Rainscreen Systems and Tropical Hardwood Species
Spotlight on Ipe, Brazilian Walnut, Lapacho
The species are based on the specifier's preference and color. Ipé (Handroanthus spp.) has a rich walnut color and is often selected due to its density and durability in exterior applications. Garapa (Apuleia leiocarpa) has a golden brown color, and is lightweight yet easy to work with. Massaranduba (Manilkara bidentata), also known as "Bulletwood," has a dark red color with a high density for heavy construction. Teak (Tectona grandis) has a medium golden brown color and has long been a species of choice for exterior applications. Cedar (Cedrus spp.) is also in demand due to its ability to be stained in a variety of colors.
The benefits of a rainscreen system are worthwhile when it comes to areas with substantial rainfall. In some areas of the United States, like the Pacific Northwest, or in some countries like Canada, builders and architects have long recognized the importance of air space behind cladding and now mandate minimum air spaces behind all cladding materials.
The U.S. Federal Emergency Management Agency has also recognized the importance of pressure equalization of cladding when exposed to high winds such as those experienced during a hurricane. Because wood rainscreen systems allow pressure to equalize throughout the system, FEMA recommended in a 2009 advisory that "a rain screen design be considered when specifying wood or fiber cement siding."
Lotz adds that "Rainscreen systems are experiencing a steady growth curve both commercially and residentially amongst design professionals who understand the science of moisture and its impact on building envelopes."
— TIMBER HOLDINGS USA
A rainscreen is a siding installation that establishes an air gap between the siding and a water-resistive barrier. This open system allows moisture to enter the system but also allows it to evaporate naturally.
SPOTLIGHT ON: IPE, BRAZILIAN WALNUT, LAPACHO
- Species: Handroanthus spp.
- Origin: Central and South America
- Common Applications: Decking, flooring, decorative veneers, boatbuilding, and turned objects.
- Characteristics/Appearance: Ipe can vary in color from reddish brown to yellowish olive brown or darkish brown. Although the appearance is similar to Cumaru, the color tends to be darker. It has a fine to medium texture and the grain varies from straight to irregular or interlocked.
- Janka Hardness Scale: 3,510 lb_f
- Comments: Being known as one of the toughest woods to work with, Ipe is one of the top species well suited for flooring and decking projects. The wood is extremely dense and durable. It has superb weathering characteristics and insect resistance.
Frequently asked questions
Which tropical hardwood species are commonly specified for rainscreen cladding systems?+
Common species include Ipé (Handroanthus spp.) for its walnut color and density, Garapa (Apuleia leiocarpa) for its golden brown color and workability, Massaranduba (Manilkara bidentata) for its dark red color and high density, Teak (Tectona grandis) for exterior performance, and Cedar (Cedrus spp.) for its stainability.
Why did FEMA recommend rainscreen designs for wood siding?+
FEMA recognized the importance of pressure equalization of cladding when exposed to high winds such as hurricanes. Because wood rainscreen systems allow pressure to equalize throughout the system, a 2009 FEMA advisory recommended that rainscreen designs be considered when specifying wood or fiber cement siding.
How does a rainscreen siding installation manage moisture?+
A rainscreen establishes an air gap between the siding and a water-resistive barrier. This open system allows moisture to enter but also allows it to evaporate naturally.
Which regions have mandated minimum air spaces behind cladding materials?+
Areas with substantial rainfall such as the U.S. Pacific Northwest and countries like Canada have long recognized the importance of air space behind cladding, and now mandate minimum air spaces behind all cladding materials.
What makes Ipé particularly well-suited for exterior rainscreen and decking applications?+
Ipé is extremely dense and durable with a Janka hardness of 3,510 lb_f, and offers superb weathering characteristics and insect resistance. Although known as one of the toughest woods to work with, it is among the top species for flooring and decking projects.
According to Lotz, what is driving growth in the use of rainscreen systems?+
Lotz notes that rainscreen systems are experiencing steady growth both commercially and residentially among design professionals who understand the science of moisture and its impact on building envelopes.