Fechino Files: A little Extra Trade Information

Words: Steven Fechino

As the masonry trade continues to improve and develop, so do associations, terms, and products. I meet many people in different parts of the trade who like to speak in acronyms, test and standard names, and sometimes associations that some know a bit about. However, many do not encounter these regularly and can get lost in the middle of a conversation. Personally, this drives me nuts because our conversations aim to exchange information, not to overwhelm someone by showing how much we know, leaving one of the participants confused. Here are a few air barrier terms that may help with the confusion.

Building systems have changed since I began in the trade. Once a residential home was framed, bituminous board covered the outer substrate, and plywood reinforced the corners. Many houses were constructed without base or window flashings, air and/or vapor barriers, weeps, and transition tape around the windows. Why? Because 40 years ago, many versions of the products we use today were not developed or even invented. We would not build like this today, but buildings from the past still perform well, in part due to the changes in basic materials and section details we use today.

Here are some products and terms that may be useful to you when discussing the building envelope system of a building. The building envelope focuses mainly on moisture control and waterproofing.

Rainscreen Association in North America (RAiNA) is an organization that promotes the use of rainscreens in the exterior wall of a structure. RAiNA consists of several committees that understand the rainscreen industry and write code and standard compliance documents that can be considered when updating the International Building Code (IBC) and International Residential Code (IRC).

Air Barrier Association of America (ABAA) is also a membership organization that promotes the proper application of air barriers in construction. ABAA is a professional source for standards that govern design knowledge, and inspector and installer knowledge certification. ABAA’s umbrella for the air barrier industry encompasses fluid-applied barriers, self-adhering and mechanically applied membranes, board stock, and the spray foam industry. Training and testing by ABAA allow one to become a Certified Air Barrier Specialist with proficiency in project design, on-site testing, material and method detailing, and site requirements.

Rainscreen has more than one definition:

Rainscreen can be described as a complete system found in sections that extends outward from the exterior sheathing to the outer face of the veneer.
As a drainage product, it is commonly referred to as a fabric that is heat-applied to nylon woven into structured strand fibers. This system consists of many small strands, creating approximately ¼-inch thick material, capable of breathability and moisture drainage.

Rainscreens can be made of several materials, such as masonry, metal panel, and wood veneer, but for our purpose, I will keep the discussion focused on masonry. Rainscreen material is useful to the masonry industry because it maintains a consistent, non-mortar-clogging air space that is very easy to handle, allowing for easy installation. Rainscreens are considered weather-resistant barriers, allowing the end user to apply rainscreen material directly to the first layer of a weather-resistant barrier, creating the two-layer system.

Air Barriers define a product found in the section of a wall, but they also serve as a general term used to talk about house wraps, WRBs (weather-resistant barriers), air and vapor barriers, air and vapor permeable barriers, fluid-applied and membrane waterproofing. I find it is a good idea to slow down most conversations that discuss air barriers to ensure that you are both talking about the same thing. This may not be a problem you have to deal with, but it has happened to me.

House Wrap, typically made of synthetic material, is available in rolls ranging from 36 inches to 11 feet. House wrap, also known as WRB, is typically applied early in the project to prevent exterior liquid water from entering the interior space. A second layer of WRB is later applied to better seal unwanted moisture that enters the building cavity and reduce air passage between the cavity and the interior space. Keene, Inc. has just developed a drainable house wrap that will be available before the first of the year. It creates a drainage plane without using valuable cavity space. House wrap is not the only material that can be used as the second-layer WRB material; LathNet and dimple board can also be used.

Membrane Waterproofing may not be encountered often by contractors handling only masonry projects, as it is typically found in specialty locations such as balcony waterproofing, below-grade waterproofing, and many roofing conditions. Membrane waterproofing is generally sold in roll form and has a self-adhering side that is part of a system when applying. It is impermeable to water, making it a perfect choice for its intended application. Membrane waterproofing is not universally used as an air barrier because it is non-vapor-permeable, a feature desirable in warmer climates.

Air and Vapor Barrier is designed to prevent air and moisture in liquid and gas form (vapor) from passing through the product. Some manufacturers like to tout energy loss prevention, but I do not think the amount of energy loss prevented would be why to select this product.

Breathable Air Barrier is similar to the air and vapor barrier, but allows moisture vapor to pass through. There is no version that is non-vapor permeable. It is typically used in warmer climates with insulation on the outward side of the wall section. No one size fits all within our association's membership area. Air passage or infiltration would be blocked with this product, but moisture movement still within the cavity allows proper wall section drying. Drying rates depend on ambient temperature, exposure, and exterior weather events (rain and humidity), so this product has great value in a significant part of the country.

Fluid-Applied Air Barrier, these are cool, just had to say it. I remember the first project I saw them being rolled on; it was rolled, smeared, filled, and leveled out. Just cool to see. This product is similar in characteristics to the air and vapor barrier above, preventing air from passing through the applied material when the substrate is prepped properly. Vapor passage depends on the fluid-applied material version you choose; you will have options. The biggest benefit for property owners is that it is seamless and can handle radii, corners, and overhead applications.

There are many "air barrier manufacturers" we purchase from every day; each company has its special twist. This article is designed as information only, not a sales pitch, as variations in the discussed products exist.

Enjoy the holidays, and be safe.

Fechino Files: A little Extra Trade Information

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