Your customer is building (or remodeling) a facility in which certain rooms require moisture control. Ensuring the right application of vapor barriers in the facility design and construction will help avoid common failures in the drying process.
Moisture exchange
Moisture exchange occurs when the amount of humidity in one room is greater than in the room adjacent, because the partial pressure of the water vapor is higher in the more humid room. Moisture will travel, in that case, from the room with greater pressure to the adjacent room. Unfortunately there is no way to completely mitigate the problem. Even a well-designed vapor barrier can only slow the rate of exchange – it cannot stop it entirely.
If the adjacent room in the example above is the moisture-controlled room – e.g. has a drying system in place – for the drying system to be effective, care must be taken to consider the rate of moisture coming through the walls from the room with higher pressure.
Designing a vapor barrier
The first question, of course, is how much dryness does the space require? This should be taken together with the amount of moisture coming into the room. Then, consider the capacity and efficiency of your drying system.
There are also a number of materials to consider here in addition to commercial vapor barriers that help keep moisture out; moisture-resistant construction materials and paints, for example.
Construction
Obviously the first, most important principle of a vapor barrier is that it must be sound; no breaks, cracks, or tears. All joints should be tightly sealed.
Care should be taken to avoid sealing water in if insulation is used between barriers. This can happen when construction occurs during humid weather, and can be overly taxing to your drying system. Of particular concern here is the effect any heat source will have on trapped water vapor. Heat will cause water vapor to expand, damaging joints and ruining the integrity of the barrier. Use drying equipment to ensure the enclosed area and the materials are dried prior to barrier installation.
Finally, consider your entrances. Doors should be solid (no cracks or openings) and weather stripped. Airlocks can help trap and remove humidity before personnel enter the space. Deploy drop curtains, shrouds, or tunnels around machinery openings and conveyors.
Ultimately, moisture will still get in. It’s unavoidable. But a well-designed vapor barrier and drying system will help you achieve the controlled environment your customer needs.
Q Applied Systems represents manufacturers of HVAC and moisture control equipment and systems, as well as fume and dust collection products. To learn more, explore our website or call (858) 435-2236 to speak to one of our knowledgeable professionals today.
