Window box, valance, cornice box, pelmet box…I’ve seen this kind of window treatment called all sorts of things. Regardless of whatever the right/official name is for them, they are easily one of my favorite ways to dress a window…especially as a budget-conscious renter! Why? Window valance boxes are pretty easy to DIY, so you can customize them to your exact window size and style preferences; they don’t require much fabric, so they are often cheaper than long curtains; and since so many rentals often have blinds pre-installed, they are a great option when privacy isn’t a concern. Over the years, I’ve always made our cornice boxes out of wood, but I recently tried a much easier and cheaper method, and it worked brilliantly! Today I want to show you how to make the ultimate budget-friendly window treatment: window valances from foam insulation!

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

I wasn’t kidding when I said that window valance boxes are one of my go-to window treatments…I’ve used them in pretty much every home we’ve lived in, including this one! Not only do I love that they give me an excuse to add more pattern to a room, but I also think they finish off bare windows really nicely!

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

CA Nursery | NC Dining Room | KS Bathroom | KS Office

Side Note: I have to admit I was pretty taken aback by these oh-so-bold-and-colorful photos of other rooms I’ve done in the past…especially in contrast to my current office shown in this post. As much as I’ve tried to embrace the brown walls in this rental, the above photos were a huge jolt of a reminder that I really, really love bold spaces. Although we don’t yet know where we’re moving this year or what kind of house we’ll have, you better bet I’m already scheming up colorful wall ideas! 

Over the last few months, I have been pulling together some final details in my home office. Naked windows, for some reason, really, really bother me so two window treatments were at the top of my list. A window valance was the obvious choice since the counters prevent my other preferred option: long curtains. But because we’re so close to moving out, I didn’t want to drill any more holes in our walls than necessary. I had heard and seen other people make window valances from sheets of thick foam insulation from the hardware store, and I figured this was a perfect opportunity to try it out!

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

The results were just as easy (if not easier!) than their wood counterparts, yet the investment in both time and money was significantly less. I’m not really sure if I’ll ever go back to making our cornice boxes out of wood again!

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

Supplies Needed

To make a window valance/cornice box/pelmet box from foam insulation, here is what you need:

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

Years ago, I used thick foam insulation from The Home Depot to make a bulletin board. However, that insulation was bright pink; and since I knew my fabric for this project was bright white, I worried about it showing through. Then I discovered that Lowes carries solid white foam insulation and that’s when I finally decided to give this a go!

Here is what you’re looking for (below). It comes in several thicknesses, so you can choose how substantial of boxes you want to make. I chose the 1″ thick sheet since that’s what we have always used for our wood versions. Plus, I felt it was the best price and would be the most manageable!

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

Yep…that says ~$11. And I was able to get two window treatments out of a single sheet with LOTS leftover! Told you this was a cheap project! 😉

Measuring the Foam Insulation

The first step is determining how big you want your window valances to be. I like mine to extend at least 5 inches beyond the window on each side and measure at least 12″ tall. We have incredibly high ceilings in this house, so I decided on a height of 15″ for my boxes this time.

You will also need to determine how far out from the wall you want them to sit. We have always used 1x4s for the returns on the boxes, so I decided on a depth of 4″.

Here’s an illustration to help you:Once you have your measurements figured out, you need to transfer them to the foam insulation. One of my favorite things about working with this product is that it has pre-measured marks down the entire sheet, so it’s very easy to make sure you’re measuring/cutting in a straight line!

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

I found using a combination of a tape measure, long clear ruler and the provided hash marks the easiest way to translate my window box measurements to the foam sheet.

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

Cutting & Assembling the Window Valance Box

Admittedly, the hardest and most time-consuming part of the whole project is cutting the foam insulation. Even with using an electric cutting knife (like the kind you’d use on a turkey), it can be very messy and slow going. I got the cleanest edges and straightest lines using the electric knife, and also got decent results using a sharp retractable knife with the blade extended out as far as possible (to cut through the 1″ foam). I tried using a serrated knife; but since it required so much back-and-forth motion, it easily snapped the foam board. Just go slow, take your time, and make as many passes as you need to get it cut clean through!

