What is Rain Screening?
In the quest to finding better moisture management and energy efficiency, more architects and builders are experimenting with exterior siding using rain screen installation methods. Basically, rain screening is a system, not an actual “thing”, that is used to create an air gap between the exterior siding (cladding) and a water-resistant barrier that is installed over the sheathing of the structure.
By creating an air cavity between the moisture barrier and the exterior siding, this double-wall construction uses the outer layer (the exterior siding) to keep the rain out, while the inner layer (an air/moisture barrier) provides thermal insulation and prevents excessive air leakage. It also allows any moisture that may pass through the siding to easily drain away, as well as accelerates evaporation of any residual moisture within the walls. In the event that any water does collect behind the exterior cladding, the air gap allows it to dry, which prevents moisture build-up and rot.
Rain screening is created by attaching vertical furring strips that are generally 1/4 – 3/8″ thick, by 2 – 3.5″ wide, using plywood or other treated wood strips, plastic mats, or other rain screen system creating materials, over a water-resistant barrier, such as tar paper. Flashing is then installed over any penetrations and all vulnerable areas where water may pool or collect to allow it to evaporate and/or drain away. Finally, the exterior siding is installed by adhering it to the furring strips, thus creating the air gap behind for airflow.
Be sure to contact your local building department for specific codes on rain screen installation in your area and follow all manufacturer’s recommendations to ensure the success of your project.
In these photos, 1×6 Alaskan Yellow Cedar dimensional boards were used as exterior siding over rain screening. Simply beautiful, durable and eco-friendly. Alaska Yellow Cedar, also referred to as Nootka Cypress, has almost always been identified by the species label nootkatensis (so named for the Nuu-chah-nulth people of Canada). However, the genus of the tree has been changed many times, with the most recent being in the Cuypressus genus.
photo and craftsmanship by Kreider Construction of Anacortes, WA
Although rain screening installation costs more than more traditional U.S. exterior siding methods, it can prevent costlier problems, such as rot and decay, later on. It can also add green benefits to your project due to the thermal insulation properties, and add to the longevity of the structure and the building materials used, thus reducing waste.
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