A good builder will come back with their own suggestions or loop in their preferred installer to participate in that decision. And yes, you'll have full SAP figures by then so it'll be a more substantiated discussion. To your other points, 1. ufh can work fine with thick carpets, so long as all the building exterior is much more thickly insulated, and you run the ashp low and slow (as is best for it anyway) the ufh heat will warm the fabric of the building and make its way to where you need it rather than being lost outside. 2. Even if you're 100% set on not having cooling, I'd still recommend running the numbers to confirm exactly what your overheating risks are, do some stress testing of it based on increasingly warm summers, and also do a little bit of future proofing thinking on what you'd do if retrofitting it proves necessary in the future. Considering window placements and external shuttering to minimise overheating is even more important at the earlier design stage than stressing over active cooling.

The architect telling you rads won't work is essentially the architect telling you they're going to design a shit house that needs more heating than you would like. Did you talk about levels of insulation and airtightness? You're doing mvhr so I'd start there, figure out some heating (and cooling) demands then decide if you need. IME architects will often speak a pile of bumkin about what is and isn't possible in terms of heating. In most cases this is based on having one bad experience and wanting to have themselves future hassle. Passivhaus/ AECB qualified architects are sometimes better, but they can swing the other way and under specify. Also in my experience you can spend many hours and pounds on iterating this at design stage, only for the eventual contractor that gets the job to rip up those plans and do something completely different. Case in point my current project (BMS for a london town house reno), I suggested ashp for heating+cooling, architect said it's not possible in a Victorian terrace, client paid M&E consultant who specified system boiler and multisplit Aircon, that was all thrown out in value engineering and re-tendering (not to mention planning application refusal), eventual contractor is now installing a single Veissman ashp to do everything via a mix of UFH, fan assist and even cast iron rads.

If you want WRAS motorised valve I'd pay the extra couple of notes for one from here. https://www.solenoid-valve.world/abvm06s Their failsafe valve requires permanent voltage (negligible current) to keep open, and uses a capacitor to run the ball valve closed when power is removed. 9-24v is rather annoying to drive from an ESP32 though, without some additional quiescent current cost

Almost. I worked on a project with a large London based passivhouse building and their preferred electrical contractor. The contractor actually had office staff updating autocad drawings, but this was mostly architectural for placement of fittings, not wiring or electrical schematics. The builder promised a comprehensive set of drawings of all M&E, but it never materialised. In fact as they had 2 different plumbers work on it (one doing the pre-slab unground routed pipes and another on 1+2 fix) without any drawings, they ended up with some duplication of pipework and I had to help them diagnose and remove redundant loop in the system. In the main post-build user & maintenance documentation is still a very unsolved problem, even on high end builds I like that French system, the schematic looks very elegant with neutrals omitted, but in a modern build using RCBOs would be a lot more busy.

This is suddenly really interesting for me right now. We completed our EnerPHit plus retro fit in 2021. It included a heat pump installed with the (brief and spectacular failure) "Green Homes Grant" and topped up with RHI. The RHI was audited a few months ago, and they raised a complaint that the EPC used in the application (mid-renovation) didn't reflect the building quality at the moment I applied. i.e. I'd spent my own hard-earned money on improvements to the house (paying VAT on it all too, of course) and hence should be granted less RHI than my neighbour that hadn't improved my house. The EPC had been specifically done a few months before for the Green Home Grant (with the newly topped up loft insulated mandated by that scheme, even though we knew we were adding new external insulation to roof and making a warm loft in months soon to come, but the process is the process). But of course mid-renovation is a silly time to pay for an EPC (solar, battery, light bulbs, and even windows not yet complete). So now 5 years own I got one done, and it came out at 89 grade B, for an energy positive house! So yeah now going through all the hoops needed to get the EPC surveyor to include correct U-values, airtightness, MVHR, waste water heat recovery, solar battery, etc. Which involves them going through hundreds of pages of evidence, and then again when they themselves are inevitably audited. They're only charging £54 for the whole certificate process, which can barely cover the cost of the site visit let alone the hours of office work this will need. And you have to love the irony that an audit on the sub-£3k RHI grant (on a build where I spent over £150k + VAT reducing energy use) will itself trigger another audit for whoever I chose for the EPC. All on top of already paying £x000 for the passivhaus certification process. It's almost like someone somewhere would rather we didn't make well performing houses, isn't it??

A few other factors come to mind that will be impacting quantity of petrol stations about. it's all a supply and demand thing, init. Increase in out of town supermarkets selling petrol as a loss-leader to get feet into the store Increased efficiency of vehicles meaning less petrol used per mile so fewer trips to the gas station needed Perhaps?? - people are commuting further for work so more likely to pass a cheaper out of town station, not just looking for the most convenient local option. Since the 1990s diesel was gradually displacing Petrol, not sure what affect that might have, however combined sales peaked in 2016 and have been decreasing since then so decreasing overall demand ... I collected my EV and promptly registered on a pair of public charging apps to calm the immediate range anxiety for the drive home (I registered with VW's own app, and the Octopus one). It is interesting to see how the marketing landscape is so different compare to petrol, being almost all online and app based rather than giant billboards visible from the motorway, for what is essentially the same use case.

