Air-Barriers in Green Building

The Control of Air Flow

Air Barrier Materials  

Air barrier materials are defined by their air permeance. Air barrier materials are combined with air barrier components to form air barrier assemblies. These assemblies are then connected to form complete air barrier systems. Air barrier material types for green homes include: 

Air Barrier Systems

Air barrier systems consist of numerous materials which are assembled to provide a complete barrier to air leakage through all six sides of the building enclosure. They control the movement of air in and out of buildings. The air barrier system is the primary air enclosure boundary that separates indoor, conditioned air from outdoor, unconditioned air. 

This system essentially “wraps” the shell of the home and protects it from the effects of air leakage. Air leakage can have detrimental effects on how a home functions and even reduces the life span of the structure. Air leakage must be reduced in a green home.

A properly functioning air barrier system provides a barrier against both the air leakage and the diffusion of air caused by 

• Wind Pressure
• Stack Pressure (sometimes called chimney effect or buoyancy)
• HVAC Fan Pressure, although this is not a particularly important problem in warm climates like the Dallas-Fort Worth.

Air barrier systems also typically define the location of the pressure boundary of the building location. In multi-unit construction such as townhouse/apartment units, the air barrier system separates the conditioned air from any given unit and its adjacent unit or units. It is also the fire barrier and the smoke barrier which separates units and must meet the fire-rating requirements.  

There are many types of air barriers to choose from, and there are many important factors to consider when determining the best barrier for a green building. The complete air barrier system is comprised of materials and assemblies, each with their own performance requirements.

A well-designed and efficient air barrier system will:

• Be impervious to air flow,  thus controlling air infiltration and exfiltration.
• Maintain constant air pressure.
• Be continuous over the entire building envelope or continuous over the enclosure of any given unit in multi-family construction.
• Reduce HVAC systems.
• Reduce home energy consumption
• Control moisture within the building envelope.
• Prohibit the growth of mold.
• Reduce harmful air pollutants.
• Protect the health of the home's  occupants.
• Be durable during construction.
• Be durable over the lifetime of the home.
• Lower noise coming from outside the home.
• Will make all components, including light fixtures, airtight when installed through the air barrier.

One way to test the effectiveness of the air barrier system is with a portable pressurization fan which is also known as the "door rater" test or "blower door" test. This test is generally the first step in renovating a home for energy-efficiency.

In summary, air barrier systems are essential components of the home enclosure. They control concentrated condensation and the associated mold, corrosion, or rot, they improve durability & sustainability, and they allow reduction of the HVAC system when the "fudge factor" covering infiltration and other unknown factors is reduced or eliminated.

Do you need a green builder/remodeler
 in North Central Texas 
or the Dallas-Fort Worth area? 
Contact Terry Jensen 
972 251-1532 or 817 545-0140