Nick Laslett

@zzPaulzz, like JohnMo, I did my install myself. Electrician connected it up. I went with Sunamp, to avoid G3. But a pre-plumbed UVC is easy for a G3 registered plumber to fit. Just a days work. We had a UVC fitted in our rental to replace the gravity fed system and it took the plumber a day. Secon Renewables have all the guides to most major brands. https://www.seconrenewables.com/heat-pump-technical-manuals-962-c.asp I went with Panasonic because at the time I thought their install guide was the easiest to understand. For a new build, you will be designing in the requirements for the ASHP. I can appreciate with retrofit there is more value a heating engineer can add. Questions like heat loss, water volume, etc, you should be able to answer, so spec of ASHP is much easier. You will also control how all this stuff comes together, so UFH manifold, UVC will all be in same place. The ASHP is only 2 pipes, 2 power cables and a control cable.

Take a look at this long thread, where many forum regulars from back in the day have a discussion about MVHR cooling.

@Tony L, I feel your pain. I resisted MVHR for the longest time, but finally rolled up my sleeves and did the reading. The earlier you can get your head around this the better it will be for your build. MVHR ducting is more of a challenge the later it is added to a design. Just play with the ACH value on Jeremy’s spreadsheet to see the effect on the heating requirements. There is a very good MVHR design spreadsheet here on BuildHub too, but this is a little more daunting than the heat loss spreadsheet. https://forum.buildhub.org.uk/applications/core/interface/file/attachment.php?id=23283

@Tony L, Jeremy’s spreadsheet is very easy to complete. All you need is the u-values for walls, roof, foundation, windows and door etc. All the room, window and door dimensions, the target airtightness, the target room temperature, the lowest winter outside temp for your location. Just using the data already in the spreadsheet for Jeremy’s house, you can change the airtightness to see how much this effects the energy use, or change the lowest outside temperature, or your target indoor temperature. It will give you a much better idea of how this all works together. There is plenty of discussion in the original thread on the details of how the spreadsheet works. My biggest takeaway when I first found BuildHub, was that you need a cooling strategy, much more than you need to worry about insulation. If you have a well built house, with good insulation and high airtightness, you will suffer from overheating. (assuming that this is not already integral to the design.) You can design in many measures to reduce this, but basically any windows except those facing north will be giving you massive solar gain during the summer and after a few days all that heat in the house has nowhere to go. Jeremy found that just the heat from his UVC was enough to make his house overheat and he needed to switch to a better insulated solution for his domestic hot water to address this. MVHR will not help with cooling. You will find plenty of help from members here on this cooling topic, but the earlier you can design it in, the better.

I used http://www.bcpscaffolding.co.uk, based at Diss. Ben Carlie is the owner. They were easily the best priced of the three quotes I got. Mention my name if you like. I had his scaffolding up for more than a year. He helped me find my roofers, and the flat roof specialist. They did require some chasing to get them to commit to specific dates. I would be very careful about how you schedule work that revolves around scaffolding.

@JohnMo Have you got aluminium fascia and soffits? This is one of the few items where I baulked at the price. It looked like you needed to fit timber first and then fix the aluminium. This seemed like almost double the work. Plastic soffits and fascias were a hard no for us, like PVC windows, plastic front doors, Hardie plank and cedral. But would have loved crittall steel windows and doors, but like aluminium fascias, just too expensive.

I think once you commit to a certain approach, you are a prisoner to that decision. We decided to do the soffits and fascia boards ourselves, and used exterior MDF. It took us 6 months to cut, paint and install them all. Every board needed 7 coatings on both sides, so each board took a week for coatings. Only had enough room to paint 6 boards at a time. The house has 6 gable ends and 2 dormers. It sounds crazy in hindsight, but before starting it made perfect sense. Once we were on this journey, how could you turn back, or bring in a trade? People would ask how it was progressing and we would talk about the same piece of work for 6 months. We are now doing the internal boarding, it took 6 months to board downstairs, and we are 1 month away from finishing boarding upstairs, which has also taken about 6 months. Again every conversation for the last year has been about the same basic task. People think you are mad. We probably are, but once you start, very hard to walk away and hand over to a trade. The crazy thing about committing to a lot of the self build work yourself, is that it is so all consuming that you have no memory of actually doing the work, how you did it, or what it looked like before. You just move onto the next task and forget. We broke ground April ‘21, so just had the 4th anniversary of the build.

@metalgear2k2, thank you for posting a follow-up on the discussion.

So true. My mate recommended Rubio mono coat.

