UFH under existing pine floor boards

[thaldine]

Am I right in thinking that installing UFH below existing pine floorboards may be problematic in terms of what may happen to the boards once the heating is commissioned ?

 

Does the answer also depend on whether the pine boards will be the intended final floor finish ?

[Nickfromwales]

Hi. It all depends on the heat requirement of the spaces you plan to install heating into, and therefore how hot you have to run the UFH flow temp to get x W/m2.

UFH is not a fit and flick the switch on solution, and needs a LOT of thought before even considering as an option. Is the space a cold ventilated ground floor, or 1st floor? How do you intend supporting the pipe? Have you considered any makes / types / methods yet? Heat source?

Edited July 11, 2021 by Nickfromwales

[thaldine]

Thanks. yes, cold ventilated as suspended bungalow ground floor. Plan is to lap joists with airtight barrier, insulation with UFH pipes clipped on and spreader plates and a vapour control layer.  Not considered any makes yet as not even sure proposed method is correctly conceived . The heat source is currently a combi boiler but would be nice to have the option to switch to a heat pump later. Small wood burning stove planned for front room.

Edited July 11, 2021 by thaldine

[Nickfromwales]

Ok. So, things like insulating the loft as much as you can, foaming around pipes etc or any places where an unwanted draught are present, and sealing around the perimeter of the floors ( heated or not ) will reduce the ventilation heat loss. In terms of insulation, how much have you space for? Type?

Aluminium spreader plates are quite good diffusers, but only work really well if in contact with the decking ( floorboards in your case ) so make sure you get some mineral wool insulation under the plates so they are distended upwards by around 10-15mm so when the deck gets screwed down they are under compression. 

I would recommend triple groove plates so there are 3 runs of pipe per joist space, and they provide iirc ~120mm pipe centres. This will give far better ( greater ) system volume and a much more robust heating distribution, but as a bungalow I fear you will not get way without at least a 50L buffer tank to help when the house is nearly up to temp but still pulling heat, just very small amounts will be needed at that point and the boiler ( or future ASHP ) will inevitably short cycle during those events. 

[thaldine]

Thanks, was unaware of the distended/compressed plate point. Still waiting to lift the boards to look but I don't think the floor joists are very deep.

 

Still worried the floor boards will have issues with the heat that will be needed !

Edited July 13, 2021 by thaldine