Thermal Performance

Thermal Performance – Part L

To comply with the 2010 edition of Part L of the Building Regulations, each floor’s thermal performance needs to be assessed individually in accordance with EN ISO 13370: 1998.

Determining the U-value of the Floor

1. Calculate the internal perimeter in metres of the external walls (P)
2. Calculate the internal area in metres of the floor (A)
3. Calculate the P/A ratio
4. Use the graphs to select the thickness and type of TETRiS required to achieve the desired U-value

u value table


Type and thickness of TETRiS required

tetris table


The Code for Sustainable Homes
Incorporating Cellecta high performance thermal & acoustic insulation products into elements of a dwelling will help reduce the building’s impact on the environment and will enable builders and developers to gain Code for Sustainable Homes credits (CSH).

Credits can be gained from four of the nine assessment categories detailed in The Code:

Category 1 – Energy [Ene 1]

15 Code credits are available for improving the DER over the TER. eg. ground floor U-values improved from 0.25W/m2 K to 0.16W/m2 K.

Category 3 – Materials [Mat 1]

Adopting a construction listed on the BRE website:, which incorporates one of Cellecta’s insulation products can result in up to 15 Code credits being awarded.

Category 6 – Pollution [Pol 1]

1 Code credit is awarded when all the insulation materials in the elements listed below only use substances that have a global warming potential (GWP) of < 5, eg. TETRiS ecoblocks:

  • Roofs: including loft hatch
  • Walls: internal and external, including lintels and all insulation products
  • Floors: including ground and upper floors
  • Hot water cylinders, pipe insulation and other thermal stores
  • Cold water storage tanks

Category 7 – Health and Well-being [Hea 2]

Incorporating one of Cellecta’s high performance acoustic treatments will also result in points being awarded. Contact our helpful technical team for further information.

The TETRiS system has been awarded a BRE Green Guide rating and gains 3 Code credits (element number 820140051).