How to Seal Air Vents (Save Big on Your Energy Bill!)

Taking the time to seal your air vents ensures your home is thermally efficient, saving you a real lot of money each year on your energy bill. So what is the best way to seal air vents?

In order to seal air vents, you must apply caulk or expanding foam between the ducts and sheetrock. Adding weatherstripping to the edges of the underside of the air vent and around the inside of the vent cover creates a better seal, which further reduces air infiltration and makes the vent more energy-efficient.

There are so many benefits to sealing your air vents beside the financial savings, and I’m going to show you those benefits later on. But first, here is a step-by-step guide for sealing your vents.

1. Inspect the vents

Usually, it is impossible to visually tell that a duct is leaking, but there are several other ways that you can tell. One of the easiest ways is to inspect the vents and air returns to see if there are any cracks in the ductwork that leads to them.

If there are cracks in the ductwork or gaps between the floor and the duct, then the duct is leaking and the air is escaping from it. Sometimes, you might be able to hear a whistling sound which can also indicate that there is a leak in your ductwork.

2. Gather your supplies

You will need the following to seal your air vents:

  • Scissors
  • Caulk
  • Expanding foam (for larger cracks)

3. Caulk

To fix the crack in your air vent you will need to put a thin line of caulk between the ductwork and the plasterboard. If you have a large gap then you will need to use expanding foam to mend it.

You’ll need to take care if you are using expanding foam as it can be hard to remove from plasterboard if it gets onto it, and it can be quite messy to use.

4. Insulating strips

You can make your air vent more energy-efficient and reduce the amount of air infiltration by adding weatherstripping to the underside of the air vent. Quite often, builders don’t add these strips even if the air vents have already been caulked.

For that, I recommend this thick foamOpens in a new tab. which has adhesive on one side. You will need to measure it for size and cut each strip and then add them to the underside of the air vent cover.

Make sure you push the edges up against each other so that you can completely stop any air from leaking out. Once you have done that, you can replace the vent and continue to the next one and do the same again.

Benefits of sealing vents

When air travels through the air conditioning system it will move very easily and efficiently until it encounters resistance. The air vent cover provides resistance which then causes the air to exit through the openings in it.

However, when the air encounters resistance it can also be pushed out through any other openings in the ductwork, such as gaps or cracks, which is why it is always a good idea to inspect it regularly and repair any cracks.

Another benefit of sealing your air vents is that it will increase your home’s energy efficiency and reduce condensation in it. This is because the space between the sheetrock and the ducting will let the conditioned air into your attic, which then makes your air conditioning system less efficient and wastes energy.

If there is air leaking where the duct connects to the register then condensation can form when the cool air from the duct meets the warmer air in the wall cavity or attic.

If condensation forms on the register then it can travel across to the nearby drywall which can then be a breeding ground for mold. For example, mold is often found on the air conditioning system in bathrooms due to the amount of humidity in there.

Sealing your air vents can also prevent moisture from building up and therefore stop the growth of mold.

Check the air ducts for damage

It is a good idea to inspect your air ducts regularly for damage as they can often develop creases and cracks that let cool air out.

This can then cause issues with the quality of the air in your home, increased humidity in the air ducts, and can cause your air conditioning system to work much harder than it needs to, which can, in turn, lead to you having much higher energy bills.

Also, if your air conditioning system is installed properly then it will greatly improve the energy-efficiency of your home as ducts that haven’t been sealed properly can cause cool air to leak out into areas it is not needed.

It can also cause the same issues as above which can lead to you having to spend more on your energy and on possible repairs.

Therefore, you should check your entire air conditioning system if you think there is a problem with any of your ducts. You should check for any gaps in connections, cracks, or kinks.

It is also important to remember to even check ductwork in difficult-to-reach areas and in the attic. Even if you find an issue in one area you should check the entire system as there could be problems elsewhere too.

Signs that there are leaks in your air ducts

There are quite a few signs that can tell you that there are leaks in your air ducts, and they are as follows:

  • You have higher energy bills even though you haven’t been using anything extra.
  • Your home is not cooling or heating evenly.
  • There is more dust in your home than usual.
  • Areas of your home feel stuffy.
  • You can see kinks in your ductwork.
  • You can hear air leaking from your ductwork

If you don’t feel confident enough to seal your air vents yourself then it might be a good idea to call in an HVAC professional to do the job for you.

Benefits of sealing air ducts

Reduced expenses

One of the main benefits of sealing your ducts is that it will save you money by reducing the amount of energy you use – it can save you up to 30% off your energy bills.

Increased comfort

By sealing your air ducts your home will heat and cool much more consistently.

Extend the life of your HVAC system

If your air ducts are properly sealed then your air conditioning system will not need to work as hard, which reduces the risk of it becoming damaged or suffering from corrosion.

Improved air quality

Usually, your air conditioning system can become filled with dust, insulation particles, and fumes from cleaning products.

When your ductwork is not properly sealed, these can blow back out into your home, which can irritate existing health problems such as asthma and allergies. When the ductwork is sealed, the number of pollutants in your home are reduced and the air quality is improved.


Appliances in your home – such as water heaters and dryers – usually release combustion gases that end up running through your air conditioning system. If your air ducts are not properly sealed then these harmful gases can enter your home through back-drafting instead of being pushed outdoors.

Joshua Milton

I want to share everything I know about home improvement in order to help you. Whether you're a home enthusiast or an industry professional, I have the information that you need.

Recent Posts