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Item 1 on the latest list is complete 😁

I've just paid £2600 for 1.5 storey about 35-40m length for 12 weeks

On the face of it, the cost of scaffolding does seem steep but it is a necessary evil unfortunately - Yes shop around as prices will vary - that said, the industry is full of H&S requirements which is often reflected in the price. Cheaper operators may be out there but does that come at a cost? The price I paid for scaffolding irked me but I put it down to just one of those costs - a bit like pouring money into the ground for foundations ! Welcome to the world of self building😁

Caught it! See series of images below…

I’d be watching for a gradual change in voltages between the two dc feeds as the sun goes round. Ok today may be a bit hopeless but still, if you catch it with zero on one feed screenshot it, it’s hard data that will be useful for diagnostics.

Good point. I’m looking at an MVHR unit that’s spec’d for about twice our size, though that was done in pursuit of quietness and longevity but clearly it would also help if we did overheat. Because we’ve had a good few hot nights here in Suffolk over the last few years we are going for an ASHP that also cools, with a deployed Fancoil in the main bedroom and probably plumbing and wiring for fancoils in the other bedrooms too. We’ll run one zone for UFH and Fancoil to start with and run just above dew point, with the option of ‘valving’ out the Fancoil if needed so we can run really cold without condensed floors. So I’m feeling ok about overheating in reality. Part O is however different. Plan is to use 90mm semi rigid (I think it’s the zhender stuff) in a radial system and I’m doubling up vents in a couple of areas. I’m hoping to hit less than 0.5 but in truth it’s the thing I’m least confidant of and in the next couple of months I need to learn more towards this. We have a narrow plot and thus thin walls and my initial disappointment with that has given way to a feeling that airtight makes up for a lot of missing U. We shall see but one lives in hope. I appreciate the input @Nickfromwales

Your build will almost certainly fail minimum sap requirements using the default values. That’s pretty much why they removed ability to use standard details. We went to our cavity insulation provider and their in house team calculated all the requisite psi values for most of the E values. Warmcel Then provided psi values for many of the R values. most sap providers will want custom values and won’t chance ‘making them up’ as they may face audit. what’s your construction makeup? Ours was a 200mm cavity so there were t any readily available.

BRE has this 2010 document with some values. https://files.bregroup.com/bre-co-uk-file-library-copy/filelibrary/SAP/2009/SAP-2009-Appendix-K.pdf And the LABC has this one. https://www.labc.co.uk/sites/default/files/resource_files/zch-thermalbridgingguide-screen.pdf ESE https://www.energy-saving-experts.com/wp-content/uploads/2011/07/Thermal-Bridging-Part-L1A-landscape-version-.pdf Should be enough there to work it all out yourself and save a few quid.

just had the same issue. Our very insulated, timber frame build triple glazed open plan with some internal steel uprights etc required a psi done before sap could be completed, all to comply with our building regs 🤷🏼‍♂️

I didn't get much mould for the first few years, but as time's gone by, I get increasing amounts building up every year. You've reminded me I need to do my annual clean. If I remember, I'll drop a photo (if it isn't too disgusting!) into the thread.

Not sure why you want it pressurised? But you would normally equalise flow and extract, this equalises pressure. If it is pressurised you would struggle to open an inward opening outside door. So I doubt you are actually pressurised, you would also need an airtight house. Any ventilation system will bring your humidity levels down to 35 to 40% in a period of sustained cold outside.

The house doesn’t look overly complex at all. I would simply oversize the MVHR system slightly to allow for effective purge ventilation, and see if that takes any other mitigatory requirements out of the picture in one swoop. I recently chatted with Nicholas Vaisey (CVC Systems, Oxford) for this exact reason, and for options to navigate this. These guys do all of my self-build clients heating / heat pump / hot water and MVHR, design, supply (and install (when I am too busy)) and this methodology provided a simple, practical, cost-effective (and elegant) solution in one box. This was considered in a set of proposals I’ve just done for a mass home builder, where I was drafted in to provide pre-construction M&E / plumbing design specifications for 2 large sites; Part O raised its head and everyone on the project just became disorientated as they weren’t used to dealing with it, clearly, with technical staff seeming utterly clueless tbh and were obvs out of their depth there! Doesn’t bode well for anyone buying one of their sausage-factory ‘boxes’….. If the house is having MVHR anyways then economy of scale says this would be the easiest and cheapest route, eg to slightly over spec at the design level at minimal cost-uplift, adding in an assumption that slab cooling via UFH / ASHP is already possible / being considered? Combatting audibility (at higher airflow rates in the summer) with some extra thought going into the design for the distribution ductwork needs to be factored in, but at that point I would defo rule out a series run setup and go for radial. What is the target airtightness score that you are aiming for? I think AT is more important than insulation as you can have a foot of PIR, but with high infiltration rates, and still see a cold house each winter.