@zzPaulzz, I went with Wundatrade for my pipes. 16mm Hdpe-Al-Pex Pipe - 100m https://www.wundatrade.co.uk/shop/home/water-underfloor-heating-solutions/joist-floor-heating-pipe/16mm-hdpe-al-pex-pipe/ I went with Emmeti for my manifold and valves. Emmeti Topway T2 Plus Manifold. https://www.cli-mate.co.uk/product/emmeti-topway-t2-plus-manifold/ Cli-mate are based in Bury St Edmunds on the Rougham industrial estate. For my design I used the serpentine counterflow pattern, with 200mm spacing and tried to make each loop 100m long. https://www.lhs.plumbing/post/the-comprehensive-guide-to-underfloor-heating-pipework-layouts Since I did my install, design opinions seem to have evolved. So basically filling the whole slab in uniform UFH pipes, ignoring walls, rooms, kitchen, etc. This is what I gathered from a recent @Nickfromwales post. The reason behind this is the whole slab is going to sit at a constant low temp, and the heat will slowly be absorbed by all the concrete as a giant heat sink. So no hot spots, or cold patches. If you want to look at any of this kit, you’re welcome to visit. I have off cuts of the pipe and you can see the manifold.

@G and J, I was the same. I found it very hard to get my head around the Hep20 plumbing and SVP. What worked for me was actually drawing a piping diagram in PowerPoint using jpegs of the Hep20 components. Here is the drawing showing from the incoming rising main, water softener, kitchen tap, outside tap to the Inlet Control Group valve before the Sunamp. (Note: the outside tap is plumbed slightly differently, because there is a non-return valve not shown.) Here is the drawing I did for the hot manifold. I have some hot pipes in the slab, like kitchen tap. The others are in the ceiling, which is why I have manifolds pointing up and down.

@G and J, if you are already on mains gas? Then there is no shame in fitting a gas boiler. Gas is the cleanest of the fossil fuels. Most of our electricity comes from gas. So even if you have an ASHP, you are using gas most of the time. Burning gas locally is more efficient than burning gas at the power station. By building a well insulated, airtight house you are already making a long term commitment to the environment. Your personal carbon footprint from using a tiny amount of gas for your domestic hot water and heating, in comparison is insignificant. This calculator is a useful tool for modelling these choices. https://students.open.ac.uk/candc/carbon_calculator/ If your situation allowed for you to easily fit an ASHP, then it would be different. But there are millions of dwelling in the UK, where fitting an ASHP will be a real challenge. Just my thoughts on this topic specific to your situation, I don’t want to upset anybody. There are far worse things than a brand new high efficiency weather compensation driven gas boiler for the environment.

Here is the NHBC technical detail for SVP boxing. This is a good starting point using mineral wool. If you stuff the enclosure with too much mineral wool, you risk creating a coupling effect which enhances the sound transfer. The air gap is important. The next step up from this is denser mineral wool with an aluminium foil backing from Rockwell, Isover, etc. Armaflex have a version with aluminium foil, edpm and foam. I went with the Tecsound FT55 AL Acoustic pipe wrap, which has the best acoustic reduction by depth, only 12.5mm for -25dB. This consists of porous felt bonded to the Tecsound membrane, reinforced with an aluminium foil. I bought it from here: https://soundstop.co.uk/products/tecsound-ft55-acoustic-pipe-wrap Ouch! This site looks like it stocks most of the options: https://www.buyinsulationonline.co.uk/blog/soil-pipe-insulation-a-step-by-step-guide Another product I bought was Muftilag R51 Acoustic Insulation Sheet, which is slightly thicker. I also used the Wavin AS+ SVP product line. This is similar to Geberit Silent-PP and Marley dBlue. There are probably other options. The acoustic soil pipe has a much thicker wall than standard SVP, but the main area where it improves the sound reduction is the female coupling and the edpm padded brackets. https://wavin.com/gb/s/C03_F011_S276/wavin-as Finally, I used Fermacell boards for my build. These are higher density boards with better sound reduction than soundblock plasterboard at the same thickness. I don’t know what board NHBC are specifying to get 15kg/m2, 15mm soundblock plasterboard is 13kg/m2. 12.5mm Fermacell board is 14.5kg/m2.

