Daylight in buildings mainly comes from the Sun, and its quality can be affected by factors like air, water vapor, and human-made pollutants in the atmosphere. A study looked at how efficiently sunlight enters spaces in Vietnam and compared it to Moscow. In Hanoi, there is a high and evenly spread outdoor light level, with maximum illuminance levels at 45.2 klx for diffuse light and 58.52 klx for total light. In comparison, Moscow's maximum levels are 28.3 klx and 53.1 klx. During winter, Hanoi receives more light than Moscow due to their different latitudes and sun movements.