NSS

Fascinating read and I have huge admiration for anyone choosing to build and live off grid. Not sure I could cope without all the creature comforts afforded by electricity on demand.

Welcome @TomBee and all the best with what sounds like an ambitious project. Ref @Conor's comment about not pushing for PH certification "as it doesn't add value", I wonder whether this will change in time? If so, and my guess is it will, if you're self-building now with the intention of living in the property for some years, and building to PH levels, then spending a few £k extra on certification seems like a no brainer. After all, if you decide to sell it in 5 or 10 years time, and PH is still seen as a bit barrier to potential sale, then you just don't market it as such.

Not the issue. We simply can't have anyone here because of shielding.

No idea yet. I haven't gone as far as getting a quote as can't have anyone round before the end of July (at least).

Apparently my SolarEdge inverter can fairly simply be converted to a StorEdge inverter that will (with LG Chem batteries) enable backup.

Hi @kaish, and welcome. Unusual for nobody to have replied sooner but you may get a better response to your question if you add a photo showing the current set up so people can better understand and advise what may be possible.

But I guess you'd need a lot of storage (and generation) capacity to go off-grid in anything approaching a typical household with all the appliances, gadgets, heating and lighting requirements. All I'm looking for is sufficient storage to power the ASHP for a few hours overnight and/or the MVHR, dishwasher and washing machine, and to provide power for the fridge, freezer, a couple of led lights and (if required) a nebuliser in the event of a power outage.

Nail on head. Sure, cost is a big consideration (and running the ASHP overnight is definitely of potential benefit in that respect), but the environment and at least a degree of grid backup are also important factors to us. We'll definitely add battery storage at some point, it's just a case of waiting for the cost to drop to a level we can live with.

Ah, not quite what I thought you were suggesting.

That sounds close to tempting. Do you mind me asking what/whose kit it involves, please?

Which is all well and good if, as you have Dave, done all the work yourself or if you've personally overseen it all. My point is that's not the case with a lot of 'self builders'.

Depends on how hands on you've been. Remember, not every self-build is self built.

But how do you know it's going to be little if you don't do a test when the house is complete? And it may not just be additional energy costs, it could affect the air quality provided by the MVHR (which was critical in our case). Also, in the context of the OP's situation, failure to meet the required ACH rate for passivhaus may not just mean losing the certification goal but needing heating where none may have been provided.

I wasn't talking about big developers (sure we all know they're results will be 'questionable') but self-builders. What's the point in kidding yourself that your house is more air-tight and hence more energy-efficient when it's you that will be paying the bills?

Appreciate that, and agree a test before plaster boarding is sensible. However, my point was that an air test on which an 'as built' SAP calculation is to be based should be conducted when it's built - fully built, even if that's a second or even third test. Anything based on an earlier test could be some way off reality.

Must admit I've wondered about the MBC air test timing, and whether people then use it as their as built SAP calculation when presumably a lot can change once they've left site and other trades move in. It's one thing to guarantee a near air tight box, but another to maintain that level through first and second fix.

Maybe I should change my user name to NickF35B ? Oh, and welcome ?

You can set the thermostat temp for the immersion to whatever you desire and excess PV (via a diverter) will lift it to that setting so long as there is sufficient excess from any other energy usage at the time.

Likewise ?

You'll no doubt recall @Jeremy Harris(hope he's okay btw?) describing multifoil insulation (and/or claims about its performance) as 'snake oil'. I wonder is there a new candidate for the description ?

Had a look back to the first page of this thread, and the two previous one's from which it emerged. These questions over SunAmp have been doing the rounds here for over 18 months and still nobody seems confident that they are a reliable, cost-effective and easy to configure/control solution (for most applications at least). Given the level of technical understanding on this forum (compared to the average of Joe Public), imho it seems hard to envisage how SunAmp can hope to be a mainstream solution in its current format - unless of course it's Joe Public's lack of knowledge/understanding that makes them attractive customers.

Possibly when it's just the two of us here, but I'm not overly bothered as most of the charging is done during daytime hours when the ASHP is often being powered by PV.

Our ASHP heats the 300L cylinder to 45C (except every Monday when it does a Legionnaires cycle to 65C) but the power diverter sends any excess PV generation to the immersion. Suffice to say we've never run low on hot water - not even back in the good old days when friends and family could come and stay with us!

Incidentally, all the readings are taken on specific spots for consistency. There is of course some variation on, for example, the floor temp depending on where measured (currently ranging between 19.2C and 20.3C).

Turned the cooling off before we went to bed last night but back on at 8.30am today. Even hotter day today but has remained very pleasant indoors. Air temp in living area at 8.30am was 24.1C and upstairs was 24.3C Air temp in the living room is currently 22.9C and the floor is 20.1C. Upstairs air temp is 23.2C. Outside temp at 8.30am was 27C and just now (5.30pm) is 30C. I currently run the ASHP at circa 18C in cooling mode so could probably drag the slab temp lower if I reduced that but have played very safe re dew-point. Will turn the cooling off around 8.30pm (not much PV by then anyway) but repeat again tomorrow.