DIY small underfloor wet heating system off combi

[simonb88]

I have a small ensuite with no room for a radiator with a tiled fllor. I want to fit underfloor heating directly under the floorboards to cover approx 2m sq.
Does anyone know if I can just take this directly off the combi ( supply or return? ) and where can I find the really flexible hose and fittings required plus diffuser plates? Thinking of bending normal plastic pipes and insulating directly below.
This must be better than no heating at all?

 

[bookahandyman]

you can use one of these.. it is quite chunky and needs to be channelled into a wall. http://www.danfoss.com/United_Kingd...lve/980b3f8a-b232-4643-8758-4e31826a754e.html
you connect the flow in one side of the valve and out the other and then run it to the floorwhere required and finish the loop back to the return. effectively created an under floor radiator.

although you would ideally have it on its own circuit controlled by its own stat and zone valve, this is due to the time it takes to warm the floor, if you just hook ibto the flow and return of existing circuit then by the time all your other rads have got warm and the room stat switches it off the floor wont be warm at all. on its own circuit it can stay on longer to heat up properly.

 

[bookahandyman]

you can use speedfit 15mm push fit pipe for this if you wish.you will get it to bend each end just enough for teh pipe runs to be approx 30cm apart.

 

[simonb88]

Sounds good but how do I insulate underneath and do I need some type of diffuser plate?

Worried that the heat will not be directed into the floor above.

 

[bookahandyman]

i have seen this used before and also installed above in kitchen floor. i would reccomend you insulate inbetween joists with the kingspan type solid board depending on depth of joist go as thick as you can leaving at least 30-50mm between board and ceiling below and about 20mm from the top of joist. John guest speedfit do metal diffuser plates that has the grooves in for the 15mm pipe to sit in. however i find when you are doing this it keeps popping out and gets very frustrating. screw the plate to the joists and i drill the plate every so often either side of the groove and cable tie the pipe to help keep in place. when choosing the flooring base use P5 chipboard or 22mm plywood. tile with flexible adhesive with silicone additive.try to keep the floor thicknes as thin as possible to allow heat through but dont risk too thin that wil crack the tiles.