How To Insulate Your Garage Door in Two Hours

Garage Door Insulation Kit

Growing up in the central/northern plains, my bedroom was on the north and west side of the house.  To top it off, it was over our garage, making for a very cold room.  A little garage door insulation probably would have made that part of the house much more tolerable.

Many garage doors these days are un-insulated and light weight metal that simply transfer heat and cold.  In the Arizona low desert, cold weather is only a concern for about 2 months, and hardly that if you live in an urban area.  But even here, garage door insulation often makes sense. In the summer the surface temperature of the garage door can reach 140 degrees!  That heat radiates into the garage, and if you have living space over the garage, it radiates straight up into your living area.

Luckily, it is very easy to retrofit insulation onto a garage door.  Fiberglass and polystyrene garage insulation kits can achieve R5 to R8 insulation values, providing not only excellent thermal protection, but also some noise reduction.  As simple as this project is, there are (as always) a few options and considerations to take into account.

The first decision is whether garage insulation makes sense for you, or not.  For me, it makes sense because I have living space over top of my garage, and it is exposed to the south in our oppressive heat.  For much of the day the sun is shining directly onto the garage.  It would also make sense in my childhood home, because of the cold climate and living space on top of the garage.

However, here in Arizona it may not be the best choice for an eastern exposure garage, for example.  Your mileage may vary depending on shading and amount of living space over the garage

Also be aware that not only will the insulation keep heat and cold out, but it will also keep heat in.  Consider how hot a car gets, and pulling it into a small enclosed space like a garage results in a lot of heat, and the insulation will only keep it in longer.  Minor behavioral changes can mitigate this concern, such as leaving the car in the driveway when you get home from work, and pulling it into the garage before bedtime; or simply vent the garage for a few hours.

The next choice is whether you want to buy a kit, or simply buy sheets of polystyrene insulation.  Kits offer some convenience, though you still end up having to cut the insulation.  Sheets are definitely cheaper but bulkier to transport and may not fit in small or even some midsize cars.

Kits come in two main forms from Home Depot or Lowes - an Owens Corning 3" fiberglass kit 3" R8 fiberglass kit, and a 1.25" Insulfoam R5 Polystyrene kit.  The Owens Corning kit is thicker than most doors and will require taping and securing (comes with the kit) - some people don't like the looks of it since it is thicker.  The Insulfoam kit fits snugly without tape in most modern doors, and looks very nice with a vinyl side flush with the door, but it is about R3 less insulation than the Owens Corning kit.

I personally ended up using the Insulfoam kit as I couldn't transport the larger sheets in my small car.  The kits only fit 8 panels, so you'll need two for a double garage door.

Insulfoam Installation

Installation takes an hour or two - you simply measure the size of the openings/panels, and cut appropriately so that the insulation will fit in the 'reservoirs' in the door.  In my case, the 1.25" Insulfoam fit perfectly, and required no tape for securing.

The polystyrene is a little messy when cut, and you will end up with little balls of polystyrene that need to be vacuumed up.

And if you decide to get sheets of insulation, be sure to measure the thickness of your doors - 1.25 seems pretty standard but they can vary.  The big box stores offer a wide variety of insulation types and thickness, so it helps to be prepared.

And to wrap things up, you may want to consider installing vinyl garage door seals to create a nice seal.