Most floor finishes will work well with underfloor heating.  Always check what the maximum surface temperature the floor finish will operate at with the manufacturer of the floor finish.

If using wooden boards for underfloor heating, it is best to use engineered boards, one layer 21 mm.  Avoid using wood on top of wood.  Maximum 25 mm is recommended for wooden boards.

If a carpet is used, the TOG for the carpet and the underlay should not exceed 2.5 TOG.

Vinyl and tiles are normally very good with underfloor heating water.  With Vinyl check that any fixing compound can be used with underfloor heating.

TOG values for different materials are Vinyl and Tiles – 0 TOG if below 5 mm.  Carpet at 9 mm or 13 mm Hardwood is 1 TOG and a deep carpet or 22 mm Laminate would be 1.5 TOG.

Pipe spacing for underfloor heating systems will normally provide a faster heat up time.  The different in heat output is not large.  For example using 200 mm spacing instead of 250 mm spacing for the underfloor heating systems will provide approximate 10 % more heat output.

Increasing the water flow temperature to the underfloor heating system with just 5 degree C will provide approximate 20 % increase in the underfloor heating output.  This data is from the CIBSE underfloor heating design & installation guide.