Posted by Webmaster on 10. November 2003 06:45
Memo (PDF 121 KB) outlining the process LBNL will use and invite comments, Oct. 2003
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Posted By: P. Marc LaFrance from U.S. Department Of Energy
November 10, 2003 6:45 AM
Please see the LBNL letter of 30 October, 2003. Sorry for the delay in getting this posted. The letter stipulates that the deadline for comments is November 15 but I am extending it to November 22. The most important item for feedback is the assumption for a SHGC baseline in the North. You can post any generic comment here regarding the workshop or the LBNL analysis. If you prefer, you can post specific technical or climatic comments under the other headings. You also can initiate a new topic. To get started, you just need to "login" (after you have signed up for the forum) from the home page then click on "view topic." You can then either post a comment, or initiate a new topic. You can read this topic and any responses without logging in, but you can only post your comment after you have logged in. If you have problems getting started, please call me at 202-586-9142. Thank you, Marc LaFrance, Technology Development Manager - Windows R&D
Replied By: Greg Patzer from Aluminum Extruders Council
19 - Nov - 2003 11:16 AM
The Aluminum Extruders Council (AEC) welcomes the opportunity to comment on the process LBNL has undertaken to outline potential methods which the Department of Energy may utilize to adopt a performance based alternative to the current prescriptive parameters of the ENERGYSTAR-Windows program. As you may recall AEC supported Option 3 of the original methodology options, which were presented at the September Workshop. We believe that overall the process suggested and likewise the anticipated results will be straightforward. We are cognizant that the selection of a Solar Heat Gain Coefficient (SHGC) baseline factor for the Northern zone is critical and may potentially be an area of issue with various stakeholders, however we do believe we have identified a logical and equitable solution relative to SHGC value.
AEC understands a base SHGC needs to be chosen for the northern zone in order to implement tradeoffs between U-factor and SHGC (i.e. a performance-based system). While we are aware of the tension between meeting or beating the IRC/IECC prescriptive code requirement of a U-factor less than or equal to 0.35 and a energy performance-based rating system, we believe focusing on the actual energy performance of windows currently obtaining an ENERGYSTAR in the northern zone holds the key to resolving this tension.
A sample of more than 9300 windows with both U and SHGC factors (a subset of the NFRC database that was used in An Evaluation of Alternative Qualifying Criteria for Energy Star Windows - DOE March 2002) chosen to illustrate product availability and to represent the more common residential window types shows that a large share of windows with a U-factor at or below 0.35 (i.e. meeting the northern zone U-factor requirement) have a SHGC of less than 0.3. Specifically, of the approximately 4700 windows available at U-factor < 0.35, 40% have a SHGC of <0.3 [36% have SHGC between 0.3 and 0.4, 24% have SHGC between 0.41 and 0.55, and less than 1% have SHGC > 0.55].
As such a large fraction of ENERGYSTAR windows in the northern zone already perform at this SHGC, the AEC recommends the selection of 0.3 as a base SHGC in the northern zone.
The AEC and the aluminum window manufacturers we represent are committed to working with LBNL and the DOE to expeditiously develop and implement this much-needed alternative. Our industry representatives are at your disposal to provide industry expertise at any time.
Director of Communications & Government Relations
Aluminum Extruders Council
Replied By: David Duly Duly from Pilkington NA
20 - Nov - 2003 11:04 AM
Pilkington North America recommends the selection of a SHGC = 0.25 for the 'baseline' value within the northern region of the ENERGY Star Windows program.
The selection of this SHGC value is based on a representative sample of actual windows manufactured today and placed within homes in this region. Also, detailed annual energy calculations using LBNL Resfen software will demonstrate maximum annual energy consumption of a house in this region attributable to the heat gain and loss through the windows when a minimum SHGC value is selected.
A performance based trade-off system between U-factor and SHGC will then allow windows that save more energy to be an alternative choice for meeting the current ENERGY STAR criteria of a simple prescriptive U-factor and any SHGC value.
Replied By: Thomas Culp from ATOFINA Chemicals, Inc.
20 - Nov - 2003 11:55 AM
Reference SHGC for North...
I agree with the previous comments of setting the baseline SHGC between 0.25 and 0.30. If Energy Star windows which are currently sold in the north with U < 0.35 have SHGC of 0.25 or even lower, this establishes the minimum performance level (or maximum energy consumption level), and any window which performs better should satisfy the performance criteria. Therefore, it is quite reasonable that the baseline SHGC for the north be 0.25, but I would also agree with using a 0.30 value as perhaps more "typical".
Tom Culp - Research Scientist for Flat Glass Coatings, ATOFINA
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