Underfloor heating - what professional/company does the calculations?

[Skithepowder]

Builder has suggested overlay panel UFH in a renovation/extension. Like the idea of it but want to be sure it will heat the space effectively and efficiently given that half of the main room being heated is an uninsulated concrete slab. 
 

What professionals plan heat loss and how effective a system will be? Should someone and if so who, be doing heat loss calculations and matching that against what they expect the system to be doing in the particular circumstances surrounding installation in our house? I would feel more comfortable if someone did something like this rather than just saying it’ll probably be ok or you’re not the first or last to do it. 

[Temp]

I have 80mm of insulation below my UFH and if building again would put in 120mm+

 

 

 

 

[Jilly]

@SteamyTeais the expert on this. You are right need loads more insulation than you think so you don’t heat the ground.

[Conor]

You can forget about UFH on an uninsulated slab. May as well take your cash outside and set fire to it.

[JohnMo]

Heat basically moves towards cold.  The insulation in a floor slows the downward migration of heat towards the ground, promoting the upward flow to the floor surface.   The less insulation you have the more downwards flow of heat you have (the more energy going into the floor that is wasted).  The hotter you have to run the UFH flow temperature to get the floor surface temperature at the temperature it needs to be to balance the heat loss.

 

So a floor area that is part insulated, part uninsulated, will require two very different flow for each part of the floor, making control very difficult. One part will be too cold, the other too hot.

 

Then as pointed out in other posts you may as well burn your money it may be cheaper than running the UFH.

[PeterW]

On 10/03/2023 at 07:26, Skithepowder said:

Builder has suggested overlay panel UFH in a renovation/extension […]

given that half of the main room being heated is an uninsulated concrete slab […]What professionals plan heat loss [….] if so who, be doing heat loss calculations and matching that against what they expect the system to be doing

Obviously not your builder who appears to not care about your bills once he’s out the door - overlay systems are not designed for uninsulated slabs. 

 

You could get a UFH company to plan it however your issue will be differential movement in the heated surfaces due to substantially different heat loss between the two halves.
 

A better approach would be to dig up the old floor and insulate it and pour one single slab with UFH in it. That would allow for better uValues plus a better control mechanism for heating.

 

Alternative option is have all the M&E designed properly from the outset so it works together rather than let the builder make decisions on the fly - out of interest what was in your building regs application ..?