HomeMy WebLinkAboutARB201600016 Correspondence 2017-09-05Margaret Ma[iszewski
From: Heather McMahon
Sent: Thursday, August 31, 201711:31 AM
To: Kurt Keesucker
Cc: Karim Habbab; Margaret Maliszewski
Subject: RE: F+R Office Building / crozet - glass sample(s)
Hi Kurt,
Thank you for coming in this morning to discuss the issue that has arisen with the glass that was approved as part of
ARB-2016-16 for the Crozet Business Office, and thank you for this follow-up email which states that issue succinctly yet
comprehensively. Margaret and I have had concurred that we will bring this issue to the ARB's attention as a matter of
"other business" at the next meeting, which will be held on Tuesday, September 5.Of course you are welcome to attend
the meeting, but I believe that with your email statement, other documents, and the samples you provided this
morning, we can relay the issue sufficiently in case you are unable to attend Tuesday.
We will be in touch if we have further questions, and of course, feel free to do the same.
Thanks,
Heather McMahon, Senior Planner
Albemarle County Department of Community Development
401 McIntire Road
Charlottesville, VA 22902
434-296-5832 x3278
hmcmaho_n@a Ibemarle.org
From: Kurt Keesecker[mailto:Kkeesecker@brucewardell.com]
Sent: Thursday, August 31, 2017 11:00 AM
To: Heather McMahon <hmcmahon@albemarle.org>
Cc: Karim Habbab <khabbab@brucewardell.com>
Subject: F+R Office Building / crozet - glass sample(s)
Hi Heather
Thanks again for allowing me to stop by unannounced and describe our glass conundrum regarding the previously
approved F+R office building in Crozet.
For reference, our Certificate of Appropriateness letter for this project is referenced as "ARB-2016-16: Crozet Business
Office" and dated 4/11/17.
Please find the following brief summary of our request to alter the glass sample for the project.
During our review process, our office provided a glass sample (that we liked, aesthetically) .... but it unfortunately does
not meet the energy code for an important performance criteria for our region. This was a mistake on our part and we
apologize for the issue it has created. The various characteristics of the originally submitted glass are:
1. 78% VLT
2. 15% VLR.
3. the solar heat gain coefficient (SHGC) is 0.62
4. the u-factor is 0.31
These characteristics give the glass a 'clear' appearance (which we were attracted to...), but is also it's downfall
in terms of energy performance .... as evidenced by the poor performance in the SHGC criteria.
In Virginia, we are required by the Virginia Conservation Code (see excerpt table below) to provide glazing systems that
provide the following:
• an SHGC of no more than 0.40 (lower than 0.40 is better, meets criteria)
a u-factor of no more than 0.38 (lower is better, meets criteria)
In design control districts in Albemarle County, the minimum VLT (light transmittance) for glass is 40Yo (higher is better)
and maximum VLR (reflectivity) is 30% (lower is better.) We have included notes to this effect in our ARB package and
Construction Documents.... the good news is there are a number of products that can achieve these VLT and VLR criteria.
But some of them are too dark for our tastes....
So, in an effort to meet the various criteria of the energy code, Albemarle County minimum design standards, and
preserve the "look" of the building that was approved, we'd like to alter our glass submittal for this project to a glass
product by Guardian glass known as 'SN68' with the following performance characteristics:
1. 68% VLT
2. 11% - 12% VLR
3. the solar heat gain coefficient (SHGC) is 0.38
4. the u-factor is max 0.29
The sample I provided to you today represents this product.
As you can see, this 'new' sample performs much better in terms of SHGC, and also slightly better in terms of u-factor.
The SN68 product is referred to as a 'Clear' product by the manufacturer. (They also produce products the label as
'green', this is not one of them.)
As you can see, a 68% VLT provides for a very clear look to the glass (it is on the upper end of high percentage VLT
products by Guardian, the manufacturer, and we believe it will work well in our window system....)
We have experimented with the new sample in our office by holding it up to exterior windows and noticed the 'tint' of
the sample is not as predominate when natural light passes through it. (In the white box, the new sample looks slightly
green....but when held to the window it has a very faint "smoke" tint in our opinion and doesn't read green to us....)
We believe the new sample is a good resolution to balancing the aesthetic quality required by ARB and the performance
criteria required by Energy Code.
We hope you, Margaret, and the ARB will agreel
For now, we trust the sample(s) and paperwork / tech info we provided are sufficient for you / the ARB to make a
determination if our substitution request is agreeable. If we can provide additional info, please let me know.
Again, thanks for your help and sorry for having to backtrack a bit on our samples....
We'll look forward to hearing from you soon
Take care
KK
kurt keesecker, alo, ncarb
senior assoc'ate
brw architects
1 - 2 4th street ne
charIottesviIIe
v 1 r g i n i a 22902
[p] 434 . 971 . 7160
www.brw-archif ects.com
Please note: Starting June 12, the brwarchitects office will be transitioning to new summer hours. We will be available
Monday -Thursday until 6pm, and closed Fridays 1-5pm. Thank you.
2012 Virginia Energy Conservation Code
indoor space through Feat transfer from the therrrialty effectrve panel surfaces to the occupants
or indoor space by thermal radiation and natural: convection and the bottom surfaces of floor
structures incorporating radiant heating shall be insulated with a minimum of R- _5 (0.62 t 2/K x
W).
C402.3 Fenestration (Prescriptive).
Fenestration shall comply with Table C402.3. Automatic daylighting controls specified by this section
shall comply with Section C405.2.2.3.2.
TABLE C402.3
BUILDING ENVELOPE REQUIREMENTS: FENESTRATION
CLIMATE ZONE
9
1 2 1 3
1 4 EXCEPT MARINE
I SAND MARINE 4
6 1 7
1 8
Vertical fenestration
Wactor
Fixed fenestration
0_50
0.50
0.46
0.38
0.38
0.36
0.29
0.29
Operable fenestration
0.65
0-65
0.60
0.45
0.45
0.43
0.37
0.37
Entrance doors
°EA0
0.83
0.77
0.77
0.77
0.77
0.77
0.77
SHGC
SHGC 0.25
0.25
0.25
0.40 1 0.40 0.40
0.45 0.45
Skylights
U-factor
0.75
0.65
0.55
0.5o
0.50
0.50
0.50
0.50
SHGC
0.35
0.35
0.35
0.40
0.40
0.40
NR
NR
t!R = No requirement