Limecrete floor too deep in my 17th C cottage?

[Doon2025]

Hello, I am renovating my early 17th C cottage in the Lake District. In order to improve its breathability and overall wellbeing, I chose to install an underfloor heating system above a geocell (foam glass ) insulation, encased in a NHL5
Limecrete floor. Unfortunately, the limecrete is overall between 15-20cm deep rather than the optimal 10cm - this is entirely due to human error in measuring the depths, as you can imagine the subsoil was extremely difficult to level off. My question for the forum is, has anyone installed pipes this deep and has the system managed to generate heat through this depth of limecrete? I am installing an air source heat pump. Thanks in advance for any thoughts.

 

[Cubist]

I don't think you need, or should, bury the pipes that deep. Typically, as I understand it, the pipe network would be laid out over the top of the limecrete slab and then covered with a screed of some kind to reach the final level for the floor. Other members here have installed UFH systems and hopefully will confirm this or correct me.

 

[Kearn]

I wouldn’t worry, both my recent floors have ended up similar, in hindsight, more RFG would have been the better option, but no issues.
My kitchen floor is somewhere 70-80mm slab, I forget the details, but then we had about +40mm bedding layer for the 22mm slabs - wasn’t sure if we were going to use much deeper reclaimed slabs, so needed the flex. Living room is 100-110 slab, probably about 15-20mm bedding layer and then 22mm slabs again.
Both floors heat up fine, yes there’s lag, kitchen possibly less than living room, but there are many variables that could drive that. It’s also a bit irrelevant, as the point of UFH is low and constant, so once the slab is warmed it stays there, it’s not an on/off system. Both stats are set to 16 deg in room temp, but we’ve only used them one partial winter, so there’s lots of fettling left to do. And neither rooms have complete walls still!

The setups with a slab, pipes, screed I can’t see being much different than pipes at the bottom, the heat from the pipes will heat the cold stuff around, so heat will go down into the slab, until it becomes protected by the insulating RFG.