The effective layer shall be treated as another layer of the fenestration system. The surface temperature of the
effective layer can be determined from the one-dimensional energy balance.
Fig. 12 shows three particular fenestration layers and the related parameters.
In order to determine the temperature profile, each layer is assigned three nodes; one node at the middle point of the layer and two nodes at the inner and outer surface of the layer. The analysis for this energy balance is based on a steady state condition and constant environmental conditions.
The temperature of each layer is determined by the condition that no net energy is absorbed or released by any layers. Since the effective layer such as a venetian blind is diathermanous due to its openness (Diathermanous refers to a material that transmits both solar and longwave radiant energy) as suggested by Collins and Wright (2006), the longwave radiant energy exchange can be present though the surface temperature of the layer next to the diathermanous layer is equal to the surface temperature of the diathermanous layer.
Therefore, the net energy balance on each layer under steady state as suggested by Finlayson et al. (1993) has to modify to account for the effect of the presence of the diathermanous layer.
The new energy balance on each layer is written as