Composite Systems

EPRO field-installed composite waterproofing and contaminant vapor barrier systems are engineered with redundant layers of protection, ensuring that your building remains safe for building occupants and safe even if one layer of the composite system is compromised. When choosing a contaminant vapor barrier composite system, you need to consider three main factors: membrane thickness which reflects robustness, quality of installation and chemical resistance .

Chemical Resistance

The chemical resistance of a barrier is gauged by calculating the rate of diffusion or permeation of a chemical through a given barrier. The rate of diffusion amongst all barrier types is relatively low and at such low numbers, it is very difficult to justify using one barrier over another — because when combined with concrete, the chemical resistance of the concrete slab and low permeability barrier — it essentially eliminates the threat of chemical diffusion through the membrane and concrete slab. Additionally, there is not an agreed-upon standard to which diffusion rates are measured. Engineers must rely on vapor intrusion barrier manufacturers to stand behind the methodology used or seek to try and distinguish the advantages and disadvantages of each methodology, a task that can be excessively difficult and tedious. With chemical resistance of membranes being relatively equal, the major concern for vapor intrusion comes from advective flow into the structure. The thicker the membrane is, the more robust the seals are around penetrations, terminations and less prone the membrane is to damage, the less likely advective flow will occur.

Membrane Thickness

The thickness of a membrane directly correlates to a vapor intrusion barrier's ability to withstand the construction process. For example, a 20 mil sheet membrane will have less resistance to damage than a 40 mil sheet membrane, and 40 mil sheet membrane will be outperformed by an 80 mil membrane. Composite membrane assemblies that incorporate sheet membranes sandwiched between a fluid-applied asphalt latex membrane will have even greater tensile strength and puncture resistance due to the multiple layers of redundancy. To provide a pathway for advective flow, all three layers of a composite system must be compromised.

Quality of Installation

The construction of buildings presents many variables that can adversely impact any vapor intrusion mitigation system. For vapor intrusion barriers, success is based on the quality of installation and confirmation that the system has been installed correctly. However, once the vapor intrusion barrier is installed, armies of workers step on the membrane to set rebar, adjust piping and set concrete forms. While these workers might be aware of the importance of the system, they are not known for delicate work habits. The thinner the system is, the more susceptible it is to damage during this time, and making repairs after this critical point of the construction can be difficult. Barriers that resemble standard water vapor barriers —10 to 20 mil according to the American Concrete Institute (ACI) — are hard for others to distinguish and may result in concrete contractors treating this membrane without understanding the membranes significance, for example, puncturing weep holes in the vapor barrier to allow for moisture that is created from the curing of the concrete slab. The best way to ensure a successful installation, one that will last throughout the construction process and for years down the roads is to choose a membrane that is thicker and, therefore, more durable to the wear and tear of a construction site.