How Do Blackout Curtains Work?

Blackout curtains are drapes made of tightly woven fabric. This fabric has double or triple lining. The curtains work by shutting out natural light flowing into a house from the outside.

They are often made of dark plain colors to create this desired effect more optimally. The layers of blackout curtains have excellent structure that makes them very effective in keeping out light for a restful night’s sleep.

Blackout curtains with cut outs

Blackout curtains with cut outs are the only ones that allow the flow of light through the cut outs. Cut outs are patterned openings that are largely star-designed.

Properly fitted and genuine blackout curtains always keep out light, including light flowing from car traffic, street lighting and floodlights.


It is impossible to see through blackout curtains from the inside or outside during the day or night. It can be possible only when the drapes have cut outs. Blackout curtains give the occupants of a room or house privacy during the night.

It also keeps all the contents of a room away from the public eye during the night as no light flows in or out of a room.

Pros of blackout curtains

Blackout curtains serve to create a dark environment in a room, reduce noise from the outdoors, and even keep light from flowing into a room at night when one needs to sleep.

Additionally, they keep away natural light from a room when one needs to take a nap. A person using these curtains is therefore able to enjoy good quality sleep.

Light flowing into a bedroom during the day or night is known to impede sleep, making one moody, irritable and grumpy for lack of adequate sleep.

  • Insulation

Blackout curtains are also good insulators. They trap heat inside a room, making them very ideal during winter or cold weather. On the other hand, they keep out heat from a room during summer or hot weather.

It has been said that thermal energy loss through windows ranges between 10 and 25%. Insulation therefore helps to conserve energy, resulting in reduction of utility bills and greenhouse gases.

  • Right fitting

Right fitting blackout curtains always deliver. Sometimes you want to sleep till late morning hours when the sun is fully out.

Morning sunrise can disrupt your sleep if the blackout curtains are not fitted properly, particularly where the curtain rod is short or is the exact size as the window.

The bad fitting allows light to penetrate through the sides of the curtain, so always ensure the curtain and curtain rod are wide or long enough for proper fitting. 

  • Melatonin production

Blackout curtains create sufficient darkness that helps in production of melatonin in the body. This is the hormone that is responsible for maintaining the sleep-wake cycle, keeping it fully functional.

Do blackout curtains work?

The answer to this question is a resounding yes. Blackout curtains work. Darkness is a necessity for quality sleep and these curtains help to create it. When the body is exposed to darkness, it receives a signal that it is time to sleep.

Exposure to light during the night alters the internal clock and one is not able to enjoy quality or quantity sleep.

Factors that make blackout curtains to fail

Blackout curtains can fail to stop light from coming in through their sides if they are not fully drawn, or if the curtains were made to fit the window size without any allowance.

They will also fail if they are short. Blackout curtains are also not able to block out light coming from the top of the curtains. Gaps around the window may not be covered by blackout curtains.

  • Poor-quality blackout curtains

Many curtains or drapes reported or marketed as blackout curtains fail to block out light from entering into a room. Instead, they only filter it.

Be very sure that you cannot see through the drapes when purchasing them to avoid being duped or buying curtains that will fail to serve the intended purpose.

  • Heat from light absorption

Blackout curtains, particularly the dark-colored ones tend to absorb more light which subsequently converts to heat.

This means a room with dark blackout curtains will always be warmer than a room with light-colored blackout curtains or ordinary curtains. This can be a disadvantage to using these curtains especially during hot weather.

  • Nature of material and heat

When you use dark curtains in a hot room, the room remains hot. This is not desirable for someone seeking coolness. However, if a room is cold and you desire it warm, thick blackout curtains will help to achieve this goal.

The color, material, thickness and placement of blackout curtains will always have an impact on the temperature of a room.

  • Tiredness

Blackout curtains, thou great in blocking out light are known to cause tiredness of the body. This is especially the case when no natural light is allowed to flow into a house during the day. This adversely affects the internal clock making it unable to distinguish between day and night. 

Darkest blackout curtains

The darkest blackout curtains or drapes also happen to be the best in achieving the purpose they are meant to achieve, which is the complete blocking out of light in a room.

These curtains are made of very thick or dense woven fabric. This fabric could be materials such as cotton or polyester. The density of the drapes is what shuts out all flow of light to the extent that no light filters in.

Dark colors

Darkest blackout curtains are made of only dark colors such as black, brown, grey, blue and green. They do not have any cut outs as these tend to allow light to flow through.

Look out for cotton or polyester lining that is coated with acrylic to make it much more effective at blocking light. Polyester in particular is rated the best for making darkest blackout curtains.

Heavy microfiber material is always excellent for use in making these curtains, especially when-triple-weave technology is used.