I have tried to answer your question based on your first preference, i.e. taking all 3 variables, Room Size, Room Layout and Lighting, at a time. I made the analysis on my white board and hence sharing the pictures of the same, since i think that way it ll be easy to explain you.
Further, there are lots of other statistics in my mind that i think is possible to do with your data. From the enclosed pictures, let me know if i am thinking in a line meaningful to you and if you are interested in my further analysis.
Based on your explanation above which is quite clearer, than the former, i think a factorial analysis of variance will be appropriate. MANOVA could also be used