jack

Just FYI, the formal test involves taking an average of pressurisation and depressurisation.

I was more referring to the general concept of an insulated screed over a structural slab being known. In that situation, all of the insulation is between the slab and the screed. I've never heard of starting with an insulated structural slab, then adding only 20 mm of insulation before adding a screed. 20 mm will have very little practical effect. Your screed (assuming concrete) will need to be something like 75 mm thick, so assuming a structural slab averaging 150 mm, you're adding at least 50% more concrete to the build for no real reason. I'm curious about why you're assuming this is how it would be done? Has whoever you're talking to said this is how they'd do it? There's a huge difference between running the odd conduit for a particular reason (we have one to get power to the hob on our island) and running all of your services through the slab. I've never heard of anyone doing the latter, and I can think of lots of reasons why you wouldn't, starting with accessibility for maintenance. @Nickfromwales, you've worked on loads of houses with insulated slabs. Care to chip in? You don't run UFH under any walls, including internal, so assuming any internal stays go through the base of internal walls, I don't see what the issue is. Again, a large number of people on BuildHub have insulated raft foundations, and the issues you've raised either don't exist or are easily dealt with.

Welcome Shaun. I don't think that's right. Lots of people on BuildHub (myself included) have an insulated raft, and I believe that the only thing that's run through it (horizontally) is UFH loops. You definitely don't run plumbing or electrics through it. The other approach you've been told about is effectively the old-fashioned screed on a slab approach, but with only minimal insulation between screed and slab. I can't see any advantage to this. You don't put UFH loops near walls, so with even a moderate amount of care, you shouldn't hit them with anything. In a well-insulated house, you don't need a fast reaction time from underfloor heating. When it's cold, you want to use the slab as a heat reservoir. If you use a low-and-slow source like and ASHP, then you don't want/need fast reaction. If you use a higher temperature source like a gas boiler, a slower response will help smooth out peaks and troughs. Personally, I think you're adding considerably cost and complexity by having a further layer of insulation and a separate screed, without really gaining much benefit.

It's a long time ago but we had a quote for £14.5k for very standard wiring of a large 4 bedroom house in 2015 in the south east i assume that'd have to be well north of £20k now.

I'm not suggesting you should, I'm just providing some perspective on the supplier @Nick Thomas mentioned.

I've been running an APU2D4 as an OPNsense router for nearly four years and it's been rock solid. Good support too - I had an issue when I first tried to use it (turned out to be my laptop's ethernet port), and they were highly responsive and helpful.

A duct or two (with draw cords) would be a good idea as well. Saves you speculating about what you might need in the future.

There's a sub-forum that's only visible when you have a certain number of posts - 10 I think it is - that has a lot of threads dealing with this issue: Until you have the required number of posts, here are a few in the current sub-forum that will give you some more detail about this issue:

Ah yes, thanks @Rob99. No tree tech in my setup (installed 2015) so didn't even consider that.

It's just the Loxone link, which is the cable that links the miniserver and its extensions. The extensions don't have to be in the same cabinet - you have several hundred metres total length to play with: https://www.loxone.com/enen/kb/loxone-link

Perhaps some in the trades are padding their quotes by extrapolating increased rates over the last couple of years out into the future. Perhaps some have been burned by having to meet their quotes despite massive increases in materials and labout costs. Also, if labour is still tight, there may be an element of needing to be able to offer high rates to be sure they can get the subbies in at reasonable notice. All speculation on my part.

Sort of. The principle of not running everything in parallel a long distance from the central cabinet makes sense, but not your original reference to adding a miniserver. The point I was making is that, if you need whatever combination of relays, dimmers and inputs for this studio, you just need whatever extensions are required for those functions. You don't need the cost/complexity of a second miniserver at that spot. The only downside is that there's a risk you'll end up with an extra extension or two overall, depending on how you split out the functionality. For example, if you need 5 dimmers in one cabinet and 11 in another, you'll probably need an 8-channel dimmer and a 16-channel dimmer if you split them as described above, whereas if they're all central, a single 16 channel would do.

Agreed. Any necessary extensions could be placed locally in the studio and connected to the miniserver via the Loxone link. That's a single cable, the same as you'd need for a separate miniserver.

Even better than that, I believe they have a guaranteed price per kWh to fall back on, for at least a couple of decades. [Edited to add:] The agreement is for 35 years, and is inflation-linked. Also, HS2 is currently looking like costing up to £100b (and could be more). Imagine if we'd used that to build out more nuclear. Even at the crazy £23b cost and insane price guarantees, we could have had at least three more nuclear plants, drastically increasing our low carbon baseload generation capacity.

There are a few discussions on BuildHub about how to finish off the EPS upstand (generally, not just where things pop out). Take a look at these threads (and links to other threads they contain):

I knew I'd done a sketch, but apparently I did one in quite a lot of detail! You do need to think about how you're going to neatly finish this area, as well as ensuring the EPS is protected from rodent attack.

We had to route our ASHP pipework from one side of an attached double garage (on a raft) to the other and then a couple of metres through the house (also on a raft) into the plant room. The insulation under the slab is 3 x 100 mm EPS, so I got the guys doing it to leave a pair of channels in the middle layer. I laid some cheap drainage pipe (50 mm?) in the channels and used some expanding foam to hold them in place. They then did the last layer of EPS and proceeded as normal. I used a block of offcut EPS where the duct came into the plant room to keep the concrete away from the duct when it was poured. Once the concrete cured, I broke out the EPS, leaving me with a duct entering an open chamber in the slab at the edge of the plant room. When it came time to install the heat pump, I threaded 32 28 mm Hep2O (with oxygen barrier) piping through the duct. A 90 degree elbow in the chmaber and we had our flow and return in the plant room. At the ASHP side, I used elbows to come up the side of the garage wall. This is one detail I don't think I gave enough thought to at the time. I should probably have converted to copper right as the pipe came out of the EPS, and done everything from there in copper and then stainless braided flex, but we went with plastic. I was concerned about rodents etc, but it's pretty well wrapped in insulation and nothing's ever shown any interest in it.

It's been ~7 years since we did ours, but I'm pretty sure I used an old bread knife. I found it a lot easier to keep centred in the gap between ridges.

Cut off about 60% of the length of each blade. Job done.

Not exactly. Stalled motors draw high current.

FYI, ours is 1.73 x 2.47. It has everything except the MVHR.

[Just noticed Johnmo and Prodave beat me to it on the price and ASHP COP] Also, depending on where you live, it probably doesn't stay that cold for the whole 24 hours. Admittedly we're in the southeast, but even during a very cold period it would be unusual for the temperature not to get well into single positive figures during the day during winter. Different if you live in the Highlands I guess That very cold week we had in the south east recently was the first time in the 14 years we've lived in our current town that the average temperature was below zero for several days.

I believe the term being discussed at the time was "eco" house. If I ever sell ours, my focus will be on getting our energy bills in front of potential buyers. Passivhaus doesn't mean as much to most as very low bills.

Welcome Paul.

Welcome to BuildHub Adam. The best way of getting fast feedback is to find the right sub-forum, and post a specific question there. If you have photos and/or drawings (especially sections for something like you're discussing), that will usually help a lot.