The Importance of Air Barrier Systems

An air barrier system is a critical component of a building. It helps control airflow and prevent drafts, leaks, and energy loss. An air barrier system can make a big difference in a building’s performance when properly installed. Most modern air barrier systems are made up of a combination of materials, including membranes, sealants, and caulks.

Here’s a brief introduction to how these systems work.

Air barrier systems are essential for two primary reasons. First, they help to control the flow of air through a building. This is important for several reasons. Airflow can cause drafts and cold spots, making a building uncomfortable to live or work in. In addition, uncontrolled airflow can lead to energy loss, increasing a building’s operating costs.

Second, air barrier systems can help to prevent leaks and moisture infiltration. Leaks can cause various problems, including mold growth, water damage, and energy loss. Moisture infiltration can also lead to mold growth and other problems.

Certain materials are better than others at preventing airflow and moisture infiltration. In general, air barriers should be made of materials that are impermeable to air and water. Your choice of air barriers will depend on the climate, the building’s design, and other factors.

How Air Barrier Systems Work

Your building’s air barrier system is one of its most important defenses against the weather. It keeps rain, snow, and wind from entering the building envelope that could damage the building’s structure, insulation, and finishes.

Air barrier systems are typically made up of several components:

  • Exterior Cladding

This includes siding or roofing materials and is often the first line of defense against weather.

  • Air Barrier Membrane

This is a thin layer of material that separates the interior of the building from the exterior environment. Air barrier membranes can be made from materials like plastic, metal, or fabric. Depending on your commercial building’s design, the membrane could be on the exterior or interior of the building.

  • Window and Door Frames

These frames play an important role in air barrier systems by sealing off the opening where the wall and roof meet. An airtight seal around the doors and windows is essential to keeping the weather out.

  • Insulation

Insulation is critical in preventing heat loss in the winter and heat gain in the summer. In order to be effective, insulation must be installed in the correct location and have an airtight seal around it.

  • Building Envelope

This includes the walls, roof, windows, and door of a building. All of these components work together to create a barrier against the weather.

Air Pressures That Cause Infiltration And Exfiltration

The most common way for air to leak into or out of a building is through the cracks around windows and doors. But pressure differences between the inside and outside of the building can also cause air to infiltrate (enter) or exfiltrate (exit).

  • Wind Pressure

The wind can create high pressure on the side of a building facing the wind. This pressure can cause air to leak in through any cracks or openings in the building envelope. Often, the wind pressure is the biggest contributor to air infiltration.

Additionally, the wind can also create a suction effect on the side of the building, facing away from the wind. This suction can cause air to leak out of the building through any cracks or openings.

When the temperature difference between the inside and outside of a building is large, it can create a pressure difference. This pressure difference can cause air to infiltrate or exfiltrate through cracks and openings in the building envelope.

  • Stack Effect or Stack Pressure

Warm air rises, and cool air falls. This natural phenomenon can cause air to leak into or out of a building through the roof and windows. This air pressure is also sometimes referred to as the chimney effect. In winter, the stack effect can cause warm, moist air to enter the building and condense on the cold surfaces inside. This can lead to moisture damage and mold growth when not addressed immediately.

  • HVAC Pressure

The heating, ventilation and air conditioning (HVAC) system in a building can also create pressure differences that cause infiltration and exfiltration. This happens when the HVAC system is trying to equalize the pressure between the inside and outside of the building. Often, this pressure differential is the result of an HVAC system that is not properly balanced.

All three of these pressure differences can cause air to infiltrate or exfiltrate a building—understanding how these pressures work is essential to designing an effective air barrier system.

Materials Used in Air Barrier Systems

Air barriers are typically made of materials that are durable, weather-resistant, and have low permeability. Materials for air barriers can include:

  • Rigid Foam Insulation

This insulation is made of polystyrene or polyurethane and is a popular choice for air barriers. It is often used in commercial and institutional buildings, as it is both durable and affordable.

  • Fiberglass Insulation

Although it is not as common as rigid foam insulation, fiberglass insulation can also be used for air barriers. It is made of glass fibers and is effective at stopping air infiltration. Fiberglass is often used in residential buildings, although smaller commercial buildings may also use it.

  • Extruded Polystyrene (XPS) Insulation

XPS insulation is made of polystyrene and is a good choice for air barriers in colder climates. Because it is extruded, it has a higher R-value than other types of polystyrene insulation. It is also moisture-resistant and can withstand extreme weather conditions.

  • Sheathing

Sheathing is the material that covers the exterior walls of a building. It is typically made of plywood, oriented strand board (OSB), or fiberboard. The sheathing is an important part of the air barrier system, as it helps to keep out moisture and pests.

Vinyl siding is a popular choice for sheathing, as it is affordable and durable. It is also resistant to moisture and pests, making it a good option for air barriers.

How to Choose the Right Air Barrier System for Your Building

There are numerous factors affecting the choice of an air barrier system for a building. The most important factors to consider are the climate, the type of building, and the budget.

  • Climate

In cold climates, it is important to use an air barrier that is moisture-resistant and can withstand extreme weather conditions. XPS insulation and extruded polystyrene foam are good choices for this type of climate.

In hot climates, it is important to use an air barrier that is resistant to heat and moisture. Vinyl siding and other materials with a high R-value are good choices for this type of climate.

  • Type of Building

The type of building also affects the choice of an air barrier system. Taller buildings require a different type of air barrier than shorter buildings. Commercial and institutional buildings often have taller walls and need a stronger air barrier system.

  • Budget

The budget is also an important factor to consider when choosing an air barrier system. Some materials, such as XPS insulation, are more expensive than others. It is important to find the right balance between cost and effectiveness when choosing an air barrier system.

Proper Air Barrier System Installation

The system mainly relies on the installation to be effective. The air barrier materials must be installed in a way that prevents air infiltration.

Some tips for proper installation include:

  • Ensuring that the air barrier materials are sealed tightly against the building’s walls
  • Using weather stripping and caulk to seal cracks or openings
  • Installing the insulation correctly so that it forms an airtight seal
  • Using proper flashing and trimming to seal around windows and doors
  • Having a properly sealed roofline
  • The air barrier membrane should be continuous across all seams and joints
  • All components of the air barrier system should be compatible with each other
  • The system should be tested after installation for leaks
  • Building codes vary by location, so it is important to check with your local code enforcement office to ensure that your air barrier system is installed correctly.

An experienced commercial contractor can help you to select and install the right air barrier system for your building. The process starts with a comprehensive evaluation of your building to identify any air infiltration points. Once the infiltration points are identified, they may suggest the best air barrier material for the job. Depending on the climate and other factors, the contractor may also recommend a specific installation method.

The contractor will then install the material in a way that ensures a tight seal against the building’s walls. This requires precision and attention to detail, so it is important to choose a contractor who has experience with air barrier systems.

Testing the system after installation is also important to ensure that there are no leaks. Leaks can cause moisture and insulation damage, so it is essential to catch them early.

Never attempt to install an air barrier system on your own – it is a complex process and requires specialized knowledge.

Final Word

An air barrier system plays a huge role in the efficiency and durability of a building. It is important to select the right system for your climate, type of building, and budget. This ensures that the air pressure can be easily controlled within the building while keeping the elements out. Proper installation is key to the effectiveness of the system, so it is important to choose a contractor who has experience with air barrier systems.

Controlling air pressure relationships between different areas of a building is essential to creating a comfortable and energy-efficient space.


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