Closeup on the corner of a piece of expanded polystyrene (EPS) cellofoam insulation being installed on a wall

Are you sick and tired of shivering in your garage during the winter months while you work on your latest project? Or maybe you have the opposite problem and face oppressive heat during the summer whenever you set foot in your man-cave.

Maybe you have both problems!

Uncomfortable temperatures can take the edge off our enjoyment of garage spaces, but there is a solution: improving the energy efficiency of your garage door.

Fortunately, you have several options to do this. Most of them are DIY-friendly, come with easy-to-follow instructions, and require very few tools.

One such option is Cellofoam, which has been successfully used by thousands of people across the US to insulate their garage doors from the extremes of temperature that standard garage doors do nothing to guard against.

If you’re wondering whether insulating your garage door with Cellofoam is the type of DIY project you should take on, we’ll answer this question and more in the rest of this article.

So, read on to find out more.

What Is Cellofoam Insulation?

Cellofoam is a foam insulation product made from expanded polystyrene (EPS), with a toughened layer on one side, making it ideal for use in garages. It’s available as a kit for insulating your garage door, reducing energy bills, and making your garage more pleasant.

Cellofoam North America Inc. has been in the insulation business for many years and offers a wide range of products used in the construction of buildings, packaging materials, and floats used in the marine environment.

Its garage door insulation kit is available from Home Depot and has much in common with similar products that do the same job.

Made from thermally-efficient expanded polystyrene with high-impact polystyrene facing bonded to one side, these insulating panels are ideally suited to use in a garage because they can withstand the odd knock or scrape.

Polystyrene blocks used for container home insulation stacked in a warehouse

The R-value quoted by the manufacturer is about 4 per inch, which is good enough to make a noticeable difference to the comfort and expense of heating your garage.

How To Install Foam Insulation Panels on Your Garage Door

The garage door insulation kit from Cellofoam comes with comprehensive installation instructions, but there’s not much to it. All you need in terms of tools is a sharp knife, a tape measure, and a straight edge to guide your cuts.

The kit includes eight individual insulating panels, which will cover a standard nine-foot garage door. If your door is more extensive than that, or your garage has two doors, you’ll need two kits to complete the job.

Each panel is designed to fit snugly into place on a door section. You might need to cut each piece to size, but you can easily accomplish this with a sharp knife.

Always remember that the panels in your garage door are not necessarily the same size, even though they might look it. Therefore, you need to measure each one individually to avoid any mistakes.

The panels have kerfs cut into the back, allowing them to bend during fitting. This flexibility makes it easy to insert the boards under the lip that generally runs along the edge of each garage door section without having to fix them with screws or glue.

Kerfs are thin slits, grooves, or notches created when a saw cuts into a piece of material. You can cut a series of kerfs into a sheet of material to allow it to bend.

A homeowner bends to break a Cellofoam insulation panel along a kerf
Courtesy of Amazon

They are widely used in carpentry for bending wood, and there’s an intriguing video on the subject here if you’d like to learn more.

The sides of the insulation panels with the kerfs are installed towards the door, leaving the smooth, high-impact polystyrene laminate face visible.

This orientation presents a nice clean surface to the inside of the garage, which looks good and is durable and washable, so you don’t need to worry about it becoming shabby looking over time.

Alternatives To Cellofoam

There are a few alternatives to using Cellofoam, which you might want to consider.

Other garage door insulation kits are available, some of which also come in foam panels, while others use fiberglass or radiant barriers that reflect heat back outside.

Foam Panel Insulation Kits

Matador and Insulfoam make kits that seem to be almost identical to Cellofoam.

Like Cellofoam, they are made from polystyrene, which can be cut to fit non-standard garage doors and easily installed in about an hour using a tape measure, a sharp knife, and a straight edge.

A homeowner uses a ruler and utility knife to cut a piece of Cellofoam insulation
Courtesy of Amazon

They are very similar in design, and all do a good job insulating your garage door.

These kits have R-values in the range of 4.0-4.8 and will help to maintain more comfortable temperatures in your garage.

Fiberglass Insulation Kits

Owens Corning and ADO make garage door insulation kits from fiberglass with a plastic or vinyl covering that encases the side of the insulation facing the garage space.

The vinyl covering keeps the fiberglass in place and prevents loose fibers from breaking off and floating around your garage.

