Do Blackout Curtains Keep Heat Out?
It is easy to assume blackout curtains are only good for better sleep. They make bedrooms darker, cut down glare, and give a room more privacy, so most people think of them as a light-control product first. But sunlight is not just bright, it is hot, and in rooms with large windows or strong afternoon sun, blocking light starts to feel like only half the job. If you are buying curtains anyway or looking to upgrade, it makes sense to want more from them.
The question then seems simple. If sunlight is what makes a room feel hot, and blackout curtains block that sunlight, does that mean they can keep the room cooler? Well, yes, but it is not quite as simple as buying the darkest pair you can find.
Some blackout curtains are great at making a room dark, while others are built with thicker fabric, lining, or thermal backing that helps reduce the heat coming through the glass. That’s why we break down everything you need to know about blackout curtains, including which type actually keeps heat out best.
Do Blackout Curtains Really Keep Heat Out?
The short answer is yes. Blackout curtains help keep heat out by blocking sunlight before it gets through the glass and lands on the surfaces inside your home. Once sunlight hits floors, furniture, bedding, or walls, that energy turns into heat, which is why rooms that get a lot of sun can feel warmer than the rest of the house.
But how well they work depends on the curtain. A standard blackout curtain can make a room darker, which already helps reduce some heat from direct sunlight. A thermal blackout curtain goes further, using denser fabric, lining, or a lighter backing facing the window to reduce heat more effectively.
The data supports this. The U.S. Department of Energy says medium-coloured draperies with white plastic backings can reduce heat gains by 33% when closed over windows receiving direct sunlight. So if heat is the main issue, the best choice is not just the darkest curtain, but one designed to block light and manage heat at the same time.
Noiréa Thermal Blackout Curtains
Sleep Deeper, Live Cosier with Elegant Blackout Drapes! Block out the light and elevate your space with the Noiréa Thermal Blackout Curtains. Designed for privacy, insulation, and timeless sophisti...
What Are Blackout Curtains?
Blackout curtains are thick, lined curtains designed to block most sunlight from passing through a window. This light-blocking effect usually comes from a dense weave, blackout lining, coated backing, or layered fabric.
Commonly used in bedrooms, nurseries, media rooms, and home offices, they make a space darker, reduce glare, improve privacy, and support better sleep. Because less sunlight reaches the room, blackout curtains can also help reduce heat build-up in sunny spaces, especially when they include thermal lining or a light-coloured backing.
Types of Blackout Curtains
Not all blackout curtains are made the same way, which is where a lot of confusion starts. Two curtains can both be called “blackout,” but one may only darken the room while the other also offers better insulation and heat control.
| Type | How it works |
|---|---|
| Standard blackout curtains | Use dense fabric or a blackout layer to block light |
| Thermal blackout curtains | Combine light blocking with insulating fabric or lining |
| Lined blackout curtains | Add a blackout lining behind a decorative face fabric |
| Coated blackout curtains | Use a coated backing to stop light passing through |
| Triple-weave blackout curtains | Use tightly woven layers rather than a separate coating |
What Type of Blackout Curtains Keep Heat Out Best?
The best blackout curtains for heat are thermal blackout curtains. They are typically made from 100 percent polyester fleece or cotton fabrics that trap warm air inside your home during winter and keep it out during hot summers.
Because they are so effective at managing temperature in both directions, they can also reduce your heating bill significantly during the colder months, which is why many people use them year-round rather than just for light control.
This comes down to how the fabric itself behaves. The layer works using the principle of conduction, the transfer of energy between two objects that are touching each other. The curtain sits between the window and your home's interior, creating a barrier so heat cannot move freely from one side to the other. It works like insulation for your window, slowing heat transfer rather than simply blocking light.
