WeatherBoards, simulated, rough-cut planks made to mimic cedar siding — and made locally by Certainteed Manufacturing of White City — were recently used on a Rogue Valley Habitat for Humanity project.

An in-siding job

When it comes to choosing the most durable siding for your home — and the greenest, too — you wouldn't have rocks in your head if you looked into stone.

From simulated adobe products to fiber-cement board, modern siding products combine the best of nature and science to give homeowners rock-solid protection from the elements.

The greenest of all dwellings might be a cave, jokes Fred Gant, a certified "green rater" for Earth Advantage Institute. But if you're not quite ready to move into Fred Flintstone's neighborhood, you have the modern-day advantage of numerous variations on the theme of stonelike sidings.

For instance, building a home clad with mortared fieldstones from your own property might be the purest green technique — after the cave thing, that is.

Given the superior insulating qualities of masonry products, the question becomes one of aesthetics. How native do you care to go? More to the point, how "native" will your neighbors tolerate?

Gant describes a growing interest in an ancient European version of adobe, called "cob," a mixture of sand, clay and straw. Such outer coatings can be fabricated from materials existing almost literally underfoot on your property. Advances in organic coloring techniques are producing richly earth-toned finishes to sidings that will keep you and your family snugly warm in winter, cool in summer and dry year-round.

One solution Gant favors is an oldie-but-goody: fiber-cement boards.

"Fiber-cement siding is probably the greenest of contemporary choices, even though it's one of the oldest," says Gant. "It's durable, easy to work with, affordable and fireproof. I used it on the certified-green home I built in Ashland six years ago, and my wife and I are very happy with it."

One type of fiber-cement board, WeatherBoards, is produced locally by Certainteed Manufacturing of White City. The simulated, rough-cut planks mimic cedar siding, and the product comes with a 50-year limited transferable warranty.

WeatherBoards recently was used to cover a new house built by volunteers for Habitat for Humanity. Jim Whitlock, project manager for Rogue Valley Habitat For Humanity, says Certainteed donated the materials for this and other local Habitat projects.

Before deciding on which siding product to choose, it's critical to remember that a house is not just a collection of green products and features. It's a system, and all the parts work together.

In a wood-frame house, walls actually are high-performance assemblies designed to control heat transfer, air flow and water penetration. The exterior-finish layer is an integral part of this system and is much more than just the decorative surface that faces the street.

Focusing too much on either the aesthetics or environmental features of a cladding choice, without considering the wall system as a whole, can seriously compromise the overall sustainability of the house.

A closely related consideration is moisture accumulation. In a wet climate, the exterior cladding should incorporate what architects call a "rain screen." This means finish materials are set a slight distance off the wall to provide a small gap, allowing water that goes behind the outside layer to drain away.

The state of Oregon now requires builders to include a gap for water drainage behind the siding.

"The latest trend is to look behind the siding for adequate moisture drainage," says Gant.

"The Oregon Legislature directed the Oregon Building Codes Division to establish what is now RC 703.1," says Dale Bohannan, a partner in Principle Building Department Services of Medford, and the official code authority for the cities of Eagle Point, Jacksonville, Phoenix and Rogue River.

"This residential-code section now requires that there be a 3/16-inch separation between the finished siding and the subsiding of every residential structure," he says. "This is a huge step forward in the weatherization qualities of a home."

Industry insiders refer to this moisture channeling as the "drain plane."

"The concept of the drain plane is that ... moisture is going to get through the finished siding product — whatever it is," explains Bohannan. "What they want to do then is keep the moisture from penetrating the wall cavity."

According to Gant, homes built with drain planes in regions like Southern Oregon, with big temperature swings from night to day, benefit greatly in terms of energy performance, livability and durability, all critical components of a dwelling's green rating.

"The cooler night air condenses moisture on the inner surface of any siding," says Gant. "As the sun heats that siding, the moisture has to go somewhere. We call this effect 'heat-driving,' and it forces the water inward to the subwall and beyond, causing wood deterioration plus mold and mildew formation.

"An approved rain screen provides channels for the water to drain downward instead of inward," he adds. "Your siding's durability improves from the inside out."

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