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

I made most of my measurements for my boxes along the clean outer edges of the sheet, so I could at least be sure I’d have one very flat edge on each box. However, once everything is wrapped up in batting and fabric, you won’t notice your messy edges at all, so just do your best to get the foam cut apart in the correct dimensions!

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

You probably notice that there are blue words all over the foam insulation, but that’s actually just a protective film covering the solid white foam sheet. I chose to leave the film in place for cutting and then removed it afterwards, thinking it would keep the mess down. I’m not entirely sure it helped (my office was still covered in white foam!) so you can remove it whenever you’re ready! (And if you’re using a thick, dark fabric, you probably don’t need to remove it at all!)

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

With the flat front and the shorter returns all cut from foam, you next need to “assemble” the box. I like to have a solid, clean board along my window fronts, so I always attached my returns behind the front panel, as shown below…

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

Here’s where the simplicity of the foam makes a big difference! All you need to do is slide some sturdy 2″ nails through the front foam panel into the side returns. Do 3 or 4 nails down the height of your valance, and take care to drive the nail into the center of the returns. No tools are needed here…just press them on in! You’ll be surprised at how sturdy they are!

Wrapping & Hanging the Valance Box

With the foam box assembled, the last step is to wrap it in batting (to give it an upholstered look) and fabric. I recommend securing one then the other (rather than trying to do both materials at once), as working around the corners can be quite tricky. After experimenting with different options for securing the batting and fabric, I ultimately landed on some 3/4″ nails (the same ones I used for this project). They slide right into the foam, yet are small and sturdy enough to keep the batting/fabric tight.

TIP! One benefit of using wood is that staples into wood hold fabric much tighter than nails into the foam. However, I found that by pushing the nails in at just the right angle and using a nail every inch or two, the fabric was plenty tight!

To cover the boards, cut a piece of batting/fabric 10+ wider and 10+ longer than your foam box (including the returns). Starting in the middle, wrap the batting/fabric toward the back, as tight as possible, and secure in place with nails. Work your way to the ends of the box, snipping and folding at the corners where necessary.

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

Besides the cost and effort savings of using foam, you might recall that my other main priority was to keep installation hole-free. Because this cornice box is so light, I was able to hang it with a single large Command strip on each side (seriously!!!)

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

TIP! To ensure your valance is nice and straight, place a small level on top of it as you secure it to the wall!

Next, repeat for however many windows you have, adjusting widths as needed for different size windows (but keep the height the same for a consistent look around the room).

I am so glad I gave this foam insulation version of the cornice box a try! Not only do I love that I didn’t have to pull out the power tools to bring it all together, but I just adore how low commitment it is! If this box doesn’t fit in our next home (or heck, if it doesn’t survive the trip in the moving truck!), it was a $20, 1-hour, damage-free project that brought some much-needed style to my bare office for our remaining time here! I’d say that’s a win-win-win!

Valance, cornice box, pelmet box...learn how to make one using inexpensive foam insulation from the hardware store!

There have been quite a few updates in the office since you last saw the room. Yes, the walls are still a horrible shade of tan, but I’ve added some new cozy chairs and finally got my Minted art pieces framed, so it’s feeling much more polished. I’ll have a room tour for you soon once I finish up a few organization details!

Budget-friendly, easy window treatments are something I’ve done a lot of over the years because as anyone who rents a lot knows…window treatments rarely work from home to home. As such, it’s really hard to invest good money in making your windows look great knowing it’s probably just for your current home. If you’re looking for some more easy ways to dress up your windows, try these other projects!

Have you ever made anything from foam insulation? Do you have a go-to window treatment you use all the time? I’m a sucker for long patterned curtains too, but when they aren’t possible, these window valance boxes are my next go to! Give them a try – I think you’ll love how easy they are!

See You Soon!
Megan