Vapor barrier installation: How To (AVOID Doing This!)

Installing a vapor barrier takes some work but it’s essential for maintaining your walls and preventing moisture intrusion into your home. When we shower or use certain appliances, we create additional moisture in the home. The airflow can also create this. During winter, it is a layer between the cold outside walls of your home and the hot inside walls. During summer, it works the other way around. Temperature differences and moisture can cause dangerous mold and moisture if it is not properly taken care of. A vapor barrier helps us with avoiding this.

 It’s also a great opportunity to upgrade your home’s energy efficiency, improve your indoor air quality, and smooth out your walls.  Read on to learn more about vapor barriers and how they can help you in your home installation.  

There is some discussion about the need for vapor barriers. Vapor barriers are not needed in some places in the USA as there is not enough moisture in the air to justify installing them. Other people argue that vapor barriers are not needed at all but this is not a common view amongst builders. 


How a vapor barrier protects your home

When it comes to energy efficiency upgrades and maintenance, a vapor barrier is one of the most significant solutions you can add to your home. These barriers work by creating a barrier between the wooden construction and drywalls  When properly installed, a vapor barrier is able to hold moisture away from the wood as this could lead to mold.

Mold can damage your walls and lead to dirty air. We have to avoid this at all costs. Especially behind walls, this should be mitigated as it can be present for a long time without any indications. This is why builders have started to use vapor barriers as they noticed that a lot of homes contained mold after a few years.

There are different types of vapor barriers: asphalt-coated paper, polyethylene plastic, plywood with external glue, vapor barrier paint, and aluminum foil. Check your local code to see what is allowed. The materials have evolved in recent years so make sure to use the right one for your climate. 

How to install a vapor barrier

Before you start installing your vapor barrier, you’ll want to consult your vapor barrier manufacturer’s instructions for specific installation instructions. There are different systems and each one has its unique requirements. However, here are a few general guidelines to follow. Some systems have to be installed outside the home, here we are going to focus on vapor barriers that have to be installed inside.

Preparing the installation

Start with checking your insulation as you can’t change this anymore when the vapor barrier is installed. Remove any nails that are sticking out by using a hammer. 

Vapor barrier often comes in rolls. Mention that you need a vapor barrier when you buy it as there are several types and systems. 

You need the following tools:



-utility knife

-glue (or acoustic sealant) and caulking gun


Installing the vapor barrier

Once you have found the right vapor barrier, you can use a stapler to attach it to the studs. You can start from the bottom to the top of the wall. This allows you to cover yourself with the vapor barrier so that you don’t get any dust on yourself. Make sure that the barrier is not wrinkled. It is not needed to use a ton of staplers, just make sure that it is properly attached. If the material is too long, you can cut it with scissors or a knife. 

You might have to cut your plastic so that it fits around the joists. A knife can be used for this. Just cut it as wide as the distance between the two joists. If there is too much material, you can cut that away. Make sure that you don’t trip over the plastic. Leave some room in the corners so that the material won’t tear when you are installing it. Just make sure that it doesn’t wrinkle or sag too much. 

To attach the barrier to the top, we are going to use special glue. This is a messy material so make sure that you find the correct angle to avoid drips! Make sure that every hole is completely sealed once you are done. Only staple in this area once the glue is applied. Otherwise, it can be difficult to get the glue behind the vapor barrier. 

You can use this glue in the corners as well to get things sealed. Using tape is also an option. We just have to make sure that it is properly sealed. If you make a tear in the material, you can use tape to close it again. 

The final step is to remove excess material. We are going to inspect the installation to make sure that the vapor barrier is properly installed. 

Finishing touches before the drywall goes in

Once this is done, we can install the outlet boxes. Cut the plastic open (inside of the box) and then apply specialized tape to make sure that the vapor barrier is properly attached to it. You can remove the plastic or fold it open around the outlet. Tape around the exposed parts. This is an essential part of the installation as we have to avoid moisture around our electrical boxes. 

At the bottom, we are going to use tape as well to make sure that everything is properly sealed. Push the tape so that it properly adheres to the wall. Remember, that we need a perfect seal. 

Around the windows, we are going to use glue and staple the barrier to the wood. 

Getting all the parts of the wall covered is essential so do a final inspection. That is it!

Only use one vapor barrier as installing multiple over each other can lead to problems.

In a lot of instances, an air barrier is added as well. This barrier makes sure that the airflow is controlled and doesn’t create problems. The terms air and moisture barriers are often used interchangeably but often different materials are used for each. 

To conclude, we can state that vapor barriers (or more precisely air barriers) are essential parts of a wall. They make sure that we don’t have mold in our walls. Mold can decrease the quality of the air in the home and damage our walls. For this reason, it is important that we avoid moisture in our walls as this leads to mold. Vapor barriers are used to make sure that this doesn’t happen. We have outlined how to install this barrier in this post. Keep in mind that the technologies and materials are always changing so it can be a great idea to have a discussion with your builder to see what they recommend.