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identified above, the precaster must provide calculations to the architect to verify the performance of the sandwich wall panels. The specifier should identify the “acceptable” R-value for the panels.  See 1.5 Submittals, C. Thermal Performance” above.

A.

Expanded-Polystyrene Board Insulation:  Rigid, cellular polystyrene thermal insulation complying with ASTM C578 formed by expansion of polystyrene base resin; <square edges> <ship-lap edges>; with aged R-value of <state value>; board stock density <state density> and thickness of <state thickness>.

Expanded polystyrene insulation is subject to variances in density and product quality.  The product is generally cut from a billet.  Depending upon where the specific sheets originate in a billet, the density of the board may vary from 1.0 to 2.5 pounds per cubic foot.  Additionally, moisture can be trapped in large voids between polystyrene beads, contributing to higher thermal conductivity.

B.

Extruded-Polystyrene Board Insulation:  Rigid cellular polystyrene thermal insulation complying with ASTM C578 formed from polystyrene base by an extrusion process; <square edges> <ship-lap edges>; with aged R-value of <state value>, board stock density <state density> and thickness of <state thickness>.

C.  Polyisocyanurate Board Insulation:  Rigid, cellular polyisocyanurate thermal insulation; complying

     with ASTM C 1289; square edged; with aged R-value of <state value> and thickness of <state thickness>.

Extruded polystyrene insulation has a higher R-value and is more vapor and water-resistant than other rigid insulation products such as expanded polystyrene (bead-board) insulation.  Un-faced polyisocyanurate and polyurethane insulation ( ASTM C591) are not acceptable replacements for extruded polystyrene in general applications.  Polyisocyanurate insulation (ASTM C1289) with aluminum/poly facer is moisture resistant and offers high thermal performance.

Select wythe connectors from paragraph below.  It is imperative that the connectors expand and contract similarly with the concrete during temperature changes to significantly reduce the likelihood of concrete cracking or spalling.  

The fiber-composite connectors are the only elements penetrating or crossing the insulation in the panels.  They perform as insulators. The low conductivity of the connectors is vital to retaining 99.3% of the insulation’s R-value.  Thermal testing has been performed at Construction Technology Laboratories and at the Oak Ridge National Laboratory, United States Department of Energy, to determine the effectiveness of the fiber-composite connectors in the elimination of loss of R-value in a sandwich wall construction.  

C.

Wythe Connectors:  <Glass-fiber and vinyl-ester polymer connectors>, manufactured to connect wythes of precast concrete panels.

1.

Provide corrosion and alkali resistant fiber composite connectors having the following physical properties:

i.

Structural component of connector comprising long glass fiber composite pultrusion with 76% (by weight) glass fibers in a thermoset vinyl-ester resin matrix.

ii.

Connector shall have been shown, by testing laboratory certified by ICBO ES, to provide static pullout capacities exceeding 1600 lbs, static shear capacities exceeding 500 lbs, and post-dynamic tension and

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