Thermal Performance

What is a U-value?

The measure of heat loss through the fabric of a building is expressed as a U-value with limiting values set out in the Building Regulations.

Building Regulations – Approved Document L

The Building Regulations set out requirements for specific aspects of building design and construction. Regulation 26 of the building regulations states that “Where a building is erected, it shall not exceed the target CO2 emission rate for the building…”, and Schedule 1 – Part L Conservation of fuel and power states that provision for conservation of fuel and power shall be made by limiting heat gain and losses and providing building service which are efficient, have effective controls and are properly commissioned and that information is provided so that the building can be operated efficiently.

Achieving Part L 2013

To fully comply with Part L, the overall dwelling emission rate (DER) must be lower than the target emission rate (TER) for a notional building of similar type, size and shape.

Part L stipulates minimum performance or fabric element values and aligns the overall building performance and CO2 emissions targets with notional models.

Fabric element values are the U-Values obtained by the specified construction types proposed for a particular build. Designers have flexibility under Part L but must ensure they keep below the TER, therefore lower U-Values may be required. The Top Sheet Flooring System provides a simple means to achieving improvements on the overall DER allowing designers to meet and exceed Part L requirements.

Our Top Sheet Insulated Flooring provides a range of U-values that will help to improve the overall DER. The table below shows an example of the ranges based on specific Perimeter/Area ratios and insulation material thermal conductivity values.

U-Value TableBased on 175mm, Standard Beams

A = 75% Full Panel / 25% Half Panel Installation
B = 50% Full Panel /205% Half Panel Installation

Grey / Grey Grey 150 mm: Infill panel
Grey 75mm: Top Sheet
Grey 150 mm: Infill panel
Grey 100mm: Top Sheet
Grey 150 mm: Infill panel
Grey 125mm: Top Sheet
Grey 150 mm: Infill panel
Grey 150 mm: Top Sheet
0.80 0.16 0.17 0.14 0.15 0.13 0.13 0.11 0.12
0.70 0.16 0.17 0.14 0.15 0.13 0.13 0.11 0.12
0.60 0.16 0.17 0.14 0.14 0.12 0.13 0.11 0.12
0.50 0.16 0.16 0.14 0.14 0.12 0.13 0.11 0.11
0.40 0.15 0.16 0.13 0.14 0.12 0.12 0.11 0.11
0.30 0.14 0.15 0.13 0.13 0.12 0.12 0.10 0.11
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