Nick Laslett

Lots of excellent posts in this thread. For me the cooling aspect of UFH, in concrete with ASHP was actually more interesting. It didn’t seem to get as much commentary. Maybe, the considerations for UFH cooling are basically the same as heating? There is the dew point issue. I put more UFH in my upstairs concrete floor than I did downstairs, purely for the extra cooling. I was always going to have a poured concrete first floor, so being able to use it for cooling was another positive. Like a lot of my buildings choices, this might be a foolish solution for cooling a house. A note about Air conditioning. I spent 12 years living in the Middle East, with A/C running 24/7. Even if you only need A/C for 2-4 weeks a year in the south of England, I was really keen to avoid having to install it.

@flanagaj, you would just remove the window restrictors after the house is signed off and you have moved in. @Bancroft Just remember to leave some cross opening windows so that you can do purge venting. I really struggled with some MVHR concepts when I first had to grapple with them. But after 6 years on this forum, I get the strong impression that there is a lot of window opening being used in conjunction with the MVHR. I believe the idea that MVHR negates the need for opening windows, in a UK context is a bit of a myth. But it is a complicated topic, with a lot of different opinions, so please do not take my comments for gospel. 😉 Good discussion here:

@EinTopaz, @craig is the forum member with a lot expertise on this topic. A 3G window will perform similar to a 2G unit if the gap between panes is too small, e.g. a 28mm unit will perform the same, whether 3G or 2G due to these gap sizes. For a good performing 3G unit the gap size needs to be 16mm as a minimum. *Apologies if my understanding on this topic has been superceded with more recent developments, very happy to be corrected by those better informed. Good discussion in this thread.

@Russell griffiths, @ToughButterCup, great looking houses, gentleman. Well done. I might have seen pictures previously, but in any case, good to see them again.

@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.