Electric UFH wood subfloor

[rookiediy]

We are embarking on a refit of our ground floor kitchen/lounge and would like to install electric underfloor heating. Any assistance on the considerations would be great.
-Large 4ft ventilated subfloor cavity ;wooden joists; chipboard subfloor.
Thinking we might use 100mm polystyrene insulation between joists; chipboard subfloor; some sort of underlay/dpm; 140w foil electric mats; 20mm engineered oak floors.
Are there any glaring issues here we can avoid??

also, I believe no UFH should go underneath fixed furniture (e.g. kitchen island). should we fit the kitchen on the chipboard then do the UFH and flooring around or could we just lay the engineered wood over the "patchy" UFH with kitchen coming last??

 

[Gteuk]

There are 2 electric underfloor heating systems that are referred to as the foil system

The silver in colour which in essence has an wire the size of an electric blanket element, which in my opinion the 140w version would be background heat under engineered board at 21mm
The other Carbon Film / Carbon Foil this is black and transparent less than 1mm thickness.

The other Alternative is Ribbon underfloor heating made from amorphous metal which is suitable for all floor coverings as a main heating system.

Insulation is always good and the more you can use the better, so if you can put some in the void that is great.
Make sure that the existing chipboard floor is fully secured afterwards and as even as possible.
Use a 6mm Polyethylene which is thermal, acoustic and built in dpm and used widely within the underfloor heating industry.
Lay your preferred underfloor heating.
Lay a moisture barrier, not always needed but some engineered board manufactures require it, 500 - 1000 gauge is more than enough.
Lay your engineered board gluing the joints with a D3PVA glue, Even if it is as click system I would still recommend gluing of the joints as it will improve stability with expansion and contraction as the floor heats and cools.

As for the kitchen furniture you do not need to go under the fixed furnishings however, I would measure out and put the underfloor heating in the other areas. I would then lay the floor throughout the kitchen for a better finish.

I have seen so many people make mistakes putting the kitchen in before the floor. Floor standing appliances can get trapped if no allowance is made for it. There is no scope for alteration in the future should you want to move the cupboards around slightly.

Depending on the floor fitter / kitchen fitter, by laying the floor after the kitchen could leave horrible cuts because they are too lazy to take the end panel off and do the job properly.