Remodeling Guides
Architecture
Architect's Toolbox: Rain Screens Up House Health
To thwart unwanted moisture and poor air quality in your home, think rain screens and drainage planes
Better materials and practices, including tighter envelopes, have made our homes easier to heat and cool and much more efficient. Gone are the days of drafty windows and doors, sky-high energy bills and uncomfortable rooms.
But, of course, there's a side effect to having a home that doesn't leak energy out of every crack and gap. Moisture buildup in our walls and a lack of fresh air coming into the home can create poor air quality. All those drafts and inefficiencies of yore actually prevented moisture accumulation and kept the air circulating.
Architects and builders recognize the issue and have developed techniques to keep moisture out of a home's walls and attic, preventing mold growth and the poor indoor air that can result. These techniques, which range from better insulating materials to mechanical systems that introduce fresh air into the home, include the installation of drainage planes and rain screens that allow positive air movement between the home's skin and its structural components.
These drainage planes and rain screens can be installed with just about any type of exterior finish material and just about any style. And lessening the risks of an unhealthy environment is well worth the small extra cost that these systems will add to your project.
But, of course, there's a side effect to having a home that doesn't leak energy out of every crack and gap. Moisture buildup in our walls and a lack of fresh air coming into the home can create poor air quality. All those drafts and inefficiencies of yore actually prevented moisture accumulation and kept the air circulating.
Architects and builders recognize the issue and have developed techniques to keep moisture out of a home's walls and attic, preventing mold growth and the poor indoor air that can result. These techniques, which range from better insulating materials to mechanical systems that introduce fresh air into the home, include the installation of drainage planes and rain screens that allow positive air movement between the home's skin and its structural components.
These drainage planes and rain screens can be installed with just about any type of exterior finish material and just about any style. And lessening the risks of an unhealthy environment is well worth the small extra cost that these systems will add to your project.
Synthetic stucco. Because synthetic stucco is a petroleum-based product, it doesn't "breathe" as natural stucco does. To compensate for this, manufacturers have specified that drainage planes be installed as part of the system. These drainage planes allow air movement, preventing moisture from getting trapped in the walls. So if you're thinking of using this type of material on your project, make sure the work is done in compliance with the material manufacturer's requirements.
Horizontal lap siding. You can still install a drainage plane even if you plan to use a traditional design and material. Materials that don't breathe like wood, such as fiber cement boards, can be installed in a manner that creates the drainage plane necessary to keep moisture from building up within the wall. The drainage plane can be an actual air space, as in the sketch above, or created by using a textured house wrap. In either case, it's worth having a conversation with your architect and builder about how to keep moisture out of your new home.
Panel systems. Many contemporary designs feature larger panels at the exterior. These panels, such as HardiePanel and Swisspearl, are engineered to be installed with rain screens. These rain screens are a necessity with this type of panel system due to the gap between panels. Because this gap is integral to the aesthetic desired, making sure there is a weatherproof barrier behind the panels is essential to the overall performance of the wall.
More Architect's Toolbox:
Connecting Home and Ground
Beautifully Layered Spaces
Finding the Space Between
More Architect's Toolbox:
Connecting Home and Ground
Beautifully Layered Spaces
Finding the Space Between
1. The gap between siding and the structural wall provides the space for air movement and moisture dissipation. This space can be easily constructed by installing the siding on furring strips, as shown. Of course, there are other methods to secure the finish siding materials to the structure. In fact, some manufacturers, such as James Hardie, have a system of channels that can be used. What's right for you depends on your style and your budget.
2. The bottom of the air space can't be left open. Several manufacturers have products that are specifically designed to be used at this spot. Most are essentially screen-type elements that allow air movement while preventing insects from getting into the air space.
3. More often than not, the landscaping (mulch, plantings and so on) is brought tight against the underside and may even bury the first few inches of the wall and siding. This will result in the wall's absorbing ground moisture, which can lead to insect infestations, mold growth and a whole host of bad things. So make sure to keep the finished landscaping at least 6 inches below the wood and siding.