Vapor Intrusion Mitigation Systems for Multi-Family Buildings
Vapor intrusion can occur in multi-family buildings such as condos, apartments, duplexes, HUD properties, nursing homes, and dorms. Vapor intrusion occurs when toxic chemicals in the subsurface turn to vapor form and rise up through the soil and enter a building through gaps and cracks in the slab. These toxic vapor forming chemicals can include volatile organic compounds (VOC’s) such as trichloroethylene (TCE), perchloroethylene (PCE), and benzene, or explosive risks including methane, gasoline, and diesel vapors. Buildings with vapor intrusion issues are typically located near current or former dry cleaning sites, metal manufacturers, gas stations, and any other industry that utilizes these types of chemicals. If high concentrations of toxic vapors are found to be inside of a structure and determined to be detrimental to the health of the occupants inside, actions need to be taken to remedy this. Health effects from vapor intrusion depend largely on the type of chemical and each individual's health history, however the most common effects include nervous system damage, kidney and liver damage, birth defects, and cancer. Fortunately, harmful vapor intrusion issues can be resolved with the implementation of a vapor intrusion mitigation system. Vapor intrusion mitigation systems are designed to deter rising soil gasses from collecting underneath a building to seep in. The most common form of vapor mitigation is sub-slab depressurization, however other methods do exist to fit unique structures. Lifetime Environmental Solutions has over two decades of mitigation experience and holds certifications for both residential and commercial mitigation. Our experienced team will lead you through the vapor intrusion mitigation process and provide the best workmanship around. Give us a call now for a free, no obligation estimate.
Sub-slab Depressurization Systems
Sub-slab depressurization (SSD) installations in multi-family buildings should always be done by a certified mitigation professional to guarantee the integrity of the structure and the health of the current occupants. SSD is a proven method of preventing vapor intrusion inside of a structure and by far the most popular type of vapor removal system. Sub-slab depressurization systems consist of a vent pipe, an in-line mitigation fan, and a manometer. Before installation of an SSD system, a certified contractor like Lifetime Environmental will survey the property and do some minor tests to determine collection point locations and the amount of systems necessary to cover the entire building (smaller multi-family buildings usually only require one SSD system while larger buildings may require multiple). Once the mitigation plan is in place, collection points are dug under the slab and the vent piping for the system is sealed to those points. The vent piping then runs vertically out of the structure and vents above the roofline to prevent vapor reentry. The mitigation fan must be placed above or outside of any conditioned living space, so it is typically either placed outside or in a non-livable attic space. A manometer is then added to the vent piping so the occupants can monitor the fans effectiveness and detect any possible issues with the system. After installation, post testing will need to be performed on the property to make sure everything is working as it should and the occupants are safe. If you would like more information on sub-slab depressurization for your apartment building, condo, dorm, nursing home, duplex ,or HUD property, give us a call today!
Vapor Intrusion Mitigation Systems for New Construction
If a multi family building is being constructed over an area with known contaminants in the soil from a spill or former manufacturing site, there are elements that can be added in during construction to prevent future vapor intrusion issues.
Below are some of the options you have to create a vapor resistant building.
Gas permeable layer - Before the slab is poured, a gas permeable layer such as coarse gravel can be laid down to allow rising soil gases to move more freely under the building. This is beneficial not only to prevent the gasses and vapors from getting trapped under the building, but also for future mitigation systems as a gas permeable layer will make it much easier to get maximum field extension with fewer collection points. This option is best used in tandem with some of the other vapor and radon resistant features that can be added to a new building.
Vapor barrier - Vapor barriers are plastic mats that can be laid down over the soil before the slab is poured to prevent soil gasses from entering. Without a vapor barrier under the slab, rising soil gasses can enter with relative ease because concrete is naturally porous and is prone to cracks and gaps. Vapor barriers are also frequently used for structures that do not have a slab on the ground level to properly cover the open soil. Vapor barriers can be used with an active mitigation system to achieve excellent results.
Drain-tile - Even if the building is not in need of drain-tile for water issues, it can still be wildly beneficial for vapor intrusion mitigation purposes. Drain-tile placed around the entire footprint of the structure will allow an active vapor mitigation system to pull airflow throughout that whole system creating maximum depressurization. Buildings with drain-tile typically require less collection points during a mitigation installation which results in a more cost effective solution.
Passive mitigation systems - A passive mitigation system is simply a vent pipe (typically 3 or 4 inch PVC pipe) that is installed vertically from the soil/gravel and through the conditioned living space venting out of the roof. Passive systems can work to reduce indoor vapor level with stack effect when installed correctly. If an active system is needed once testing is done after the building has finished construction, the passive system can be activated quite easily and for a lesser cost.