Fiberglass can attract dust and odors and does break down over time, so you might need to replace it in the future.

It’s also heavier than the foam board kits, which can affect the opening mechanism of your garage door. The added weight could mean you need to upgrade the motor or replace the door springs so they can handle the extra load.

The manufacturers state these fiberglass products have R-8 performance, which is enough to make a significant difference to the comfort of your garage during extreme temperatures.

Radiant Barriers

Radiant barriers work by reflecting heat back outside using reflective foil.

They are better suited to keeping heat out of your garage than keeping it in, especially where the door is often in direct sunlight.

They are not so suitable for cold climates where keeping warm is the main issue because radiant barriers do not prevent heat transfer via conduction, only radiation.

Several radiant barrier squares being installed on OSB over a wall in a home

However, some products combine radiant layers with bubble insulation, which in theory can give the best of both worlds. But, if you need to keep your garage warm, you would be better off with foam panels or fiberglass.

Replace Your Garage Door with an Insulated Door

The very best option for keeping your garage warm during the winter and cool during the summer is to install a brand-new insulated garage door.

An insulated garage door will have an R-value between 6-19, which is good enough to maintain a comfortable indoor temperature during extreme outdoor weather.

They incorporate a foam core inside the body of the door and come with the correct size of motor and springs to ensure they open and close effectively.

This construction avoids the problems that some people report after retrofitting insulation to an existing door, where the opening mechanism fails to work due to the added weight.

Even though the insulation material is lightweight, it can add up to enough of a difference to prevent your opener from working correctly, which requires extra work, and money, to put right.

Although a factory-made insulated door is the best option for the result, it is also the most expensive. If you don’t have the budget, then one of the insulation kits would be a good alternative.

Also, if the rest of your garage isn’t adequately insulated, just insulating your garage door won’t make much difference. You can read our article on the pros and cons of insulating your garage to understand better whether you should protect the whole of this space.

How Much Difference Does Insulating Your Garage Door Make?

Insulating your garage door with an insulation kit can significantly affect your comfort level and heating and cooling bills.

Dad’s Garage on YouTube did a great video showing the installation process for foam panels and gave his analysis of the benefit.

Screenshot from Dad’s Garage on YouTube showing the installation process for foam panels on a garage door
Courtesy of Dad’s Garage

He used the Insulfoam product, which provides an R-value of 4.8 and has a nice smooth finish on the side facing the garage’s interior.

His garage door faces west in Texas, so it gets the sun’s full heat during the day. He regrets not spending the extra money on an insulated garage door but was hopeful that the insulation kit could improve matters for him.

The panels he used were very light and didn’t affect the opening mechanism of his garage. He paid $95 for each of the two kits required to insulate his door, which he said was good value.

The installation process was very straightforward, and the father and son team completed the project in less than an hour. Immediately after they completed the installation process, Dad’s Garage said he had already felt the difference.

Before he installed the insulation, there was a difference of 10–20 degrees between the temperature outside the garage and inside.

After insulating the door and waiting about five hours for temperatures to stabilize, he noticed an improvement of 2-3 degrees. This differential works out at a 15-20% improvement.

He thinks the temperature is kept a little more stable and feels more comfortable. Well-worth the $200 he spent on the project.

One takeaway he gave was that you need to be realistic with your expectations. It won’t make a huge difference but is still worth doing.

Although, if he were to renovate his home all over again, he would spend the extra money on a brand-new insulated garage door.

Summary

Temperatures in your garage can get rather uncomfortable during very hot or frigid weather because the doors tend not to be insulated and provide a vast area for heat transfer into or out of your garage.

The best way to insulate this part of your garage is with a specially-designed new insulated garage door. However, this is the most expensive option and not something many people want to allocate a budget to.

Garage door insulation kits are a great way to improve the comfort of your garage space and lower your heating and cooling bills.

Insulation kits come in the form of foam panels, fiberglass batts, or foil sheets, although the foil sheets are less well-suited for insulating doors in cold weather because they are primarily designed to reflect the heat of the sun away from the door.

Cellofoam garage door insulation kits are easy to install, significantly improve the comfort of your garage, and reduce your HVAC bills. They are low-cost and a great solution for garage door insulation.

If your garage has been fully-insulated and still feels uncomfortable, you could add a mini-split to control the temperature better. We’ve written an article about this here.

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