Timber-Frame Home: Design, Construction, Finishing by Tedd Benson

Author:Tedd Benson [Benson, Tedd]
Language: eng
Format: epub, mobi, pdf
Publisher: Taunton Press - A
Published: 2011-07-21T22:00:00+00:00

Advantages of EPS

• It is easy to manufacture. Polystyrene beads are compressed together under heat and pressure to make a large block, or “bun.” The bun is then slabbed with a hot knife to the required thickness to create panel cores.

• EPS is light and easy to work with.

• When hot wires are used instead of a router to make cuts, there isn’t a problem with dust.

• EPS accepts various glues and mastics, and generally bonds well to the skins.

Disadvantages of EPS

• Because EPS panels are so easy to make, some are produced in uncontrolled conditions. Panels fabricated under the apple tree are sold alongside those made in well-tooled facilities with good quality control.

• EPS is a hazard in high heat and fire. It loses its structural integrity at about 180°F and melts at 300°F. In a fire test I witnessed, heat from the fire quickly melted the panel into a volatile liquid. Therefore, consider using type-X drywall (half-hour fire rating) as an interior skin for EPS panels.

• EPS panels have potential for radical molecular creep. Tim Johnson, a technical researcher at Massachusetts Institute of Technology, reports that over a 16-ft. span loaded to 40 lb. per sq. ft. for 90 days, EPS panel samples shifted 6 in. because of creep. This is a big load and little time; I worry about small loads and lots of time.

• Most panel manufacturers keep costs down by using 1-lb. instead of 2-lb. density EPS. Yet a 2-lb. density foam would give better compression strength, a higher R-value, and a lower perm rate. EPS panels are generally the least expensive, but not because they are on sale.

• Low R-value per inch means more inches of thickness are necessary for good performance. The lower price of the material is offset when the R-values are equivalent. Window and door jambs and roof edges require more lumber for framing and finish.

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