joth

@Nickfromwales thanks for the reply. I am no doubt misusing terminology - by thermal store what I mean a placeholder for "something" I can dump heat/electricity into when it's cheap (coming from the PV, or E7/10 if we decide to go that way in future) and that we can take heat out of for DHW and space heating at other times of day. The exact selection could be SA, UVC, or a full fledged Thermal Store TBD. But the key thing is being able to bank up energy when the sun is shining, ideally enough to cover over a day or two of overcast, not for throughput it delivers. (2 simultaneous showers every day, 3 very occasionally) Back of envelope, 160m2 house will have 4000kWh annual heating requirement, which worse case (ignoring any PV generation) looks like about £200 p.a. more on E7 vs gas (using 8p vs 3p per kWh). So at today's rates the boiler should pay for itself. What could throw all this off kilter will be the cost of moving the gas head. If that's too much, it might push us over to just having it disconnected and going fully electric. Saving on ongoing maintenance would be nice too.... but it all makes me fear we'd then be obliged to get into ASHP and that's not something I'm ready for yet. (The noise, mostly). GSHP would seem ideal, except for the price.... Anyway.... regardless of what our specific design ends up, I'm still academically curious of which is "best" place for a boiler, inside or outside the envelope

https://newatlas.com/cct-silicon-energy-battery-thermal-energy-storage/59098/ https://www.fircroft.com/blogs/worlds-first-thermal-battery-could-revolutionise-energy-storage-99111535454 Edit to add: possibly the first one going into production, that can return the stored energy as electricity?

@jack That helps a lot. Obviously for majority of windows they should really be certified else the penalties would add up. But for the odd awkward one we can negotiate it. Very helpful input to be heading into detailed design with. Thank you. Yep the goal is certified EnerPHit.

Yes, by Passiv I meant PH certified, editted to clarify. This will be on a 45° roof. I was using the Fakro product selector and pricelist: the U8 seems to be the only PH certified opening windows, but they're not list on pages 18-19 with all the other electrically opening units.

We're planning skylights in the faulted ceiling over the hallway -- 2.5 stories up. It will make great stack cooling, but that means electric (and ideally automatable) opening. Velux do one, but I've heard mixed things about it so at least want to explore a second option. Fakro can do PassiveHouse certified OR electric opening, but not both together, AFAICT. Any others I should look at, or just make Velux work?

Should have mentioned, still in planning, haven't completed full PHPP so don't know the exact heating requirements. We have a fair bit of the SW face of the house is glass so we think we'll do alright for solar gain. (Certainly inspired from reading on here about using the UFH to help circulate that around the ground floor slab) But yes, if the boiler looks like it will be in use more often than on rarely, putting it inside the envelope makes sense because then the heat put out by the unit itself is captured inside the house. Still curious if it is a leaky box for airtightness. If we do put it outside the envelope, putting it in its own insulated box sounds a nice idea. The garage will get fairly cold as it's currently detached from the house; we're building an extension up to join us to it, but this will be the highest speced part of the house insulation wise (being the new-built part)

Probably some silly questions, but just getting started with water/heating design so bear with me! In an energy efficient home with a lot of solar PV, would there be a case for installing a system boiler outside of the airtight envelope? We're planning an EnerPHit home with 8kW of PV. Using a thermal store for DHW and heating (UFH downstairs; towel rails upstairs). In summer all DHW needs will be from the immersion heater, in winter it will just be on coldest and shortest days, and with lots of guests (e.g. Christmas) we expect to need to drop back to the boiler. Possible locations for boiler are in the laundry room (inside envelope, next to the thermal store) or just the other side of the wall in the garage. The garage was not a obvious choice, but now wondering about it as presumably keeping the flue etc entirely outside the envelope is better for airtightness, with just a pipe having to penetrate it. These pipe runs could be very short (straight through the wall). What I don't know is if a boiler out in the cold will have more maintenance issues, the frost prevention should protect it but might be wasteful for generating heat we don't actually need, and if there are other drawbacks. So question 1 is, anyone done this? Or, having put the boiler indoors and found significant issues with it ruining airtightness? (Or any tips for avoiding that?) Second, loosely related question: what type of boiler make sense for a system backup? Ideally we'd make it the smallest size viable for the worst-case heating requirements in winter (i.e. should be fairly low) but that might result in a long wait for a hot shower should the cylinder get emptied on Christmas morning. Would anyone consider using a combi boiler for a backup? So the DHW could flip over to be fed direct from combi instead of the thermal store when it is depleted. Downside is more complex plumbing and control system, more maintenance needed for a rarely used combi(?), and more cost. And I think this would really imply boiler inside the envelope. (Obviously in this situation we couldn't happily run all 3 showers from the combi, but I think that's a reasonable compromise). So, again, anyone done anything like that?

Bit late to the thread but GB-Sol RIS is the other one I know. AIUI the unique thing with these is, as they manufacturer their own panels they can specify them to fill to any shape and dimensions.

I've been 'lurking' around here for a few months now but thought it time to make it official. We're in planning for an extension and renovation in North Herts, with goals for EnerPHit. I found the site via searches for UFH and cooling in a PassivHaus and stumbling on a whole world of opportunities and challenges I didn't know I needed in my life! So yes you'll find me mostly posting my questions in the Energy sections.