Performance Criteria for Coated Glazings in Windows

A.Roos, J.Karlsson

This paper investigates the heating and cooling energy impact of low thermal emittance values for architectural glazings. The importance of low emittance values and the sensitivity for small changes in the emittance is investigated for three very different climates and for two different types of buildings. The results show that low values of the emittance is important for the performance but also that small variations in an already low value is of no significance for the annual performance. Thus, a window coating with an emittance value of 0.03 is not necessarily better than one with an emittance value of 0.06. In fact other parameters, such as light and energy transmittance, take over as being of prime importance. For the customer it is always a balanced combination of the parameters which is relevant, and stressing a low emittance value as a sales argument may, in fact, mislead the customer.

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