saveasteading

There is another that goes to self build exhibitions. It's worth phoning one or both. They will know the rules and wrinkles, if you can do this in retrospect ( I thought you couldn't) and how to present it. Ask how they charge for this too. Good luck and please report back. Lots have this issue.

So KwH is a Kelvin weeny Henry. Good to know.

They would need rather a strong flow speed to ensure the expelled air is sent clear. It's simple hydraulics so presumably that's been factored in. I once discounted mvhr totally because none of the manufacturers had thought of this. In those says the heat exchangers were inefficient too. That mostly explains my resistance to mvhr... but 15 years or so is a long time for things to improve at the expense of early adopters.

The pir is horrible to squeeze in when 100 or thicker. Very much easier at 50mm.

The wonders of science. I despair that some people are not prepared to do that.

Me too. I don't like grey wood. I've done this loads of times. We used Sika stain on treated timber. That's 2 layers resisting wasps on the outside, and still 1 on the inner faces. The treatment had to be one of the 'not green or dark brown" ones: your BM will get it in if not their standard.. To keep it looking original we used the Sika 'light oak' colour which you can barely see when applying it. But the timber stays that colour, maybe becoming yellower, and is very long lasting. (Dark colours fade in sun over 10 years). Perhaps the next shade towards brownish is better for rural effect. We didn't try other brands. NB paint overlapping boards before fitting, to allow for movement. I've had wasp nests in the attic and hate to think where their harvest is from. They will also chew pir to form a cavity but that ends up as dust.

You'll get more understanding on BH, not necessarily all agreeing, than from the industry who just do what they do, and repeat what their suppliers have told them. The greatest ignorance and resistance I have found is re air to air. The plumbers, which is what they are, don't understand it in my experience, or simply their supplier doesn't do it. Screeders only screed. Neither understands structure or building geometry. It's a big decision and you might (should) redesign your building methods to suit.

That must be Kelvin weeny Hookes.

And if it doesn't quite? It should work well.

So keep looking. It's truet that the pir market is very competitive. But so should be bats. I got a better price fir PIR from the local than from online, incl from "seconds". And it meant I could order for no waste and get more if necessary. The trouble with pir is that your roof will not be standard cc. 600cc +/- 2? Deduct 45mm width +/- 1. Then allow for twists in the timber. Builders end up cutting small and putting squirty foam in. A pragmatic solution for 150mm fill is 50mm pir, with some gaps, then 100mm mineral wool bats, which push in tight.

If the bco isn't asking perhaps letc it run. An example: in our case the fire service asked for a 10m3 water tank. But bco ignored that. So don't overthink. I agreed btw as, although there is no mains, an appliance could drive adjacent ( and we have 3m3 drinking water). I don't know if the bco gave it that much thought. But bco did ask about fire doors and alarms. Best ask them.

A bad thing to do. Explained elsewhere many a time. The driver is not allowed to do that without your signature. So when it cracks it is not their liability. How flat and level do you want it? The standard test is that you don't see any 3mm gaps under as 3m straightedge whatever the position and direction, even pressing down one end. A slight slope might not matter to you. 30mm is a lot of screed.

That's my usp. I get that. My feet are at 36°C so even the recent heatwave has been lower. Cooled floor at what? 16? So it's a feel-good for the feet, if choosing to go barefoot, but it hardly cools the body. And it's the air temperature that we need cooler. Don't we want to be at 18°C max for deep sleep? It's a luxury to have cool feet and go barefooted ( I find that unpleasant on hard surfaces) and that's an individual choice.

Fwiw. In the steading it is ufh on the ground floor but rads upstairs because headroom did not allow ufh. Rads also happen to fit in the 1.5 storey setup. It works well. It can be done. Current project has huge ceiling heights so is ufh both storeys. Why not Rads? would have been enormous. Because there is no carpet intended. Because we can. I rather like the pragmatic suggestion of @joth. Tell the Architect you note their opinion, but to design for rads for the present and you will review after research. I'd add that I was fairly ignorant on ufh until recently. Had done it twice but in easy, large spaces, and if I learnt one thing, it was that the 'specialist' contractors didn't understand it and just did what they did. The same applies to most designers... the info comes from the trade. I'm dubious about cooling. Hot air is up at the ceiling, and i would suggest is not much affected by the floor or rads being cooler. But your feet won't be hot. The pros and cons inter-relate with construction method and layout. You will be the expert soon.

I wrote this many hours ago and forgot to send. I'd say it needs to be at least as big as the sink being emptied. It will force the equivalent water through to the other side and into the outlet very quickly. The inlet should be at mid height and horizontal* so as not to disturb the silt and floating stuff. The commercial traps tend to be much smaller and depend on their being a low flow, not a sink emptying quickly. * that may require bends from the high inlet down and back again. Remember that the outlet controls the level and the trap volume is all below that.