How To Insulate A Mail Slot [5 Great Ideas]

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Insulating a mailbox may not be something you think about her regularly. It's common to assume that these slots are so small that they aren't worth insulating, but this isn't necessarily true. So how can you insulate a mail slot? And what materials can you use? We have researched the best ways to do this.

Here are some ways that you can insulate your mail slot:

  1. Seal and caulk the edges of the slot
  2. Use insulating foam
  3. Apply weatherstripping
  4. Install a mail slot cover
  5. Install a DIY insulation material

Insulating your mail slot can help prevent cool air from seeping inside your home. It can also prevent warm air inside your home from escaping to the outside, leaving the inside cooler than desired. Continue reading to learn more about ways to insulate your mail slot effectively.

A newspaper left in the mail slot, How To Insulate A Mail Slot [5 Great Ideas]

Ways To Insulate a Mail Slot

Before insulating your mail slot, ensure that the slot is correctly installed. This means ensuring that there are no cracks and gaps between the slot and the door and that all of the screws are tight and secured firmly on its top and the bottom.

A green door with gold plated fixtures and a gold mail slot

1. Seal and caulk the edges of the slot

Insulating your mail slot can help to prevent unwanted drafts and air leaks near the door area. If the slot has any holes or cracks around it, it'll be fairly easy for air to penetrate the opening.

The opening itself, even when closed, presents an opportunity for cold air to get inside your home and warm air to escape—though we'll address how to insulate this area in a moment.

However, one of the best ways to reduce this is to seal and caulk the edges of the slot properly. The easiest way to do this is to place your hand around the perimeter of the slot and feel for any cold drafts.

You may also be able to visually see any holes in the space between the sides of the slot and the door. If you do, take your sealant or caulk and apply it to these areas. Be sure to wipe down the area with a cleaning solution and dry it completely so that the caulk sticks properly.

Click here to see this caulk on Amazon.

2. Use insulating foam

You can also use expanding and non-expanding foam insulation to prevent air from getting inside of your home.

If your mail slot fits properly around the door, expanding foam may not be necessary. In this case, the non-expanding foam may be better. Apply the foam to all four sides of the slot to keep warm air inside during the winter (or cold air in the summer).

Click here to see this insulation foam on Amazon.

3. Apply weatherstripping

Another simple and easy way to insulate your mail slot is by applying weatherstripping. Weatherstripping is affordable, readily available, and easy to use on various surfaces. You can purchase weatherstripping made of open-cell foam, felt, vinyl, or different types of metal.

However, you may want to use a softer material such as felt or foam so that the mail slot flap is not difficult to open.

Weatherstripping typically comes with adhesive backing and can be applied after being cut to size. Felt weatherstripping can be especially beneficial, as it is typically thicker and denser—not to mention it's typically cheaper.

However, vinyl weatherstripping is more durable and resistant to moisture, which is great if you're applying it on the exterior of the slot. So, for example, if you're replacing the weatherstripping on the exterior of the slot, rubber or vinyl may be ideal, while felt may be better for the interior.

Click here to see this weatherstripping on Amazon.

4. Install a mail slot cover

Another option is to install a cover on the exterior of the mail slot. Mail slot covers help prevent drafts and precipitation from seeping through the mail slot, which is perfect for extreme weather conditions.

You can also add to their efficiency by including another layer of thin insulation (such as weatherstripping) between the cover and the top of the mail slot exterior.

They're also helpful in preventing potential intrusion from burglars and mail thieves by making access more difficult. You can find these covers at your local hardware store or online and have them installed in a matter of minutes.

Click here to see this mail slot cover on Amazon.

5. Install a DIY insulation material

You can also use materials such as pieces of heavy curtains, old comforters, or blankets as insulation materials for the back of the mail slot flap. Essentially, you can use any dense, thin fabric to insulate the mail slot.

However, it's best to use these materials on the interior of the flap to prevent them from becoming wet from moisture from the outside. It's also best to use them in conjunction with an exterior slot cover on the outside to prevent water and precipitation from reaching them.

How high should mail slots be?

Homeowner document and other document stuck in the mail slot

Most mail slots in the US will have an average height of about 30-40 inches up from the floor. This height makes and easier for postal workers to easily slide the mail through the slot without having to bend over too low.

Is a mail slot in the door safe?

Mail slots located on doors can pose a significant danger when it comes to accessing your home. For example, potential thieves can just slide a cord or hooked wire inside the slide to unlock the door and gain access to your home.

However, there are ways to prevent this and secure the mail slot without removing it completely. Here are a few tips on how to do it:

Install a mail slot cover

One of the quickest ways to make your mail slots less appealing to burglars is to simply cover it up. Mail slot covers can be bought at a local hardware store and then drilled into the door to plug up the mail slot.

There are different types of covers to choose from, though if you live in an area with extreme weather conditions, it's best to choose one made of insulative, weather-friendly materials such as vinyl or rubber.

Install a second deadbolt

When you install a mail slot in your door, it creates a hole that can weaken the integrity of the door. This can make the door easier to kick down during a burglary. One way to prevent this is to install a second deadbolt.

Another deadbolt can help to provide protection and support if an intruder tries to break into the door. When shopping for deadbolts, look for ones with consistent customer reviews and impressive safety standards.

Click here to see this deadbolt on Amazon.

Install an air vent diverter

You'll normally find air vent diverters on the side or the back of a home's foundation. These are used to vent air from home drying machines and other appliances. Surprisingly, they're also a great deterrent when it comes to protecting mail slots from burglars.

This is an effective and fairly cheap way to prevent a burglar from easily sliding their hand in your mail slot and reaching up to access the lock. You can install the air vent diverter in as little as 15 minutes, and you can find them in local hardware stores and online.

Click here to see this air vent diverter on Amazon.

Can you put a mail slot in a glass door?

It's highly unlikely that you'll find a glass door that comes equipped with a mail slot directly in the glass portion of it. It's also extremely difficult to cut into a glass door without it breaking—unless you have special tools designed for this type of task.

The best way to get a mail slot in a glass door is to purchase a door that has a metal or wood partition near the middle or bottom. You can install the mail slot in this part of the door.

You may often find glass doors that already have these partitions and included mail slots as well. You'll see these a lot in professional buildings.

Are mail slots a standard size?

A gold plated mail slow and door knob on the red door

Mail slots in the U.S. are typically about 9 inches wide and 3 inches long. This slot size is large enough to accommodate standard letter and magazine sizes. However, you can find customized slots that are larger.

Wrapping things up

A newspaper left in the mail slot

We hope this post has helped illustrate the various ways that you can insulate your mail slot. Remember, it's best to use water-resistant materials when insulating the exterior of the slot.

Before you go, be sure to check out these other posts:

R13 Insulation: Use, Thickness, Cost, And More

Does Yellow Insulation Contain Fiberglass?

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