There are few possibilities and options in considering the correct sized windows for your room which will give you the required amount of natural light.
First of all it helps if you understand what amount of natural light is recommended for the type of room and total floor space. In general, the rules for habitable rooms focuses on the ratio of light to floor space which should be 1:8. This equates to 12.5%, for other types of rooms the ratio is regarded to be 1:12 or 8% of the floor space.
So in the example given we have 9m x 4m = 36m2 of floor space, it’s a habitable room so we require somewhere around 12.5% of the total floor area as natural light.
To make life easier we show in our catalogue the actual glazing area in m2, so we can now calculate the windows required to give the correct amount of daylight.
The correct amount of natural light in the room is calculated by the proportion of the surface of the windows glass area to the total floor area. The higher up the window is fitted the greater the spread of natural daylight into the room. In a room for habitable purposes this proportion should be at least 1:8 (approximately 12.5%), and other types of rooms not used as habitable living spaces the ratio should be at least 1:12 (approximately 8%).
The higher up the window is fitted, the greater the spread of natural daylight into the room. It is recommended that the glass area should be at least 15-20% of the total floor area for best and brightest results.