joth

How many rooms do you have? If a single room demands 1kW then I think it's the 5kW ASHP itself that'll quickly become the limiting factor. (My whole house has a heat load of 2kW on PHPP and we're still planning on 8kW ASHP but that's for faster UVC reheat times)

I think fan coil units will need their own dedicated (insulated) ducting and outlets to recirculate air around at a higher rate. Duct cooler is normal for MVHR pipes and means the supply ducts need insulation as you say. Did you have a specific fan coil unit in mind? I literally might buy mine in Italy and get couriered over, they're so hard to source here PS planning to plan is exactly how I roll too ?

Wow. I've passively thought about this balance (Indeed last week I just moved to Agile for import; and I'm not planning any battery storage as mentioned before), but now you call this out, our 8kW PV array will be entirely SW facing so I really should think closely about export maximization during this time window. The fact I'm on agile for import is already incentivizing behaviours & designs to allow this, even before the PV goes on. (Right now, the only power is that used by our contractor, they knock off by 4.30pm hence why getting on Agile import during the build seemed to make sense. Aside: it took less than a week for them to switch out SMETSv1 meter over from ovo to Octopus, so far better than the 'median' expectation I'd set for it)

Network switches are trivial to change at a later date. Indeed if I moved house I'd probably take my switch with me. Thus I'd really not sweat debating which switch is used, it's akin to debating what brand TV or vacuum cleaner you have. That said, you'll probably find all your devices are either PoE or have a realistic need of 10Gbit - hard to imagine anything that needs both, so I'd personally get 2 switches, one optimized for speed one for PoE, it'll probably be more priceworthy and this has benefit that when the PoE switch dies (they all seem to eventually) you don't loose all connectivity. Just my 2p. Thinking about things that are more integral to the build and harder to to repair / replace if they fail or don't live up to promise: Fakro windows - Consider the FTT U8 as it's much better U-value and I can't imagine the external aesthetic is that much difference. Liebherr fridge - Pros: reportedly very reliable and serviceable (they make the fridges for Miele). A++ ratings available. Cons: these oversized ones are hard to move and seem to get discontinued very regularly (happened to us this Jan, and we had a chance of heart then too). On the plus side if you make a space big enough for that beast in your layout, you'll be able to put any other fridge you ever want into it. Bora, Liebherr, Fakro, Neff, Sapienstone, Eclisse - all going into our build so ping me in the new year for updated opinions :-) You haven't selected main windows yet? That probably is the single biggest thing that impacts the build, so worth putting effort there.

How much of the fixed price contract is left to run? It sounds like someone under quoted and is now trying to wriggle out of it. If you're going to be dealing with this for many weeks I'd definitely think twice about continuing with him. Alas surprise fees are par for the course. In most cases they come down to "cock up" rather than conspiracy, but that doesn't make them any more palatable. At least no one has got shirty when I've brought this up, and indeed they have started to adapt and be a bit more proactive in flagging and fixing costs on variations before doing the work. Infact now I say this, the ugly reaction here does reinforce the impression this is someone caught with their hand in the cookie jar...

Situation: Meter is in the garage (outside thermal envelope) with a small CU for the garage plus (planned) henley blocks connecting fused SWA runs to ASHP, shed, and into the house. It will be about ~20m of SWA to bring the mains in through a wall, through half the house and to the main CU (on the first floor landing, mostly chosen for shortest distance radials for all lighting). Ordinarily it would be 3 core x 16mm SWA with 80A fuse. I'd like to through in an extra core incase I add battery storage in future and want to have a separate "backed up" supply in addition to the direct grid connection. Question is should this additional supply have independent L & N, or can they share Neutral? Basically can we get away with 4 core (or even 3 core if running a separate earth!) SWA, or does it need upgrading to 5 core? (I will of course discuss this with the electrician, but I don't yet have that conversation and I'm trying to do my research in advance of that, as I imagine this is not a usual request)

Cheers! yes, I was imprecise in my explanation, I think the point was more about where it's applied rather than what specific product is used. I'll get a photo and that'll paint a thousand words

OK just had a chit chat with our contractor and they're already discussing something similar to this but using Iso Bloco (which I think gives back some of the acoustic and thermal benefits of the missing Compriband too) Now I have the full picture, the reason to not use Compriband makes good sense to me: it would only have sealed the window to the OSB box it sits in, but the outside edge of the OSB box would remain exposed to the weather. Whereas the externally applied tape will join from the window frame right over the OSB box and onto the wall weathering layer, sealing the whole lot together. Driver 1, backseat driver 0 (But still, I much prefer being an "informed consumer" than just tagging along for a rollercoaster ride)

I am of course being a bit melodramatic, I'm sure you'll agree everything seems so much more emotional when you're right in the thick of it. Most of the frustration stems from having transferred responsibility for all expensive details to the main contractor I now have little control over those details, I'm the worst kind of back seat driver constantly trying to check the work and still mistakes happen that I get worked up about I'm conscious how vague I'm being. I'll do a full write up when I have the benefit and lucidity of hindsight.

