This paper analyses two main renovations of a University building façade retrofit from the viewpoint of annual daylighting improvement. Currently, this building consists of some teaching rooms connected by a hall but it is expected that this arrangement will change in order to accommodate two open-plan spaces for architecture students. The renovated design will increase the height of the North-East windows and introduce shading devices on the South-West facade. These renovations were explored to determine if the internal luminous conditions will maintain adequate levels. Five degrees of visual screening (100, 90, 70, 45 and 34%) and two slats positions (horizontal and vertical) were evaluated in relation to the building with no screens. Climate-based daylight modelling (CBDM) was carried out by using Diva-for-Grasshopper. The study revealed that effectiveness of convergence testing depends strongly on the choice of CBDM metrics employed as a diagnostic - an important consideration when modelling light transfer through louvres. Results recommended using louvred panels with no more than 70% of visual screening as higher percentages decrease useful illuminances over the range 300-3000 lux (UDI-a), to less than 50% of the occupancy time. Furthermore, vertical louvres were better suited to increase UDI-a than horizontal slats.