Hi all,

I am working on a daylight report for a project in London which is heavily overshadowed by other buildings. My guesses before running simulations were that lux levels would be less than 80.
I ran my model through radiance, for a worst case scenario picking the 21st of December at 12.00 with a CIE overcast sky. My design sky is 4000 lux.
As i expected, my results were of an average of 50 lux, reaching as low as 30.
I also needed to calculate daylight factors, and i know this is a specific value that doesnt have to do with date and time, but with altitude and building design.
I saw though that Radiance uses also the 21st of December as day to calculate the daylight factors.
The weird thing is for the same areas that achieve 30-50 lux, show that have a daylight factor of around 3% or more, reaching to even 30-40% !! I checked different floors, and the results I got were the same.
I didnt change any parameters between running the two sinulations each time, for luminance levels and daylight factors respectively.
I cannot understand why I get this result, as for 30-50 lux in a worst case scenario, the corresponding daylight factors should be around 1%, and the minimum I am getting is 2.8%.
i attach corresponding images for your concern.
Please note that I have checked having 2 windows in the same place, and have set double glazed windows with a transparency of 0.73, all other materials are set to brick timber frame.
Any fast reply would be more than welcome, as I have to issue this report.

Many thanks,

Lydia Yiannoulopoulou

Sustainability consultant

HOARE LEA