The thermal performance achieved by the floor is critical for the overall energy efficiency of the building. Approximately 15% of heat is lost through the floor and insulation can reduce this.

The minimum standard for new dwellings is calculated as a notional building using the limiting values in Table 4 of Approved Documents L1A, L1B, L2A and L2B. Assessing the performance of the dwelling by calculation of TER and TFEE.

TER – The Target CO2 Emission Rate is calculated and expressed as the mass of CO2 emitted in kilograms per square metre of floor area per year

If the building is constructed using the notional building specification the CO2 target will be met. It is allowable for the builder/designer to vary the specification provided the same overall TER and TFEE are achieved in the calculation of the actual or as-built performance.

If the building is constructed to the notional building specification the CO2 target will be met. It is allowable for the builder/designer to vary the specification provided the same overall TER and TFEE are achieved in the calculation of the actual rates.

For specific applications, the guidance and recommendations contained in BS EN 1991-1:2002 and BS EN 1990:2002+A1:2005 should be followed, and this will help the designer ensure that the strength of the floor will be sufficient to support any applied loads over the loaded area.

Condensation within the fabric of the building is not a problem except when it occurs within or adjacent to a moisture sensitive material such as timber or mineral wool insulation.

Building fabriccondensation occurs when moisture from inside the building escapes through the fabric and is trapped by a moisture resistant barrier.

The best methods to eradicate or reduce this problem are to use an appropriate vapour control layer (VCL) in the correct position or to create a ‘breathable’ construction. The VCL is always on the warm side of the insulation.

Without underfloor heating, this is a good option. The chipboard over the insulation prevents the heat sink, as described above and provides a warmer underfoot experience than concrete or screed and is faster to install as there is no drying time for the screed.