Experiences with light weight water based underfloor heating systems

[DundeeDancer]

I am at the design stage of renovating a 2nd floor, 3 bedroom apartment and I'm considering installing a water based underfloor heating system.  

 

Thinking a good option would be to take up the floating chipboard floor and take away the old radiators from the apartment.  

 

Then place down on top of the solid concrete floor, insulation boards the ones that have the pipe channels pre-cut.  

 

Seemingly this approach means the tiles can be applied directly on top of the insulation board with only a 5mm or so of tile adhesive layer.  

So the system is lightweight compared to other screed methods which normally need around 40mm of screed.

Example links to a system I like the look of is given below:-

http://www.theunderfloorheatingstore.com/insulation-boards/water/25mm-solid-floor-panels

 

http://www.theunderfloorheatingstore.com/water-underfloor-heating/prowarm-water-heating-systems/prowarm-multiple-room-water-underfloor-heating-kit

 

Wondering if anyone on the hub has experience of using similar products and what have their experiences been like?

 

Have the systems been fairly easy to control the room temperature to a constant level?

I stayed in a B&B with underfloor heating this February past and even though I set the room control to be -2 of the normal setting, which was 20c, the room still managed to rocket up to nearly 25c at midnight, wasn't easy trying to get to sleep! 

 

Has anyone used these lightweight systems in a very insulated building and has the system operated OK or does it have a tendency to overheat rooms?  

(I intend to make the apartment very energy efficient to near passive standards)

 

Can these lightweight UFH systems be directly connected to a normal gas combi-boiler or was there a need to have a buffer hot water store?

 

Thanks in advance for any advice.

 

Best wishes, DD.

[Temp]

The main problem I see with your proposal is that the insulation is very thin so there will be heat loss down into the concrete slab and from there into the room below and/or the walls. You might be able to live with the increased running cost but the response time will be a lot slower. Do you have the headroom available to use thicker insulation say 80mm+?

 

There is nothing peculiar to UFH that causes overheating. My guess is something else was going on. Perhaps too much solar gain?  It is possible to have an issue with varying solar gain and a slow response time. Sometimes on a sunny winters day we get a lot of solar gain so the UFH switches off. Then when the sun sets the UFH takes awhile to respond to the loss of that heat source. The result is a small dip in temperature while the UFH catches up. 

 

They can be connected to a gas boiler using a mixer without a buffer tank. A correctly sized fully modulating boiler would be recommended if no room for a buffer tank. Buffer tank can help improve the efficiency but must be well insulated.  

 

 

 

 

 

 

[Nickfromwales]

If connecting to your existing boiler, is it a fully modulating one? If not, it's likely a small buffer would be needed tbh. 

+1 on more insulation, but if the tiles are smack on top of these boards then the floor will get hot enough, problem is that the medium to dissipate the heat is not great. Your pipes need to get hotter than normal, say in a screeded install, and you'll only have the tiles to absorb and convey the heat so may well prove to be uncomfortable if being used to heat an air leaky / high heat loss space.

Retro fitting Ufh is not the best way, so if you choose this route be aware that you'll probably never turn it off in the heating seasons, just up and down ( comfort 21oC and economy aka setback at 16-17oC ) according to occupancy. That'll allow the house to stabilise and reduce response times. You can't increase the flow temp to speed up the warming times as you'll then get the overshoot that is mentioned above. Tbh that example is most likely just a poorly commissioned setup with way too high a flow temp so best not used as a benchmark. UFH works incredibly well, when fitted accordingly and commissioned properly.