How to Properly Insulate a Window AC Unit

As springtime becomes summer, you might want to use your window air conditioning unit as temperatures rise. However, if your AC unit isn’t properly insulated, it might not keep your apartment as cool as you want. Below, learn how to properly insulate a window AC unit in your apartment. 

Why insulate your window AC unit?

If your window AC unit is not properly insulated, you might be inclined to set its temperature lower since it may seem to not be working well. A poorly insulated window AC unit can thus raise your energy bill. If you notice any cracks around your window AC unit, it’s best to fill the space between the top and bottom window panes to avoid hot air and pests entering your apartment.

Luckily, many air conditioners come with insulation foam that you can cut and shape to fit your apartment’s window. Window AC units also come with plastic curtains that slide out from the sides, though these don’t necessarily stop hot air from coming into your apartment. They’re better at preventing pests from entering. 

How to Properly Insulate a Window AC Unit

How to properly insulate your AC window unit

If your window AC unit did not come with insulation foam or its insulation is worn out, you can easily insulate the unit with a few supplies from the home improvement store. Once you have your supplies, follow the below steps:

1. Look for cracks around the top of the unit

Even if your window looks like it’s tightly closed and fully securing your AC unit, sometimes there’s a little space between the unit and the window. Outside air can enter your apartment through these cracks. 

2. Check your window sash

It’s best to check your window sash area to identify any insulation problems. Look whether the accordion side flaps are properly filling in the cracks. If there’s a single crack, you may be able to seal it temporarily with duct tape. Even if there are no cracks, you should replace the flaps If they look yellowed or worn. 

3. Clean the unit before insulation

It’s best to remove dirt, dust, and grease from your AC unit. This way, you ensure that your unit properly adheres to your window, thus making your insulation effective and long-lasting. 

4. Use caulk on the outside of the unit

In some cases, you can fix insulation issues with caulk. It’s best to use caulk outside the unit to seal it in place and reduce the chance of air flowing in and out. To make sure the caulk insulation is effective, caulk the outside of your window AC unit when the weather is dry and cool. Experts recommend using caulk when it’s about 40 degrees Fahrenheit outside. 

You can press rope caulk into gaps around your window AC unit. If you have large gaps, you may need to press two pieces of rope caulk around the outside of your unit to properly insulate it.

5. Use spray foam, but do so with caution

If you’re not planning to remove your window AC unit during the winter months, you can use spray foam to effectively seal and insulate gaps. Spray foam is highly effective at sealing cracks, but you’ll need to use it cautiously. It sets almost immediately upon application, and it can be extremely difficult to remove.

What other AC unit insulation tips do you have? Sound off in the comments!

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