Floor Structures
It should be possible to fit UFH systems into any normal floor without requiring significant changes to the floor structure.
However there are some basic requirements that must be adhered to:
(a) The temperature within the floor structure must not be raised to a level at which the strength and characteristics of the floor are adversely affected.
(b) Insulation of adequate thickness and value must be provided to limit the downward heat losses from the UFH system and floor so that they are very little more than they would be if any other form of heating were used, see BS EN 1264 Part 4.
(c) A continues conducting path from the UFH pipes to the floor surface must exist to enable effective heat transfer to the underside of the floor finish to be affected.
(d) The floor finish must have a sufficiently low resistance to the passage of heat to enable the heat to be emitted into the room or space above.
(e) Considerations must be given to any other servicers contained within the floor structure that may affected by the increasing temperature.
The two standard flooring systems within which most UFH systems are installed are:
- The screed or solid floor system
- Timber floor systems
Solid floor systems
The screed or solid floor systems rely on the conductivity of the screed or concrete to conduct the heat from the UFH pipe surface to the underneath of the floor finish. In order to achieve good results the UFH pipe spaced closely enough tighter to heat the floor surface without grate variations in floor surface temperature. Because the screed or concrete is itself heated to conduct the heat to the floor surface it tends to store considerable amounts of heat and thus provide a slow response when both heating up and cooling down.
A typical UFH system in a screeded floor structure is shown 
in figure A and consists of the following elements.
• Floor finish
• Screed or concrete conducting layer
• Edge insulation
• UFH pipe
• Floor insulation
• Floor slab or oversite concrete
Timber floor system
UFH in timber floor systems rely on the conductivity of the components fitted within the floor to conduct the heat from the underfloor heating pipe surface to the underside of the floor finish.
Usually a metal (aluminium) heat transfer plate is fitted to conduct the heat from the UFH pipe to the floor surface, although some systems rely on thin screed or a heated air layer immediately below the floor deck.
In order to achieve good results the UFH pipe must transfer their heat evenly to the floor surface without creating sharp variations in surface temperature across the floor. This is particularly important with natural wood boarded floors so as to prevent unsightly shrinkage at any hot spots caused by inadequate heat dissipation system. Because the mass of the floor structure is 50% less than the mass of a screeded floor systems, the response of a timber floor system is usually much faster than that from a solid floor system and control is easier.
It should also be noted that heated air below or in timber structures can result in significant local reductions of moisture content and associated problems.
A typical UFH with a suspended timber floor structure is 
shown in Figure B and consists of the following elements.
• Floor Finish
• Sub floor
• UFH pipe
• Heat transfer plate
• Counter battens over floor joists
• Insulation beneath the UFH pipes
UFH is also used with floating floors as is illustrated in Figure C and consists of the following elements.
• Floor finish
• Sub floor
• UFH pipes
• Heat transfer plate
• Grooved insulation panel
The floating floor is only suitable for sheet flooring or some stronger laminates. The grooved insulation is structural and is usually supplied in 30mm, 500mm or 70mm thicknesses. Additional insulation may be required to ensure compliance with Building Regulations and to minimize downward losses.
