Heidi Wachter was a senior editor at Experience Life magazine for 10 years. She has written for publications like Experience Life, Shondaland, and betterpet.

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If you live in a climate with extreme hot or cold weather, you may already know that curtains are more than window dressing, as they help regulate light and heat. Replacing windows is a good strategy for reducing energy bills and planet-heating emissions, as well as increasing your comfort, but this can also be pane-fully expensive. It's also not an option for renters.

Thermal curtains, on the other hand, are a comparatively inexpensive method to stop drafts. Made of several layers of materials and fabric, they are designed to provide thermal resistance (known as R-value) and prevent thermal transmittance conductivity (known as U-value). 

It can be challenging to find these curtains made of sustainable fabrics and materials. Still, working together, the layers can improve the overall energy efficiency of our home or office. They can reduce heat loss by up to 25% in the winter months and reduce solar gain by 33% in summer months.

Here are some of the best thermal curtains on the market today:

Moondream offers multiple OEKO-TEX®-certified options. This independent certification for textiles guarantees that fabrics were produced without the use of harmful substances.

This panel is 99.97% polyester. The reinforced, rust-proof 1.6-inch diameter grommets allow for easy and durable hanging on most curtain rods. It's easily adjustable to the height of your window with included iron-on tape. They are light-blocking and machine-washable.

For those on a tight budget, Target offers this mega-affordable room-darkening thermal panel. It's made of 100% polyester and is OEKO-TEX® certified. That means it won't emit funky fumes or chemicals into your room.

It's available in multiple colors. Order online and have it delivered, or pick it up at a location near you and block out the lights tonight before bedtime.

Made with Thermaweave®, an innovative, 100% polyester woven design with insulation, it provides the look and style of naturally flowing curtains. The reverse side is the same color as the front panel.

Perfect for any room with a patio door, the extra-wide SolarShield patio panel is an energy-efficient alternative to vertical blinds. They not only improve heat retention, but also block noise and light, and are machine washable.

Looking to darken your bedroom so you can sleep in after the sun is up? These black-out options block out 100% of sunlight and UV rays, and are also great for folks who live in cities where the lights stay on all night.

These curtains are constructed from five layers of fabric in a certified OEKO-TEX® factory. They have a faux-linen decorative finish, which is available in five different color options, and the curtains come in a range of sizes. Machine wash in cold water when necessary.

The silky soft texture of the decorative side of these curtains looks expensive and feels expensive, but this is an affordable option for those who don't want a bulky window treatment.  

The silver-coated window side makes multiple functions as it blocks out sunlight, insulates, and darkens. Grommets allow for easy hanging. Note that this single-panel curtain must be hand washed.

This single-panel option comes in multiple sizes and multiple colors. The darker the color, the greater the light reducing capability.

The innovative triple-weave construction blocks out most of the sun's UV rays. Grommets are sized to fit most curtain rods. They are machine washable.

Tired of hearing your neighbor's dog bark while you try to sleep? NICETOWN'S thermal curtains feature a black yarn layer sandwiched between insulating microfiber layers. They seamlessly block out 99% of sunlight and reduce external noise. Home theater lovers will also love the sound-block ability of these curtains.

They are topped with 1.6-inch grommets that are suitable for hanging on most standard curtain rods. One of the 20 colors options is sure to match your favorite duvet cover. They can be machine washed.

Even though they’re white, these insulated curtains block out 70% of light and noise. That makes them ideal for use in the living room, bedroom, or to create total darkness for your home theater system.

 The thermal backing guards against drafts in winter and heat in the summer. They’re composed of durable polyester and topped with grommets that are compatible with most curtain rods.

If you're looking for a sustainable option that offers room darkening as well as thermal insulation for your windows, Moondream (view at Amazon) offers an array of choices and colors that are OEKO-TEX® certified.

If you want to take your UV-blocking ability outdoors, then Deconovo (view at Amazon) is a good option.

Most thermal curtains are made of three (but two and four layers are available). Like any curtain, there is a layer of decorative fabric that faces into the room. These are typically made of woven materials like cotton, polyester, linen, wool, or silk.

Then there is a middle layer composed of thermally resistant material like foam, felt, flannel, or thick cotton batting. The third layer, known as the backing, protects the inner layer from sunlight, and sometimes condensation that forms around windows. Sometimes a fourth layer is added to serve as the vapor barrier.

If you live in a particularly hot area or want a window treatment for West or South-facing curtains, choose light-colored backings to reflect light and reduce solar gain.

A standard curtain has an R-value of R-1. But a properly fitted insulating curtain can boost that to R-6.

Get the most bang for your buck by hanging your curtain as close to the window frame as possible. Choose those that drop to the windowsill or floor. 

Once you've hung the curtain, seal it on all sides with Velcro, magnetic tape, or self-adhesive weather stripping to reduce thermal transmittal most-effectively. You can add a valance above the drape to reduce air infiltration. Eliminate gaps by generously overlapping the curtains in the middle. 

Open your curtains during less hot parts of the day in summer or warmer parts of the day in winter. This will also alleviate condensation build-up. Close them at night to reap the benefits of their insulating, privacy, and sound-reducing properties.

Heidi Wachter has been writing about health and the environment for over a decade. A DIY devotee, she is always seeking out sustainable ways to reduce the energy footprint of her 107-year-old home.

"Energy Efficient Window Attachments." U.S. Department of Energy.

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