Mr Blobby

I think you're right, and thank you for pointing this out. Googling around, what you say appears to be bang on, the air flow can move both ways and the ply should be inside the VCL. Looking again at my build-up, however, I'm not sure why there is a need to have the ply on top of the rafters, when the PIR could be attached directly. Maybe architect thinks the OCF between the rafters can't be sprayed against the underside of the insulation. I think I need to chat with my architect about this.

Do you think the VCL in my build-up should be above the ply then? I thought the warm moist air would come from inside the building and so a VCL underneath would potect the ply from condensation. Is that not how it works?

Its part vaulted ceiling upstairs and I like the MVHR and storage in the warm lofted bit. Also running services and light fittings from loft through ceiling is challenging if that is the airtight boundary, is it not?

I'm hoping the VCL under the ply on top of the rafters will stop condensation. Will it not?

No its a cut roof with ridge beam, no trusses.

Thanks @ProDave , that makes a lot of sense to me, and ensures continuity with the membrane that is plastered into the wall. What about insulation between the rafters? Still use OCF between rafters and then membrane under rafters?

We are finalising the construction details for our block cavity passive house and I would really like some feedabck from the group on the roof detail. The warm cut roof will be suspended on a ridge beam, so no trusses or complicated structure in the loft. The architect has suggested open cell foam to provide the air tight layer and insulation. Is this the best approach? What other options are there? For completeness, here is the roof detail: My concern with open cell foam as the airtight barrier is the risk of it not being done well, what then? I dont want to use PIR as insulation between the rafters. Open Cell Foam for air tightness - Yes or No? And if not, why not?

Node red. Very interesting, and not heard of it before so thank you for mentioning it. I have installed the HA add-in and will take a look. You're right of course but we're on a noisy stinky main road hence trying to cool with windows closed if possible. Will be interesting to see how well it works.

A few people (who suspisciously dont use ashp for cooling) warned me to avoid cold floors hence we were plannig to install some fan coils upstairs instead of using the UFH for cooling. Which introduces extra cost and complexity. Am I making a bad deceision here? Should I keep it simple and cool the floor?

Very nice. My architect would love this. So how much do the panels cost for a standing seam roof like in the picture? I assume the Standing seam would need a ventilation gap underneath the panels?

We're going to install a 3 phase inverter in our new build to balance the phases. Why are you installing only 4kW pv when you are not restriced by a single phase connection? Sounds like your quote is for a single phase installation. Maybe think about dual MPPT 3 phase inverter without optimisers over two PV arrays?

Interesting what you say about the inverter configuraiton. Agreed, the 14 panels are to go on the front section. For the panels I was looking at the JA solar 370 panels to give 5.3kW. I guess the only way it works is for a 3 phase hybrid inverter, and dual MPPT for the other panels at B or C. That is what I was planning, something like the Solis 8 kW dual mppt hybrid 3-phase model. I'm assuming here that the inverter will balance the phases. Otherwise I need to split across single phase inverters with a max 4 kW on each phase?

Where should I site the panels on our new build? Options are... 14 panels on A + ( 14 panels at B facing north east or 8 panels at C facing South West ) Which is best, more panels on roof B facing North East or fewer panels on the smaller roof C facing South-West ? We have 3-phase supply into house so not limited to 4KW pv. Also, we are at home all day with EVs and a battery. I don't plan to ever get out of bed early to go to work again so early morning and evening generation is not a priority. My architect and M and E consultants say I should put the panels on the North-East roof. I'm not so convinced. Comments please.

That's what I would have thoiught too. ? This would also be the case with a buffer tank without a coil, would it not? Both types of buffer tank have a stat to call heat from the ASHP. So both systems would heat the buffer tank when the heating system is on. Is that right?

After reading through the very informative and helpful posts on here and other forums I'm left with some schoolboy questions about ASHP and buffer tanks. So, for background, we will be building a 280 m2 passive house with single zone ufh downstairs heated by (probably 5kw panasonic) ashp with a buffer tank. As I understand it, it is the buffer thermostat that calls for heat from the ASHP, thus eliminating short cycling that would otherwise arise from the low heating requirement. The room thermostat triggers only the pump in the UFH manifold. (and pump between buffer and manifold?) (I'm ignoring the DHW loop here and the switching between heating and hot water) 1. Is my understanding of the basics correct? 2. Would the buffer thermostat require a wide hysterisis, or maybe two thermostats one at top the other at bottom of tank? 3. Some buffers have a coil (like @joe90's), while others don't. Which one is best? Which one is easiest to set up? 4. For buffer tank without a coil then should it be configured with a 2-pipe or 4-pipe connection, or does it really make much difference? 5. Does the panasonic range of ASHP allow seperate water temperatures to be set for DHW and heating? 6. Some ASHP require a minimum volume, how does a buffer tank with a coil, hence very low volume, satisfy that requirement? 7. Does a buffer tank with a coil support a defrost cycle ok? Thanks in advance for all comments.

It took some googling to find it... .. what a good idea. Thank you very much for this.

How would we seal inside the duct? Silicone? Foam?

