Annual energy window performance vs. glazing thermal emittance - the relevance of very low emittance values

This paper investigates the heating and cooling energy impact of low therma l emittance values for architectural glazings. The importance of low emitta nce values and the sensitivity for small changes in the emittance is invest igated for three very different climates and for two different types of bui ldings. Our results imply that minor changes in the parameter values lead t o very small changes in the energy performance and are mostly insignificant for the end user. Furthermore, the relative importance of the solar transm itting properties is recognized. For instance, if the thermal emittance is reduced by 2-3% and at the same time the total solar energy transmittance i s also reduced by 2-3%, the energy performance of the window is worse if it is used in a south facing position in a residential building in a heating dominated location (Stockholm). (C) 2001 Elsevier Science B.V. All rights r eserved.