From what I understand UVB exposure isn't necessary for a BP, but it is not a bad thing if you want to provide it.
I do not use UVB lighting in my enclosures.(I did buy white LED lights for my incoming apcages but that is more for ease of viewing when its dark, not for the snakes) I am in the habit of opening my blinds in the morning when I get up, and closing them at night before bed. This seems allows enough natural light in for my snakes.