JBED Winter 2010
Journal of Building Enclosure Design
An official publication of the National Institute of Building Sciences
Building Enclosure Technology and Environment Council (BETEC)
National Institute of Building Sciences: An Authoritative Source of Innovative Solutions for the Built Environment
The National Institute of Building
Sciences Building Enclosure Technology and Environment Council
1090 Vermont Avenue, NW, Suite 700
Washington, DC 20005-4905
Phone: (202) 289-7800
Fax: (202) 289-1092 [email protected]
Henry L. Green, Hon. AIA
Earle W. Kennett
Matrix Group Publishing
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Shoshana Weinberg, Pat Andress,
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©2010 Matrix Group Publishing. All rights reserved. Contents may not be reproduced by any means, in whole or in part, without the prior written permission of the publisher. The opinions expressed in JBED are not necessarily those of Matrix Group Publishing or the National
Institute of Building Sciences/Building Enclosure
Technology and Environment Council.
The Future of Window
A Bottom Line Look at Architectural Glass
Glass For Building
Developing The Next
Three Generations of
New Advancements in
Glass Bring More Design and Performance Choices
Than Ever Before
Message from Institute President
Henry L. Green
Message from BETEC Chairman
Guest Message from MC² Mathis
Consulting Company President
On the cover: City Center Plaza in
Bellevue, WA, is clad in triple-silvercoated, solar control, low-e glass.
The 26-story, 574,970 square foot building officially opened on May 19,
2009 when Microsoft took occupancy of floors two through nine. The building features a large atrium-style lobby that opens onto a two-anda-half acre urban landscaped plaza.
Photo courtesy of PPG Industries and
Winter 2010 5
Message from the National Institute of Building Sciences
Henry L. Green, Hon. AIA
IN My MESSAGE to you in the Summer 2009 issue of Jour-
nal of Building Enclosure Design, I discussed the need to raise awareness to improve building enclosures. I outlined several examples in that article, such as recognizing David Altenhofen for his efforts to establish Building Enclosure Councils
(BECs) throughout the country, the work Congressman Russ
Carnahan (D-Mo.) is doing to bring awareness to the issue of high-performing buildings, the programs held at the 12th
Canadian Conference on Building Science and Technology, and the December 2009 Ecobuild America Conference held in Washington, D.C.
Each of these examples addressed a consistent theme: education. These examples all focused on the need to improve our knowledge base to better utilize the latest technology to advance our building systems and to gain greater return on our investments. Investing in education is money well spent.
Numerous reports predict that the expected new construction in 2010 will amount to less than one percent being added to our nation’s building stock. Therefore, it is vitally important to focus our attention on existing buildings and how we can retrofit existing buildings effectively.
approximately $496 million of its fiscal year 2010 budget for repairs and alterations, $40 million of which will focus on energy- and water-conservation measures as well as high– performance, green buildings. While the amount attributed to retrofit and green buildings is only about 10 percent of that part of the budget, GSA has also requested significant resources to devote to other major limited-scope programs that will include upgrades to current technology and systems to improve the sustainability and energy efficiency of the federal building stock. This is but one example of the effort at the federal level. Other agencies are also devoting substantial budget allocations to this effort and emphasizing the need to improve existing infrastructure.
In order to achieve the desired results, a collaborative and expanded effort is necessary to understand the complexities associated with retrofitting and improving our existing building stock. Programs such as the upcoming BEST2 Conference in Portland, Oregon, to be held April 12 -14, provide an opportunity to learn more and gain a greater appreciation for the work needed to meet this challenge. This three-day conference has a variety of programs scheduled that will include information on best practices, improved theories and case studies on retrofitting buildings. I hope to see you there.
Henry L. Green, Hon. AIA
National Institute of Building Sciences
Recently, the discussion on buildings has become concentrated on the current building stock and the impact these buildings will continue to have on our society as we move forward.
Numerous reports predict that the expected new construction in 2010 will amount to less than one percent being added to our nation’s building stock. Therefore, it is vitally important to focus our attention on existing buildings and how we can retrofit existing buildings effectively. In order to achieve the goal of improving our existing buildings, we need to become educated on the opportunities, technology and systems available to relieve our nation of high-energy buildings, thereby reducing costs and improving our built environment.
We are beginning to see a greater emphasis on the federal government’s focus on the need to retrofit existing buildings.
The U.S. General Services Administration (GSA) has allotted
Winter 2010 7
Message from the Building Enclosure Technology and Environment Council
Wagdy Anis, FAIA, LEED AP
WARM WINTER GREETINGS TO ALL!
I’d like to report on the Building Enclosure Technology and Environment Council (BETEC) Annual Meeting, which convened December 9, 2009. Open to all members, it was part of the greater National Institute of Building Sciences
Annual Meeting held in conjunction with the Ecobuild
America Conference in Washington, D.C. The day before, the BEC National Committee met. Representatives from a dozen Building Enclosure Councils (BEC) chapters discussed
BEC priorities and business, including a meeting with the
American Institute of Architects (AIA) aimed at solidifying
AIA support for the BECs.
A very important initiative emerged from these meetings, namely a proposed educational webinar program on building science topics. The webinars would be nationally televised to the BECs utilizing star presenters as part of a plan to reinforce building science education. Hopefully, this initiative will emerge in 2010 as a joint program with AIA to benefit the design and construction industries.
The BETEC Board also discussed the important topic of whole building commissioning. In 2006, BETEC published the NIBS Guideline 3-2006: Exterior Enclosure Technical
Requirements for the Commissioning Process. The guide was part of the family of commissioning guidelines produced within the structure established by ASHRAE and the Institute, using Guideline 0: The Commissioning Process as the guidance document. Recently, ASTM announced the formation of the
E06-55-09 Task Group, which was charged with producing a new standard, Exterior Enclosure Commissioning.
A number of E06 members joined the BETEC Board discussion. The BEC National Committee brought a proposed action to the BETEC Board that the BEC chairs felt was extremely important to the industry. Based on their proposal, the BETEC Board voted for two things: first, that an update of
NIBS Guideline 3 was required, and second, that Guideline
3 and the ASTM document be “consistent, compatible, and complementary” and, therefore, not in conflict with each other.
The BETEC Board expressed two other action items urgently needed. One is the call to reinforce building science education, both in academic venues and in the construction industry as a whole. The second is the issue of the lack of energy efficiency of fenestration framing.
The BETEC Board was pleased to hear that the BEST 2
Conference (www.thebestconference.org) is on track, and proceeding with extensive U.S./Canadian collaboration on its substantial content. Hosted by BEC Portland and scheduled for April 12-14, the theme is “A New Design Paradigm for
Energy Efficient Buildings.” Please join us this spring in
Lastly, I’m happy to report that the BETEC Symposium on
Retrofitting Building Enclosures for Energy Efficiency and
Sustainability, held December 10, was sold out. BETEC action on the subject of energy efficiency of our existing building stock, both in its white paper (JBED Fall 2008) and followup action by Institute President Henry Green, have brought national attention to the topic and resulted in an intensified focus on Capitol Hill on this subject. The BETEC Symposium continued the necessary dialogue, and its presentations on retrofit techniques were extremely well received by the attendees.
Happy 2010 to you. I look forward to seeing you at BEST2!
Wagdy Anis, FAIA, LEED AP
Chairman, BETEC Board
Chairman, JBED Editorial Board
Principal, Wiss Janney Elstner
Thermal Performance of Exterior
Envelopes of Whole Buildings XI
December 5-9, 2010
Sheraton Sand key Resort
Clearwater Beach, Florida
This conference, sponsored by BETEC, ASHRAE and CIBSE, and organized by the Oak Ridge National Laboratory (ORNL), will present two concurrent tracks: Principles - Devoted to Research; and
Practices - Focusing on Practical Applications and Case Studies. Special topic workshops will be presented before or after the conference.
Since its inception in 1979, the “Buildings Conference” has taken place once every three years allowing time to develop new research and technology applications and to record the findings. Attendance is international and draws heavily on the advanced techniques of all our global experts.
For additional information, visit www.ornl.gov/sci/buildings/2010/index.shtm or contact Pat Love at [email protected] or (865) 574-4346.
Winter 2010 9
Guest Message from the Mathis Consulting Company’s President
R. Christopher Mathis
THE DEMAND FOR improved energy efficiency in buildings has followed a few predictable patterns since the early 1970s.
From insulation to appliances and now to windows, we have a) the need for ratings, b) the standardization of testing and calculation methodologies, (c) ratings, labels and third-party certification, (d) code adoption and utility programs, and
(hopefully) they all lead to (e) consumer awareness and protection when making buying decisions.
Unfortunately, even with all of the marvelous technologies showcased in the magazines (from new low-e coatings, triple and quadruple glazing systems, new inert gas fills, new frame materials, etc.) windows are STILL the poorest performing elements of the building envelope.
But we continue to insist on taking perfectly good walls
(well insulated and properly installed, of course) and we cut holes in them to accommodate windows. We do this for many reasons, including wanting natural light, on-demand ventilation and access to views.
Think about the challenges for the window industry. They take a combination of materials—from wood to glass to space age composites—and make products that meet wind loads, structural requirements, acoustical requirements, operability requirements and energy requirements, all the while making something that is CLEAR so we can see through it!