Features that make the difference:
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Dense polyester fleece or cotton construction
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Multi-layer fabric that resists heat movement in both directions
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Light-coloured or white backing facing the window to reflect sunlight
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Full length fit that extends beyond the window frame for maximum coverage
Blackout Curtains vs Thermal Curtains vs Standard Curtains
Blackout curtains, thermal curtains, and standard curtains can all look similar once they are hanging, but they do not perform the same way. The difference comes down to what they are actually designed to do.
| Curtain type | Blocks light | Helps with heat | Best use |
|---|---|---|---|
| Standard curtains | Somewhat | Limited | Styling, privacy, and softening a room |
| Blackout curtains | Yes | Moderate | Bedrooms, nurseries, media rooms, and glare control |
| Thermal curtains | Sometimes | Strong | Temperature control and insulation |
| Thermal blackout curtains | Yes | Strongest | Sunny bedrooms, living rooms, offices, and summer heat |
Standard curtains are mostly decorative. They soften a room, add privacy, and reduce some light, but heat control is not what they are built for. Blackout curtains do better because blocking sunlight directly reduces how much solar energy reaches the room.
Thermal curtains are more focused on temperature than darkness. They may not always block light as completely as a blackout curtain, but the construction is specifically designed to slow heat transfer. A thermal blackout curtain combines both, which makes it the strongest option if the goal is a room that is darker and cooler at the same time.
Mistakes That Stop Blackout Curtains Working Properly
A lot of people buy blackout curtains, hang them up, and then wonder why the room still feels too warm. Usually, the issue is not that the curtains do nothing. It is that they are being asked to do the job under the wrong conditions.
The most common mistakes are:
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Closing them after the room has already heated up
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Buying panels that only just cover the glass
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Choosing based on colour instead of lining or backing
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Leaving gaps at the top, sides, or centre
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Using standard blackout curtains when the real issue is heat
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Forgetting to close them before direct sunlight hits the window
We recommend closing draperies on windows receiving direct sunlight during summer days to prevent heat gain, and also note that many window coverings stay in the same position every day even though adjusting them strategically can improve performance.
Hanging also matters. Draperies perform better when they are close to the window and fall to the windowsill or floor. Overlapping panels in the middle and reducing side gaps helps create a better barrier, which is especially important on windows that receive strong direct sun.
Sleep Deeper and Stay Cooler with Noiréa Thermal Blackout Curtains
Looking for curtains that do more than just block light? The Noiréa Thermal Blackout Curtains are a triple threat. They are blackout, thermally insulated, and designed for privacy all in one panel. That combination makes them one of the most practical options for anyone dealing with a room that gets too bright and too warm at the same time.
The fabric is a lightweight microfibre blend with thermal insulation built in, which means it works in both directions, keeping warmth in during winter and blocking heat out during summer. They hang on a rod pocket, come as a set of two panels, block up to 90% of sunlight, and go straight in the washing machine when needed. If you want one curtain to handle glare, heat, privacy, and sleep quality without compromise, this is the one to start with.
Add Pattern Without Losing Shade with Modern Wave Pattern Blackout Curtains
Who says blackout curtains have to be plain? The Modern Wave Pattern Blackout Curtain brings in a geometric wave print that gives the window a more finished, decorative feel without sacrificing any of the practical benefits of black out curtains. It is the kind of curtain that makes a room look considered rather than just covered.
Under the pattern, the soft microfibre blend blocks harsh sunlight and provides gentle insulation, making it a great fit for rooms in your house where both glare and privacy matter. You get the blackout performance you need and a curtain that actually adds something to the room rather than just hanging there.
Bring Soft Texture and Shade with Elysian Leaf Blackout Curtains
If you are after something that feels softer and more decorative without losing the blackout function, the Elysian Leaf Blackout Curtains are exactly that. The delicate vine embroidery on a calm backdrop makes them feel more like a styling choice than a utility purchase, which is rare for a curtain built around light and heat control.
Made from a smooth microfibre blend that blocks sunlight and insulates against heat or cold, they are ideal for bedrooms, nurseries, or calm living spaces where the goal is comfort and quiet without the room feeling dark or heavy. Available in grommet or hook top styles, they are also flexible enough to work with most existing window setups. If you want blackout performance with a softer finish, this is the curtain that delivers both.
Find the Perfect Blackout Curtain for Your Home
Casa and Beyond's blackout curtain collection comes in a range of colours and styles, from clean neutrals to decorative prints, so there is something that works regardless of how the room is already decorated. Every curtain is made from durable polyester that holds its colour over time and won't fade or yellow from sun exposure, which matters when the whole point is keeping the curtain closed during the brightest part of the day. Now you know what to look for when someone asks whether blackout curtains keep heat out. And when you are ready to buy, choose a curtain built for the job without sacrificing on design.
