Do Room Darkening Curtains Keep Heat and Cold Out and How Much?

Last updated on October 14, 2023

Room darkening curtains can help you control the temperature in your home by insulating your windows to some extent. Here’s how.

Compared to blackout curtains, room darkening window treatments are not as effective at keeping the heat and cold out. In fact, most types of curtains will insulate the window to some extent as much as hanging a cloth over the opening would. However, energy-efficient curtains will do a better job at that. 

Room darkening curtains can indeed keep heat and cold out. But they have to be marked as thermal insulated. If you live in an area where there is snow during the winter months, then you probably want to get some room darkening curtains. These curtains block out light and keep your room darker, making it easier to sleep at night. They also keep heat in during the summer months because they prevent sunlight from entering your home.

Thermal insulated curtains keep the heat and cold out of a room. The thermal insulation keeps warmth inside while keeping cool air outside. This makes them perfect for areas that are hot or cold. Thermal curtains can be used in any season but are best suited for hot climates.

The Fabric

There are many different fabrics available for room darkening curtains. Some are made with natural fibers like cotton, while others are synthetic materials. Cotton is excellent for warm weather since it’s breathable and absorbs moisture quickly. Synthetic materials are better for colder temperatures since they don’t absorb as much moisture. You may have to experiment to find what works best for your climate.

Fabric options include:

  • Cotton – Great for warm weather
  • Polyester – Best for cooler temperatures
  • Poly/cotton blend – A combination of both
  • Linen – Great for warmer temperatures
  • Foam-backed curtains – These are usually more expensive than non-foamed ones. Foam helps make the curtain thicker and stronger. It’s also good for blocking noise.
  • Triple weave blackout fabric – This type of material has three layers of thread woven together. The first layer blocks light; the second one blocks sound; and the third one blocks heat.
  • Heavy fabric – These curtains weigh more so they’re less likely to blow around in high winds.
  • Cellular shades – These curtains use a mesh screen that lets in lots of light while keeping heat and cold out.

Layers of Fabric

You might notice that some room darkening curtains have multiple layers of fabric. Each layer has its purpose. For example, one side of the curtain could be polyester while another side is made of cotton. Polyester is warmer, so it keeps heat in during the day. Cotton is lighter and lets in more light, so it allows sunlight into your room at night.

This type of curtain is called a layered curtain. Layered curtains are great for rooms that need extra insulation. They help keep heat in during the day and let in enough light at night.

How Room Darkening Curtains Keep the Heat Out

Room darkening curtains help keep the heat out by blocking out light. Light reflects off surfaces and bounces around, causing heat. When you use room darkening curtains, the light doesn’t bounce around as much, and therefore less heat will enter your room.

When you open your curtains, you allow more light into your house, which causes the temperature to rise. By using room darkening curtains, you can reduce this effect.

How Room Darkening Curtains Keep the Cold Out

Cold air tends to move towards warmer objects. It’s why when you step outside on a freezing day, you feel cold immediately. Your body heats the air around it until it reaches equilibrium.

If you put a curtain between yourself and the source of the cold air, the air won’t reach you. This means that the air stays cooler longer than if you weren’t wearing anything at all.

By using room darkening curtains, you can make sure that the air stays cooler longer.

How to Improve the Thermal Insulation of the Curtains

You can improve the thermal insulation of the drapes by adding extra layers of material. For example, you could add two layers of heavy-duty polyester instead of one layer of regular polyester.

Use curtain liners – Adding lining to the bottom of the curtains helps increase their insulating ability. Linings are usually made of flannel to trap air and keep the curtains from touching the floor.

Add a blackout liner – Blackout liners are designed to block out light completely. This is useful for rooms that need to stay dark at night.

Add a frosted liner – Frosted liners are similar to blackout liners except that they aren’t opaque. Instead, they’re translucent so that some light still gets through.

Choose a heavier weight fabric – Heavyweight fabrics hold more air than lighter weights. They also tend to be thicker, so they provide more insulation.

Another option would be to buy a pair of blackout curtains. These curtains are designed specifically for rooms that need to stay dark. They’re usually thicker than regular curtains, so they provide more thermal insulation.

Also, consider using thermal curtains to insulate doors and passageways. They can function as well as room dividers.

The Choice of Colors

Colors play an essential role in determining how well a room darkens. Three primary colors affect how well a room darkens.

  • Black – Black is the darkest color. It blocks out most light and makes a room appear darker.
  • White – White is the brightest color. It allows light to pass through and makes a room look brighter.
  • Gray – Gray is somewhere in between black and white. It reduces the amount of light passing through but not as much as black does.

