How to weather seal a window air conditioner

Weather sealing your window air conditioner with insulation foam can ensure you have an airtight seal around the unit, where heat cannot escape the space easily.

Home air conditioning systems are great for cooling your home in warmer, more humid climates. Your air conditioner cools the rooms in your home by ensuring that cooler air is released while warmer air and humidity is extracted from the room and dispelled or vented outside.

In colder seasons, when an air conditioner is no longer required for cooling purposes, it is essential to protect your window air conditioner and your home from the cold and any air leaks or gaps that exist where your window AC unit is installed.

Weather sealing window AC units

When winter arrives, there is no need to use an air conditioner for cooling purposes. If you have a window air conditioner, it is important to prepare for the winter season by inspecting all the areas around your window unit and identifying any possible gaps in the window.

You should weather seal them to avoid dealing with air leaks that allow cold air to enter the house from the outside and warm air to escape to the outside. This can make it difficult to keep warm.

How to weather seal a window air conditioner

The process of weather sealing is also known as insulating. It seals any gaps around the window unit.

Weather sealing your window air conditioner in winter keeps the unit safe during the colder seasons and prevents the loss of heat due to the open spaces around the window unit.

To weather seal your window AC for the winter, you need to buy a flexible window air conditioner foam seal, which you use to fill up and seal any gaps you may find. You can find a range of insulating foams on Amazon.

Identify any gaps you can find that need sealing, then clean the areas to make it easy for the adhesive of the foam seal to stick securely. Measure the length and width of both the sliders to determine how much foam is needed.

Cut the foam according to your measurements and always try to mark a longer piece than you need. Not cutting a slightly longer piece or a piece that is long enough does not help in preventing air leaks effectively.

For your window unit you will need to have three panels cut out. Stick each panel of foam to the air conditioner and the sides (use duct tape to secure them better as adhesive might not be strong enough in some cases).

Some people choose to seal their window unit from the outside. Some of the covers available on Amazon are:

Insulation tools Description Amazon Price
Forestchill insulation foam

Buy it on Amazon
·   Premium foam seal tape made of NBR and PVC foam

·   Environmentally-friendly, flexible, and soft

·   High resilience to compression and deformation

·   Excellent cushioning properties and prevent vibration and noise effectively

·   Strong backing and waterproof adhesive to stick to surfaces

Afeion insulation cover

Buy it on Amazon
·   Fit for most 3 000 to 7 000 BTU window ac units

·   High-quality 420D waterproof material

·   Protects unit from wind, rain, snow, and ultraviolet rays as well as dust

·   Blocks cool air entering the room and prevents hot air escaping

·   Two adjustable straps with buckle and extra internal drawstring at the bottom


How to cover the outside unit

For extra protection, some people choose to weatherise or cover the outside of their window air conditioners, though this is an optional step in protecting your air conditioner from the cold.

You can do this by using the foam to create a foam box and covering the outside portion of the unit on all sides. This helps increase insulation and keep cold air out.

Some people also remove the window AC’s outer cover and tape a plastic bag around the unit’s inner components and return the cover. This provides added protection from the effects of the rain.

Using an insulation cover

Another way to insulate your window air conditioner is to purchase an insulation cover for the outside section of the unit. These can also be found on Amazon in many different sizes.

A drawback of these covers is that some do not cover the sides of the unit, so looking for covers that cover the sides is best as a large portion of heat loss occurs through the spaces on the sides of window units and not the AC unit itself.

A cover should not be your only solution, instead it should be an additional measure.

How to check for air leaks and how insulation helps you

Checking for air leaks can be difficult as it is not easy to see the smaller gaps.

An easy way to identify these gaps is to light a candle lighter, hold it indoors near the window AC unit, move the burning lighter around the perimeter of the window unit and where there is an air leak, you will see the flame flickering.

Weather sealing your window air conditioner helps you save money on your utility bills when heat is not lost in the heating process.

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