I have often said that the window industry has the toughest job: selling the “invisible”. They have to find a way to include invisible low-e coatings, gas fills and other efficiency improvements that we do not want to see but we definitely want in the final product.
So we improve window and glass technology. We improve coatings, gasses and durability. We improve the energy codes and computer tools. We improve window efficiency education materials and programs like ENERGy STAR. We constantly work to improve product ratings and labeling. But after all these improvements, windows remain the “weakest link” in accomplishing our overall building efficiency objectives (and yes, I know we still have to address uncontrolled envelope air leakage).
Our computer programs can show us all types of recipes for meeting some energy targets. Mathematical trade-offs
R. Christopher Mathis
Mathis Consulting Company have become the norm, marketed as “options” to meet those energy performance targets, often with apparent disregard for unintended consequences of the recipes.
For example, what if the occupant is uncomfortable with a recipe that meets a computer-defined energy target? Their only option is to adjust a thermostat, rendering the computer predictions immediately irrelevant. What if the product’s durability is untested? What if that super performance only lasts three months or three years? And what if the manufacturer that sold that window is now nowhere to be found?
A few rules can serve to protect the consumer, builder, architect and engineer in this age of evolving window technologies.
First, demand NFRC ratings and labels. It is the only chance at even getting close to reliable performance ratings.
The U-factor and SHGC values on the label provide your first line of assurance at meeting code and performance requirements. Beware of “R-value” claims. These not only don’t meet the code, they don’t tell the whole product performance story. My rule: if there’s no NFRC label or certification, don’t use it. Choose windows with certified U-factors below 0.35 and SHGC values of 0.30 or less as a starting place—for every residential or commercial project.
Second, beware of warranties that sound too good to be true. They probably are. Sure, embrace new technologies, but in the absence of proven durability, protect yourself (and your client) with substantial warranties. My rule: compare warranties and demand at least 20 years of coverage on the sealed insulating glass unit integrity. Most of the efficiency technology is embodied in the glazing system, so make sure it is protected (for more on window warranties see www.ornl.
Third, never trade off window performance in energy models. Remember, they are still the weak link in the building envelope. The code defines the minimum performance values. These minimums provide some support for meeting your expectations of heating and cooling efficiency, and occupant comfort. Trading window performance is a recipe for comfort complaints and unexpectedly higher cooling and heating bills. Make sure your windows at least meet the code!
Fourth, when increasing window area, make sure window performance increases by a commensurate amount. The more window area you want, the better the windows need to be.
Extreme care should be taken when selecting or comparing windows and the many different technologies available.
There are literally thousands of different glass coatings, gas types and fills, and frames and spacer combinations that deliver a wide array of performance. Whole product U and
SHGC ratings that meet the code are just the first step in the decision process for this all-important hole in the wall.
Winter 2010 11
The Future of Window
By Dr. John Straube, P.Eng., University of Waterloo
WINDOWS AND CURTAINWALLS are ubiquitous building enclosure components. Like all parts of the building enclosure, they have to meet the fundamental functional requirements of support, control and finish (Straube& Burnett, 2005). They need to do all of this AND be transparent, thin, and in many cases, operable! It should be no surprise then, that windows and curtainwalls cost more per square foot than any other part of the enclosure. What designers often forget, however, is that these components perform their support and control functions at a level that is far below that of other opaque components: the fire, thermal, solar, impact and sound resistance are all very low.
Modern aluminum curtainwalls and windows often have thermally broken frames, solar control and low-emissivity coatings on the glass, gas fills such as argon in the glazing space, and increasingly use insulating spacers. A combination of all of these technologies allows the U-value of the vision glass section of a curtainwall to reach a value of only around 0.3 to 0.4 (R-values of 2.5 to 3.0). It is difficult to achieve a whole-window R-value of even 4. Similarly, the percentage of solar heat gain that enters remains the same over the year, even though such heat gain is undesirable during warm weather and desirable in cold. Just as limiting is the fixed ratio of visual light transmittance to solar gain:
• whether it is dull or bright, the same proportion of light enters (see BSI-006: Can Highly Glazed Building Façades Be
Green? at buildingscience.com).
The benefit of high-performance windows and curtainwalls are becoming more widely known:
• Significant improvements to comfort by improving the
Mean Radiant Temperature (MRT) avoidance of cold films falling off the glass and wide temperature swings;
Major reductions in peak sizing of air conditioning; and
Major reductions in annual space conditioning and lighting energy (Carmody et al, 2004).
Increasing the R-value and airtightness of walls and roofs to R20, 40 and even 60 is now well developed and can be deployed in almost all projects if desired (Straube & Smegal,
2009). High-performance window technology is more expensive and has not been as widely adopted. Changes are occurring, however, with a range of new products being released, both from established firms and new technology firms.
Double-glazing has reached the limits of what is practical. With coating emissivity values as low as 0.03 and cavity fills of krypton or even xenon, the R-value at the center of glass cannot reach even R5. Hence, other approaches are
Figure 1. A composite foam and wood frame with aluminum cladding, and integrated operable shading (Courtesy of Holz & Form Canada).
used. The most obvious approach is to add another layer of glazing. This is a time-tested and reliable method, which, when combined with noble gas fills and low-e coatings, can deliver center of glass R-values of 6 to 9. Quadruple glazing takes this approach another step further to deliver centerof-glass R-values of R10 to 12 and higher.
The technical drawbacks to adding sheets of glass include increased thickness and weight. If this is a problem, there are solutions to both: the interior glazing can be replaced with a thin and lightweight sheet of plastic or film, and narrower cavities can be used if the argon gas fill is replaced with krypton. Center of glass R-values of over 9 are achievable with current technology in a 1” (25 mm) glazing package, and R20 in a 1 3/8” (35 mm) quintuple-layered system.
Vacuum glazing is another approach to increasing the Rvalue (decreasing U-value) of glazing. By drawing a vacuum on the space between two sheets of low-e coated glass, and using closely spaced small glass “posts” to support the glass, the conduction and convection heat transfer can be virtually eliminated, much like a thermos. There are only a few such products available, with center of glass R-values of less than 5. However, products are improving, and relatively thin (3/4”) triple glazing with 4 low-e coatings theoretically has the potential to deliver well over R20.
Winter 2010 13
fiberglass extrusions with wood interior finish and aluminum outer weathered components. All of these offer the possibilities of R6 to R8 frames, and all are commercially available (or are close to being available). These frames still have more heat flow through them than very-high-performance glazing, but can reduce heat flow by two to three times when compared to standard window frames.
Aluminum window frames with thermal breaks over ½”, and up to 1” are available and can provide acceptable performance
(e.g., R6 frames). Combining such large thermal breaks with non-conductive exterior pressure plates and filling the voids with materials such as aerogels can deliver frames with an Rvalue approaching R10, or 5 times as much as normal frames.
Figure 2. Quad-pane high R-value glazing and insulated wood frames, with operable exterior shades.
FRAMING ThE PROBLEM
The limitation with all of the high R-value glazing technologies is heat lost through the spacers and the framing systems. Warm-edge spacers have become quite affordable and widely available, but most insulated glazing units (IGU) still have more heat lost through the spacers than center of glass.
Much more significant is the heat loss through the frame.
As high-performance glazing units deliver higher R-values, the heat loss of poor frames begins to dominate. In residential construction, a normal wood or vinyl frame may have an R-value of just 2 to 3. A commercial aluminum frame, even thermally broken, rarely has an R-value of better than
2. Hence, the energy-saving potential provided by multiple glazings, coatings and gas fills are bypassed by low-performance frames. This is a very significant penalty in practice: an R9 3’ x 5’ triple-glazed glazing unit in a standard thermally-broken aluminum frame can have a whole window thermal resistance of only R4.
Frames of high-performance composite materials, commercially available as fiberglass frames, offer most of the strength, stiffness and durability of aluminum with the thermal performance of wood. Composite frames have been demonstrated in the lab and are becoming commercially available. This includes foam-filled vinyl frames with aluminum exterior claddings, wood frames with polyurethane foam thermal breaks (
), and slender foam-filled
The maximum rate of heat flow through a window does not occur on the coldest night of the year, but during sunny days. Of course, this heat flow is due to solar heat gain. The ratio of solar energy that becomes heat inside a building to that which falls on a window is defined as the Solar Heat Gain
Coefficient (SHGC). Dark tinted windows and reflective coatings were used in the past to reduce the solar gain. However, these approaches significantly reduce the view and daylight.
Modern windows use spectrally selective coatings which reduce solar gain with only a small effect on daylight.
As impressive as spectrally selective coatings are, large windows will still allow very large amounts of heat to enter a building when exposed to direct sun. Windows in full shade can allow nearly half as much heat to enter as windows directly exposed to the sun. For well-insulated, airtight, lowenergy buildings, even limited areas of low SHGC (e.g., 40 percent window to wall ratio in an office, with SHGC=0.33) can define the peak air conditioning load. At the same time, solar gain can be useful in cold weather, and daylight is usually welcome if it is not too intense.
