How To Build An Insulated Exterior Door

Chloe Meltzer
by Chloe Meltzer

Insulated doors are great for keeping cold weather out in the winter, hot weather out in the summer, and air leaks into your home. After implementing an insulated door into your home you will notice the difference in your energy bill! The only negative aspect regarding insulated exterior doors is the fact that they are extremely expensive. So expensive that they simply cost too much for an average consumer.

Despite insulated exterior doors being very expensive, there is a method to build an insulated exterior door on your own. All you need is a bit of wood, insulation foam, and to follow the following steps. You’ll need to prepare your planks, cut the panels, attach the edges and then insulate and seal!

In this article we will take you step by step through the instructions so that you can build your own insulated door! Just take your time and follow the steps thoroughly to ensure a job well done.

Do You Need Exterior Door Installers?

Get free, zero-commitment quotes from pro contractors near you.

Before You Build

Choose Your Insulation Layers

The larger the number of insulation layers you have, the better it will do its job of insulation. You will need to choose how many layers you need based on the climate you live in. When building your own insulated exterior door you have three main options to choose from.

  • One layer: Usually when you choose to insulate your door with only one layer, that layer will be made from the same material as the door. These one layer doors do not provide much insulation and are not truly insulated for temperate climates.
  • Two-layer: When insulating a door with two layers you will not only have the outer layer, but also an inner layer. This layer is usually made of polystyrene which actually insulates the door. These doors are appropriate if you are insulating a home with mild-to-moderate weather conditions.
  • Three-layer: The three-layer insulated door has two layers along with the outer layer. These two layers are usually composed of polystyrene or polyurethane. These doors are good for extreme climates.

Construction Materials

Another choice you will need to make before building an insulated exterior door is your construction materials. These materials are stronger than most doors used on a home, and are typically used for constructing garage doors.

  • Steel: Since steel is extremely strong and low-maintenance, it is a good choice for an insulated door. Not only is steel available in many different options, but it can also be easily maneuvered around foam or vinyl insulation layers. This allows you to easily make two, or three-layer insulated doors.
  • Aluminum: This material can look very modern but is not as strong as steel. If you are looking for the most insulated material, steel is a better choice over aluminum.
  • Glass: Although it is possible to use mainly glass for your exterior door, you are also going to need to use some type of metal frame with this as well. It will add to its insulating properties as well.
  • Wood: With wood, you get to have a beautiful look that can appear modern or traditional. Wood doors are generally a preferred choice. This is due to their natural insulation properties, and the ability to layer. This is the material we will work with for this method of building an insulated exterior door.

Tools And Supplies You Will Need

  • Pencil
  • Circular saw
  • Goggles
  • Gloves
  • Dust mask
  • Two ¼’’ sheets of plywood
  • Four 1’x4’ wood planks
  • Sixty 1’’ wood screws
  • One 1’’ sheet of rigid insulation foam
  • Wood glue
  • Clamps
  • Measuring tape
  • Miter saw
  • Drill with a drill bit

How To Build An Insulated Exterior Door

For this method of how to build an insulated exterior door, we are going to base it off of a standard size insulated exterior door. These are usually 4’x6’.

Step 1: Prepare Your Planks

Take your miter saw and cut the 1’x4’ planks into a few different planks:

  • Two, 68-inch planks
  • One 40-inch plank
  • Two 48-inch planks

If you can purchase this pre-cut ahead of your project then it will definitely save you time.

Step 2: Cut The Door Panels

Now you will make your door panels. Do this by marking a 72’’x48’’ rectangle on both sheets of your plywood with your pencil. Then take your circular saw to cut our these areas on the plywood.

However, before you cut you will need to make sure the lines are straight and the measurements are correct. Since you’re cutting, you can’t really fix a mistake if you cut too much off of the door.

A good rule of thumb is to measure twice and cut once. This will help so that you ensure the correct measurements before cutting your door. If you don’t get the same numbers the first two times, measure a third time.

Step 3: Attach The Horizontal Edges

Now you will be attaching the horizontal edges to your insulation frame. To do this, take your wood glue and put it all over the faces of both your 48-inch planks that you previously cut.

Lay both of your wood panels on the planks and clamp them on the horizontal edges of the planks. Then take your measuring tape and mark every 8 inches. Drill wood screws into these intervals and then remove the clamps.

Step 4: Add The Vertical Edges

This step is going to be extremely similar to the previous step, but instead of horizontal, it is vertical. Spread wood glue on the faces of both the 68-inch planks that you previously cut. Be sure to liberally apply the wood glue.

Lay both of your wood panels on each plank, clam the edges once again, and mark every 8-inches. Drill wood screws into each mark you have made and then remove the clamps.

Step 5: Place The Middle Plank

At this point, you will be using the 40-inch plank. This plank is extremely important as it will serve as the support point for the entire door.

To add this plank you will need to place it on the vertical midpoint of the door, and glue it with wood glue. Be sure that all of the edges of this plank are fully within the interior frame of your 68-inch plank. Finally, screw the original 40-inch’ plank into place.

Step 6: Fill With Insulation

If you look at the work you have completed, you will see that you have two 40”x32” frames. Although these will both be hollow, it is now time to fill them.

Cut your rigid insulation foam so that it will fit inside of these frames. Be sure to fill it so that the frame’s interior edges support the insulation. Make sure they are not so big that they do not fit, but also not too small so that they do not fully fill out the frame.

Spread glue on the frame and press the foam into it. Apply pressure until the foam stays inside the frame without your help.

Step 7: Seal Your Door

Now you have almost finished your task. You have fully built an exterior insulated door, and the only step that needs to be done is to seal it.

To do this, take the rest of your plywood and place it directly onto the door’s frame. Clamp it into place and mark 8-inch holes that go along the central interior plan. Do this on the perimeter as well.

Finally, drill screws into these holes, add hinges, and then a door nob, and you have a fully insulated exterior door!

Related Questions

Why would I want to insulate an exterior door?

Insulated exterior doors can help you to keep out noise and cold while keeping the heat in. Rather than spend huge amounts of money on your electricity bill you can use an insulated door instead. By insulating your exterior doors and windows, your furnace or air conditioner doesn’t need to work as hard to heat or cool your home. 

Is it difficult to insulate an exterior door?

Insulating an exterior door requires a bit of handy work. If you are able to cut and measure wood, glue, and drill screws, then you should have no problem insulating an exterior door. Just make sure when you’re measuring that you do it slowly and accurately as this will be an issue if you measure wrong and cut the wrong way.

What is a good R-value for an exterior door?
Most fiberglass clad entry doors and steel doors range anywhere from R-5 to R-6 for their R-value, as long as it’s excluding a window. If this type of door is installed the correct way and it’s not bent then this door would not need any further weather stripping for added insulation.

Do You Need Exterior Door Installers?

Get free, zero-commitment quotes from pro contractors near you.

Our Takeaway

Instead of buying an already insulated exterior door, you can get your hands busy by creating your own! You simply need a few tools, and simulation material to do this project.

By taking your time and following the instructions that are above, you’ll be able to make your own insulated door in no time. Just remember, don’t rush the job and always measure twice and cut once!

Chloe Meltzer
Chloe Meltzer

Real estate agent and copywriter, originally from California. Chloe brings her real estate expertise into her writing to create effective and helpful home guides for you! When not writing or selling homes, she spends her time as a digital nomad traveling the world.

More by Chloe Meltzer