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Do thermal curtains work?

Do thermal curtains keep cold out? What about heat in summer? Discover why and how insulated curtains can work as temporary window insulation in this guide.

Do thermal curtains keep cold out? What about heat in summer? Discover why and how insulated curtains can work as temporary window insulation in this guide.

Looking to help your house feel better (and save some energy)? Thermal drapes can be a short-term solution for uneven temperatures and drafts that show up around your windows.

But here’s the thing: What most people don’t realize is that installing thermal curtains can actually mask an underlying problem in your home. 

So do thermal curtains work at all? Do they help with energy efficiency? Are they worth the investment? (They’re not exactly cheap if you’re installing them on every window!) 

This guide will help you determine if insulated curtains are the right choice for your home. You’ll cover the following questions:

How do thermal curtains work in summer and winter? 

Windows are responsible for approximately 25–30% of your house’s heating and cooling costs (1). But a house without windows wouldn’t feel like a home at all, so many homeowners choose to use blinds, shades, and curtains to add additional protection against changing temperatures. 

Insulated curtains are often thought of as a cold-weather fix, but in some cases they can help with keeping the heat out in the summer, too. 

This is how thermal curtains work:

Each thermal curtain panel is made of 3 or 4 layers of materials. These thick, extra layers of fabric against your window create a thermal boundary between the outdoor air coming in through and the room itself. So the curtain traps the cold or hot air behind the fabric panels and keeps it from moving around your space. In fact, technically thermal curtains serve as moveable insulation.

If you know anything about insulation, you know R-value is really important. R-value is a measure of thermal resistance or the ability to create a thermal boundary between the inside of your home and the outside. Basically, R-value indicates the level of protection against the transfer of heat inside and outside your home.

To give you some perspective, according to the Kansas City University Engineering Extension, an insulated wall has an R-value of anywhere from 12 to 19 and a double-pane window has an approximate R-value of 2 (2). And you know those pink batts of rolled up fiberglass insulation that you see in home improvement stores? Those have an R-value of about 3 to 2.5 per inch of thickness.

When comparing a double-pane window’s R-value to a solid wall or actual insulation materials, it makes it easier to see why you might want to add an additional layer of thermal protection over your windows.

But why do hot and cold air pockets happen around windows in the first place? 

Here’s How Cold and Hot Air Gets Through Your Windows

If your windows haven’t been properly insulated or air sealed, they often have gaps and holes around the seams of the windows that allow outside air to come inside your home. This is why some windows can feel drafty—it’s not the window itself (air cannot travel through glass, after all). It’s the gaps and seams around the window that are letting outside air in.

That’s why so many homeowners are surprised to discover that they still have window drafts—even after an expensive window upgrade. 

The permanent fix for window drafts is professional air sealing and insulation (but more on that later.) 

However, insulated curtains can act as a short-term block for air traveling through those gaps and seams around your windows or heat-producing sunshine coming through the glass, which can help minimize temperature fluctuations and stop some heat loss in the winter and heat intake in the summer.

What are thermal curtains made of?

Thermal curtains are made from multiple layers of thick fabric sewn together. Depending on your preference and style, they come in a variety of fabric types—from natural materials like cotton-blends to synthetic fabrics, like polyester and microfiber. 

Multiple layers of fabric, including a light-blocking, heavy material, is sewn in between layers of decorative fabric. This thick layer is what adds R-value to the area around your windows and creates a thermal boundary between window air leaks and outside temperatures—although a temporary one.

So, do thermal curtains save energy?

While some sources might give you a quick yes answer to this question, estimating the exact reduction in energy costs from installing thermal curtains is difficult to do. Remember, windows are responsible for approximately 25–30% of your home’s heating and cooling costs (3), but adding window coverings will not automatically reduce your energy bills by 25–30% like some window companies and window-covering makers may claim. 

Here’s why. There’s a common saying in the home performance industry: “Your worst wall is still better than your best window.” 

Basically, that means that even your worst, most poorly insulated wall is going to do a better job of creating a solid thermal boundary for your house than the most energy-efficient window. Windows are purposely designed to allow light and fresh air to enter your home. That means they’re a natural path for hot and cool air to enter and escape from your house. 

But don’t fret: At Sealed, we know how to help you reduce energy waste in your home for good—and make your home feel better at the same time. (We help you create a customized plan to do so.) Learn more.

Cost of thermal curtains: A quick breakdown

Are thermal drapes worth the investment? Here’s a breakdown of what it could cost to install thermal curtains throughout your home. 

Ultimately, your costs will depend on the amount of windows in your home, their size, and what supplies you already have on hand. But based on the above estimates, you could get a brand-new, energy-efficient dishwasher, washer and dryer set, or refrigerator for those costs. 