To allow solar heat and daylight through a window when needed (a high SHGC), and reject it more effectively when not (eg, a SHGC below 0.1), advanced technology is required
(Selkowitz & Lee, 2004). Exterior shading, operated by automatic controls, can deliver this level of performance. For example, as the light intensity in the building reaches a predetermined threshold, the shades may deploy to fix the light level. If solar gain can be usefully harvested, the shades remain fully open, or pivot to bounce the light off the ceiling, thereby collecting the heat without glare.
The same high performance can be delivered without any visible shades through the use of electrochromic glazings.
Several technologies are available, but ultra-thin coatings that change their tint when a small voltage is applied are now available. One product silently changes its SHGC from 0.48 to
0.09 in a few minutes with no moving parts.
For the U.S. Department of Energy’s Solar Decathalon competition, the Team North entry (University of Waterloo, Ryerson University and Simon Fraser University, www.
team-north.com) explored many of the available high-tech
14 Journal of Building Enclosure Design
options. The result: a Serious Materials product with quadruple glazing, krypton fill, 3 low-e coatings, and proprietary non-conductive spacers to achieve a center-of-glass
R-value of 12, a visual transmittance of 0.58, and a SHGC of 0.44.
The high-performance glazing was held to glulam wood frames with structural silicone and a nylon, extruded cover cap. Despite having almost no thermal bridging through the frame, the frame’s R-value is still the limiting factor with an
R-value of less than 7. Still, the whole-window has an R-vaue of around 10.
For such a high-performance building, the ability to control SHGC actively is critical, or over-heating even on bright sunny cold days will occur. A Colt exterior venetian blind system with special controls was developed for the competition.
The high-level blinds could be controlled separately to allow daylight harvesting while providing privacy and still controlling solar gain.
The total system has worked exceptionally well in the field and is very attractive to many. Windows and curtainwalls have seen tremendous development over the last 30 years.
Low-e coatings, gas fills, warm-edge spacers and thermally broken frames have become available at reasonable cost. Given the performance demands of the new breed of high-performance buildings, these available technologies will need to be deployed along side multiple-layer glazings, dynamically controllable shading, and highly-insulated frames. The good news is that after years of laboratory research, many of these pieces are falling into place.
John F. Straube, Ph.D., P.Eng., is a specialist building science engineer who has been deeply involved in the areas of building enclosure design, moisture physics, and whole building performance as a consultant, researcher and educator. He is also a faculty member in the Department of Civil Engineering and the School of Architecture at the University of Waterloo where he teaches courses in structural design, material science and building science to both disciplines.
Carmody, J.; Selkowitz, S.; Lee, E.S.; Arasteh, D.; Wilmert, T.
Win dow Systems for High Performance Commercial Buildings.
New york: W.W. Norton and Company, Inc. 2004.
Selkowitz, S.E.; Lee, E.S. 2004. Integrating Automated Shading
and Smart Glazings with Daylight Controls. Tokyo, Japan:
International Sympo sium on Daylighting Buildings (IEA SHC
TASK 31). 2004.
Straube, J.; Burnett, E. BSD-018: The Building En closure.
Westford, MA: Building Science Press. 2006. See extract at www.
buildingscience.com – Building Science Digest.
Straube, J.; Smegal, J. RR-0903. Building America Special
Research Project: High-R Walls Case Study Analysis. Westford, MA:
Building Science Press. 2009. See extract at www.buildingscience.
com – Research Reports.
Winter 2010 15
A Bottom Line Look at
By Wayne E. Boor, P.E., PPG Performance Glazings
ARCHITECTURAL GLASS HAS long been a favored building material, thanks to its relatively low cost and aesthetic versatility. Now, with the green building movement continuing to expand and mature, glass has become the focus of intensive research and development aimed at maximizing its two most environmentally attractive traits: the ability to transmit light and block heat.
In recent years, these efforts have engendered a number of significant advances, from the introduction of uncoated spectrally selective glass to the rise of multi-cavity insulating glass units. While these developments clearly hold promise, the desire to enhance the performance of glass coatings remains a top priority among the industry’s scientists and engineers.
A major step toward that objective took place four years ago when glass manufacturers introduced the first commercially viable triple-silvercoated, solar control, low-emissivity
(low-e) glass. This development produced a dramatic leap in glass performance as measured by light to solar gain (LSG) ratio, a common standard architects use to compare the environmental attributes of competing architectural glasses.
Although the introduction of a triple-silver-coated, solar control, low-e glass marked a significant industry milestone, it was merely the latest step in a steady march of performance improvements in low-e glass over the last quarter-century. Unfortunately, despite these advances—and prodding from the U.S. government to use more energy-efficient glass—architects and building owners continue to specify less sophisticated products such as dual-pane tinted glass for many commercial buildings.
The reason is simple. They cost less. But are they really less expensive?
To answer that question, a nationally known energy and environmental firm was commissioned to measure and compare the potential real-world performance of six commonly specified architectural glazings. The results showed that, despite their higher initial costs, high-performance, solar control, low-e architectural glasses are well worth the investment, not just from a fiscal perspective, but from an environmental one as well.
Figure 1. Located in Seattle, The Terry Thomas Building is a 4-story, 40,000 square foot commercial structure. The building was designed based on the principles of sustainable design and is LEED Gold certified.
PARAMETERS OF ThE STuDy
As stated earlier, the purpose of the study was to gauge the relative environmental performance of commonly specified architectural glazings. To ensure the accuracy and objectivity if its results, the testing corporation used the U.S. Department of Energy’s (DOE)
2.2 Building Analysis Tool, which is regarded as a reliable and well-documented whole building energy analysis software in the United States.
The DOE 2.2 tool works by calculating hour-by-hour energy consumption for prototype buildings over an entire year. Input includes hourly climate data for the building’s location as well as local utility costs, heating and air conditioning systems and controls, interior and exterior building mass, enclosure insulation, shading and fenestration, hourly scheduling of occupants, lighting equipment, thermostat settings and numerous other variables.
16 Journal of Building Enclosure Design
In the architectural glass study, the testing firm modeled five glazing types. They were:
• Triple-silver-coated, Magnetron
Sputtered Vacuum Deposition
(MSVD), solar control, low-e glass
Double-silver-coated, MSVD, solar control, low-e glass (clear);
Tinted, MSVD, solar control, low-e glass (blue-green tint);
Pyrolytic-coated, spectrally se-
• lective, tinted, passive low-e glass
(blue-green tint); and
Dual-pane, spectrally selective, tinted glass (blue-green tint).
Relevant performance data for each glazing type is included in
. with 1.3 watts of lighting and .75 watts of equipment per square-foot.The school building was modeled according to a different set of assumptions.
The 200,000 square-foot, singlestory structure was equipped with a packaged VAV air-handling system,
DX coils for cooling, an economizer, hot water boilers for the heating plant, and a gas water heater for hot water service. Operating hours were from
7:00 a.m. to 9:00 p.m. on weekdays from September to June, and from
10:00 a.m. to 3:00 p.m. on weekends during the summer (July and August).
The heating temperature was 72°F
(22.2°C) and the cooling temperature was 76°F (24.4°C).
Internal peak load assumptions were as follows: 125 square-feet per occupant, and 1.1 watts of lighting and .45 watts of equipment per square-foot.
Each of the six architectural glasses was tested on two building prototypes: an eight-story office building and a single-story middle school. Each was modeled with two glazing design scenarios: one with punched windows on each façade and the other with complete window walls on each exposure.
The eight-story office building totaled 270,000 square-feet and was equipped with a VAV air-handling system, a centrifugal chiller cooling type plant, an economizer, and hot water boilers for both the heating plant and hot water service. The cooling and heating temperatures were set at 75°F (23.8°C) and 70°F (21.1°C), respectively, and operated according to a yearly schedule of 7:00 a.m. to
6:00 p.m. on weekdays and 8:00 a.m. to 12:00 p.m. on weekends.
Internal peak load calculations for the facility were based on occupancy of one person per 448 square-feet,
Both building prototypes were tested against climate data files for
12 major North American cities. They were Atlanta, Houston, Mexico City and Phoenix in the south and Boston,
Chicago, Denver, Ottawa and Philadelphia in the north. The remaining cities were Los Angeles, St. Louis and
In addition to representing a widerange of environmental conditions, these cities had widely fluctuating tariffs for natural gas and electricity, which were obtained and factored into the models.
In the end, 288 energy-modeling simulation scenarios were produced.
They generated calculations for building load, cooling equipment size, energy costs and HVAC cooling costs for each building prototype in each city with each glazing option.
Triple-Silver-Coated, Solar Control, low-E Glass (Clear) vs. Dual-Pane
The study demonstrated architects and building owners can lower their costs when they specify highperformance, solar control, low-e glasses in place of dual-pane tinted glasses. These products not only cut energy consumption, they also lessen requirements for total HVAC capacity.
In fact, simply by substituting triple-silver-coated, solar control, low-e glass for dual-pane tinted glass, the study showed that the owners of the prototypical, window-walled, office building, in Los Angeles or Atlanta could realize HVAC capital equipment savings of up to 20 percent. These equipment cost savings, which were estimated at more than $400,000, were comparable in Boston, Chicago,
Philadelphia and other cold-weather cities.
