The lack of light in the bathroom would not directly cause the mold growth.
Mold in bathroom ceiling and walls.
Squeegee shower walls and glass doors after every use to help remove the moisture that encourages the growth of mold on your walls and also prevent unsightly hard water and soap scum buildup.
Mold can often be found in the shower and the bathtub.
I recommend replacing the fan with a constant flow unit such as the panasonic whispergreen fan.
The main cause of mold on a bathroom ceiling is a broken or ineffective exhaust fan.
Pour into a spray bottle.
Here is a link.
If you apply the mold resistant paint to the ceiling you already have a fool proof solution to mold problems in that region of your bathroom.
Scrub thoroughly and wipe clean then spray again and let sit for 10 minutes before wiping.
Nothing beats this practical solution to mold in the bathroom ceiling.
Bathroom mold occurs primarily because mold loves damp dark isolated spaces says larry vetter of vetter environmental services in smithtown n y.
Cleansers with bleach or even white vinegar can often keep the slimy hairy growths from taking root in the bathroom.
Combine two tablespoons of borax with 1 4 cup white vinegar and two cups of hot water in a bowl.
Grime from body oils and soap scum which is washed off and onto the shower or tub create a food source for mold to feed on.
If that s outside of your budget you can install a timer switch on the existing fan.
Removing mold from painted or wallpapered walls.
Typically a bathtub shower or entire bathroom remains damp enough for mold growth just from showering or bathing common causes of bathroom mold.
Mold and mildew resistant paints are naturally designed to prevent mold and mildew from growing in the house.