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Hi PeterW, there is no requirement for UFH. Total space heating load for the property is only 2kW which will be supplied with the duct heater and supplemented by circa 300W electric heated towel rails in the three bathrooms. There could be some merit in using a small ASHP for preheating the DHW prior to the SunAmp (as suggested by tonyshouse ) using excess energy from the Solar PV (6kW array). Its very marginal on ROI currently but, of course, energy costs will only rise over time! A we know ASHP's are not efficient at the higher temps needed for DHW but preheating the water through the SunAmp would considerably extend the SunAmps effective capacity. I have already been looking at air to water ASHP's for around £1000 but also need to factor in costs (and space) of a buffering tank , pump and controls of course. The practical issue of not installing some form of additional DHW heating is that once the 10kW of the SunAmp is depleted then will have to wait for an hour or so before we have more hot water at an adequate flow rate. The 3kW element in the SunAmp is clearly not capable of delivering any more than about 2 lpm from cold! So an ASHP is definitely a consideration on pracatical terms as opposed purely ROI.

SunAmp update. For those interested in the SunAmp products I can confirm that I am are now definitely going with a SunAmp solution as opposed to reverting to a thermal store. I did not want to revert to a thermal store for several reasons, one significant one is the potential overheating of adjacent spaces in summer, even with the Akvaterm stores. After several emails and telecons with SunAmp personnel I have confirmed that they will deliver a 10kW PV unit which comprises of 4 x PCM cells and 22mm pipework throughout. This is already a proven solution although not yet on the open market. With this configuration I can realistically expect circa 25 to 30 lpm flow rate, which is good for 2+ "power" showers simultaneously. An added benefit of the SunAmp solution is the extra space in the plant room where I can now locate the three digital shower valve controllers adjacent to the SunAmp DHW supply. MVHR first fix will continue this week as I now have the electric inline duct heater(s). I have opted for 200mm diam 3kW units. My PHPP calcs suggest I only need 2kW but the difference in cost (about £4) meant I have gone for extra capacity. Duct temperature will be thermostatically controlled with a setpoint of between 40 and 50C (adjustable) so the added wattage is not an issue. The 200mm dia. units will be reduced to 160mm dia to fit in the 160mm duct work. The added dia. of the duct heaters should minimise the reducton in flow due to the heating elements. I am awaiting schematics of the SunAmp which I will post once received.

Currently no plans for cold water storage. A lot depends on your supply of course! Our last new build I installed 32mm MDPE pipe and insisted on a 22mm water meter. That house had over 6 bar pressure which I regulated down. We could run four showers simultaneously at around 8 lpm. For our current build we have also stipulated 32mm MDPE for the incoming feed. In a new build you will always distribute water both hot and cold around the house in 22mm pipe using 15mm take offs for showers and baths and probably 10mm takeoffs for taps other than baths. If you dont have the possibility of decent flow from your mains then you have to go to cold water storage and a fully pumped system. Previous house I have had I always installed a fully pumped system due to inadequate flow. Its not a big issue with the latest negative head pumps as you can store the cold water anywhere suitable in the house. Cheers Roger

PS The reclaim form requires you to declare that you are only reclaiming VAT on goods "bought or imported from a VAT registered supplier" (para 25). https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/487894/VAT431NB_form_and_notes.pdf Most companies will put their VAT number on the invoice and that includes reputable EU/German companies. Perhaps check of their VAT/MwSt number is on their web site?

Yes, Megabad -- except that we haven't actually claimed yet since you can only put in the claim once after the building is signed off as complete. The reclaimable element is the actual VAT claimed at the exchange rate which pertained at the transaction so you will need a record of your CC bill or Fx deal so that the HMRC can verify the actual £/€ rate used.

So this is where the process is broken !!! Someone on here did their own design - and I've done a lot of tweaks to ours too - so I doubt there is any SE or architect that would be involved on either of those builds. My SE has purely done steel calcs - the rest of the "structural" design is standard elements as per the Building Regulations or robust details etc and will be signed off by the BCO. So how do the HSE want to work with that one..?? The other query I have is how HSE are going to track these builds with the "estimate vs reality" calculations on labour. For example, according to the QS estimate for my build I have an estimated 22 week duration with 2213.45 hours (!!!!!) effort involved. Based on a 6.5hr working day, that equates to 340 man days effort, or an average of a little over 3 people per day on site. None of those figures will trigger the HSE F10 at the start of the project and its within a good margin before it could (at 500md / 20+ for 30 days) So in completing the paperwork, as it doesn't need filing then no-one is checking to see if there is a PD and the PC is me with subs. In the end we will get a building that is built to someone elses initial design, with SE calcs for bits, and a BCO signing off that it meets stat regs..! Oh, and a warranty by another company just for good measure..!