While the HVAC equipment costs savings are significant, the report showed the greatest return on investment would result from year-to-year energy savings. As
highlights, annual energy cost savings could range from $43,000 (12.9 percent) for the window-walled office building in Seattle to nearly $100,000 per year
(11.4 percent) for the same building in Boston. Over the 25- to 40-year lifespan of a building, these savings could ultimately amount to several million dollars.
Dual-Pane Tinted Glass
Solar Control low-E Glass (Clear)
Tinted MSVD Solar Control low-E Glass
Passive low-E with Spectrally Selective
Tinted Glass (Blue-Green Tint)
Triple-Silver MSVD Solar Control low-E Glass
Solar heat Gain
light to Solar
Gain (lSG) Ratio
Winter 2010 17
Double-Silver Coated, Solar Control, low-E Glass (Clear) vs. Dual-Pane
Double-silver-coated, solar control, low-e glasses have been on the market for more than a decade, yet they are still specified at significantly lower rates than dual-pane tinted glass and other less-expensive glazings. Although double-silver-coated glasses incorporate older coatings technology, they still offer significant opportunities to save money by reducing HVAC equipment needs and long-term energy consumption.
compares the energy and equipment costs of a window-walled, eight-story office building in six cities. One is glazed with dual-pane tinted glass and the other with a clear, doublesilver-coated, solar-control, low-e glass.
(dual-pane tinted and tinted solar control, low-e glasses will be compared in
Annual energy savings across the six cities ranges from $27,488 (6.3 percent) in Phoenix to more than $60,000 (9.2 percent) in Chicago.
As a percentage, equipment cost savings are even larger. In Atlanta and
Chicago, a prospective building owner would lower capital investment in HVAC equipment by more than 10 percent when specifying double-silver-coated, solar control, low-e glass instead of dual-pane tinted glass. The savings in the other six cities ranged from 8.7 percent in the cold-weather city of Boston to 9.5 percent in sun-baked Phoenix.
Tinted, Solar Control, low-E Glass vs.
Dual-Pane Tinted Glass
One reason architects specify tinted glass is for solar control. The other is for aesthetics. By specifying a tinted solar control, low-e glass, architects and building owners can achieve the appearance they want, along with enhanced cost savings and environmental performance.
compares two similarly tinted blue-green glasses in the same window-walled, eight-story office building. One features a solar control, low-e coating. The other is conventional dual-pane tinted glass.
shows, the savings realized in on-going energy and upfront equipment costs are more than enough to justify the expense of the superior glass technology. In Boston, the owner of a prototype window-walled, eight-story office building could cut cooling-related energy bills by more than $82,000
(9.6 percent) per year by installing tinted solar control, low-e glass instead of dual-pane tinted glass. The same owner pockets more than $400,000 (13.9 percent) from lower HVAC equipment requirements.
In Atlanta, where the cooling load is much higher, annual energy savings
City Annual hVAC Operating Expenses
Control low-E (Clear)
Chicago los Angeles
Eight-story office building, window wall.
Total Floor Area: 270,000 ft 2 .
Total Glass Area: 50,976 ft
Total hVAC Equipment Cost
Solar Control low-E
City Annual hVAC Operating Expenses
Chicago los Angeles
Eight-story office building, window wall.
Total Floor Area: 270,000 ft 2 .
Total Glass Area: 50,976 ft
18 Journal of Building Enclosure Design
Total hVAC Equipment Costs
Solar Control low-E
of $69,556 (10.2 percent) combine with equipment savings of $343,134 (16.2 percent) to generate a first-year cost reduction of more than $412,000 (8.5 percent).
As energy prices rise, the annual energy savings will continue to escalate in value.
The environmental benefits of highperformance architectural glazings
While lower energy and equipment costs represent the most tangible benefit of high-performance glazings, their widespread use can positively impact the health of the environment as well.
In the United States, commercial buildings account for nearly 40 percent of the country’s total energy consumption, and more than 75 percent of its electricity use. That means commercial buildings also represent our largest source of greenhouse gas emissions.
The potential cost savings associated with these energy-saving attributes already have been substantiated. However, using multipliers developed by the
DOE, the same study can be used to estimate the greenhouse gas emissions from each building type and each glazing scenario.
compares the energy usage and cooling-related greenhouse gas emissions associated with three glazing types in a window-walled, eight-story office building in Atlanta.
As the table demonstrates, the specification of tinted solar control low-e glass in place of dual-pane tinted glass has the potential to reduce annual cooling-related CO
emissions by more than 260 tons, which is equal to removing 43 passenger vehicles from the road or eliminating the CO
2 emissions from burning 550 barrels of oil.
-emissions savings are even more impressive with the clear, triple-silver-coated, solar control, low-e glass. The 327 tons of carbon emissions prevented from entering the atmosphere represent the total from 54 cars or 690 barrels of oil.
It is estimated that there is approximately 77 billion square feet of built space nationwide, with another seven billion projected to come on-line in the next five years. If, in a perfect world, all the existing buildings and newly constructed buildings were to incorporate triple-silver-coated, solar control, low-e glass, the country would cut its energy consumption by approximately 2,134 trillion BTUs per year, a net cost savings of nearly $40 billion in natural gas and electric utilities.
Beyond these bottom-line benefits, the installation of these glazings would also cut domestic annual cooling-related carbon emissions by 123 million tons. That is the same as removing 204 million passenger cars from the road annually, or about 80 million more than are currently registered in the entire country.
When considered in terms of cost and environmental health, it is clear that advanced architectural glazings represent an investment that can pay for itself many times over, and in more ways than one.
Wayne E. Boor, P.E., is Manager, Architectural Quality for PPG Performance Glazings. He is a 30-year veteran of PPG Industries who has worked in all facets of its glass business, including manufacturing, research, commercial development and technical services.
City Annual hVAC Operating Expenses
Tinted Solar Control low-E (Pyrolytic)
Chicago los Angeles
Eight-story office building, window wall.
Total Floor Area: 270,000 ft 2 .
Total Glass Area: 50,976 ft
Total hVAC Equipment Costs
Table 5: Energy Consumption and Greenhouse Gas Emissions
City Glazing Type
Dual-Pane Tinted (Blue-Green
Tinted Solar Control low-E
Triple-Silver, Solar Control low-E (clear)
Eight-story office building, window wall.
Total Floor Area: 270,000 ft 2 .
Total Glass Area: 50,976 ft 2 .
Winter 2010 19
Electronically Tintable Glass For Building
By Helen Sanders, Ph.D. and Lou Podbelski, SAGE Electrochromics, Inc.
WE LIVE IN a dynamic environment which changes season by season, day by day and hour by hour, yet the traditional building envelope cannot respond to these ever-changing conditions. The static nature of regular glass, especially, leads to significant problems related to the control of ever-changing incident heat and light, occupant comfort and productivity, and energy consumption.
Glass is ubiquitous in buildings because of the positive impact that natural daylight and the connection with the outdoors has on health and well-being.
Despite these desirable benefits, according to the U.S. Environmental Protection Agency (EPA), windows are the largest source of unwanted heat loss and heat gain, which must be managed by the heating, ventilation and air conditioning (HVAC) system.
While a full range of glazing products have been developed, from highly reflective glass to spectrally selective low-emissivity (low-e) glass, these are still static in nature. Consequently, a designer must make compromises in addressing a building’s combined need to manage solar energy, daylight and glare, while maintaining the window’s intended use by trading off visible light transmission with solar heat gain performance. Building occupants typically resort to using shades or blinds to control glare, which negates the purpose of the window, increases lighting energy use and still does not solve the problem of heat gain in the building.
Durable¹ electronically tintable electrochromic (EC) glass has been on the market for a number of years now.
shows the EC insulating glass unit in the clear and tinted states. EC glass can help building owners, designers, contractors and occupants avoid such compromises and challenges because it can provide active control over the transmission of the sun’s light and heat. The solar heat gain coefficient and visible light transmission can be varied to let as much light and heat into a building as desired based on outside environmental conditions and the needs of the building occupants without loss of view to the outside. EC glass can harness increased natural daylight and solar heat (for example, on a cloudy or cold day), and can also block the solar heat and unwanted glare as needed on hot or sunny days.
In this way, a building envelope with dynamic glass has significantly more potential to save energy than one with static glass, as well as providing greater occupant thermal and visual comfort.
illustrates the large variation in visible light (62 to 3 percent) and solar heat gain coefficient (SHGC)
(0.48 to 0.09) that EC glass can provide compared to the performance of static glass products.
ENERGy SAvING BENEFITS
cent of commercial buildings’ energy is used for lighting and as much as 80 percent of this lighting energy results in heat, which must be removed by air conditioning. Additionally, HVAC systems account for more than 35 percent of energy use in commercial buildings.
In fact, an EC window performance assessment by the Lawrence Berkeley
National Laboratory reports that daily lighting energy savings of up to 60 percent can be achieved by using EC.
(DOE) estimates that commercial buildings relying on EC window systems could save up to 28 percent in energy costs when compared to buildings with static, spectrally selective, low-e windows. A DOE research lab, the Lawrence Berkeley National Laboratory, estimates:
The EPA estimates that up to 30 per-
The U.S. Department of Energy
10 to 20 percent operating cost savings;
15 to 24 percent peak demand reduction; and
Up to 25 percent decrease in HVAC system size.
