Moisture is one of the biggest challenges for a building envelope. Effective moisture management requires designing and building wall systems that have a greater “drying potential” than “wetting potential.” To do this the best starting point is to first, reduce wetting, which could come from sources such as rain and groundwater. Then, second, utilize all the available mechanisms of drying including the sun and air flow.
Four tips to reduce wetting and maximize drying potential
1. Incorporate foundation drainage systems with proper site grading. This is a great way to keep the water on the ground from putting pressure back on the building.
2. Use a soffit or overhang. Protruding details are good for helping rain water drip off the building rather than run down its surface.
3. Properly integrate flashings in rough openings and install long-lived sealants to keep rainwater out of joints. This provides extra protection around areas of vulnerability. On some buildings, these are areas that don’t receive much inspection during their service life, so it is important that they are done correctly the first time.
4. Create breaks in the components. This may seem counterintuitive, but small cavities will prevent moisture from migrating through all the layers of materials. Allow these spaces to drain and vent to the exterior so drying can occur.
The role of material selection
You’ll also need to take your material selection into consideration. For example, a brick cladding system generally relies on draining techniques as it is usually only open at the bottom, while a natural lap siding may require a coating to prevent absorption (absorption = moisture storage). Stucco must be installed as a water-managed system with drainage capacity and one should avoid installing it as a barrier system. While, some stone veneer systems are manufactured with their own drainage system others are not. Choose systems that have the greatest chance for being installed as they are intended- ask yourself, “how could someone mess this up?”, because if there is a way it will be found.
The key to moisture management is to ultimately achieve moisture balance by finding strategies to reduce the amount of wetting while providing a greater potential for drying. To read the full article as it originally appeared in Building Enclosure.
1.Bulk water movement (rain, snow, or groundwater)
2.Capillary action (capillarity)
3. Air transported moisture
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