U Value / WER calculator

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Welcome to the REHAU online thermal calculator

This calculator is an easy to use tool which will demonstrate the energy efficiency of REHAU systems. This program has been designed to calculate the thermal transmittance (U Value) of windows and doors following the principals of BS EN ISO 10077-1 using REHAU window profiles.
The results are approved and accepted by FENSA and Certass.

This calculator also provides a Window Energy Rating (WER) based on the conventions and methods outlined in the Approved Document L. The results are approved and accepted for use with the BFRC Simplified Energy License Scheme (S.E.L.) and with the Certass Thermal Rating Register.

This program will allow the user to demonstrate compliance of installed windows and doors with Building Regulation Part L following the guidance rules as set out in L1(a) Section 4.

The other options available will enable the user to calculate U values for specific sizes and styles of windows and doors. Further information can be found in our user guide.

There is also a Quick Check Calculator to enable the user to quickly compare results between different REHAU systems and glass types and to assess the cost saving that could be achieved when purchasing a window without compromising on the energy efficiency.


If you have any requirements which are not covered within this calculator tool or you have any questions relating to its use please contact us.

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