  • Thermal curtains
    • Cost per set: $40-$50
    • Cost for a 1,700 sq. ft. house: $680-$850
    • Cost for a 2,600 sq. ft. house: $1,040-$1,300
  • Curtain rods
    • Cost per set: $15-$40
    • Cost for a 1,700 sq. ft. house: $255-$680
    • Cost for a 2,600 sq. ft. house: $390-$1,040
  • Total estimated cost for curtains and rods
    • Cost per window: $55-$90
    • Cost per 1,700 sq. ft. house: $935-$1,530
    • Cost per 2,600 sq. ft. house: $1,430-$2,340

For this cost estimation, we’re using the following basic data: a 1,700 square foot house has an average of 17 windows, while a 2,600 square foot house has an average of 26 windows, according to official EPA averages (4).

Set on thermal curtains and want to save a bit of money? You can DIY them (more on that later in this article). 

Next, we’ll dig into the pros and cons of using insulated curtains—that way, you can have a better idea if they’re the right fix for your home.

Pros and Cons of Using Insulated Curtains in Your Home

With any short-term home improvement fix, there are advantages and disadvantages. Let’s look at some of the pros and cons to using thermal curtains below.

Pros to using thermal curtains:

  • Insulated curtains are an excellent option for renters. If you don’t own your home, thermal curtains are a great option for adding temporary insulation around your windows.
  • Thermal curtains can cut down some of your energy waste. While you won’t see a huge improvement in your heating or cooling bills, you might be less inclined to adjusting the thermostat back and forth once you install curtains to stop drafts and outdoor air intake.
  • When shut, thermal curtains can add an R-value of R-3 or R-5. This R-value is estimated, but it does improve upon a window’s average R-value of 2. 
  • Thermal curtains can reduce some of the drafts or hot air you feel (when they’re closed). Got a really chilly living room? Or does your upstairs bedroom feel like a sauna in the summer? Closing the blinds and adding closed thermal curtains can reduce some of those uneven temperatures. You can learn more about fixing drafty windows in this article.
  • Installing insulated curtains is something you can do yourself. Most of the time, you just need a few simple tools to install curtain rods: a drill, screwdriver, stud-finder, and a level. Enlist a buddy to help, and this is a project you can do yourself on a day off work.
  • Curtains can add a decorative flair. Adding textiles and drapery in your style of choice can be a great way to personalize your space and create a comfortable home that you love.

Cons to using insulated curtains:

  • Insulated curtains are a temporary solution. They mask the problem of open air leaks around your windows, rather solving it through professional air sealing. Learn more about house sealing and why it works in our Guide to Air Sealing
  • They block natural light from entering your home. Thermal curtains work best when completely closed, so using them as a long-term solution to uneven temperatures means you’re also blocking natural light from your home. While that might be great for sleeping in, you might miss seeing the sun during the day with blackout curtains always pulled shut! And letting the sun shine through in winter can actually warm your home (for free) during cooler months, so you’ll be missing out on natural heat, too.
  • They’re not a home-value boosting upgrade. As seen above, insulated curtains aren’t a cost-effective fix. And this isn’t an upgrade that adds to the marketability of your home when you go to sell. On the other hand, professional air sealing and upgraded insulation can increase the value of your home (and permanently fix the uneven temperature issue at the same time). Check out our guide to energy efficient home improvements to learn more.
  • Installing thermal curtains is more expensive than you might think. Depending on the number of windows and window sizes in your home, this short-term solution can get really pricey.
  • They can cramp your style. While there are plenty of styles to choose from, insulated curtains come in heavy fabrics and may not complement your taste in home decor.
  • Thermal curtains block the view. Again, insulated curtains should be closed completely for them to be the most effective. That means those lovely trees or that city skyline out your window will be covered up year-round for you to resolve any uneven temperatures and energy waste. 
  • Insulated curtains don’t solve poor insulation and airflow problems. If you have uneven temperatures between rooms in your home, thermal curtains won’t help here. They’ll temporarily assist in blocking window drafts that come into your home through air leaks, but that’s about it. 

What are the best thermal curtains?

The best thermal curtains are designed with insulation in mind and have several layers of fabric in the panel. For the best draft protection, choose insulated curtains that:

  • Have 3 or 4 fabric layers
  • Reach the floor (if your thermal curtains don’t reach the floor, air will flow out from underneath the curtain panel)
  • Extend past the edges of your windows
  • Overlap in the middle to fully close and trap cold or hot air

If you want to save on some of your costs or have more control over the look of your thermal curtains, check out how to DIY thermal curtains below.