@flanagaj, for me the procurement process was the most difficult and fatiguing part of my build. Every week across my build I was having to buy something, or researching buying something. It was very draining. Inevitably you sometimes get the wrong stuff delivered and have to sort out the returns process. Three toilets were wrong (wall mount vs standing), ordered 10mm Fermacell, they delivered 12.5mm. Very carefully specced order for all SVP materials and they delivered 1 wrong item. For the insulated raft foundations, the fitter told me on the day, he needed the DPC, so off to the BMs to get it as quickly as possible, all ideas of any cost savings out of the window. Many times trades will need something, where time is the most critical factor. There are £000’s to be saved with good procurement practices, like at least 3 quotes, asking for discounts, large volume orders, etc. But these things are easy to say, but hard to do week in and out during the build. I could not get a bathroom tiler for love or money, had to beg one guy just to do the plant room. Another big issue is what you choose to spec materials wise. If you go off the well trod path, then you lose all optionally with pricing. For example I wanted to use Siniat Resilient Metal Framing for my stud walls, this is a product aimed at student accommodation market, schools and hospitals. The amount I need for the few stud walls, meant I had no leverage. You can get free shipping if you meet the minimum spend threshold, this sometimes means you have to bunch items together, even though the BM might not have the best price for all items, but you make the saving on no delivery charge. I wanted a particular material to sound insulate my SVP pipes, the only merchant that would sell it online had a £100 delivery charge, the materials were £150. Sometimes you just have to take the price hit. They sold nothing else I needed, it was a specialised item. Did I need this solution to sound insulate my SVP? I don’t know, but I did not want to finish the house and have noisy SVPs and regret the £100 delivery charge.

@Dunc, looks great. You should be pleased with the results. The “mars bars” are much better than the “rebar chairs”. I had a mix with my SVP stacks of female coupler and just male ends, all protected with gaffa tape. No idea why I had both. You just use a slip coupler to start the new run from the FFL.

@metalgear2k2 If you are worried about potential thermal bridge, you could bolt some timber to the EPS, like how you would construct a stud wall, and then use the starter bars. Like @JohnMo, most of my internal walls, are stud walls.

I don’t think so, but could be wildly wrong on this one. My understanding was that with EPS ICF the external insulation is all that matters, the internal EPS is entirely sacrificial, it could be removed and it wouldn’t affect the U-value of the wall. Of course it is not as simple as that, but my understanding is that from a U-value calculation the internal EPS is ignored.

Here’s a good video.

You just need the right wall ties. Something like this: https://pamties.co.uk/product/wall-starter-kit-2/ https://www.vistaeng.co.uk/product/v63-universal-stainless-steel-wall-starter-system/ Cut back the EPS where the wall is going to start and treat it like you would adding a block wall to an existing block wall.

This sounds a bit similar to the topic 3 weeks ago about insulated raft and door threshold. My doors all sit 100mm back on the concrete. This also makes them level with the concrete in the walls. The Thermohouse ICF blocks have a ‘check reveal’ which dictates where the doors and windows go, unless you want to cut it away. With ICF the concrete is where the cavity would be on a traditional block construction. I appreciate this isn’t helpful to your situation.

Video of original install with older spec model. Do you have a pressure reducing valve in your configuration? Around 2021-22 they updated the models and changed the installation instructions to include a “Inlet Control Group Valve”. Video with revised install method and new model.

One thing I don’t miss about the house build is looking at building regs. They are just so badly written and hard to navigate. The fire regs for structural elements table seems to have grown massively since 2019. https://assets.publishing.service.gov.uk/media/67d2bb074702aacd2251cb94/Approved_Document_B_volume_1_Dwellings_2019_edition_incorporating_2020_2022_and_2025_amendments_collated_with_2026_and_2029_amendments.pdf So as others have already said, 2 storey dwelling needs 30 minutes protection for structural elements. British Gypsum white book has a plethora of solutions https://www.british-gypsum.com/specification/white-book-specification-selector/steel-protection Here is one with 12.5mm FireLine board

I came across this website when researching stairs. https://www.knostairs.com/kno-how/draw-stairs/ They seem to have lots stuff to support this process. https://www.knostairs.com/kno-how/draw-stairs/staircase-and-handrail-drawing-courses/ They use RhinoCAD, which has a 90 day free trial.

@Walshie, 3.6kW is loads of energy. Don’t feel bad. Outside the oven, kettle and tumble dryer that is everything else covered for 8 months of the year, assuming you have gas central heating. Just get a solar diverter for your hot water tank. Then 6 months of the year the solar is heating your domestic hot water. The tank is your battery. Obviously an EV car is also a good place to put excess solar energy and is also a massive battery. In 5 years time vehicle to grid will be a more viable system setup. My long term plan has been to use my EV battery when that approach becomes available.

Great suggestion. I did a few areas of my slab where we had EPS in place to be removed later. We used this approach to drop the threshold level for the patio doors. @WannabeBob, you should try to avoid having any finished parts of the house in place until as late as possible.