wet ufh

[jonnyp1]

Hi currently have radiators off boiler. knocking out rooms and extending to provide large kitchen din lounge. Pulling up carpets and underlay and 22mm floor boards found a concrete slab over existing building. I assume i have approx 40mm for ufh and 10mm tile. Is that enough for ufh? Can i get kit and connect everything except manifold and boiler side? The boiler is in the kitchen one of the rooms to be heated, what would i need and what do i need prof to do? If i heated the open area approx 65m2, im also putting on a new hall would it be better to rip up floors on all of ground floor and take out existing rads and extend ufh? We sleep downstairs so upstairs rads would only be on occasionally to stop damp and once in blue moon for guests? Or keep rads in snug hall and bedroom where rapid heat increase/decrease might be useful?

 

[Deleted member 281264]

You need at least 100mm insulation to make UFH worth it

 

[jonnyp1]

thanks wont the size of existing concrete slab come into play come into play in providing heatable mass?

 

[Deleted member 281264]

No you need insulation in between or will lose heat into the ground

 

[muggles]

You'd definitely be looking at a retrofit type kit for that depth rather than a pipe in screed system. Something like Variocomp 100 https://www.variotherm.com/en/produ...variocomp-panel-with-100-mm-pipe-spacing.html

 

[Madrab]

Unless you can guarantee that the slab has at least 100mm insulation below it then you would need to add that if looking at traditional UFH.

There are few retrofit products now available - Low profile EPS400 systems are now available that are perfect for your situation - they are also fast reacting so the system is used more like a radiator system rather than a thermal mass whose heat needs constantly maintained. Was your floor a 22mm P5 chipboard or actual wooden boards and was there any styrene below that on top of the slab?

You can use carpet with them too but that takes some extra covering (6mm cementitious boards) but all doable with a min loss in height.

 

[jonnyp1]

cheers ill have a look at the system you suggest, no it was a concrete slab depth as yet undetermined with old floor boards hammered down on top with underlay and carpet, i dont know when laid but assume pre insulation but wont know until i take down walls. The existing room will be some 4m wide with the existing slab and then extending 2m out from there which we can do what we like with, would you split it and have new with traditional ufh and rest eps400?

 

[jonnyp1]

Talking to builder he says split full traditional on new extension and eps 400 type on old, plumber friend says never mix they are different approaches and never work well in same room should pour slab on new to same height existing slab and put in eps over whole floor?

 

[Madrab]

That's why builders are good at building and plumbers are good at plumbing. Your plumber chap is spot on, I would never mix the 2 systems, traditional thermal mass UFH needs to be run constantly to maintain the temp in the mass and ensure it is effective. EPS/low profile systems are run like radiators, turn the system on and the floor covering is warm within the same time frame that rads would have warmed up, they would not work well together.

Level off the floor and then EPS overlay the whole space, possibly with 2 circuits. If you use 16mm PEX with 100mm centres you may get away with 1 as long as you serpentine the runs to ensure correct heat dissipation. Just ensure the floor space is calculated properly for m2 output and what system temps/flows you'll be running at and floor types to be used

 

[jonnyp1]

cheers rob