Just have red foil at the back side but even when if I remove it they still look comfortable the only time when they panic is when I water their sand.
So yes they are exposed to light but they doesnt look like they mind it. But for winter I will put them in a box and right in the basement it will be like 10-12 degrees in there or meybe even in the fringe.
i usually try to darken the whole nest (both sides) because otherwise mine don't dig next to the glass and they'll leave the glas covered with sand