How to change modifier properties of the soil?

Hi all,
I am testing the impact of the street width on the average illuminance in my building. It seems that when I make the street width narrow (i.e. 2m), I see an irregularity that the ground floor achieves more illuminance than the first floor. This makes me think that the soil impacts the reflection of light. So, how can I change the modifier properties of the soil?
I am doing annual daylight simulations (HB annual daylight).

Hi Berrak,

Welcome to the forum!

I think we need more details to understand your problem. What software are you using? What is in your building model and how was it created? How are your materials defined? Basically, we need enough information to reproduce your results, whatever they might be.