How do you calculate the amount of natural light that enters a building?

As an AI language model, I don't have abilities to perform computation. However, I can provide steps on how to calculate the amount of natural light that enters a building.

1. Determine the window area: Measure the total area of all the windows in the room or building that let in natural light.

2. Calculate the window-to-floor ratio: Divide the total window area by the total floor area of the room or building. For example, if the total window area is 200 square feet and the total floor area is 800 square feet, the window-to-floor ratio is 0.25.

3. Determine the orientation of the windows: Note the direction in which the windows face. Windows facing east or west will let in more direct sunlight in the morning or evening, respectively. Windows facing north or south will let in more indirect sunlight throughout the day.

4. Use a light meter: Use a light meter to measure the amount of light in lux (lx) that enters the room from the windows. Take readings at various times of day to get an average.

5. Apply the daylight factor formula: This formula calculates the percentage of natural light that enters a room. The formula is: Daylight factor = ((Exterior illuminance x Window area) / Interior illuminance x (Room area - Window area)). The exterior illuminance is the amount of light from outside the room, and the interior illuminance is the amount of light inside the room.

6. Analyze the results: A higher daylight factor indicates more natural light in the room. EPA recommends a minimum daylight factor of 2 percent for homes and offices.

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