Due to demand and potential value, contaminated sites are routinely being considered for redevelopment. Toxic vapors detected on these sites, which are often former industrial properties, landfills, dry cleaners, or gas stations, can present health risks if not properly cleaned up before development. In these situations, contaminant vapor intrusion barrier systems can be a valuable mitigation tool to make the site safe and expedite construction. While the chemical resistance of these systems is very important, it also must be assessed alongside other critical factors, including physical durability, waterproofing ability, constructability, and longevity. Deficiency in these characteristics can result in material failures that allow toxic vapors and/or moisture to enter the building envelope.
To meet these modern construction demands, vapor intrusion barriers have evolved over the years from simple film systems to multiple layered composite barrier systems. These systems are comprised of multiple layers of unique materials, each providing properties that enhance the overall system performance. Optimal composite barrier systems should exhibit high performance in all aspects of building construction as well as protection from moisture and chemicals. When evaluating and selecting the right composite vapor intrusion system for your site, the following attributes should be considered:
Tensile strength is a way to measure a product's ability to handle lateral stress. This form of stress can be expected in construction environments when concrete is placed and cures over the vapor intrusion membrane. Due to its weight, pressure is exerted around critical areas such as penetrations, termination points, and elevation changes.
Elongation is another stress indicator and occurs when forces are applied to the system unequally. The higher the elongation, the better as the composite barrier will be able to withstand movement of the slab during the concrete pour and the curing process as concrete settles and expands and contracts.
[Check out the video to learn more about EPRO's Geo-Seal vapor intrusion barrier systems]
Puncture resistance is the critical metric for barriers used to mitigate vapor intrusion as these systems have to be able to withstand the construction process. After VI barriers are installed, and quality control procedures are performed, multiple trades will work on top of the completed system before concrete placement. Often, smoke testing can detect the smallest of holes which are then sealed before the system is complete.
For performance of barriers that are specifically installed for VOC vapor intrusion, chemical resistance is the most important factor when evaluating a product's ability to be protective.
The building foundation type is critical when selecting the proper vapor intrusion barrier. The construction process is already complicated, but different foundation types and configurations can impact the system's overall integrity.
For example, large flat areas, common for industrial buildings, provide large wide-open areas that make application easy. In this case, seam integrity is the key consideration, and the schedule often dictates that the vapor intrusion barrier be installed as quickly as possible.
Pile-supported buildings are on the other end of the spectrum, commonly used when the underlying soil cannot support the structure's weight or when differential settlement may occur under the building. When this foundation type is utilized, it will require the barrier to adhere to the building foundation and seal to piles or onto pile caps.
Many other factors at play can determine which vapor intrusion barrier is ideal for your site needs, which is why it is paramount to enlist the help of a trusted manufacturer. At EPRO, we have both single-sheet barriers and composite systems and can help you dial in the right level of protection. Reach out to us to share your site conditions, and let’s come up with the best solution, together.