This European Standard specifies a method, based on EN ISO 8990 and EN ISO 12567-1, to measure the overall thermal transmittance of a roller shutter box in a hot box. This includes all effects of geometrical and material characteristics in a test specimen. Edge effects occurring outside of the perimeter of the specimen are excluded. Furthermore, energy transfer due to solar radiation is not taken into account, and air leakage is excluded. The method is designed to provide both standardised tests which enable a fair comparison of different products to be made, and specific tests on products for practical application purposes. The former includes window standardised specimen sizes and applied test criteria. The determination of the overall thermal transmittance is performed for conditions which will correspond to a similar situation of the roller shutter box in practice. Information on the design of the calibration transfer standard is given in EN ISO 12567-1.