Dreadnaught

Yes. In the event of freezing weather and the realistic prospect of a power cut lasting 24-hours or more, I'd probably just turn the isolation valves and disconnect the pipes to the heat pump and let it drain. I have a ground-mounted installation which isn't up against a wall so simple to do with easy access. I will have a short length of 28mm Hep2O pipe (suitably well insulated and protected from UV) connecting the heat pump to the duo insulated pipe that emerges from the ground so won't even need a spanner, just a Hep2O key.

Haha, no comment but we each choose our own level of risk according to our own comfort levels 😄 Ah yes, I was just now buying the 28mm connection bits for mine (and have 32mm duo insulated pipe under my raft foundation).

Oh, no I don't. No idea at all. In reality, the probability of a power cut lasting 24h-duration is remote at any time. And I am a natural risk taker

Yes, I am in the south (Cambridge) and, after reading this very helpful thread and some of the links presented, especially that from Graham Hendra, I have decided to do without both when I commission my own heat pump. Then I shall pray that there isn't a power cut that lasts for more than 24h which coincides with freezing weather.

Yes, had my electrician on site a few days ago on this precise issue. He said the same. Either 450mm down or surface mounted (even just above the soil level) but not in between.

I found this YouTube video informative on the subject:

In case anyone is interested, I just received one of these, plumbed it in, and it really does work. Impressed! I ordered it as a test and have installed it on my temporary site toilet. Will probably now use it on the finished ones when I get to that stage. The model I bought is Samodra Minimalist Bidet, dual nozzle. I paid under £20 for it. Happy to answer questions if there are any.

I have purchased rails for automatic curtains from Somfy, which I will install flush to the ceiling (I am still at First Fix so they are not installed yet). I am holding off buying the motors that fit the tracks until the company releases ones that use the Matter Standard.

I bought my nine rooflights from: https://roof-maker.co.uk in Leicester. It wasn't entirely plain sailing but I am content with the result. Happy to provide more of my story if you like.

Good to hear. Not tempted by one yourself?

Buy a normal toilet and add one of these? https://www.samodrahome.com/collections/bidet-attachment/products/samodra-minimalist-bidet?variant=40198313509062 They are available on AliExpress, Wish, eBay, etc. If you search, you can find lefthanded ones too. I don't have one but its a solution I am considering.

I am puzzling over biocides for my central heating system. My system will be UFH and a ASHP, brand-new plastic pipes and with no radiators. Its a low temperature-system and so might be prone to bacterial growth and biofilm formation. But on the other hand, tap water contains chlorine. Reading the Vaillant manual for my UniTower (an all-in-one UVC) it says: "Do not use any unsuitable antifreeze and corrosion inhibitors, biocides or sealants". And then does not list any biocides on its approved list. So should a biocide be added to an UFH system or not I wonder? What have others done?

@ProDave, did you ever get to the bottom of this? I am currently mulling what additives I will need to add to my heating circuit, if any, when I set it all up.

If have a void, but not ventilated. The void is for heave only. And is created using large crushable ground-heave protection panels (I used the Jablite version) made of polystyrene. They sit below the insulation, atop the compacted MOT sub-base.

The screwpiles was one of easiest part of my project so far. My foundation was designed by a specialist company in Ireland that others have also used on this site. There were three parties involved with the screw piles themselves: the screw pile provider, who was in the neighbouring county, his screw pile engineer, who specified the size & required torque needed for each of the individual piles based on my ground survey report, and the screw pile installer recommended by the supplier. The installation was done over two days by the installer using an excavator with a special head (he is the most skilled person I have ever seen using an excavator … he even used the excavator to load his tools in his side-door van at the end of the job!) and he noted the screw pile torque figures for each pile on a sheet of paper as he proceeded. I then received a copy of that report and, in turn, submitted it to building control so that they were satisfied. After the installation of the screw piles, another team then arrived to shutter and cast the raft, which sites atop the top-plates of the screw piles. That raft was indeed insulated with thick PIR insulation. The design of the raft was such that it had extra thickening to form an integrated ring beam and cross members so it was not one consistent thickness across its entire span. All carefully designed with UFH and plumbing embedded within. All in all, the following engineers were involved with the screw piles: 1) ground surveyor (I inherited this survey when I bought the plot) 2) foundations designers, in Ireland 3) specialist screw-pile designer in Suffolk All in all, the process ran smoothly and, I thought, the screw piles were quite inexpensive at about 3.5% of my overall build budget.

Yes, true. I spent ages planning out all the penetrations, etc., with help from experts. And then those that poured my raft submerged two of them under the concrete, requiring a bit of remedial SDS work to find them again. Having said that, they did a good job with my raft overall. I put all my hot and cold pipework in the raft. One pipe, for cold water, has come out in a slightly wrong location, a bit far from the wall. I am told it is possible to chip away at the concrete and wiggle the pipe in to its correct position and then make good with some self-levelling compound or sand-and-cement. Haven't done it yet though.

Yes, the anaconda-like insulated double pipe is very difficult to bend. To take it from horizontal to vertical as it emerges from the ground, it needs to dive down deep before bending up so as to emerge vertical given its poor bend radius. Quite difficult to achieve. My pipe has 2x32mm MDPE pipes within it, so bigger than the typical one. My run under the raft is about 12m long so I wanted the larger diameter of pipe to ensure the pipe's flow resistance remained low.

I think it depends on where you are choosing to site your heat pump. In my case, as I am choosing to ground-mount my heat pump so the insulated double pipe emerges about 1500mm away from the external wall of my dwelling adjacent the chosen ground-mounting location. However, if I had chosen to mount it on the external wall, I would have arranged for the insulated pipe to emerge in a location suitable for that. I am just this week doing the planning for constructing the heat-pump's base, which is a surprisingly complicated exercise, requiring precise locations for that insulated pipe, but also a small soak away drain underneath the heat pump, plus two concrete piers for the anti-vibration feet to be mounted, and the runs for the duct for the electrical supply and control cable. The insulated pipe and the two ducts are all in place under the raft but I may dig them up again where they emerge from the raft and finely adjust their routes a bit so that they emerge exactly where I need them under the heat pump base.

!?!?!

Same here.

I have an L-shaped bungalow and have 26x screwpiles because of tree roots. And then a concrete raft foundation atop. I can provide the benefit of my experience if desired.

It was the manufacturer Ubbink/Brink.

I chose them because the manufacturer was relatively local to me (Leicester, while I am in Cambridge) so I could visit the showroom and factory in person. And because of the Passivhaus certification of the particular units I purchased suggested good thermal performance. As sometimes occurs in self-building, the delivery of the units had a hiccup, but it was resolved satisfactorily by the manufacturer, and I am happy with rooflights, which are now all installed.

Thanks all. I wonder why the instructions for the shower mixers all say something like this then… (This one selected at random from Google – for "Heritage Bathrooms".)

Off topic. I have been reading online that shower mixers need a minimum hot-water-feed temperature of 55º to 60º to function correctly. Does keeping your tank at 48º cause your shower mixers to go haywire 😄?