What is The Purpose of an Air Barrier?

Proper airflow in the home is of the utmost importance, as it has a direct influence on both heat and moisture flow. Airflow is responsible for carrying moisture through the materials, walls, ceilings and floors of your home, and this impacts the longevity and performance of these surfaces.

With all this information in mind, we can come to understand the necessity for air barriers in our home environment. One of the key strategies to control airflow is using air barriers. The airflow in a home affects indoor air quality, as well as thermal energy use, two very important factors of a house’s internal environment.

But what is an air barrier exactly? Lucky for you, we’ve done our homework and can explain how air barriers work to keep homes and homeowners happy.

Here's everything you need to know about air barriers

What is an air barrier?

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Air barriers are a designed system of materials that have been constructed to control airflow between conditioned and unconditioned spaces. Conditioned air is the air inside of a space, while unconditioned air is air coming from the outdoors.  Air barrier systems are in place to resist the air pressure differences that act on them. For this reason, rigid materials such as gypsum board, plywood or oriented strand board work as effective air barrier systems if joints and seams are correctly sealed.

Spray foam is another effective air barrier system when it is externally applied over structural elements of the home or internally applied within the cavity systems. The system itself can be located anywhere within your home's enclosure, either on the exterior, in the interior or any location in between these two poles.

In areas with colder climates, air barrier systems are built into the interior of the home work to control the exfiltration of exterior air, preventing wind-washing through insulation systems in your home. Wind-washing is the movement of unconditioned air around your home, diminishing the thermal performance of your house. Therefore, in those colder months of winter, air barriers are of the utmost importance. 

What should air barrier systems do?

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An air barrier system's most important job is to be impermeable to airflow. Water vapour is carried into our walls through air leakage, and this moisture can easily lead to drywall deterioration or walls in the home.

Open spaces provide space for insects and rodents to enter and nest. Not only this, without air barriers, your home’s energy, heating and cooling costs will greatly increase. Further, pollutants and debris can collect inside walls, causing further damage and deterioration. Therefore, the overall goal of the air barrier is to slow the migration of air through the walls and surfaces of your home.

Air barriers should be made durable enough to withstand any air, heat and moisture forces that they come up against, and should be expected to withstand the lifetime of your home. The essential components that an air barrier should possess are that they need to be continuous, with no visible gaps, cracks or openings. They should obviously be impermeable to the leakage of air, as well as rigid and supported in both directions. As we’ve stated, they should last the lifetime of the building, and be accessible and repairable if damage should occur.

How to determine if you need air barriers

The most common air leaks happen at the seams and cracks between different materials, an example of this is where the floor meets the wall, or where walls meet ceilings.

Although most homeowners might think that the gaps around doors and windows are the most common contribution to air leakage, this would be incorrect. The most significant air leakage comes from areas that are hidden. These hidden leaks, sometimes referred to as “thermal bypasses,” will not cause obvious drafts and therefore, most homeowners are unaware that they exist.

Areas that may often be poorly sealed are as follows: holes cut for plumbing underneath tubs and showers, cracks between floors and baseboards, plumbing vent pipes, fireplace surroundings, cracks between ceiling-mounted ducts and drywall, incorrectly weather-stripped attic hatches as well as cracks between partition top plates and drywall.

Tracking down these air leaks can be tricky, especially for homeowners who are unfamiliar with the process. For this reason, it is important to ask an expert whether your home requires air barriers. 

If you notice that your attic is a conducive place for air infiltration, check out our article on eco-friendly attic insulation solutions!