Furthermore, EC glass is a key component of the DOE’s roadmap to achieving zero energy buildings in 2030.
Figure 1. An EC insulating glass unit in clear and tinted states.
22 Journal of Building Enclosure Design
Figure 2. Graph of Visible Light Transmission (%) vs. Solar Heat Gain
Coefficient. This chart shows the heat gain and light transmission range of an EC product compared with standard static glass.
Figure 3. EC windows find applications in restaurants where the view is particularly important, as it is in this establishment situated on the edge of a lake in Wisconsin. Note that shades or blinds are not necessary.
Figure 4. EC glass in a library in a tertiary education college in
Minnesota. The top three and bottom rows are EC glass; the middle rows are static, tinted, low-e glass.
Figure 5. The exterior view of the EC skylight installation in
Connecticut. The photovoltaic panels that power the skylight system run along the bottom of the skylights.
Electronically tintable glass has applications in the built environment wherever light and heat control is required. Applications include restaurants, commercial office spaces, and schools and medical buildings (see
FIGuRES 3 TO 7
). In restaurants, dynamic glass is used to control uncomfortable glare while preserving the views that enable those businesses to command premium pricing (
It has been shown in studies that access to natural daylight promotes learning.
In schools dynamic glass can provide access to more natural daylight while also providing a comfortable learning environment
The top two complaints by occupants of commercial office buildings are, “It’s too hot,” or “It’s too cold”.
Dynamic glass can be used to improve the thermal and visual comfort around the perimeter zone without loss of view to the outside, positively impacting worker productivity. An example of such an application is shown in
FIGuRES 5 AND 6
where a skylight (2,500 sq.ft. of glass) is installed over a large office space in Greenwich,
Conn. The original method for controlling heat gain and glare from the skylight was to pull a tarpaulin over the entire skylight in the spring and remove it in the autumn!
Although the tarpaulin blocked the heat and glare, it also closed in the space which eliminated the natural daylighting and removed the connection to the outside. During a renovation late in
2008, the owner re-glazed the skylight with EC glass.
Winter 2010 23
The EC control system takes power from building integrated photovoltaic panels installed along the bottom edge of each side of the skylight and provides automatic intermediate state control, based on a user-defined light level in the occupied space. The result is a comfortable work space that provides natural light, heat and glare control for the occupants.
Electrochromic glazings can be comparable in cost to (and in some cases lower than) today’s static glass solutions. Even with high-performance static low-e, additional methods of solar control (exterior sunshades, interior shading systems, larger HVAC capacity) are frequently required to
Figure 6. East- and west-facing banks of the ridge skylight are programmed to change according to the location of the sun. The roof can also be completely tinted or completely cleared, or switched in any combination of its eight zones.
24 Journal of Building Enclosure Design
complete the static glass solution.
When adding up these initial costs (in addition to the higher ongoing energy expenses), the similarity in costs becomes apparent.
With the static glass system, the building owner also has the potential reduction in productivity due to comfort issues, which is a great deal more costly than other operating expenses.
Worst of all is the loss of the primary reason we put windows in a building in the first place—to see out. Furthermore, as with all new products, manufacturing scale and efficiencies will drive costs ever lower until the product becomes a standard. and work in buildings and need the view and connection with the outside, and the health and well-being that access to natural daylight brings. For this reason, coupled with the need to dramatically reduce energy usage in buildings to deal with climate change and energy security, we firmly believe that dynamic fenestration will soon become the standard choice for building envelope design.
Dr. Helen Sanders is an executive at SAGE Electrochromics with 15 years experience in the glass industry. Since joining SAGE in 1999, Dr. Sanders has been involved in a number of business areas including product development, sales, developing a technical and customer services organization, and most recently, leading manufacturing and delivery operations.
Lou Podbelski’s primary responsibilities as an executive at SAGE are marketing and sales. He has over 28 years of experience in the marketing and selling of construction products and services, 16 of which were in the glazing industry.
We ask groups all the time, “Why do we put windows in buildings?” It’s because of people—because people live
E2190 Specification for
Insulated Glass Unit Performance and
Evaluation and E2141-06 Stan dard
Test Methods for Assessing the Durability of Absorptive Electrochro mic Coatings in Sealed Insulated Glass Units.
IEA Task 31/45,
Seminar on Research and Practice.
Pacific Energy Center, San Francis co.
April 21, 2005. Presented by Eleanor
Lee, Law rence Berkeley National Laboratory (LBNL).
Heschong Mahone Group (1999).
Daylighting in Schools. An in vestigation into the relationship between daylight
and human per formance. Detailed
Report. Fair Oaks, CA. Heschong
Mahone Group (2001). Re-Analysis
Report. Daylight ing in Schools, for
the California En ergy Commission.
Published by New Buildings Institute (www.newbuild ings.org). The
Heschong Mahone Group (2003).
Windows and Classrooms: A Study of
Student Performance and the Indoor
Environment – CEC PIER 2003.
Re sults from the International Facility Management Association’s (IF-
MA’s) 2003 Corporate Facility Moni-
Winter 2010 25
Developing The Next Three
Generations of Zero-Energy Windows
By Brandon Tinianov, Ph.D., P.E., LEED AP, Serious Materials
IT IS WITHOUT question that building façade and envelope design is an extremely complicated science. Thousands of materials come together to create a dynamic interface between a constantly changing outdoor environment and stable indoor conditions.
Advanced glazing has great importance due to its profound impact on total building energy performance. In some cases, the glazing may have the single greatest impact of any single building component. In fact, research indicates that highperformance glazing is critical in “fulfilling the vision of zeroenergy buildings”.
Analytical tools and policy have matured in the last several years, providing additional impetus for its adoption. Additionally, advanced glazing is in the midst of a technological revolution which heightens its potential energy savings and accelerates the payback period (and financial rationale), both in new construction and in energy retrofits of existing buildings. For these reasons, a brief overview of stateof-the-art glazing is in order.
A NEW MARkET FOR GLAzING
One of the key influencers to the expanded discussion of advanced glazing systems is the restructuring and refocus of the current and future construction market. Traditionally, code-mandated building energy requirements have been modest and most insulated glass systems could meet these basic performance demands. However, there is a growing market demand for green or high-performance buildings that mandate energy efficiency beyond code minimums. In many cases, the total building consumption must be reduced by 15 to 40 percent. Advanced glazing is a key enabler to these targets.
A second, important market influence is the shift from new construction to retrofit construction activity. New buildings represent only 2.5 percent of the U.S. building market, while retrofitting provides an enormous market opportunity for owners and green builders and, recently, energy service provider companies (ESCOs).
Currently, energy-focused and green building comprises 5 to 9 percent of the retrofit and renovation market activity by value. This equates to a $2 to 4 billion marketplace for major projects. By 2014, researchers estimate that the share is projected to increase by 20 to 30 percent, creating a $10 to 15 billion market for major retrofit projects in only five years.
Act (ARRA), which will provide significant funding for renovations to federal buildings, the total potential market for major green renovations in the commercial building sector could grow to as much as $400 billion, according to another study.
Boosted in part by the American Recovery and Reinvestment
“ThREE GENERATIONS” OF ADvANCED GLAzING
In my opinion, advanced glazing in the mid-term future will take the form of “three generations” of technology. These generations, in order of market availability, are:
Generation 1 – low U-factor glazing (U
Generation 2 – dynamic glazing; and
3. Generation 3 – building integrated photovoltaic glazing.
Other interesting technologies, façade elements and glass features may take shape along the way, but these three advances will be the landmarks along the path of fenestration improvements and the establishment of zero energy buildings.
GENERATION 1: hIGh ThERMAL PERFORMANCE
Fenestration systems with low U-factors reduce the heat flux (both into and out of) the building. We must improve on
Figure 1. Cutaway of a triple pane insulated glass unit.
Courtesy of Serious Materials.
Figure 2. Cutaway of a quad pane window including the frame.
Courtesy of Serious Materials.
Winter 2010 27
GENERATION 2: DyNAMIC GLAzING
In the context of this article, dynamic glazings are those that can modulate their transmission properties to improve energy efficiency while allowing daylight to offset electric lighting requirements and encourage a connection to the outdoor environment. A secondary role of some user-controlled systems is that they can act as light shades or privacy glass as needed.
Dynamic glazing can admit solar heat when it is needed to offset heating energy needs, reject solar gain to reduce cooling loads, possibly reduce a building’s peak electricity demand, and offset much of a
Figure 3. Chart depicting the high relative performance of suspended film glass systems over standard dual pane systems. Courtesy of Serious Materials.
common dual pane low-e systems (full frame U-factor of 0.50 to 0.25) using super insulating systems that achieve U-factors of 0.20 to 0.10 or less. There are multiple, well-established methods to achieve these benchmarks, with the greatest sucbuilding’s lighting needs during daylight hours. To do so, the solar heat gain coefficient (SHGC) of the window may vary from approximately
0.50 to 0.05. The trigger for this performance switching can be controlled either actively (user) or passively (environment).
The energy-saving benefits of dynamic glazings are highly cess found in three or more separated coated panes (with internal panes of either glass or suspended coated films) having the greatest commercial success.
