Air Barriers

Air Barrier Systems are used to enhance building performance. The primary purpose of an air barrier system is to negate the air from leaking into and out of the building enclosure. Using a cavity wall air barrier ensures the occupants are more comfortable, are provided draft free space, and are protected from pollutants from entering the building. These pollutants can range from pollens, suspended particulates and odors to biological contaminates o the other side. Air barrier systems are essential for getting rid of moisture that gets behind masonry walls. Typically installed on the outward-facing side of a structural wall, air barriers help keep water out of the building envelope.

F.W. Walton Roofing is certified through the Air Barrier Association of America (ABAA). We can provide a complete system including spray applied, roller applied, or sheet applied materials. Air barriers must be a complete system.

About Air Barriers from Air Barrier Association of America

Air Barriers control the unintended movement of air into and out of a building enclosure.

Air barrier systems are comprised of a number of materials which are assembled together to provide a complete barrier to air leakage through the building enclosure. The building enclosure includes all six sides of the building and may include separations within a building. This system essentially “wraps” the building shell and ensures that it protects the building from the effects of air leakage. Air leakage can have detrimental effects on how a building functions and reduces the life span of a building.

A properly functioning air barrier system provides a barrier against both the air leakage and the diffusion of air caused by wind, stack and mechanical equipment pressures. For the occupants to be comfortable, we condition the air in buildings. In summer or in cooling climates, we normally cool and dehumidify the air to a lower temperature and humidity that the exterior environment. In winter or heating climates, we normally heat and humidify the air to a higher temperature and humidity than the exterior.

When this conditioned air leaks out of a building and unconditioned air leaks into a building we must then use additional energy to then condition this air. Air leakage can result in an increased use in energy costs of up to 30-40% in heating climates and 10-15% in cooling costs.

Buildings which have a properly installed air barrier system can operate properly with a smaller HVAC system as the mechanical engineer does not have to compensate for a leaky building. In some cases, the reduction in mechanical equipment size and cost can offset the cost of the air barrier system.

Air barrier systems also provide a barrier to pollutants entering either the building or the building enclosure. Water vapor, suspended particulates, dust, insects, smells, etc are all pollutants which we want to keep out of either the building in general or the building enclosure. Water vapors that leaks into the building enclose (from the inside in heating climates and from the outside in cooling climates) can condensate and forms liquid water a key ingredient to corrosion and the potential development of mold.

WHY USE AN AIR BARRIER SYSTEM?

  • Reduces building enclosure moisture problems
  • Improves indoor air quality
  • Reduces building heating and cooling costs
  • Reduces greenhouse gas production
  • Improves acoustical isolation
  • Isolates the indoor environment
  • Results in sustainable, durable buildings

Open-Cell and Closed-Cell Foams: What’s the Difference?

The importance of distinguishing between the two types of spray polyurethane foam cannot be understated. When it comes time to insulate a home or commercial building, you must opt for open-cell foam or closed-cell foam, or a specific combination thereof. Each type of foam distinctly impacts project costs, application methods, and building performance. There are two major factors distinguishing closed-cell and open-cell foams: structure and density.

Cell Structure

The structure of open-cell foam consists of tiny bubbles or cells that aren’t fully encapsulated–they are broken, torn, ripped, etc. Because they’re broken, air fills the open space inside the bubble, which results in a soft, spongy material.

Closed-cell foam differs in that every bubble or cell that makes up the foam is completely encapsulated and packed tightly together. The bubbles aren’t filled with air, but rather a gas that aids foam expansion and insulation properties. This results in an altogether harder, stronger material than open-cell foam.

The blowing agent, which aids in forming the bubbles or cells that make up SPF’s foam structure, is usually water for open-cell and high-R-value chemicals for closed-cell.

Material Density

Closed-cell foam is roughly four times as dense as open-cell for insulation applications. To ascertain foam density, one cubic foot (cu. ft.) of foam material is weighed. Open-cell tends to be roughly 0.5 lb./cu. ft. in density, whereas closed-cell ranges from 1.7 to 3.0 lb./cu. ft. in density, or even higher for certain applications. (Note: these density figures are rough averages. Every SPF product will vary based on its formulation.)

Properties

Of the two types of SPF, closed-cell foam is stronger, is a better insulator, and is more resistant to the transmission of air and water vapor. Because closed-cell foam is denser, however, it requires more chemical material per unit volume than open-cell, and is therefore more expensive to install–even if comparing the cost-per-R-value. Open-cell foam, while offering fewer overall benefits, is a superb sound-deadening material and is still a superior insulating material compared to fiberglass and cellulose.

Insulation Value

R-value is a way to denote a material’s insulating properties and the higher the number per unit thickness, the better the insulation value. Closed-cell spray foam has an R-value of about 6.0 per inch (R-6), while open-cell SPF comes in at roughly R-3.5. (Note: these R-values are rough averages. Every SPF product will vary based on its formulation.)

Usage

The deciding factor in opting for either open-cell or closed-cell foam is frequently based on application-specific performance characteristics like the structural integrity, control of water vapor, and the amount of available space to install the foam. For example, closed-cell foam is really the only option for residential roofing adhesive, due to its strength characteristics.

In addition to the situation-specific considerations, there are more general considerations to make when deciding between open-cell and closed-cell foam. For instance, open-cell is typically inappropriate for below-grade applications or any applications where it could come in direct contact with water, while closed-cell foam isn’t advisable for sound-deadening applications, as open-cell foam is superior and less expensive.