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LBNL Assumptions for Analysis (30 October Letter) SHGC in North

Posted by Webmaster on 10. November 2003 06:45

Memo (PDF 121 KB) outlining the process LBNL will use and invite comments, Oct. 2003
Download Adobe Acrobat.

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

AEC Comments...

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.

Greg Patzer
Director of Communications & Government Relations
Aluminum Extruders Council


Replied By: David Duly Duly from Pilkington NA

20 - Nov - 2003 11:04 AM

Senior Engineer...

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

Replied By: P. Marc LaFrance from US Department Of Energy

24 - Nov - 2003 5:42 AM

Garrett Stone Comments...

THESE COMMENTS ARE FROM GARRETT STONE AND ARE BEING POSTED BY DOE. 1025 Thomas Jefferson Street, N.W. Eighth Floor West Tower Washington, D.C. 20007 Tel: 202-342-0800 Fax: 202-342-0807
November 21, 2003
To: Dariush Arasteh, Steve Selkowitz, Joe Huang and Robin Mitchell
From: Garrett Stone
CC: David Garman, Mike McCabe, Rich Karney, Mark LaFrance
Comments on October 30, 2003 Memo from LBNL
Per your request (and the request of Mark LaFrance), I have set forth below our
comments on items 5 and 6 from your memo dated October 30, 2003.
1. Comments on Limits to Implement for Energy Star Performance Trade-offs
(item 5 in LBNL Memo):
We think that the first three items identified by LBNL in their memo are the critical ones
(consumers can readily determine on their own whether to purchase reflective glazing).
Our comments as to the appropriate limits are set forth below:
A. Meet Code
As we have discussed in detail separately, the values for each zone must be limited to the
requirements for all replacement windows from the 2000 IECC. These requirements are
as follows:
Zones U-factor SHGC
North 0.35 NR
North Central 0.40 NR
South Central 0.50 0.40
South 0.75 0.40
Under the IECC, the U-factor requirements explicitly apply to each replacement window
' there is no option for a weighted average approach. Thus, any trade-off above these
requirements for any window would explicitly not meet the IECC.
As is apparent from the table above, the code requirement and the Energy Star criteria for
U-factor are the same in the North and North Central zones. As a result, there can be no
trade-off for those zones.
B. Comfort and Condensation
The U-factors set forth above to meet code are also reasonable levels to address winter
thermal comfort and condensation.
However, there should be concern about summer comfort issues from high SHGCs, even
in the North and North Central zones (while the cooling season may be shorter in the
north, summer HVAC design temperatures for the north are not significantly different
from those in the south). As a result, we would normally recommend the 0.40 SHGC in
northern zones, as well. However, since the Department disregarded this
recommendation in the recent Energy Star criteria-setting process and set a 0.55 SHGC
window maximum (0.40 for skylights) for the North Central, we would recommend 0.55
as the maximum (0.40 for skylights) for both the North Central and the North as at least a
limited effort to address summer thermal comfort.
The risk in not properly addressing thermal comfort issues is obvious ' at least some
homeowners will set lower thermostat temperatures for cooling to offset uncomfortable
solar gain. Such lower set-points will result in additional energy usage far exceeding any
apparent benefit from the higher solar gain in the winter. Moreover, if Energy Star
windows are to be successful, they cannot be perceived by consumers as resulting in
significant discomfort.
LBNL's own research dramatically illustrates why a 0.40 SHGC is the only reasonable
choice from a comfort standpoint, even in northern climates. According to the ASHRAE
paper submitted by LBNL, P. Lyons, D. Arasteh and C. Huizenga, 'œWindow
Performance for Human Thermal Comfort,' (August 1999), direct solar heat gain in the
summer (as reflected by the product's SHGC) and summer inside glass surface
temperature both have significant occupant comfort implications. High solar gain
products create potential summer comfort problems due to both of these issues as shown
by the percentage of persons dissatisfied based on the type of window selected
(depending on the level of clothing) and other data set forth below from pages 6 and 10
of the paper:
Glazing Types Occupants
Dissatisfied at 0.8
Clothing Insulation
Inside Glass Temp
(degrees F)
Summer Direct
Insolation
(Btu/h.ft2)
Single Clear Between 70-80% 75 203
Double Clear Between 60-70% 89 169
Double High Solar
Low-E
Between 70-80% 99 139
Double Low Solar
Low-E
Between 10-20% 83 86
In other words, double pane windows with high solar gain low-e is worse from a summer
