Homeowners will usually focus on expensive interventions that improve efficiency, like installing heat pumps or filling cavity walls with insulation. However, there is a far more affordable approach: switch to thermal fabrics in custom-made-to-measure curtains. 

We’ve written this guide to explain this whole process in more detail. You’ll learn about the science of thermal curtains, how to fit them with zero gaps, and proper installation for superior performance. 

So, let’s get going, shall we? 

The Science Behind Thermal Curtains: How Do They Work? 

Thermal curtains are a bit like blankets for your home. They prevent heat from escaping through windows, the most vulnerable exterior portion of your house. 

Thermal curtains have what’s known as an R-value. R is just a measure of thermal efficiency and insulation. The higher it is, the better. 

Most thermal curtains have R values of between 2 and 5. This compares to windows, which are rated at just 1 on this scale. 

Thermal curtains can retain heat because they are made of multiple layers of material. These act as a conventional block while also trapping warm air, preventing draughts from leading to sustained heat loss from rooms. 

Some thermal curtains also attach to wall segments, reducing the risk of drafts further. The zero-gap concept has been something of a revelation in the industry, which we discuss in more detail below. 

How To Save Energy With Custom Thermal Curtains

So, what can you do to start saving energy with custom thermal curtains? In this section, we find out. Here, we provide a step-by-step guide you can follow to get it right. 

Step 1: Choose Your Thermal Fabric

While you might think there is only one thermal fabric out there, there are actually several. Granted, their performance is similar, but not identical, so you’ll want to take that into consideration when purchasing. 

The basic entry-level thermal fabric is acrylic-coated polyester. This material is affordable, suitable for all seasons, and has an R-value of 3.5. 

The next level up is thermal suede. As you might expect, it’s about 50% more expensive than polyester, but has an R-value of 4.2, making it even more suitable for colder climates. 

Wool interliners with cotton outers have a similar heat-trapping performance. However, many people actually prefer them because of their eco-luxury appeal. 

Finally, top-rated insulating curtains use microfibre to trap heat with aluminium. These can reach R-values of around 5, which is pretty good performance for something so thin. Just be aware that the aesthetics might not be quite what you want. 

Step 2: Achieve A Zero-Gap Fit

Next, you want to ensure you fit the custom thermal fabric to the window opening. We recommend going with a four-inch overlap on each side of the window for fullness, and then opting for floor-to-ceiling coverage where possible. 

If going all the way to the floor, a 1 to 2-inch breach is recommended. In other words, you want the curtains to spill out and make contact with the flooring. The same overlap is recommended for sills. 

If you’re worried about the sides, you can also add magnetic PVC strips. These are handy for sealing the edges, but make sure the alignment and magnet strength are calibrated properly. If it’s too strong, it’ll make your window coverings less practical. During this process, account for the fact that some fabrics may lengthen slightly when hung over time. (One reason why it’s a good idea to get professionals to do your installation for you.) 

Also, be wary of vents and other obstructions. Try to keep these open and work around them where possible. 

Step 3: Keep Layering For Higher R-Values

Finally, you can keep layering to achieve higher R-values once the curtains are in place. For example, you could add an interliner from a brand to increase insulation by around +R 2.0. You could also include a face fabric or a backing. 

Most people find they can save money with thermal window dressings, increasing the return on investment. Average savings are often in the hundreds of pounds per year in reduced heating costs, leading to full paybacks in two years or less. 

How To Install Thermal Curtains For Proper Airtightness

You can improve the performance of your thermal curtains by installing them in the right way. As we like to tell people, how you set them up makes a world of difference. 

We suggest starting with a regular double rod setup. Thermal rods allow you to put thermal curtains on the back and then decorative additions at the front. 

Once in position, use wrap-around returns. These push the fabric towards the wall, preventing curtains from losing heat from the sides. 

If you’re living in an area with extreme cold, you could look at ways to attach the bottom of the curtain to sills. Some people even use Velcro, but there are other low-key methods available. 

Common Thermal Curtain Mistakes You Should Avoid

Of course, installing made-to-measure thermal curtains on your property isn’t without risk. A lot of people make mistakes that later backfire. 

The most common problem is people thinking a single-layer blackout curtain is enough. It’s not. Usually, you’ll need to add an interliner, preferably with an R of 2.0 or more. Otherwise, you could be wasting your money. 

Also, if you have a gap at the bottom of your curtains, that’s a big no-no. Convection currents can scoop warm air out of your home and out of your house, so always leave around two inches draped over your floors or sills. 

Finally, beware of shrinkage. After you wash some thermal fabrics for the first time, they can shrink in size. That’s why it’s a good idea to prewash them before installing. 

Wrapping Up

So, to conclude, thermal fabrics are an exceptional way to save energy in your home. However, you need to install them correctly. Failing to do so could lead to a much lower return on investment. Make sure you check out the made-to-measure curtain options in our shop.