Effective U Value Calculator

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This calculator is based upon EN ISO 14438:2002, ‘Glass in building. Determination of energy balance value. Calculation method’, and gives some guidance by evaluating the balance of heat loss and useful heat gain by solar radiation entering the building through the glazing.

The result is an average rate of heat loss or gain for the period over when you would expect to use heating in the building and referred to as the ‘energy balance value’. This enables a comparison of performance for glazing products but it is not intended for the determination of the energy use of a building or heating capacity calculations.

Glass Technology Services Ltd (GTS) is a leading provider of independent analysis, testing and consultancy services throughout the glass supply-chain – from raw material to finished product. For architectural glass and glazing manufacturers, processors and users we provide a range of specialist services including on-site technical consultancy, failure analysis, initial type testing and determination of key performance criteria such as impact resistance and thermal and solar performance. Please see our architectural and glazing services area for the full range of support available.

Centre pane values:

Further information:This calculation is based on the centre pane performance of the glazing in terms of U value and g value (also known as total solar heat transmittance or solar factor), which is available for each glass product from the glass manufacturers or supplier.  The resultant value is independent of the framing or the  dimensions of the unit - unlike Window Energy Ratings, which calculate window performance on the basis of a theoretical window configuration with all locations within the UK in one value and all orientations - which may not be representative of the dimensions installed or  the location and aspect of the building.

Disclaimer: this tool is provided for estimation only, the results of which are not accredited. We have provided this calculator as a useful reference tool in order to help those in the glass supply-chain to estimate useful specifications to be considered when specifying glass.

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