At the time of publication, such a window, which employs two external glass panes and three internally suspended coated films, is currently listed as the National Fenestration Research Council’s (NFRC) highest performing assembly, with a full-frame U-factor of 0.09.
An example of a stand-alone insulated glass unit is shown in
FIGuRES 1 AND 2
One advantage of this system is its well-understood energy saving benefits (demonstrable via energy models) and its design and performance flexibility. Multiple layers and a broad library of low-e coatings allows for systems that can be tuned for low or high solar gain, tint and U-value in all of the forms and styles that architects are comfortable using. Other technologies to improve glazing thermal performance currently in research or undergoing initial market adoption include vacuum glass panes and evacuated insulated glass. These units may soon be widely available. As with many emerging technologies, the shortcomings of these new methods are that they are costly, difficult to fabricate across a range of typical dimensions, and are unproven over a typical 20+ year service life.
This first generation of advanced glazing is being widely adopted in the national building market right now. This is not because the technology required is new (suspended coated films have been available and in service for over 30 years), but because their unit pricing is now attractive to architects and building engineers. A U-factor 0.15 Generation 1 system may have a comparable cost to many “performance” dual pane systems and may have a very short (2 to 5 years) premium payback period when compared to a commodity glass system with a U-factor of approximately 0.5. Such Generation 1 glazing should enjoy rapid adoption because 2× performance is possible at little or no incremental cost (
). case specific and vary with building type and climate, but can be profound at a national scale. A 2004 study of optimized applications of dynamic glazings was done by Lawrence Berkeley
National Laboratory. It concluded that “perimeter zone primary energy use is reduced by 10 to 20 percent in east, south and west zones in most climates if the commercial building has a large window-to-wall ratio” when compared to insulating static glazing, and that peak demand in these example buildings was reduced by 20 to 30 percent. The study also found that at
40 percent market adoption, dynamic windows with daylighting controls could save approximately 9 × 10 13 BTU in the year
Dynamic windows can be based on a number of possible technologies, including electrochromic layers, reflective metal hydride coatings, suspended particle devices, or thermochromic liquid crystals. Previous researchers have classified ideal dynamic glazing into three types whose transmittance switched over different spectral ranges: the entire solar spectrum, the visible spectrum only, or the solar infrared spectrum only. Additionally, each of these activations can take place either by absorption or reflection.
At this time, several companies are offering versions of passive, active, absorptive and reflective systems. Of the possible variations, by far, the most common are active electrochromics blocking full spectrum light via absorption.
The advantages of this current technology approach is that unwanted solar gain can be controlled by either building environmental controls or users, and that they can be readily incorporated into traditional glazing systems (including Generation 1 technology).
However, there are several disadvantages to current EC technology. By far, the greatest is cost. Existing EC products can cost $60 to $100 per sq.ft., far exceeding the energy savings. Second, the approach is full spectrum absorption, so artificial lights must be used when the glass is active.
Dynamic glass will see widespread adoption when it is
28 Journal of Building Enclosure Design
Figure 4. Image of a commercially available “light thru” BIPV product. Courtesy of SunTech Corp.
Figure 5. Image of a commercially available “see thru” BIPV product.
Courtesy of SunTech Corp.
demonstrable that the incremental cost of the technology can be recovered as energy savings within a 10 to 15 year period.
Given the current trend in energy costs and climate policy, it is reasonable to expect that dynamic glazing technology with an incremental cost of $5 to 10 per sq.ft. would enjoy broad market adoption. Last, it is important to note that for full energy savings, dynamic glazings must be paired with low U-factor systems. Without such a combination, the solar gain passing into and heating the building is immediately lost through the poorly insulating glass.
GENERATION 3: BuILDING INTEGRATED
The last generation of energy efficient fenestration is one that generates its own renewable energy, effectively reducing the total building consumption. Generation 3 fenestration products are commonly known as building integrated photovoltaics (BIPV). For the purposes of this discussion, I will consider fenestration BIPV as that which incorporates photovoltaics into the viewable area.
Third generation BIPV will come in two main forms: partially opaque/light transmitting; and transparent. As implemented today, light transmitting BIPV consists of solar cells made from thick crystalline silicon either as single or poly-crystalline wafers (
). These deliver about 10 to 12 watts per ft² of PV array (under full sun). Such technology is best suited for areas with no light transmission requirements (e.g. spandrels) or shading areas such as overhangs and sunshades.
Transparent BIPV systems are thin-film products that typically incorporate very thin layers of PV active material placed on a glass superstrate or a metal substrate using vacuum-deposition manufacturing techniques similar to those employed in the coating of architectural glass (
). Presently commercial thin-film materials deliver about 4 to 5 watts per ft² of
PV array area (under full sun). Thin-film technologies hold out the promise of lower costs due to much lower requirements for active materials and energy in their production when compared to thick-crystal products. Although the thin film technology is designated as transparent, its actual light transmittance is typically between 1 to 10 percent. Such systems are not currently suitable for high transparency applications, but are well suited for atriums and glass canopies.
In order to be more than a technology showpiece, BIPV incremental costs need to come down to the point where they can demonstrate a financial payback period comparable to other non-building integrated PV.
Now is an exciting time for advanced building glazing, as building energy has caught the attention of both technology companies and energy policy advisors. Along the path of future glazing technologies are three generational milestones: low U-factor, dynamic properties and energy generation. Developing the next three generations of zero-energy windows will provide products for both existing buildings undergoing window replacements and products which are expected to be important contributors to a zero-energy building future.
Brandon Tinianov, Ph.D., P.E., LEED AP, is the Chief
Technology Officer at Serious Materials.
1. Arasteh, D.; Selkowitz, S.; et al. Zero Energy Windows, Proceed-
ings of the 2006 ACEEE Summer Study on Energy Efficiency
in Buildings. August 13-18, 2006. Pacific Grove, CA. LBNL-
2. SmartMarket Report: Green Building Retrofit & Renovation.
McGraw Hill Construction, 2009.
Energy Efficiency Retrofits for Commercial and Public Build-
ings. Pike Research, 2009.
4. In all cases the U-factor is given in English units of BTU/ h·ft2·˚F and represents full frame values.
5. As manufactured by Serious Materials. www.seriousmaterials.com.
6. Vacuum glass panes are being produced under the name
Spacia (www.nsg-spacia.co.jp) and vacuum IGUs created via a metal-to-glass diffusion bonding process are under development by EverSealed Windows Inc. www.eversealedwindows.com.
7. Lee, E.; y azdanian, M.; Selkowitz, S. The Energy-Savings Po-
tential of Electrochromic Windows in the US Commercial
Build ings Sector. Completed April 30, 2004. LBNL-54966.
8. At the time of publication, SAGE Electrochromics is the leading manufacturer of commercially available EC glazing (www.
Winter 2010 29
New Advancements in Glass Bring
More Design and Performance
Choices Than Ever Before
By Chris Dolan, Guardian Industries Corp.
DAyLIGHTING IS TAKING
center stage in many of today’s healthcare and educational buildings as architects and designers look for new ways to improve energy efficiency and productivity while creating a tranquil environment conducive to healing and learning. To achieve these benefits, architects are looking to the latest developments in glass to deliver the right balance of solar control and light transmission.
Historically, hospitals and other therapeutic settings have used darker or more reflective glass to achieve patient privacy. But with today’s advances in glass technology, professionals who design healthcare buildings have better options that provide desirable light transmission with medium to low light reflection, either from inside, outside or both, depending on the design requirements. They have access to glass that is neutral in appearance and fills interior spaces with natural light, while reducing solar heat gain in warm weather and preventing heat loss in cold weather.
Today’s low-emissivity (low-e) glass can now provide a range of visible light transmission, between 40 and 70 percent, while also offering lower reflectivity than was possible in the past. These products are available in a variety of colors, with emphasis on the neutral range of light gray or green to slightly blue in reflected color.
A study by Fair Oaks, CA-based consultant Heschong Mahone Group, “Daylighting in Schools,” highlights some of the remarkable results of daylighting, including superior math and reading skills improvement for children in well-daylighted classrooms. Similarly, a California Energy Commission study discovered that call center workers with outdoor views performed 10 to 25 percent better on tests of mental function and memory recall, adding weight to the case the role of natural light plays in human productivity and performance.
The use of sunlight to light a facility is not new. The incorporation of natural daylight in today’s school and heath care facility designs signifies a return to lighting concepts from more than 50 years ago when the sun was used as a facility’s main light source. While daylighting trends frequently appear in current building designs and facilities, there are several factors to consider before moving ahead with the design.
SPECTRALLy SELECTIvE LOW-E OPTIONS
Traditionally, architects and designers have relied on heavily tinted or highly reflective products to achieve energy performance. Today, they are looking for glass that is neutral in color with natural light transmittance but does not transmit the heat and glare.
The glass industry has responded with high-performance low-e products that use a super-thin metallic coating to allow natural light inside while reducing heat transfer. Emissivity is the measure of the glass’s ability to radiate energy, and the lower the emissivity, the less heat that is transferred in or out. The newest generation of low-e technologies includes spectrally selective coatings that reflect between 40 to
70 percent of solar radiation normally transmitted through clear glass, while still allowing in large amounts of light. Advanced glazings with spectrally selective coatings can reduce cooling requirements in hot climates by approximately 40 percent.
