Finished floor coverings removed, looking at installing UFH upstairs.

Has anyone done a cost to benefit calculation on various methods?

I'm thinking:

A. 50mm PIR insulation between joists sat on roof batten, 16mm pipe in a 50mm biscuit screed (potential issues for weight?)

B. Spreader plates with rockwool insulation below

C. Any other alternatives whilst the boards are up?

We have approximately 100m2 of upstairs floor area to do. Finished floors will be 18mm OSB with underlay and carpet...

My system which was installed when the house was built 14 years ago is option B and has proved to be more than adequate.
its cheap and very easy to fit

Very occasionally you get a creak when heating up. My floors vary most are 19mm engineered hardwood with no other finish however the bathroom is 19mm flooring chip board with vinyl overlay and the study is 19mm flooring chipboard with carpet tiles all produce adequate heating.

We did option B in the barn conversion. Despite being careful I still managed to put a screw through a pipe when building a stud wall, luckily the plumbers are very good and easily repaired my error.
It was where the loops of pipe crossed over the floor joists, we chiselled them into the top because the joists are existing and very old and rock hard pitch pine. Should probably have gone through half way down but that would have been even more epic.
Low temperature for us due to GSHP usually 30-35 degrees C
We used 18mm solid oak floorboards as the structural floor and finished surface I had to be very careful screwing them down (hidden fixings through the tongue) to avoid any pipes.
I prefer hard floors to carpets.

It was quite funny to have a look at this again about 3 years later, how time flies. It's only one half of the upstairs, I must have started on the "easy" side and then realised that I had to plan it more carefully. The spreader plates had options for 3 or 4 grooves, with 4 the pipe comes back to the same end that you started, with 3 it ends up at the far end. It took some head scratching!
Top left is "under bath", and there are some void areas over MVHR pipes because there just wasn't enough room for everything in the floor void.

I was also surprised by the flow temperature that is required, the boffins at Kensa explained it to me in detail, something to do with the surface temperature being lower than the flow temperature and lower than the room temperature….
In my head 20 degrees water in the pipes would give 20 degrees in the room, but I was soon disabused of that concept.
I guess the heat loss of the room/building is critical, it’s needs heat input faster than it loses it.

Posted By: Gareth JRegs are regs though I guess.

What regs are there nowadays?

Good question. I don't know! But if it can be shown that heating rooms below will meet whatever the regs require, could save a lot of people a lot of installation.

I'm not sure the regulations make any requirements of heating - our neighbours Passive build had only a couple of plug in radiators initially (they've now installed a single Air-Air heat pump unit)

Posted By: Rexwhat annoys me is every time the heating come on, the floor pop and bangs. I figure it is the expansion of the pipe where it is a push fit into the plates, but it is really annoying and frequently wakes us in the early morning.

Interesting. What's your flow temperature? suspect it's far too high. Our Wunda overlay system in fibre mats with spreader plates has never made any noise but flow temp is 21-30ish.

Posted By: Dominic CooneyWe resorted to Oil-filled radiators in the bedrooms in the last place we did, because they could get too cold in winter. We assumed that heat would rise, but obviously it didn't do so quick enough. Which is why we put the UFH in upstairs this time. Insulation in the walls wasn't as good as it could be though, due to space constraints.

That's the thing. We're over 3 floors (tall narrow townhouse). The top floor gets cooler but is probably OK, the middle floor where our bedroom doesn't need the UFH).

Ultimate solution now is probably Wet UFH on ground floor and air-air for upper floors as top up/summer aircon (which is justifiable if you're powering off your own solar).