Out of interest, do you have any source for this? Ideally I'd like something that quantifies the improvements. Trying to understand if this is small marginal gains or a fundamental point any passivhaus should have insisted on Cheers

Similarly, our PHPP say 2kW, but traditional room-by-room would like 4.7kW Also looking at a 300L tank. We were going with a 8.5kW Ecodan but had the offer today to use 6kW R32 model instead, as it's about £500 less than the 8.5. I am awaiting the numbers on what this will do to DHW reheat time

Thanks for confirming I'm not in the least surprised, but at least know we're lapping EWI and render over the outside of the frame anyway which will go someway to mitigating this. Still it feels every single step of the process in ordering and installing windows comes with a massive side helping of disappointment.

OP appears to be using Compriband inside a timber frame - this is interesting as our installers turned up with rolls of the stuff but refused to use it because the windows were being installed inside OSB boxes, where they said airtight tape and squirty foam is a better finish and that the Compriband only makes sense when the windows are installed directly into brick/block finish walls. Any truth in that?

If it's any consolation, it's still a heck of a lot cheaper to change this now rather than after the building is built and you (or future owner) decides a need to retrofit more insulation.

(Missing some context as this thread was about alternatives to a 5kW ASHP) You'll need planning permission to install >1 ASHP These don't appear to be inverter driven so the surge current and noise of two of them running could be quite high. You'd need to design the control system to run one or both depending on demand.

If that is too much bother to use, it would be easy enough to pop those pink wires out and put into your favourite flavour of wago.

Unless you're in a conservation area it can go on the front of the building and still qualify for permitted development, no Planning application needed https://www.planningportal.co.uk/info/200130/common_projects/27/heat_pumps/2 (These might be rights you only gain after the property is signed off as complete?)

RHI is valid even if it's used for space heating only, there's no policy requirement it contributes to domestic hot water heating, let alone that it must provide 100% of it. In fact the rules around Legionnaires pretty much requires there's a secondary DHW heat source. https://www.ofgem.gov.uk/environmental-programmes/domestic-rhi/applicants/eligible-heating-systems Heat pumps don't have to provide domestic water heating to be eligible, but may do so

Right, my point is the OP said they wanted to achieve PH+ and didn't mention a requirement for batteries at all, so rather than trying to design a DC vs AC system I'd recommend starting with no batteries, check if you can meet the project goals with that, and go from there OK think I see what you're saying -- DC batteries that directly feed DC equipment without any AC stage? (I was thinking more of AC vs DC tie from batteries to PV). Certainly more efficient, but this means a DC distro around the house as well as AC so I didn't even consider it (might have done for a few select items like the lighting controller rack / LED drivers - but there's no way I'd make enough usage to be worth it, given I don't care much about off-grid backup). But still I'd go back to my first point that if the goal is PH+, put all the $ into fabric and reducing consumption and installing microgeneration (e.g. PV), and leave battery design (if any) driven as a separate decision point. This was true for us too (although being EnerPHit+ the thresholds are a bit different) detailed over here: (gosh a whole year ago)

PH+ hasn't got anything to say about batteries, having no batteries at all is by far the simplest way to achieve the certification. They just look at (predicted) generation output vs (predicted) energy consumption. Doesn't matter where the generated energy is used. Personally (as someone half way through an EnerPHit PH+ retrofit) I'm deferring installing batteries [and on upgrading to an EV for that matter] as they also require some additional spending, don't aid the core goals of the project, they are still rapidly dropping in price, and after a year or two in the house I'll have far better idea what I can actually benefit from. FWIW though - if you really want DC coupled batteries that tends to rule out SolarEdge PV inverter. The Luxpower stuff looks a good integrated/hybrid option.

Nit: 8kWh (I've not checked the calc, just corrected the units)

These are very interesting details, but to confirm they're solve a different need up providing hidden uplight to wash the ceiling, rather than hidden downwash light onto the wall? I'd imagine the builder's detail for the latter would look something like a drop ceiling with a vertical shadow gap at the edge before it meets the adjoining wall, and the LED strip/profile is mounted i.e. something like this (excuse repurposing!) ?

Do you mean strips, or battens? The former are usually 12V and come on a roll of with a sticky back, the latter are mains and in an enclosure that's a drop in replacement for Fluorescent tube light. vs

Increasingly my attitude with ESPHome is to try and build autonomous devices that do not need the Home Assistant server running to operate (and ideally not even the WiFi local network) and just use the Home Assistant TCP smarts as a convenient development and monitoring platform. Being able to adjust code and reflash it insitu, and stream debug logs and monitoring graphs, all from a web-browser, suits me very well. My ESPhome devices are all on my "IoS" VLAN with no access to the public internet and limited connectivity to my main VLAN (basically, just to the Home assistant server) so the attack surface is very reduced, if not removed all together. For an example of autonomous behviour, I can have a single D1-mini both read the current export value from the main meter (modbus interface) and control the SSR to adjust the immersion load (simple analog output). This needs to Wifi or IP connection to work (unless I split the functions over 2 boards via UDP). The IP network would just be used to control "boost" or "eco" mode on the immersion (i.e. override ON or OFF for a period of time).

Here's the front curtain wall mid-demolition, and post demolition with bottom half rebuilt As you see, the main structural component front and rear is 300mm I joists