Two spectrally selective low-e options are sputter-coated
(also known as soft coat) glass, and pyrolytic-coated (also known as hard coat) glass. To create sputter low-e coatings, optically transparent silver along with other metals is deposited on the float glass off-line in a vacuum chamber, after the base glass is manufactured. Sputter low-e includes one or more layers of silver between layers of metal oxide in a vacuum. Pyrolytic low-e is produced by applying metal oxides during the molten stage of float glass manufacturing.
Sputter-coated glass provides high visible light transmission and optimal transparency, and dramatically lowers heat gain or loss, while pyrolytic low-e coatings typically allow more solar heat to be transmitted than the latest generation of sputter-coated glass.
Manufacturers are offering spectrally selective low-e glass with a clear transparent appearance and solar heat gain coefficients (SHGC) as low as 0.28., which means 72 percent of the solar radiation is reflected back outside. Given the same
U-values, decreasing the SHGC from the .37 of the standard commercial low-e glass to .28, and the visible light transmittance from 67 percent to 54 percent, add up to significant energy savings.
ENERGy EFFICIENCy AND SuSTAINABILITy
In addition to controlling the solar heat gain inside a building, the correct glass can affect the size efficiency of the heating, ventilating and air conditioning (HVAC) equipment as well as daylighting systems.
Most buildings, including healthcare and educational facilities, are typically designed to perform well in worstcase scenarios. This means the type and size of the HVAC
30 Journal of Building Enclosure Design
equipment is often based on the most extreme temperatures and the highest levels of occupancy. Preparing for the worst case often leads to the purchasing of larger than necessary equipment, which means a higher capital expenditure upfront and higher usage costs over time. What’s more, when an HVAC unit runs at less than 50 percent of its full capacity, its ability to use energy efficiently declines exponentially.
But there are ways to reduce the size of an HVAC unit. First on the list is minimizing solar heat gain through low-e coatings. An independent study by engineering company Enermodal Engineering Inc. pegs the upfront potential savings generated by lower SHCG glass at as much as $2.50 a square foot due to downsizing the chilled water and air distribution systems. When compared to traditional high-performance low-e glass, operational costs savings of up to
$1.60 per foot of glass can be achieved by the newer glass in buildings with glare and daylighting controls.
The glass effectively blocks 72 percent of solar energy, while transmitting 54 percent of natural light. Meanwhile, the cost differential over standard high-performance low-e glass can be measured in pennies.
Cost savings is just one of the benefits manufac-
Guardian Industries and fabricator JE Berkowitz provided SunGuard® Super-
Neutral 68 for the University of Michigan Cardiovascular Center’s cylindrical, glass-enclosed atrium. The atrium uses natural light as both a healing element and an energy-saving feature.
turers are seeking by turning out greener products. Thanks to technological advances that make glass stronger and more durable, there are more manufacturing plants throughout the
United States, meaning glass is more readily available, which cuts down on transportation costs. Local production adds to sustainability and eligibility for LEED credits.
When broken, tempered glass fragments are usually relatively small and less likely to cause serious injury, so it qualifies under building codes as “safety glass.”
Spandrel glass: Spandrels are opaque glass panels designed to conceal building components and match or contrast with vision glass. They’re used to conceal such building components as columns, floors, HVAC systems, wiring or
ChOOSING GLASS FOR STRENGTh, SAvINGS AND
Today’s designers and architects have many choices for glass that keeps energy costs down, lets in more natural light, provides added security—all while creating striking designs.
Insulating glass: Insulating glass units (IG units) improve thermal performance by providing a thermal break—two or more lites of glass separated by a sealed air space. This enables the glass to meet two very different requirements; keeping heat in during colder weather and keeping heat out during warmer weather. When used in conjunction with low-e and/or reflective coatings, IG units perform even better for conserving energy and complying with local codes.
Laminated glass: By code, laminated glass is considered
“safety glass.” Laminated glass consists of two or more lites of glass that are permanently bonded by heat and pressure with one or more plastic interlayers of polyvinyl butyral (PVB).
Heat-strengthened glass: With a surface compression at least double that of raw glass, heat-strengthened (HS) glass provides additional strength against wind load and thermal stress. HS glass has been subjected to a heating and cooling cycle during the manufacturing process and is generally twice as strong as annealed glass of the same thickness and configuration.
Tempered glass: Even stronger than heat-strengthened glass, its surface compression is four times that of raw glass. plumbing. Designs calling for large areas of glass, such as curtain walls or structural glazing, often include spandrels.
Silk-screened glass: The printed patterns of silk-screened glass can provide extra privacy and interesting design options. Silk-screened glass is named for the printing process that creates a design or pattern by applying ceramic frit/paint to the glass surface. It offers designers exciting opportunities to customize both exterior and interior glass with patterns and colors. It also reduces glare and increases occupants’ privacy.
For designers and architects of healthcare and educational buildings, advances in glass technology are making it possible to explore more striking designs while meeting new standards in sustainable building. Glass is one of the first design elements to consider and is also one of the most important materials for delivering meaningful energy savings and sustainable practices.
Christopher G. Dolan serves as Director of Commercial
Glass Products for Guardian Industries Corp., a position he has had since 2002. His responsibilities include sales and marketing, new product development and overall program management of Guardian’s commercial glass product line, including
SunGuard® coated glass products.
Winter 2010 31
By Jonathan Baron, AIA, Shepley Bulfinch
BEC-Boston continues to meet monthly (except for August and December) at the BSA headquarters in Boston’s Financial District. Recent presentations have included Air Barrier Research by Laverne Dalgleish of
Building Professionals Consortium; Designing with Daylight, by Marilyne
Andersen, Professor at MIT; and Deep Energy Retrofits for Existing Homes, by Betsy Pettit of Building Science Corporation. We typically have 20 to 30 attendees and there is always spirited discussion with the presenters.
The BEC-Boston is preparing another Building Enclosure Award program. The call for entries was released in November 2009. Visit www.becboston.org for more information. The award will go to the building that best demonstrates innovation in design through the craft, science and engineering of high performance building enclosures in New England.
We are beginning a study of the impact of Massachusetts’ Energy Code on the energy efficiency of buildings. We hope to look at energy consumption within a group of sample buildings and to possibly conduct airtightness testing.
Upcoming meetings will focus on glass and glazing. More information about future and past meetings can be found at www.bec-boston.org.
By Tony Wolf, SmithGroup
The Greater Detroit BEC was organized in late 2008 and since then, we have been sponsoring program meetings once each month (except December and the three summer months). Attendance at each meeting ranges from 60 to 80 members. Even the Detroit Chapter of the AIA has remarked that our growth and profitability is almost without precedent.
In October 2009 we held a successful day-long symposium, which drew approximately 110 attendees. Our speakers included:
• Brad Burdic, National Group Manager, Owner Services, for JME3co., a Johns Manville Company spoke on the topic of Solar Solutions for
Commercial Roofing Systems.
Rochelle Jaffe, Senior VP/Quality Officer in Asset Preservation at NTH
Consultants, Ltd., spoke about Controlling Masonry Cracks and Leaks.
Mark Michener, a Senior Roofing and Waterproofing Consultant at
SME Consultants, covered A Forensic Approach to Roofing Failures.
• Dr. Joseph Lstiburek, B.A.Sc., M.Eng., Ph.D., P.Eng., a Principal of Building Science Corp., spoke about Building Envelope Fundamentals: Don’t
Do Stupid Things.
The titles of our the regular monthly programs from last year and the slideshows are available at www.aiami.com/Chapters/Detroit/committees/bec/aiadet_comtee_bec_home.htm.
By Robert Matschulat, AIA, CSI, CCS, CEFPI, NCARB, edutecture LLC
BEC-Colorado is approaching its fifth anniversary and is thriving. Attendance at our monthly first-Wednesday programs has continued to grow, ranging from 25 to 72 participants in 2009. The success of these programs required mid-year relocation to larger venues, including an oversized classroom at the University of Colorado Denver campus.
Here is a summary of the BEC-Colorado program topics presented since our last report: December 2008: Air Barriers; January 2009: Rain-
screen Systems; February: Curtain Walls & Storefront Systems; March: Archi-
tectural Aerodynamics Using Wind Tunnel Modeling; April: HVAC Systems
& Their Effect on the Building Envelope; May: Designing for Moisture Pre-
vention in Masonry Walls; June: Building Enclosure Sustainability; LEED /
Green Globes Comparison; July: Wind Design for Roofing Systems; August:
2006 IECC and/or Case Studies on Energy Improvements to Existing Build-
ings; September: Weather Barriers and the Annual Seminar.
In addition to the monthly programs, BEC-Colorado hosted our third annual half-day building enclosure seminar, which attracted more than 90 attendees on September 30, 2009. The seminar topic was Air and Moisture
Transmission through Walls at Transitions and Details, presented by Vince
Cammallleri, AIA, and Michael Louis, P.E.
