Volume 50, Issue 11 - November 2015

GANA Perspectives

The Next Step
A Close Look at Commercial Energy and Green Codes

by Tom Culp

Over the last 18 months, the ASHRAE 90.1 committee has been working on the next step in the main fenestration requirements for ASHRAE 90.1-2016. At the time of writing, the proposal is currently in its second public review, but at this point in the process, any changes made in response to further comments would likely be minor. Some of the key highlights include:

• Northern U-factors were reduced by 8 to 14 percent in climate zones 4 through 7, and a larger 13 to 22 percent in zone 8 for northern Alaska and Canada;

• Southern U-factors were reduced by a smaller 0 to 10 percent in zones 2 through 3;

• Southern solar heat gain coefficient (SHGC) was lowered to 0.22 in the new climate zone 0 (outside the U.S.), but left at 0.25 in zones 1 through 3, which is already appropriately stringent;

• SHGC in the middle of the country was lowered by 5 to 10 percent from 0.40 to 0.36 in zone 4 and to 0.38 in zone 5, to smooth the transition between the south and north;

• Importantly, there are no changes affecting window area or visible transmittance (VT).


Getting Tougher

The proposed criteria continue the trend in increased stringency in the energy codes. U-factors were lowered by approximately 10 percent between ASHRAE 90.1-2010 and 2013, and are now being lowered by another notch for 2016. This also brings the ASHRAE 90.1 values closer in alignment with those of the 2015 IECC. These are meaningful changes and can be achieved with existing technology. Roughly, the new criteria will generally require:

• Zone 1: Low-E double glazing;

• Zones 2-3: Low-E glazing, thermally broken frame;

• Zones 4-5: Low-E glazing, thermally broken frame and pick 1 of the following:
- Argon
- High-performance thermal break
- Two low-E coatings (No. 2/No. 4);

• Zone 6: Low-E glazing, thermally broken frame and pick 2 of the following:
- Argon
- Warm-edge spacer
- High-performance thermal break
- Two low-E coatings (No.2 /No. 4);

• Zone 7: Low-E glazing, thermally broken frame and pick 3 of the following:
- Argon
- Warm-edge spacer
- High-performance thermal break
- Two low-E coatings (No. 2/No. 4);

• Zone 8: All of the above in double glazing, or more likely go to triple glazing.

In addition to the core U-factor and SHGC criteria, there are also separate proposals that further encourage lower SHGC and/or external shading on the east and west sides of buildings as part of building-orientation requirements (which are unique to ASHRAE and not used in the IECC), and also make corrections to the SHGC credit given for exterior shading. These do not require different glazing types on different sides of the building as some previously suggested, but allow multiple options such as proper orientation of the building, better distribution of glazing, lower SHGC on the west, exterior shading, or use of dynamic glazing.

Map It

Another change in ASHRAE 90.1-2016 will be the use of new climate zone maps. Climate zone boundaries have moved as a result of updated weather data, with about 8 to 10 percent of counties changing to warmer zones. For instance, Milwaukee and southern Wisconsin will move from zone 6 to zone 5, and Dallas/Fort Worth will move from zone 3 to zone 2. There is also a new climate zone 0 for extremely hot regions, although this does not include any part of the U.S., and mainly affects places such as the Middle East, India and Indonesia.
Finally, there is a proposal on envelope commissioning which is focused on building-air leakage and air-barrier inspections, but will also result in increased attention to detailing at the window-wall interface for glazing contractors.

As ASHRAE 90.1 wraps up its 2016 edition, work is starting on the 2018 IECC, as well as the 2018 International Building Code and International Residential Code. Proposals are due January 11, and hearings will occur next spring and fall. Those wishing to learn more and participate in the development of code proposals addressing energy, structural, and safety issues are encouraged to join the Glazing Industry Code Committee.


the author

Dr. Thomas Culp
of Birch Point Consulting in La Crosse, Wis., serves as code consultant for the Glass Association of North America and the Aluminum Extruders Council on energy and green codes. He was also recently appointed as co-vice-chairman of the ASHRAE 90.1 committee.


USG
Copyright 2015 Key Communications Inc. All rights reserved.
No reproduction of any type without expressed written permission.