comfort perspective than even double pane windows with clear glass and is about as bad
as single pane windows with clear glass. Only low solar gain low-e (generally a 0.40
SHGC or less) achieves reasonable summer comfort.
C. Control of Peak Demand
As the Department has already recognized in setting the Energy Star criteria, summer
peak demand is substantially impacted by SHGC. This issue is properly addressed by the
0.40 code requirement in the South and South Central zones. Trade-offs above this level
should not be allowed.
Similarly, as with summer comfort, we would normally recommend the 0.40 SHGC even
in the North and North Central zones to control summer peak demand. However, since
the Department disregarded this recommendation in the recent criteria-setting process and
set 0.55 as the SHGC maximum for the North Central, we would recommend 0.55 as the
maximum for both the North Central and the North, as at least a limited effort to address
summer peak demands.
Because winter peak demands (electric and/or natural gas) typically occur during hours
where there is no sunlight, these demands are a function of U-factor, with the lower the
better. The code levels discussed above appear to be reasonable caps on the U-factor to
address this concern.
2. Comments on Baseline for Energy Star Performance Analysis in the North
Zone (item 6 in LBNL Memo):
We do not think a performance analysis (or baseline) should be developed for the North
zone at this time.
First, there is no SHGC criterion/requirement for the North zone. Therefore, any choice
of an SHGC baseline in the North zone is simply arbitrary. However, if the Department
insists on establishing a North baseline, perhaps the least arbitrary would be to use the
0.55 SHGC from the North Central zone.
Second, establishment of an SHGC baseline without a criterion in the North also is
inconsistent with the approach proposed for the other three zones. For the other three
zones, the criteria are also used for the proposed baseline, even though they do not
represent real products. (For example, in the South Central, the typical product ' a wood
or vinyl low solar gain low-e, would have a U-factor and SHGC close to, if not below
0.35, yet the 0.40 prescriptive criteria is proposed as the baseline for both.)
Third, by establishing no SHGC criterion in the North zone, the Department has, in
effect, ruled that no particular SHGC level is preferable and is making no choice between
the two technologies ' high and low solar gain. (After all, the Department had the
opportunity to set a criterion in the North and elected not to set one.)
Fourth, when any SHGC qualifies in the North, how can we allow someone with a higher
(or lower, for that matter) SHGC to increase their U-factor and still qualify? In short, if a
consumer wants a high solar gain product, they can easily obtain one with a qualifying
0.35 U-factor ' allowing a higher U-factor is simply reducing/relaxing the stringency of
the requirements. In fact, with the newest version of NFRC 100, U-factors decreased for
virtually all windows, effectively reducing the stringency of the Energy Star program,
and making it possible for a reasonably designed, efficient window, whether high or low
solar gain low e, to satisfy the 0.35 U-factor. At some point, trying to find ways for more
existing products to qualify for Energy Star defeats the purpose ' the objective should be
to encourage product improvement in order for the product to become Energy Star. Even
worse, with the new NFRC procedures and a performance trade-off, window
manufacturers may very well begin to remove improvements they previously
implemented to meet the criteria (i.e. argon, better spacers, etc.).
Fifth, there has been no demonstration of any burning need for a performance approach
in the North zone. Unlike the aluminum products in the South Central zone, there is no
obvious group of products in the North zone with a compelling argument that might
justify the development of a performance trade-off. The 0.35 U-factor criterion for the
North zone has been in place since the inception of the program, unlike the improvement
of the criteria in the southern zones.
Sixth, we do not believe that it can be demonstrated that higher SHGCs justify permitting
higher (less stringent) U-factors, despite the claims of the high-solar-gain contingent to
the contrary. In fact, with a reasonable set of assumptions, we think that energy
consumption would remain relatively neutral (within any reasonable error band) in the
North regardless of the SHGC. With that fact in mind, why would we want to encourage
trade-offs that run counter to comfort, peak demand and the code as discussed above?
Finally, and perhaps most importantly, as discussed above, a baseline and a performance
approach are unacceptable due to the 0.35 U-factor energy code requirement in the North
zone.

