Procedure to Measure Translucent Panel VT, CMA Focus at NFRC Spring Meeting
March 27, 2012

by Sahely Mukerji,

The Translucent Panel Visible Transmittance Task Group of the National Fenestration Rating Council (NFRC) has developed a procedure to measure visible transmission of fenestration products, either overhead or vertical, according to Yossi Vinograd, president of CPI Daylighting in Lake Forest, Ill., and chair of the group.

"The problem is that these translucent panels are sometimes homogenous and sometimes not," says Ross McCluney, research physicist at SunPine Consulting in Chattanooga, Tenn., and a member of the group. "We resurrected an old ASTM standard that allows you to put a light meter in a shallow box, 3 feet square, and you lay the light meter in the box. It collects light from the panels from all directions. It calls for translating samples between measurements. You average those and divide the average by the incident light level. It's the ratio of those two levels that gives the correct reading."

The procedure will go through the board of directors to be approved, according to McCluney.

The task group met today during NFRC's spring committee meeting, currently underway at the Omni Hotel in Austin, Texas.

According to Ray McGowan, senior research and technology manager at NFRC, an update to the Software Subcommittee was provided by Catherine Best of the Component Modeling Approach (CMA) Software Tool Advisory Technical Group. It included:

  • A top 10 list of CMA improvements developed and to be considered by membership, but these may depend on document modification and budgetary constraints;
  • A simplified method for creating a curtainwall in CMA being considered;
  • Condensation resistance (CR) being considered for CMA inclusion based on a now completed research report under the NFRC research program; and
  • The CMAST calculation speed has been greatly improved by modifying the software.

"There was the same old debate about whether to continue to expand on the NFRC CR number or the American Architectural Manufacturers Association's Condensation Resistance Factor tool, what should be done long-term, whether to have one matrix for the industry, or to develop something new that looks at condensation resistance on a project location specific basis under real conditions," says Tom Culp, president of Birch Point Consulting in La Crosse, Wis. However, he said no resolution was reached.

The NFRC spring committee meeting opened yesterday. Steve Strawn, NFRC chair, opened the event. Afterwards, the Research and Technology Committee block got underway with three subcommittees convening: the Optical Properties Subcommittee, the Research Subcommittee and the Thermophysical Properties Subcommittee. Later in the afternoon, the Technical Committee subcommittees, including the U-factor Subcommittee, the Solar Heat Gain Subcommittee, and the Annual Energy Performance Committee, met.

The meeting ends tomorrow.

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