Thanks SuperJohnG. That's a really helpful and reassuring post. Your climate in Ayrshire will be almost identical to ours 20 miles away across the sea.

If I remember rightly, SAP is mostly a nonsense calc anyway with a black box algorithm and the ‘assessors’ are allowed to ‘assume’ significant details about construction. It would be much better if we used PHPP calcs which are, at least, open and transparent (well as long as you’re happy to trawl through German-language research papers). So you have a couple of options: + do as they say. + ask them to use the fallback default value first and see what the result is and whether you (and BC) are happy with that. Both of you may well be if the build is to a good spec and you’re not worried about boasting about your great EPC rating. + you can also do the psi calcs yourself using Therm or similar - at least to see how different the results are from the default numbers. Not trivial, but not hard either. BC may not accept your values in the official calcs (as you’re not an accredited ‘expert’) but at least it gives you some control over the situation (and you may learn something useful things about your construction also). Standing back, this often seems to be how these new rules get introduced: (a) industry organisations / academics steer government to introduce new ‘rules’, (b) a new little industry is minted to milk housebuilders by creating or supporting a new monopoly industry organisation that promptly develops a new accreditation scheme to fleece new wannabe ‘experts’, (c) often accompanied by an actual or virtual or contractural monopoly - often for a private equity company, Capita etc. At least this rule-making process and economic milking process need to be made a lot more transparent.

Psi-values are required as part of the SAP calculation input. The accredited construction details can no longer be used so option is to use default psi-values (which makes BR compliance very tough) or calculated psi-values (or mixture of both). There is lots of published data on masonry and timber frame psi-values - see trade associations, building product manufacturers. For non-standard construction such as SIP, insulated formwork, light steel frame etc bespoke calculations may be only option, they are complex and time consuming hence costly!

And if you don't fancy making something, try open energy monitor - they do a great bit of kit with up to 6 sensors that can be used to monitor the whole house and several appliance circuits as well as up to 6 temperature sensors -> https://openenergymonitor.org/ Their systems are all open source, based in Wales and doesn't rely on any cloud servers if you connect up to a local system. More data than you can shake a stick at as well of plenty of graphing options and apps to waste hours and hours of time on.

I went for the rather more modestly priced Accur8 6in1 circa £120 (which seems to have morphed into a 7:1 for a few more bucks).

Yes, but which model. The Davis Vantage is the best. (I got a Met Office Weather Station not that far from me, the ionising radiation collector is impressive. https://www.davisinstruments.com/pages/vantage-pro2

Sounds like a Personal Weather Station for Christmas then 👍🏻 Highly recommend for weather/data watchers.

We have a Sunsynk inverter which can be connected to their cloud through a wifi dongle or an ethernet connection. You can also attach a modbus interface - I've done this because their app which accesses the cloud data only updates every 5 minutes, so doesn't really give real time data. So you could simply disconnect the wifi dongle and not connect a LAN connection and just use the local modbus interface - of course you won't be able to use their app but while that is comprehensive it ain't brilliant... Ours btw is still connected to the Sunsynk cloud whiel we're still tinkering. For modbus I've half-inched a nodered set of flows -> https://powerforum.co.za/topic/8451-sunsynk-inverter-monitoring/ to read the data and feed it through to a local open energy monitor server -> https://openenergymonitor.org/. The flows are very comprehensive and also include setting parameters and there's a pretty amazing nodered dashboard . I reckon if any other inverter has a modbus interface, you could use a lot of the flows with only a bit of adjustment. Not massively pretty but below is a dashboard from an openergymonitor server on a Pi Zero 2 which we're using at the moment as we get used to the new batteries and inverter. PV and house load are fetched every 5 seconds and the more slowly moving things every minute. The diverter data is from our Eddi.

Considering this question for my own house - it's going to be a new build, quite small only 100m2 and I can get a Daiken with a 90l/120l hot water cylinder water heating option too. I think A2A works best in a retrofit though. Another primary benefit is direct cooling. I could live with the slight noise and draught, in an ideal world I'd get A2A for the bedrooms / office and A2W for the ground floor! Still heavily leaning on A2W for my house as it's a 3 bedroom with a bath and I'm not sure the smaller A2A tanks would work well on the hot water side and take too long to recharge. An A2W is better suited for my situation. The other con though is cost, the A2W is closer to 20K all in with the underfloor heating loop. An A2A would be much cheaper. Treated floor area 101.0 m² Heating demand 14.91 kWh/(m²a) Heating load 11.06 W/m² I could run refrigerant pipe, Electrical & Drains to all the proposed locations so it's easy to retrofit later but would I ever use it? https://www.daikin.ie/en_gb/product-group/air-to-air-heat-pumps/multiplus.html What do people think about using the heat pump manufacturers integrated cylinder vs getting a separate one? Any advantages / benefits there? Thanks!

@SteamyTea Ah, that explains it all. ⁉️