Patterns don’t have a significant impact on thermal insulation, but they have a big impact on the appearance of a room. Popular patterns include a geometric pattern and floral patterns.

How to Install Room Darkening Curtains Correctly

Installing room darkening curtains correctly isn’t difficult, but it does require some planning. The first thing to do is measure the width of the window opening. Then, measure how far away from the window you want the curtains to hang. Next, determine where you’ll place the rod or pole that holds the curtains in place. Finally, choose the type of curtain that will work best for your needs.

Measure the width of the window opening. The first step in installing room darkening curtains is measuring. Measure the distance from the top of the frame to the bottom of the sill. You’ll need this measurement to figure out how many panels you’ll need for each side of the window.

Calculate how far away from the window you want the curtains to hang. Once you know how wide the window opening is, you can calculate how far away from the window you’d like the curtains to hang. Multiply the width of the window opening by 2. 

Decide where you will place the rod or pole that holds the curtains in place. Next, decide where you’ll install the rod or pole that holds the curtains in place. There are three main options:

Use a standard curtain rod

Standard curtain rods are easy to use and install. However, they don’t offer much support, so they may not be suitable if there’s a lot of wind outside. If you have an open window with lots of drafts, you might consider buying a stronger rod.

Grommet curtain rods are another option. Grommets allow you to attach a curtain directly to the wall without needing any additional hardware.

Use a pole-and-cord system.

A pole-and-cord system uses a metal pole that attaches to the wall and a cord that hangs down from the ceiling. It works well because it provides plenty of support while allowing you to adjust the curtains’ position easily.

Use a track

Track systems are used when you want to hang heavy curtains. Track systems consist of two tracks on either side of the window. Each track has a groove that allows the curtains to slide up and down. Some track systems come with hardware that makes hanging the curtains easier.

Other Benefits of Room Darkening Drapery

  • Noise reduction – When the sun shines into a room, it heats up the air inside and creates noise. Rooms with room darkening curtains reduce the amount of sunlight entering the room and therefore reduce the amount of heat created. This means less noise.
  • Energy savings – Rooms with room darkening curtains save energy by reducing the amount of sunlight entering the room.
  • Privacy – Rooms with room darkening curtains help create privacy. This is especially helpful when you live in a multi-unit building.
  • Heat control – Rooms with room darkening curtains help regulate temperature. By blocking the sun’s rays, rooms stay cooler during hot summer days.
  • Security – Rooms with room darkening curtains provide added security. Windowsill lights can attract unwanted attention.
  • Comfort – Rooms with room darkening curtains make rooms more comfortable. Sunlight can cause glare which causes eyestrain.
  • Safety – Rooms with room darkening curtains make rooms safer. A darkened room helps prevent accidents such as falling objects.
  • Peaceful sleep – Rooms with room darkening curtains help promote peaceful sleep. Research shows that people who sleep in darker bedrooms tend to experience better quality sleep.
  • Beauty – Rooms with room darkening curtains look great!
  • Machine washable – Many room darkening curtains are machine washable. You can simply throw them in your washing machine with other laundry.
  • Easy maintenance – Most room darkening curtains are very easy to maintain. Simply wipe away dust and dirt.

Energy Efficiency and Saving

The average home spends about $1,000 per year on heating and cooling costs. That’s why many homeowners choose to add insulation to their homes. Adding insulation reduces your monthly bills by 10% or more.

Insulation also helps keep your house warmer in winter and cooler in summer. Adding insulation can increase the value of your home by 5%.


Do blackout curtains block heat and cold?

Yes, they do. Blackout curtain panels have a thermal insulation layer that helps with temperature control.

Do blackout curtains keep a room warm in winter?

They will to some extent. However, if you have a problem keeping your house warm in winter, there is something wrong with your insulation. You should talk to an expert.

How long will blackout curtains last?

Blackout curtains last for years if properly cared for. However, if left untreated, they can fade over time due to exposure to UV radiation.

Are blackout curtains safe?

Yes, they are. Blackout curtains are made using special fabrics that filter out harmful UV rays. They also use a coating that blocks 99% of all visible light.

Do dark curtains keep a room cooler?

They can help maintain the temperature. However, if you’re looking for a better way to cool off during the summer months, then consider installing awnings or blinds.

What type of fabric does a blackout curtain use?

Most blackout curtains use polyester or nylon material. These materials are durable and easy to clean.


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