NOTE FROM DOE: THIS INPUT INCLUDES TABLES, IF ANYONE WOULD LIKE ME TO SEND THEM THE PDF THEN JUST EMAIL ME. THANKS MARC LAFRANCE marc.lafrance@ee.doe.gov IN THE FUTURE WE WILL TRY TO OFFER IMPROVED FORMATS.


Replied By: P. Marc LaFrance from US Department Of Energy

24 - Nov - 2003 5:55 AM

RICHARD VOREIS COMMENTS...

NOTE: THESE COMMENTS ARE BEING POSTED BY DOE. Consulting Collaborative
3316 Westminster Avenue
Dallas, Texas 75205-1429
214.361.2130

November 22, 2003

 

Richard H. Karney, P.E., Manager
Energy Star Program
Department of Energy
Office of Building Technologies Program
1000 Independence Avenue, SW
Washington, DC 20585

Subject: Energy Star Performance Based Standard

Dear Rich:

As you know, I have been a long standing supporter of a performance based standard as it applies to qualifying for an Energy Star label. When the new Energy Star prescriptive standards are implemented later this month they will essentially eliminate aluminum residential windows in about 95% of the United States. Clearly, if aluminum windows can meet or beat the energy usage of a prescriptive standard, it is unfair to exclude them from the marketplace.

Following our DOE Workshop in Washington, DC on September 30, 2003 I became encouraged that LBNL will continue their research to find a way to implement a performance based standard as an option to the Energy Star prescriptive standard.

It is my understanding that two related issues require input from fenestration industry authorities such as myself. In that regard, I have the following comments:

Method

I prefer Option 3 (zone based equations) that LBNL presented at the DOE Workshop because it seems to be simple, easy and accurate. Additionally, it should be timely in its implementation.

Solar Heat Gain Coefficient (SHGC) for North Climate Zone

I have been shown independent research indicating that in a sample of 9,300 windows with U-Factors and SHGC's in the NFRC database that the largest percentage of windows with U-Factors at or below 0.35 had a SHGC of less than 0.30. Therefore, I recommend a base SHGC of 0.30 for the North Climate Zone.

I appreciate you seeking out opinions from those of us in the fenestration industry who relate to this important project of developing a performance based alternative for Energy Star. To repeat for emphasis, the performance based standard as an option to the Energy Star prescriptive based standard is essential for the good of consumers and the fenestration industry.

Please call on me at any time if you need additional input, etc.

Sincerely,

Richard D. Voreis

Richard D. Voreis
Chief Executive Officer

Copy: Marc LaFrance


Replied By: Thomas Culp from ATOFINA Chemicals, Inc.

25 - Nov - 2003 6:38 AM

SHGC for North...

In response to Garrett Stone's posting, a baseline SHGC of 0.55 in the north makes absolutely no sense. It is not even close to reality for actual products with U < 0.35 which more commonly have SHGC around 0.30. Furthermore, choosing baseline criteria of SHGC = 0.55 with U = 0.35 would mean that most current Energy Star windows (including windows from Mr. Stone's client) would actually perform worse than the baseline criteria because they have significantly lower SHGC. What kind of message is that for Energy Star, if most of the windows which meet the Energy Star prescriptive criteria actually perform worse and do not meet the performance based criteria, which is a better measure of actual performance?


Replied By: patrick muessig from azon

25 - Nov - 2003 12:32 PM

SHGC recommendation...

Azon proposes a baseline SHGC of 0.30. After researching the SHGC associated with products that have a U-Factor of 0.35 we have found many below this proposition. The talk about Energy Star being just another label, given the proposed IECC codes, is only by those who are still focused completely on U-Factors. Saving energy is the goal and setting the SHGC at the suggested 0.30 as a minimum will assure that Energy Star products out perform those associated with any other code.


Replied By: Ken Nittler from WESTLab

01 - Dec - 2003 9:13 AM

California Climates...

Item 2 - More California Climates Needed:
I think the California climate zones proposed under represent the booming inland climates 13, 14 and 15 (Fresno, High Desert, Low Desert) where more than 20% of the new housing starts are located. I recommend either adding one of these hot climates like CTZ13 or perhaps CTZ15.


Replied By: Ken Nittler from WESTLab

01 - Dec - 2003 9:15 AM

Baseline Products...

Items 4/5/6 ' Consistent Use of Baseline Products:
I recommend that we be consistent and either use actual values for each region or use the criteria values for each region, but not a mix of the two. Some have commented that 0.30 SHGC or even lower should be used in the North. If this logic is adopted for the North, then it should be adopted in all regions to be consistent. For example, a typical vinyl product that will meet the 0.4 U-factor / 0.4 SHGC criteria in the South Central in reality has actual values more like 0.37 U-factor / 0.33 SHGC. The energy savings attributable to Energy Star right now benefit from this free ridership. If the tradeoff is based on 0.4 U-factor / 0.4 SHGC this savings is lost anytime the tradeoff is used.

Overall, this is a tough call. If you use actual values across all regions, then it is going to be difficult for tradeoffs in the southern regions as most compliant products already have SHGC values substantially lower than the criteria. If you use the criteria values as the baseline, then I believe that the most consistent choice would be to use the 0.55 SHGC from the Central region for the North region as well. It doesn't make sense to use 0.30 SHGC for the North where there is no SHGC requirement, and then to have the South and South Central based on 0.40 SHGC.


