This key-word indicates to SYRTHES not to activate algorithm used to smooth the view factor and ensure a strict conservativity of the global radiative energy.
If checked, the field located at the right is activated. In that case, the temperature of the exterior has to be specified. In that situation, the external domain behaves as a black body (emissivity of 1 can be specified)
If possible authors suggest to use preferably the imposed temperature functionality. It has the drawback to oblige users to mesh explicitely the opening but then the general algorithms are used ensuring conservativity at the radiation level and an emissivity different from 1 can be specified and can vary from one region of the opening to another.