This is the key bit: scrap your car and move to EV if you drive more than ~4500 miles per year. If you have very low annual mileage, like @sgt_woulds, it makes no sense. If you have extremely high mileage, then of course moving to a lower cost-per-mile vehicle will pay off very quickly (for both financial and environmental cost) We drive about 5000-6000 miles most years; I've put off getting an EV thus far because of this low mileage but as it's now 10 years old, and there's now a better range of equivalent EV available, so I should be picking up an ID.7 Tour tomorrow. Weirdly the insurance quote is actually less than my current Skoda - perhaps because this will be a company owned car (although my guess would have been that would only add to the premium). /shrug

The problem with both proposals is in a few year's time good luck finding it if there's a fault, let alone if there's a new home owner. Personally my preference is to put them all in a somewhat central location per floor, e.g. next to the consumer unit or in a cupboard with (above) ufh manifold, next to the network panel, or something like that, depends on the floor layout. (In my own projects they go in the home automation control panel, of course). People often worry about voltage drop on long lines, but upsizing cable to 1.5mm2 and always use 24V rather than 12V strip. In practice if thought out a bit the cable run will likely be under 10m anyway. You can put isolator switches in that same place for things that don't have any more obvious locations. Just makes it all a bit more maintainable.

Aside from the whacky surprise it leaves to any future electrician working on it, I'd be concerned fire alarms come with a "test monthly" sticker or similar, and this thing frobbing off so regularly will decrease lifetime of the rcbo and relay base, and increases odds it gets forgotten and not re-enabled

lol That's my gut feel too, and usually I'm all-in on smart (home) tech. However smart breakers are coming and could indeed eventually make a lot of the need for local isolators obsolete, if one actually has a vague idea how to remotely connect to and trip-off the appropriate circuit. https://kb.shelly.cloud/knowledge-base/shelly-pro-cbs https://www.infineon.com/application/solid-state-circuit-breaker Despite my scepticism I do see the attraction of having per-circuit current/power monitoring built into each breaker. And digitally tripping off circuits could be a tidy way of implementing centrally coordinated load-shedding e.g. if failing over to battery during a grid outage. But as a mechanism for home owner or handyman to randomly frobnicate circuits on/off when doing misc maintenance... I don't buy it. Just too much cognitive overhead vs having a good old switch at the location. ... btw I'm skipping over the elephant in the room for the devices listed above - at least the shelly - are MCBs not RCBO, and is taking up a double-module width at that. And I imagine lack 18ed approvals. Makes it a complete non-starter right now, but it's just immature product and totally solvable in due course. It's the fundamental usability for a safety critical application I'm doubting.

In the real world these decisions are really a dialogue, not a mandate. But can be an asymmetric dialogue if the customer isn't informed of the alternatives. Either way point is to start that dialogue early rather than push it into brinkmanship. Many self builders are not in the position to be able to fire their electrician on a whim over the position of one isolator switch, so better to have the conversation at first fix rather than after the walls and floors are sealed

It's best to check with whoever will be completing the EIC as appropriate location of isolators is in the regs and quite subjective. Ours insisted on putting them in the very nearest cupboard, which has resulted in a few getting knocked by large items being shoved into said cupboard Recently I've seen on other projects that electricians seem much less concerned these days, either putting all isolators together next to the CU, perhaps using minigrid switches, or even omitting isolators completely (e.g. for outside blinds). If they're happy signing the EIC then fair game. Pretty sure they had more conventional isolator for anything over 13A.

Yeah, you are right that if it's lower humidity (and temperature) inside then the enthalpy exchanger should help. I was thinking of the case where it's (much) higher humidity inside than out, but that isn't what we have here today Funny you ask - I was literally looking at options immediately after posting here. I'd like you that starts (or resumes) operation after main power is cut and restored, so I could easily put it on a relay switch to control only running it when really needed (and ideally, during cheap energy window), but got bogged down as the cheaper units all seem to need a push-button press to start operation, or have their own smart/cloud/app integration that I really don't want. It's something I may yet do if I find a good option. Good news is connecting continuous drainage is easy in the plant room, so doesn't matter if it only has a small internal condensate pan. In the meantime, I've tweaked around my logic to allow the FCU flow temperature to drop a bit under the dew point if cooling load gets high, and let it drop much below dewpoint if the house starts to overheat. I figure a short(ish) period of condensation on all the pumps and valves is tolerable; it's long term dampness on them all I'm concerned about for causing corrosion and parts to fail. (In all cases the UFH flow is hard-limited to not go below dew point )

Dew point in our house normally sits around 15°C but in the current weather it's been slowly creeping up, just about to hit 20deg. There's a double whammy here: the very warm outside air is a able to hold more moisture, and as it is staying warm around the clock it is gradually is doing so, raising humidity of air coming in. The system is not able to keep up with the cooling demand (ironically largely due to the dew-point restriction on flow temps - I could get it super cold if I ran it blow 10°C) so the inside air temp is crawling up likewise increasing dew point. Behind it is another irony, that we were warned force-air heating from the FCUs [which are never actually used for heating in practice] causes the air to dry out so went with an Enthalpic heat exchanger to retain indoor moisture, which is now working against us in pushing that dew-point calc up making cooling mode less effective. If I ran the FCUs below dew point for a couple hours they will of course extract moisture from the air (sending it down the condensate drain) thereby reducing internal RHI, dropping dew point, and allowing the system as a whole to work more effectively once again while sticking above said dew point. Ho hum

For an a2a system, yes definitely. For a2w I'd recommend provisioning for it if it's not too difficult, but in practice I'd always run the water flow temperature above dew point so the condensate is not needed (and actually just creates a liability of drying out and creating bad smells)