The Beauty of Bales

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It's also very important to remember that laboratory tests are conducted under steady state conditions. In the real world, consistent conditions rarely exist for more than a minute or two. The true test of any material is the amount of energy required, over time, to maintain a reasonable level of comfort. Rather than measuring just R-values, it is essential to consider the overall contributions of a wall's thickness and the thermal mass provided by interior and exterior coatings. Together, these provide comfort and thermal performance much greater than R-value alone would indicate.

MOISTURE GUIDELINES FOR STRAW BALE HOUSES

Straw is a magnificent building material that can provide increased levels of comfort and aesthetic appeal, but it must be kept dry. Likewise, good indoor air quality depends on healthy walls. Fungal growth and mold can result in severe health problems.

1. Avoid building moisture into the walls.

Build only with bales that have always been kept dry. Bales that have gotten wet and then later dried out should not be used because straw fibers easily deteriorate during the drying-out process. If possible, build the structure and roof first.

2. Reduce exposure to rain.

Driving rain is responsible for many of the moisture problems that occur in all types of buildings. Keeping water off the walls will greatly reduce potential problems.
• Select a site that is sheltered by natural features and not subject to strong winds and driving rains.
• If possible, plant trees and shrubs as windbreaks, and use other screens.
• Good site drainage around the perimeter of a building is needed to direct surface runoff away.
• Roofs need generous overhangs. Wrap-around porches are even better than eaves for rain protection.
• The top of the foundation should be a minimum of eight inches above grade, and exterior stucco or plaster should also stop well above grade. Protection from rain splash-back at the base of walls is essential.
• Gutters with downspouts can prevent roof runoff from falling near the base of walls and then blowing back against the walls.
• Use water-repellent coatings that are also vapor-permeable on exterior stucco and plaster to prevent absorption of rainwater. Siloxane is one product that meets these criteria.
• Provide good window detailing, using head, jamb and sill flashing, sloped sills and drip edges to shed water away from the wall.
• Flash and/or caulk all joints between different materials to prevent unwanted intrusion of moisture or critters.
• Use berms to reduce the impact of snow, rain and wind.

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