Replied By: Ken Nittler from WESTLab

01 - Dec - 2003 9:15 AM

0.35 U-factor Tradeoff...

Item 6 ' Tradeoff of 0.35 U-factor in North:
One disturbing issue I've noticed is that the debate over this issue seems to be ignoring the fact that the newer NFRC 2001 rating system typically results in U-factors that are 0.02 to 0.03 lower for low frame conductance products like wood and vinyl. This means that a majority of low conductance products can hit the 0.35 target with either low or high solar low emissivity products, argon gas and better spacer systems. Why trade off U-factor in the north when there are many efficient products available that meet the criteria?


Replied By: Ken Nittler from WESTLab

01 - Dec - 2003 9:17 AM

General Comments...

I'd like to note that not everyone agreed that the right approach was to pursue tradeoffs. My first preference would be that the new criteria be left unchanged as there are many products that can meet the specified performance criteria. While the new criteria isn't a tradeoff method, it should be noted that this is a performance standard in the sense that it does not specify explicit material or design requirements.

If change is necessary, my opinion remains that the Energy Star window program would be better served by a very simple approach that addresses the original apparent political need to provide relief for aluminum products in the south. Moving the 0.4 U-factor criteria in the South Central to 0.45 would accomplish this with a minimum of disruption and would keep the Energy Star program simple and clear.

In reality, there is no energy savings available on SHGC tradeoffs in the south as the same low solar low emissivity glass products are likely to be used no matter what the frame material. So a calculated tradeoff doesn't make much sense. Also in reality, in colder Northern climates, the residential window market already overwhelmingly uses lower U-factor products due to many factors in addition to energy efficiency such as condensation and comfort. Creating a criteria that provides tradeoffs for higher U-factor products to qualify as being Energy Star will likely be ignored by the marketplace and may damage the Energy Star brand message.


Replied By: charles mcevoy from western extrusions corp

05 - Dec - 2003 5:59 AM

Exec. Vice President...

In response to the LBNL Analysis. Any material should be usable in windows as long as the window meets the standards. Allowing aluminum to be used in windows means more competition, better products and lower prices for consumers. My understanding is there are two issues that require input from industry participants. Regarding method, I prefer Option 3 (zone based equations) that were presented at the DOE Workshop because it seems to be simple, easy and accurate. Additionally, it should be timely in its implementation. Also regarding SHGC for North Climate Zone, I have been shown independent research indicating that in a sample of 9,300 windows with U-Factors and SHGC's in the NFRC database that the largest percentage of windows with U-Factors at or below 0.35 had a SHGC of less than 0.30. Therefore, I recommend a base SHGC of 0.30 for the North Climate Zone.


Replied By: Mike Manteghi from Traco

09 - Dec - 2003 10:32 AM

TRACO Comments...

During the DOE work shop on September 30th, the LBNL gave a presentation that illustrated the tradeoff options for South and South Central regions ONLY. There was not sufficient time for the LBNL to perform RESFEN analysis, which the LBNL agreed to accomplish for the North and North Central regions. The LBNL needs to determine a SHGC value for the North and North Central region.

Based on the AEC analysis, it identifies a SHGC between 0.25 and 0.3 for the North and North Central region. TRACO supports this analysis and the Performance base standard explained in Option 3 of the Performance Based Rating for the ENERGY STAR Window Program document. Option 3 will simplify short term annual energy performance calculations but the long term solution will be developed by NFRC AEP subcommittee in order to simplify for the consumer.


Replied By: from

30 - Apr - 2006 2:44 AM

better zone...

i'm a member and have been for years. And i will get right to the point . in cal. they have better zones than the rest of the u.s. why, because they know the country has an energcy problem and i see that the energcy star program is there to help large manufactors that have money and not to do watts right. there are manufactors that are out there care about there bottom line then whats right, window manufactors sell there windows in the north with lower-solor heat gain because they can and it's cheeper to perduce then a high solor heat gain. all i know is whats happening ,is things are beening done it's for the wrong reasons. wee need to better insulate our homes with the best windows out there even though it cost us more money in the long haul it will pay for it self and cost less. thank you g.c.


Replied By: from

30 - Apr - 2006 2:47 AM

better zone...

i'm a member and have been for years. And i will get right to the point . in cal. they have better zones than the rest of the u.s. why, because they know the country has an energcy problem and i see that the energcy star program is there to help large manufactors that have money and not to do watts right. there are manufactors that are out there care about there bottom line then whats right, window manufactors sell there windows in the north with lower-solor heat gain because they can and it's cheeper to perduce then a high solor heat gain. all i know is whats happening ,is things are beening done it's for the wrong reasons. wee need to better insulate our homes with the best windows out there even though it cost us more money in the long haul it will pay for it self and cost less. thank you g.c.



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