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Why do you require an Air Barrier?

The leading cause behind moisture condensation concerns within the building is a temperature difference. However, it is pretty easy to handle with the right equipment like air barriers. It cannot regulate the temperature outside, but the temperature within can be to minimize pressure discrepancies.

The greater the temperature differential, the greater the drive through a wall. As a result, it worsens during the frigid winters. Temperature is what causes air and vapour leakage and simple heat loss via the building envelope.

The direction of the wind is also crucial. A high or low-pressure region is formed depending on the wind direction, pushing or drawing moisture through the building shell. It has a beneficial influence on the windward side and a negative influence on the leeward side. Depending on the way the wind blows, the walls exhibit a variety of effects.

What Are The Potential Sources Of Moisture Within A Home?

Moisture may enter a home through a variety of channels. Showers, dishwashers, and the inhabitants are examples of these. However, the residents are responsible for nearly 60% of all moisture created in the house.

Moisture travels through the envelope in three ways and passes through the structure inside or outside.

Diffuse flow circulates through an assembly, and as it cools, it changes to water, then to ice. This settling of the water might be an issue. This can be reduced or eliminated by introducing an appropriate material into the wall assembly. Every substance has distinct permeance, which influences the quantity of moisture that may flow through.

The other is through channels and channel flow. Moisture flows through and inside a wall assembly via air spaces and gaps between materials or components of a wall assembly.

Orifice flow is the third. Windows, doors, and structural features are examples of these.

The air barrier’s primary role is to restrict external air penetration into a structure and the exfiltration of internal air to the outside. This holds whether the air is wet or dry. However, air leakage can lead to moisture buildup in the walls, energy loss, and rain infiltration.

An air barrier differs from a vapour barrier in various ways. An air barrier prevents air movement via fractures in the wall, whereas a vapour barrier prevents vapour from diffusing through the wall.

In contrast to vapour barriers, which are often poly films, air barriers are systems. Furthermore, the air barrier is continuous, and all seams must be sealed appropriately.

Air Barriers Must Also Be More DurableAir Barriers Must Also Be More Durable

The three most essential aspects in air barrier design are as follows:

  • Continuity
  • Durability
  • Impermeability


Continuity entails more than simply being without gaps. Because the component that serves as the air barrier moves from wall to window and then the roof, continuity requires these assemblies linked together to guarantee that the airtightness of the envelope is not compromised.

Air Impermeability

An air barrier must have a high resistance to air passage but not to water vapour which is crucial. This is because if a material with high resistance to water vapour is put on the exterior of the wall, it will not let out any moisture trapped within the wall cavity.

Plywood or OSB is a prime example of this. Although these goods are not employed as air barriers, they behave as air barriers outside a structure. However, they also operate as vapour barriers, which is an issue. As a result, moisture is trapped within the wall assembly. Most construction rules now require plywood and OSD to be constructed with gaps at their joints to let the moisture escape.

These materials cannot achieve absolute air impermeability, such as glass, sheet metal, gypsum board, cast-in-place concrete, and an adequately supported polyethylene sheet. On the other hand, they provide significantly more excellent airflow resistance than porous materials like concrete blocks, fibreboard sheathing, and expanded polystyrene insulation. A second critical issue is that individual panels be connected to form an airtight assembly. For example, taping the connections between gypsum boards is quick and easy, as is lapping sheet metal panels with tape and sealing precast panels with rope and sealants.


The airtightness system must outlive the structure. To achieve this, the materials utilized must have an established track record, or the material must be placed in a way that allows for inspection and maintenance.

Durability is not an inherent quality of a substance; instead, it is determined by how a material interacts with a specific environment, such as moisture, temperature, ultraviolet light, and the presence of other materials.

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