We had a SE involved in the design and BC approved their drawings and calculations,.but the SE is not in any way supervising the build. BC have inspected the completed bare shell and agreed they are happy it has been built to the approved design and don't want any further inspections until completion. so it appears you don't "need" an engineer involved to supervise the build.

It's not just random guesswork. the designer of my house did a moisture analysis that shows there is no condensation risk. It also shows a thermal time constant of 13 hours so it should not heat up / cool down to quickly. (interestingly the analysis shows on a hot day, the house will reach peak internal temperature about midnight) u-wert-berechnung (10).pdf

Great stuff there is so !much collective knowledge in a group like this to tap into

Someone on the forum (Prodave?) used wood fibre board. You can render straight onto it, and it also insulates which is something that may suit your requirements with the steel frame.

Use the light on the boom of your digger!! My sister has one of them pir led solar lights. Not a bad light of it. http://www.screwfix.com/p/led-solar-light-with-pir-sensor-solar-led-floodlight-with-pir-granite-grey/98013

FYI, I am an MBC customer, so I have a PoV. However, let me look at the wider Q. I think that it's difficult to make a true comparison because the various suppliers include different components in their price bundle, and you need to factor this scope of supply into price comparisons. For example, MBC offer a total package including: a passive slab including the UFH loops, the frame, insulation, roof and roof cladding, all necessary air-tightness works in order to achieve a contracted and independently tested 0.6 ACH equivalent. If you are wanting a passive house then all of these components are pretty much essential; you need to design them in and implement them either with your frame contractor or with another subcontractor. There's little point in choosing a frame that is £15K less, say if you have an extra £15K of other subcontract work to do -- plus addressing any design issues across subcontractors and the integration risk. We chose MBC because we felt that their bundle meant that we had a single supplier who were addressing a whole bunch of issues that we would otherwise have to address ourselves. However, if you have an experienced site builder who understands and can manage these risks, then this might not be such an issue for you. So long as the construction quality is good, I think that the framing technology is actually secondary. Most suppliers do a twinwall Larson-strut style frame and a single timber frame. We've got roughly 8% of our wall space as windows at a 0.12 : 1.0 U value ratio. We decided to go for a .12 U spec rather than a 0.16 single wall, but I have a friend who has roughly 33% of his wall space as windows. In his case the decision of whether to use a 0.16 or 0.12 U value for the walls is dwarfed by the design decision to have all of that glass. It's almost impossible to achieve anything like 0.6ACH with that amount of large openings so air tightness is also secondary. By going with that % glass, you are taking the path of having large vistas and a modestly energy efficient house -- that is compared to a passive house, though almost certainly far more energy efficient than a stock build minimally complying to 2013 BRegs. In terms of airtightness, you just have to ensure that you've effectively filled all of the cracks, holes and permeable surfaces and in a way that isn't going to rapidly degrade over time. There isn't a single best solution. but there are standard weakness that your design and implementation must address: around the windows, doors and cassettes, around the joists and joist ends, and ensuring that services don't breech or compromise the airtightness. Miss any of these and you won't have an airtight house.

Don't forget you can buy useable baths from 1500mm upwards. Captains baths are usually 1500-1600 long . I would do away with the bath tbh, and accept that a family with small children won't buy. Doesn't sound like that's your target audience anyhoo. Id do everything in my power to put a shower room upstairs, no bigger than needed, and fit ( retain ) a downstairs WC with wash hand basin only. Forget the downstairs shower IMO as no buyers will be expecting two bathrooms in this size house and will deffo not appreciate the lost space / size of the rooms sacrificed to achieve that. Make sure there is good ventilation and only part tile so your buyers can change the colour with different paint.

If you ask my wife, after this long without one (well at least one that's plumbed in) she would I'm sure say a bath is an absolute must! Tbh there are times I find a shower just doesn't cut it when you want to soak the aches and pains away.

Welcome to the issue of broad brush implementation of legislation that doesn't get properly assessed ...!!!