Päivänvalofaktoria

Päivänvalofaktoria, translated as daylight factor, is a dimensionless measure used in building design and lighting engineering to quantify the amount of diffuse daylight received indoors from the sky. It is expressed as a ratio of the illuminance inside a specific point in a building to the illuminance at the same time on a horizontal plane outside the building under a standard overcast sky. This factor accounts for light loss due to architectural features such as window size, orientation, glazing properties, and interior surface reflectances.

The daylight factor is a crucial metric for assessing the potential for natural lighting in a space and is often used to predict daylight levels throughout the year. A higher daylight factor generally indicates better natural light availability, which can reduce reliance on artificial lighting, leading to energy savings and improved occupant comfort. Standards and guidelines in many countries specify minimum daylight factor requirements for different types of spaces, such as classrooms, offices, and residential areas, to ensure adequate illumination and promote well-being.

Calculating the daylight factor typically involves sophisticated software or simplified analytical methods. It is important to note that the daylight factor is a static representation and does not account for direct sunlight, which can cause glare and overheating. Therefore, it is usually considered alongside other lighting design parameters to achieve a comprehensive understanding of the interior lighting environment.