Habitation Solutions

Construct water-proof building envelopes

Most often, when we talk about green/sustainable buildings, we discuss energy-efficiency, air-sealing, insulation, and efficient HVAC systems.  However, there are other very important features of green buildings, such as water-proofing/water management.  Maintaining control over water and water vapor in a building is far more important than energy-efficiency.

Moisture related problems, such as bulk water leakage or water vapor intrusion into the building cavities, can damage a building badly.  A building can be damaged to the point where it is no longer useful.

Water gets into a building in a variety of ways.  Water gets into the building in the form of bulk water—rain, flooding, or plumbing leaks.  Water gets in via capillary suction—wicking up into wood or permeable materials.  Water also gets into a building by air leakage and vapor diffusion.

In order to prevent water related damage, thoughtful planning, design, and construction is required.  The ENERGY STAR for Homes program requires water management in order for a home to be certified as an ENERGY STAR Home.  Water management is the act of building a home so that water is prevented from entering.

The ENERGY STAR for Homes water management program addresses all parts of the home—the Site and Foundation, the Wall Assembly, the Roof Assembly, and Building Materials.

Water Management at the Site and Foundation consists of a variety of common-sense practices. Among these practices, water must slope away from the house at a quarter of an inch per foot for ten feet at paved surfaces and a half inch per foot a grade.  Another practice is to provide damp proofing at below grade concrete foundation walls.

At Wall Assemblies, important Water Management techniques consist of providing a fully-sealed drainage plane behind exterior cladding.  And, all exterior window and door openings must be fully flashed.

Roofs are a common source of water intrusion and water management is very important.  At roofs, best practices water management techniques consist of step flashing at all wall-roof intersections; these flashings must in integrated into the drainage plane.  Gutters and downspouts should be provided.  Downspouts should have lateral returns that deposit water more than five feet away from the foundation.

Appropriate and appropriately installed building materials are important best practices for water-management in buildings.  Building materials with visible signs of water damage should not be installed in any building.  Cement board should be installed as a backing material behind tub and shower enclosures.

When done correctly, Water-managed construction techniques will result in a more durable building that lasts longer that a building where these construction techniques were not employed.  Buildings constructed with these techniques have better indoor air quality, as mold growth is less likely to occur. And these buildings are better places to live and work.

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