What percentage should the total net area of window glass in a room ideally cover compared to floor area?

The ideal percentage of window glass area in a room compared to the floor area is commonly considered to be around 10%. This guideline ensures that there is an adequate amount of natural light entering the space while still maintaining energy efficiency and comfort.

When this ratio is adhered to, it enhances the livability of the space, providing sufficient daylight to reduce the reliance on artificial lighting during the day. Additionally, it helps balance heating needs by taking advantage of solar gain without overwhelming the room with excessive heat in warmer months or creating potential energy loss.

In residential design, this standard also takes into account factors such as window placement, orientation, and the local climate which can impact the effectiveness of windows in terms of both light and energy efficiency. A percentage lower than 10% may not provide adequate illumination, while a percentage much higher could lead to overheating issues and decreased energy efficiency, especially if not properly managed.