Who’ll Stop the Rain?


With the Arterra, San Francisco’s first LEED certified San Francisco condos, just about ready to go into pre-sales it’s no surprise that some visitors in the sales office appear from curious to confused.

Some prospective buyers who drifted around the sales office came for the Green factor but others don’t know green from pink. The salesroom doesn’t exactly push the green aspect. Those who don’t have an attention to detail could easily miss the bamboo kitchen floors, and the dual flush toilets. Even so, one green product continually baffles potential buyers – the Trespa rainscreen system. It more than baffles, it disturbs some.

We’re not exactly fans of bedding down in high-end coffins, except maybe during Halloween, so people here should get over their fears of something new. The rainscreen system isn’t exactly the new green kid on the block. Builders have been using this overcladding technology since the 1940’s in Scandinavia.

For too many years America builders and engineers have sought to resist nature rather than embrace it. You can’t beat Mother Nature and why should we? Traditional thinking has been to prevent rainwater from entering buildings by use of barriers and sealants. However we don’t live in a vacuum so do to poor workmanship, material degradation and building movement (here in SF?) that system breaks down.

The beauty of rainscreen overcladding comes from the fact that the technology uses the effects of the wind to control rain water from entering the building.

The design uses simple pressure effects of the wind to dissipate the rain water energy. The specially designed drainage paths direct the water away from the opening.

The project manager at the Arterra describes the Trespa rainscreen system like a kind of Gore-tex as it actually allows moisture to flow in AND out. Most other buildings are hermetically sealed which don’t allow any evaporation which traps moisture in the walls and can lead to mold or other hazardous problems.

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