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REQUEST TOPIC ACCEPTANCE REQUEST (RTAR)

TC/TG: TC 4.5 (Fenestration), and SSPC 90.1

Project ID No.:

TITLE:

Determination of U-factors, Solar Heat Gain Coefficients and Visible Transmittances of

Standard Fenestration Units made from Representative Fenestration Frame and GlazingSystems to Update Tables 4, 6, 13, 15, and 16 in the Fenestration Chapter of Handbook of

Fundamentals.

Research Category: 3 Energy Conservation; Building/HVAC system design

Research Classification: Basic Applied

TC/TG Priority: Highest

Estimated Cost: $60,000

Possible Co-funding Organizations:NFRC, U.S. Department of Energy, Fenestration Manufacturers

Handbook Chapter to be Affected by Result of this Project:Chapter 31; Fenestration

BACKGROUND:

Tables 4, 6, and 16 in Chapter 31 contain a large number of U-factors and Tables 13, 15 and 16contains numerous Solar Heat Gain Coefficients (SHGC) and Visible Transmittance values (VT)for typical fenestration systems. These data are being used and referenced by variousprofessions, from fenestration manufacturers to architects and system designers. Whenever thereis a need for generic window data, in the absence of more detailed information, the values givenin the tables within Chapter 31 are used. Those tables are clearly the most commonly referencedinformation in Chapter 31.

These tables were last updated in 1996, through an ASHRAE supported research project. Thetables were produced using the VISION/FRAME (ref) and WINDOW 4.1 (ref) computerprograms, in accordance with NFRC 100-91, NFRC 300-92, and NFRC 200-01. A series ofexperiments, performed at a number of accredited laboratories both in the US and Canada, wereused to validate the results. At the time, the table reflected the most up-to-date procedures andproducts available to the Fenestration T.C.

JUSTIFICATION AND VALUE:

The values in Tables 4, 6, 13, 15, and 16, need to be reconsidered for a number of reasons.

1. The NFRC has revised its standard procedures since the publication of these tables. Inparticular, it has adopted the modeling of one standard size for rating fenestration

Deleted: 45

Deleted: U-factors, visibletransmittances, or SHGCs of commwindow types

Deleted: data

Deleted: It is probably no exaggto say that t

Deleted: (

Deleted: ), and calculations werusing the VISION/FRAME and

WINDOW 4.1 computer tools

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products, and changed some of the heat transfer models used for calculation purposes.The WINDOW 4.1 software also been updated to include these new models. Althoughthe previous software produced results to within scientific accuracy (i.e., the newmodels cannot be shown to produce better results), the standard size issue still needs tobe addressed.

2. Industry professionals use these tables to calculate the energy performance offenestration system despite the fact that they are not intended for that application. The

values are intended for worst-case design and rating purposes, and are notrepresentative of the in-situ (dynamic) performance of the product. During theproduction of the existing values, much of the information that would facilitate adynamic analysis was stripped away and lost. The recovery of this data, and it'sinclusion in a series of reformatted Tables is an important goal of the T.C. 4.5 2009Handbook committee.

3. The current focus of ASHRAE (and others) on energy efficient buildings dictates that anumber of new and more efficient windows be included. Of note, the thermally brokenframe products currently included in the tables do not reflect the high-performance ofsome commercially available products. If the tables are to effectively reflect the benefitsof such products, they must first be included. The products included in the currentTables need to be rethought and updated.

OBJECTIVE:

The objectives of the proposed research project are:

1. Select and document representative fenestration products by contacting appropriatefenestration manufacturers, and modify and update the product types of typicalfenestration systems for which representative U-factors, visible transmittance values,and SHGCs would be calculated.

2. Perform detailed simulations of thermal performance of selected fenestration productsusing software that includes the latest methods accepted by the NFRC. Determine U-factors, visible transmittances and SHGCs for each product and glazing and spaceroption at standard NFRC size.

3. Validate all results using the experimental data from ASHRAE ????-RP, or in the caseof new products, run the appropriate validation exercises.

4. Consider the inclusion of data and methods which will facilitate the use of the Tablesfor building energy analysis.

5. Update Tables 4, 6, 13, 15, and 16 in Chapter 31.

REFERENCES:

1) NFRC 100-1991: Procedure for Determining Fenestration Product U-Factors, NationalFenestration Rating Council. Silver Spring, MD.

Deleted: The National Fenestrat

Rating Council procedures have bthe basis for fenestration product tratings and are widely referencednumbers in the industry. The NFR

procedures have been developed wsignificant participation from ASH

members and incorporate results frASHRAE research. A new generacomputer programs have been devthat incorporate the latest algorithmdeveloped by ASHRAE and NFRU.S. Department of Energy has fu

the development of THERM andWINDOW computer programs, wprovided to general public at no coThese programs are used in NFRCsystem and they can easily be adopthis research project. These calcul

would result in more accurate valu

fenestration products then currentlvalues in the tables of Chapter 31 ASHRAE Handbook of FundameAlso, the ratings for residential ancommercial windows at NFRC arereported for one size, so it would pgreater consistency if the new valu

the tables within Chapter 31 are refor those same sizes.

Deleted: using THERM 5.2 andWINDOW 5.2 or their more recenreleased versions, if available

Deleted: with these new values

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2) NFRC 200-2001: Procedure for Determining Fenestration Product Solar Heat GainCoefficient and Visible Transmittance at Normal Incidence, National Fenestration RatingCouncil. Silver Spring, MD.

3) NFRC 300-2004: Test Method for Determining the Solar Optical Properties of GlazingMaterials and Systems, National Fenestration Rating Council. Silver Spring, MD.

4) ISO 15099: Thermal Performance of Windows, Doors and Shading Devices DetailedCalculations, International Organization for Standardization, Geneva

5) Wright, J.L. (1994): VISION, Glazing System Thermal Analysis Program, AdvancedGlazing System Laboratory, University of Waterloo, Waterloo, Ontario, Canada.

6) Finlayson, E.U., Arasteh, D.K., Huizenga, C., Rubin, M.D., and Reilly, M.S. (1993):WINDOW 4.0: Documentation of Calculation Procedures, Energy and EnvironmentalFRAMEplus5.1, Lawrence Berkeley National Laboratory.

AUTHORS:

Bipin Shah, Dr. Dragan Curcija, John Hogan, William C. duPont, Mike Collins