The success of BEC-Colorado is due, in large part, to the support of our sponsors A-1 Glass Inc.; Ambient Energy; Andersen Windows; Building Consultants and Engineers; Elliott Associates; Fentress Architecture;
Georgia Pacific; HDR Architecture; Sto Corporation; Vapro Shield; and WR
For 2010, BEC-Colorado has identified more program topics than months are available to present them! We will continue to investigate the applicability of our programs to qualify for the new AIA continuing education “sustainability” credits. We plan to host a fourth annual BEC seminar in September or October and again, send our chair to the National
By Dave Herron, BOKA Powell
In October 2009 our BEC took a walking tour of the new Kansas City
Performing Arts Center, which was under construction. At our November meeting attendees enjoyed a presentation by J.B. Howell of Novum Structures. And at our December meeting we learned a lot from a presentation given by the Josef Gartner Group, a division of Permasteelisa Group.
We are currently in the process of soliciting sponsors to help fund our
2010 sessions so that we will be able to bring national expertise to the Kansas City AEC industry.
By Karol Kazmierczak, AIA, ASHRAE, CDT, CSI, LEED-AP, NCARB,
Morrison Hershfield Corporation
In Miami we continue to meet monthly and the attendance is growing as an increasing number of construction professionals get familiar with
BEC-Miami. We are proud to say we marked our second anniversary in July
2009! We head into the new calendar with a small change: the day of our meeting will now be the third Tuesday of each month.
Recent speakers and topics include Alex Hidalgo-Gato of Formas on
Rainscreen Facades; Ed Crim of Kawneer on Storefronts and Curtain Walls; and Dawn Griffin of Henry on Moisture in Exterior Walls. We look forward to having Thomas Schwartz of SGH in February.
In November, we were supposed to learn about anti-terrorism and blast mitigation in aluminum glazing systems but, for the very first time in our history, the speaker did not show up. Fortunately, our member
Dean Kautheen organized a projector, and I gave an impromptu lecture on Sloped Glazing instead.
In December, we participated in the BEC and BETEC meetings at the
Ecobuild Conference in Washington, D.C. We look forward to participating in the BEST2 Conference in April.
We also stepped firmer into the world of internet technology. We expanded our webpage and ventured into digital social networking by establishing a LinkedIn group. We also plan to experiment with getting our
Winter 2010 33
meetings videotaped and transmitted over the internet. One of our members drives over 350 miles one way to meet in Miami every month!
2010 is the year of the annual AIA Convention, which is taking place in
Miami. At the event our BEC-Miami chairman will speak about façade engineering to the attending architects.
Florida was particularly hard hit by the recent real estate bust, but we look forward to the year 2010 to see the emergence from the economic crisis.
By Judd Peterson, Judd Allen Group
In August 2009, the Minnesota BEC hosted Erick Filby, a representative from Traco Windows, who presented information on the latest thermal break technology of Traco’s NexGen line of products.
During the month of August we also discussed educational efforts by
BETEC and local BECs, in particular the ones modeled or done in conjunction with RCI certification programs that are already established. The
University of Minnesota then took a simultaneous interest in developing a curriculum to address building enclosure technology. We had further discussions with John Carmody, Director of the Center for Sustainable Building Research at the University of Minnesota, and his research fellows Rich Strong, Garrett Mosiman and Kerry Haglund, with regard to setting up some education for building enclosure technology through the
University of Minnesota.
The University of Minnesota made the news when their ICON Solar
House finished in fifth place overall, and first place for Lighting Technology, in the 2009 Solar Decathlon in Washington, D.C. The competition, hosted by the U.S. Department of Energy, took place at the National Mall.
The U of M Team was among only 20 universities from around the world that competed in the event.
In October, we had a roundtable discussion on the current status of spontaneous failures in tempered glass due to nickel sulfide inclusions, particularly as it pertained to some local occurrences of the phenomenon.
In November, the annual AIA Minnesota Convention was held. Also in November, Stanley Gatland, Manager of Building Science Technology for CertainTeed Corporation, was a guest presenter of a seminar on thermal and moisture properties in building envelopes and how this relates to
Minnesota’s recent air barrier code requirements.
By David C. Young, P.E., RDH Building Sciences, Inc.
The Portland-BEC is off to a great start this year! We’re very happy to be resuming our lunch presentation schedule at the new (historic restoration) University of Oregon White Stag Building, in Old Town Portland.
The best news is that we now have the ability to broadcast our speakers’ presentations over the U of O’s teleconferencing system. This will allow all other BEC members to benefit from our program. When they become available for broadcast, BEC members across the country will be able to login and follow along, similar to a webinar broadcast.
The theme of our presentations this season is the “Mad Building Scientist.” In my mind, this conjures images of the Dr. Lstiburek and Mr. (Dr.)
Straube duo, and I assure our presentations will be no less entertaining.
The theme is really about pushing the envelope in building enclosures (or is that pushing the enclosure in building enclosures?).
Of course, the main thrust of the Portland-BEC executive this year is the BEST2 Conference. The event will showcase the beauty (and wine) of
Portland in April. There will be some fantastic tours set up and the program of speakers for BEST2 is excellent. Please join us in Portland on April
By Peter M. Ryan, AIA, Wiss, Janney, Elstner Associates, Inc.
In September 2009, the Seattle Building Enclosure Council (SeaBEC) kicked off our sixth year of operation with a keynote presentation by Mark
LaLiberte of Building Better Homes. He helped outline this year’s educational program theme: building envelope energy efficiency and energy savings. With some of the lowest energy costs in the nation and our moderate summer and winter temperatures here on the west-side of the state, most of our presentations over the last five years have dealt with stopping, or as we say “reducing,” water infiltration through the exterior enclosure during our six-month-long rain event each year. However, we hope to attract new members with our new energy efficiency-focused direction. The remainder of our year will be rounded out with presentations on building commissioning, photo voltaics and air barriers.
Recently a group from our board drove to Vancouver, British Columbia, to attend the BEC’s Annual Conference and Educational Seminar.
The purpose of our attendance was to evaluate the possibility of producing our own seminar event in the Seattle metro area. The SeaBEC board was impressed with BC-BEC’s program and is now in the process of preliminary planning to produce our own program, for the Spring of 2011.
We also had the opportunity to meet with the BC-BEC President Joel
Schwartz, their Vice-President and Conference Chair Sophie Mercier, and their past President Douglas Watts. The SeaBEC Board enjoyed exchanging ideas and came away with some great ones. Thank-you BC-BEC for your invitation to meet. We were all quite impressed with your dedication and fine work.
This past spring our group participated in the Rebuilding Together program by supporting a local senior center’s effort to revitalize their resale shop. Fifteen SeaBEC members took part in the one-day event, which was part of a larger volunteer effort throughout the nation. Our members helped refurbish double hung wood windows, infill a back door and install new lap siding. They also removed an unsafe deck structure.
This past year we have also been attempting to support the Portland-
BEC in their efforts to host the BEST2 Conference in April 2010. We are looking forward to providing continued support as this event draws closers.
If you ever find yourself in Seattle on the third Thursday of the month
(except July and August) please stop in for our monthly meeting. For more information, visit our website at www.seabec.org.
By Joe Schultz, AIA, Kahler Slater
BEC-Wisconsin is in its second year and generally speaking, monthly meetings have been well attended with 20 to 25 guests. One of our current initiatives includes taking steps to improve leadership as well as attendance at our events. To do this, we have a larger core group helping to organize and arrange speakers.
What’s most exciting for BEC-Wisconsin is our outreach throughout the state. The meetings are offered through the internet and we have host sites in Milwaukee, Madison and UW-Eau Claire. As we become more comfortable with the webinars, we are looking to expand to other areas of the state. While we are still adjusting to the new format, we are excited about the outreach and collaboration to more professionals in our state.
34 Journal of Building Enclosure Design
The Marshall Group, Ltd. ................................................................ 35
Architectural Glass and Windows
Oldcastle Glass ........................................................................... 20, 21
The Glass Association of North America ......................................... 32
Below Grade Water and Containment Barrier
Polyguard ........................................................................................... 4
Construction Consulting International ............................................ 24
Building Sciences and Restoration Consultants
Read Jones Christoffersen ................................................................ 25
Commercial Insulation Supplier
Thermafiber Inc. ................................................................................. 8
Consulting, Commissioning, Engineering, Testing,
Certification and Inspections
Architectural Testing ....................................................................OBC
Retrotec Energy Innovations, Ltd. ................................................ 3,15
The Energy Conservatory ................................................................. 26
Engineered Curtain Wall and Window Wall
Oldcastle Glass ........................................................................... 20, 21
Entrance Systems Spare Parts
Oldcastle Glass ........................................................................... 20, 21
Float and Fabricated Glass Products
Guardian Industries ......................................................................... 37
Glass Wall Curtain Manufacturer
McMullen Incorporated ................................................................... 24
Industrial Glass Supplier
PPG Industries ........................................................................... 38, 39
Omegavue / Judd Allen Group ......................................................... 10
Mineral Wool Insulation
Roxul Inc. ........................................................................................... 6
Silicone Products Supplier
Dow Corning Corporation ............................................................... 12
Structural Engineering Design and Consultants
WJE .................................................................................................. 23
Windows, Energy Efficiency
The National Fenestration Rating Council ...................................... 35
Sto Corp. ....................................................................................... IFC
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40 Journal of Building Enclosure Design
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