Centrally together with the other panels feels the right thing to do but does the battery and inverter need to be near to the consumer unit too? The MVHR ducting, electrics and everything else will be fully specified in the plans before building starts in the spring. Garage is outside of PH boundary but it will be well insulated. The garage door will be insulated too but not too airtight. (I think EVs charge far more efiiciently in a warm garage, but I may be proven wrong ?) I agree, but it's nice to be able to build it for us, not the next occupants.

I'm currently trying to allocate space for all the electrics and other plant and need some reassurance and guidance. Its a block cavity passive house on insulated slab and warm roof. ASHP, UFH, active cooling with fan coils and 8kW pv. Plans are like this: ... with plant originally planned to be housed in 2 plant rooms (each about 3m by 1.2m) like this: Room A: ASHP outside, UVC and buffer tank. Room B: MVHR and patch panel/hub etc. ( part to be split into towel store at some point) I had originally anticipated the meter tails would also enter room A and the consumer unit would be in that room, with the inverter outside. However, the scope has expanded to a hybrid inverter with battery so it can't really go outside any more. I explained to my M and A consultants that I would prefer to keep the heat generated by the invertor outside the thermal envlope (something they had never heard of before) and so their proposed solution is to run meter tails through a conduit from meter box M under the insulated slab to position C in the garage, where the the inverter and battery and consumer unit would be installed. While this seemed like a good idea at the time, I am concerned that (i) the garage, being well insulated and more airtight than most commercial houses (and not ventilated by the MVHR) may overheat anyway, and, (ii) having the CU in the garage (which is outside the airtight envelope) may invite trades to penetrate into the garage to access the CU leaving various cable runs through holes in my otherwise airtight plaster. So, having paced up and down scratching my head since yesterday, what do you all think? 1. Is the CU in the garage a bad idea for airtightness, or am I overthinking this? 2. Where should I put the inverter / battery / CU? 3. Running conduit under the slab for meter tails from M to C seems terribly overengineered when I could run the tails into room A, is it over-complicated? 4. Similarly, the M and E proposal to run openreach fibre from P1 to P2 in conduit under the slab goes against my principles of keeping things simple. Why not go through the wall into the ceiling void? 5. Should I move the MVHR into the warm roof and the CU/inverter/battery into room B? 6. Maybe bring the meter tails into room A and the CU in the boot room next door? With fan coils planned to go in loft above room B for cooling, then maybe that is the right place to avoid invertor overheating ... ? So, where should I put all this stuff? Should I stick with my M and E advice and leave as is? All comments welcome. I need all the help I can get.?

Does anyone ever apply a primer to the blockwork reveal so that the airtight tape has better adhesion? Like blowerproof paint or even a parge coat before sticking the tape down?

Why Loxone over KNX ?

Thank you for the image. That's the sort of overhang I want. So looks like we'll be getting a quartz worktop. The ceramics like Dekton just aren't strong enough for more than 25 cm overhang, and the cutout for the prep sink makes it even worse.

Speaking to two kitchen designers for our new build and its a nightmare. This is still a work in progress, but Designer A has provided the following design, with the unsupported corner. Sorry about the crap resolution. Worktop is quartz. Designer B, a German kitchen designer whose components we actually quite like, is very keen to remove the prep sink and move the hob into the centre of the island. He was very keen to persuade us that sinks on islands are always a bad idea because they always splash and require mopping up. Wife was symapthetic as she's never been overly keen on the prep sink but I detected a whiff of bullshit. On reflection I suspect the real motive here is maximum profit for least effort by designing a rectangular island under a dekton worktop with unsupported 20cm overhang on two sides. The more I think about a 20cm unsupported Dekton overhang the less keen I am, but would be very grateful for any comments and answers to the following in case I am being overly cautious. 1. I still think the prep sink on island makes sense, with Quoker tap because its at the tea end away from the work end. I am mindful of course of costs and impact on services required under insulated slab. Those that have both prep sink with boiling tap and hob on island, would you do it again? Any downsides? Is the prep sink a good idea or should I cave in and resort to a single sink? 2. Am I right to be concerned that a 20 cm overhang is not big enough to sit comfortably on stool with knees under? 3. Does Dekton chip at the edge as comments in other threads suggest and if so then should I go for quartz instead? 4. Does quartz have better strength for (depending on thickness I guess) unsupported corner overhangs? Is a 35cm unsupported corner overhang on a quartz worktop a good idea, or is it likely to break? 5. Would it be better to replace the corner overhang with a supporting carcass and instad have three stools in a line under a deeper overhang (facing the ovens in the image above) that is then supported at both ends? Intuitively this would be stronger. 6. Is Silestone another brand of Quartz? 7. What is generally the cost difference between Dekton and Quartz? Any other comments on our kitchen design most welcome!

Thank you for sharing this, your panasonic FCUs and mixing valve look like a really neat solution to get cooling (and heating) upstairs (without rads) while also cooling the UFH. I assume the mixing valve works ok when heating, with, say, >=40 C flow to the FCUs and <=25 C to the UFH? How about the physical install? Did you install in the loft (asuming a warm roof) with cooled-air ducting to the walls or ceiling? What about the air intake? I assume you can just let this recircuate loft air without any ducting?

Agreed on the velux, we are inserting at least one at the highest point to vent the heat. Architect is far more keen on this approach than blinds. Initial PHPP overheating days are a bit too high. Some modelling tweaks to go yet, but would certaily be easier to avoid external blinds.