If DIY isn’t your thing (hey, we get it!), feel free to skip over the next section. Or have you already decided that thermal curtains aren’t right for you? Jump ahead for a list of thermal curtain alternatives.

DIY Thermal Curtains

If you’re handy with a sewing machine, creating your own DIY thermal curtains could be a way to save a bit of cash. And they’re generally a simple sewing project. 

Materials Needed for DIY Thermal Curtains:

  • Sharp sewing scissors
  • Decorative fabric of your choice (for the outer layer)
  • Shield liner or vapor barrier fabric (for the inner layer)
  • Batting fabric (for inner layer of insulation)
  • Tape measure
  • Thread 
  • Iron (for pressing fabric)
  • Pins for holding the layers together

Steps for Sewing DIY Thermal Curtains:

  1. Measure your window width and length. Add enough width and length to your measurements to cover the entire window and overlap at the center, so there won’t be any gaps.
  2. Measure and cut your fabric accordingly. Cut two curtains each of each fabric type to create your layers. Assemble the layers with the decorative fabric on the exterior and the batting and vapor barrier fabric on the interior of the curtain.
  3. Iron and pin the layers together. Once your layers are cut and assembled, iron them to flatten and straighten and use pins to secure in place before sewing. 
  4. Sew all sides of fabric layers together. Use your sewing machine to sew together all the layers. Sew the fabric together on all sides and create a secure hem. 
  5. Add clip-on curtain rod rings. One of the simplest, fastest ways to finish your DIY thermal curtains is to use clip-on rings. Once you’re done sewing your panels together, clip these on and hang them up. And your DIY insulated curtains are complete!

Insulated curtains FAQs:

Do thermal curtains keep the cold out?

Thermal curtains can work as a short-term solution to help keep cold air from leaking through air leaks around your windows in winter. They help trap cold air drafts behind multiple layers of fabric to keep it from moving around the room. However, you do have to keep them closed for thermal curtains to be effective. 

Ready for a long-term fix to keep the cold out? Check out How to Fix a Drafty House Permanently.

Do thermal curtains work in summer?

Technically, yes, thermal curtains can help reduce hot air entering your room in the summer through air leaks along your windows. They trap heat behind the layers of fabric. But the overall reduction in energy waste is small, as thermal curtains don’t reduce your overall air conditioning load. 

Do thermal curtains keep heat out?

According to Energy.gov, about 76% of sunlight that falls on a double-pane window becomes heat inside your home (5). So when your thermal curtains are shut, you’re blocking sunlight from entering your house and producing heat. 

Thermal curtains can help minimize heat coming into your house on hot summer days, but their overall effectiveness in keeping your home comfortable in the summer is pretty minimal. 

Why? Because when you have a too-hot upstairs or one room that’s warmer than another, upgraded insulation and air sealing is the proper long-term fix. But if you’re a renter, thermal curtains can add an additional layer of temporary insulation to your windows and help reduce heat intake in the summer that might make you a couple of degrees more comfortable. 

Too-hot house? Discover how to fix a stuffy house (and get rid of stale, hot air) for good.

Thermal curtain alternatives

Thermal curtains aren’t exactly an inexpensive fix if you add them to every window in your home—plus, they aren’t the most foolproof way to reduce energy use. And what if you don’t want to block natural light and your view all season long? 

Here are 2 alternatives to thermal curtains that won’t require you to cover up your windows:

  1. Insulated custom-fit interior storm windows. Custom-fit interior storm windows are made of a clear acrylic pane that you can pop in over your existing window. They add an additional layer of insulation over the windows themselves, but they won’t resolve any open gaps or seams around the window that allow outside air inside your home.
  2. A better thermal boundary for your home. To permanently solve window drafts, uneven temperatures, and energy waste, professional air sealing and insulation are the right fix. When air sealing and upgraded insulation are paired together, they create an effective thermal boundary for your home, keeping inside air in and outside air out. (And you can keep your windows uncovered without worrying you’re letting in hot or cold air!) Plus, upgraded insulation and air sealing work together to make your home feel incredible—even on summer days when you let the sunshine come through your windows. 

Tired of drafts and heat around your windows? Get the permanent fix.

At Sealed, we’re the home performance experts. That means we work with homeowners to make their houses feel incredible and cut energy waste (which is better for you and the planet!). 

If you’ve got an uncomfortable house that suffers from uneven temperatures, rooms that are too hot or too cold, and annoying window drafts, we can create a customized plan to fix it all—and you can get the work done at zero upfront cost. (Yes, you read that right!)

Get rid of your thermal curtains and enjoy the sunshine again. Take our quick quiz to see if your house qualifies.

May 20, 2022