When You Need A Window - Solar Design - Bec

BUILDING ENCLOSURE CONSULTING

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When You Need A Window - Solar Design

Introduction

Windows are as old as buildings, the word itself derived from the ancient Norse language in times when Vikings raided North Europe. How to design a window? How should an architectural glass be chosen? Vikings are long gone, and we found the knowledge remains common among architects in the North Europe, but has not spread much ever since. For example, it seems distinctively absent in the U.S. How do we know it?

Examples are numerous:

We were recently called to investigate a brand new building, in response to occupants complaining about getting (undesired) sun tan in their offices.

We attended many "educational" lunch&learn glass seminars, and we never heard a speaker mentioning the glass coolness factor, which some glass experts believe to be the most important solar glass benchmark.

Dr. Joe Lstiburek at his seminars shows a picture of a mosaic of miscellaneous interior window blinds on building elevations, described them as signs displayed by occupants telling the architect "you are stupid."

We took many similar photos we use in a simple quiz to make attendants guess which units in buildings are occupied. To avoid offending the architects who designed them, we alternate the photos before glazing seminars they attend.

These interior sun shades not only add to the cooling energy expenditures, they also ironically make buildings quite dark inside. We recently investigated such a building certified by the U.S. Green Building Council. You probably guessed it: the artificial lights were lit because sunshades were closed throughout the day.

An architect specified the VLT lower than SHGC for the glass in a fully glazed office tower, with a 50% window-to-floor ratio. The glass coolness factor of the glass was less than 1. The occupants are hot, and we are not talking about sexual attractiveness. We elaborate on this case in the paragraphs below.



An architectural office requested a UV fading protection to be added to the impact resistant windows 'specification.

A famous, award-winning, architectural office specified tempered glass in the full-height glazed windows of a skyscraper, absent any transoms and guards, and larger than the window which sent Mr. Garry Hoy 24 stories down to his death in the famous Toronto accident. The architect explained the glazing is code-compliant, and we agreed. Unfortunately, the architect never attended our seminars in which we explained this very building code loophole. The general public would be well-advised to avoid this building for their own safety.

A Northern architectural office requested a glazing condensation risk assessment analysis to be performed for the project located in a hot climate.

An architect had specified 5% VLT glass in 8% window-to-floor sized windows, and was surprised by the letter from the owner's lawyer. His design was code-compliant, he said, and we must agree on this point. We elaborate on this case in the paragraphs below.

A famous, award-winning, and green Miami architect specified non-rated glass storefronts, windows, and doors in the High Velocity Hurricane Zone, in spite of the opening protection requirements placed in the Florida Building Code. The owner currently considers the full replacement, in spite of their good technical condition. The exterior masonry walls would have to be redone as well, because the reinforcement necessary to take the structural reactions from glazing was neither designed nor produced. What good are LEED credits if the actual life cycle is reduced to ten years?

Architects specified a single-pane glazing in spite of the minimum 0.5-U-value required by building codes in a mixed climate. The glazed exterior doors are the most commonly overlooked by designers. Some lawyers specialize in ADA violations demonstrated by the same entrance doors, so we are surprised they do not add this code violations to their negligence lawsuits. We observe it so often, that we would bet you probably can find such non-compliant doors in your building as well.



What is a Window?

In the era of widespread curtain walls and sloped glazing merging into vertical glazing, the question is posed mainly in context of the code requirements. Building codes are far behind, and people involved in high-rise and high-end construction are so far ahead that the question should not be dismissed as overly elementary.

One of the frequently quoted industry standards, AAMA /WDMA/CSA 101 "Standard/Specification for windows, doors, and unit skylights" defines window as "An opening constructed in a wall or roof and functioning to admit light or air to an enclosure, usually framed and spanned with glass mounted to permit opening and closing." To further complicate things, the code introduces the noun "glazing," which, depending on context may be interpreted as a synonym of "glass "or "window." Another interesting and unexplained code term is "the net glazed area."

IBC (and FBC) treat the window as too obvious a thing to devote a definition to any of these terms, and apparently rely on rationality of a designer. Designers in turn rely on building codes to establish the minimum performance requirements. As illustrated on many quoted examples, neither seems to be a good idea.

Why Do We Need a Window?

The Bottom Threshold.

Once we agree, that a window is the portion of building enclosure which lets the light in, it becomes clear that its primary function is to provide the natural light to the occupants. And this is how the code implies it, establishing the bottom threshold: "1205.2 Natural light. The minimum net glazed area shall not be less than 8 percent of the floor area of the room served." This would be a scary requirements several hundred years ago, when glass was prohibitively expensive, production limits severe, and the real estate tax charged per window in some places.

This is why the high-rise housing of our friends in Paris, France was purposefully built without windows, making their and their neighbors' lives miserable in that respect.

The requirement seems simple, yet it frequently ends up misconstrued. Strictly read, and obviously against the apparent code intent, it allows to count e..g. opaque glazed spandrel area against the 8 percent floor area requirement.

A good example is the dispute raised by an angry Northerner, whose architect designed 5% visible light transmittance (VLT) vision glazing in windows sized to comply with the minimum 8% window-to-floor ratio mandated by code. What does it mean?



5% VLT is like wearing two pairs of sunglasses. It'd nice to have outdoors in full sunshine. However, when you enter the building interior it's dark like in a cave. You can find your way around only if you have a have a good sense of hearing, touch, and smell. In those distant places far North, like in the New York City, where it's dark and cold half a year, such a design may be understandably objectionable in spite of the demonstrated building code compliance.

It would not have happened if either the glass salesperson or the architect actually knew what the daylight factor (DF) and visible light transmittance(VLT) are and how to use them. It would also not happened if the daylight analysis were ever performed. If you read this article you wouldn't make the same mistake, richer with the advice we are going to give you.

The 8-10% code requirement was developed in days when a tinted glass was only used in vitrages, and the glass installed in windows was invariably clear, with the visible transmittance roughly 80%. Therefore, substituting a 5% glass would logically require 16 times larger net glazed area, making the interpolated window-to-floor ratio close to 130%. This doesn't sound like a good idea and it's also seldom feasible in the typical construction. There must be a better way.

This is why we were happy to see another, voluntary requirement which came with the LEED credit 8.1 "Daylight & Views." In the era of intuitive and easy computer simulations afforded by fast computers and improved software, it seems reasonable to expect that the habitability of building spaces should be verified by

New for some designers, the engineering simulations and their use come under growing attack from those who are all too familiar with them and who noticed the discrepancies between the virtual and real world.

The models and simulations are only as good as the data fed to them. Such data includes physical characteristics of materials and spaces, e.g. visible transmittance and reflectance of surfaces, which are generally misunderstood by architects.

Architects are typically in charge of coordinating the collection and the flow of the data. Therefore, we found collecting a reliable data from architects the most challenging part of any engineering task.

We also found that similar or entirely redundant analysis (e.g. photorealistic renderings, daylight, , glare, artificial lighting analysis, etc.) are often performed by a number of consultants and delegated design teams presenting different levels of data starvation, and seldom coordinated with each other. They are sometimes interesting to compare.

Additional challenge comes in play when the assumed and calculated physical characteristics need to be captured in the construction documentation for the benefit of the future construction.

These and other conditions affecting engineering estimates should be well communicated with all parties to avoid misunderstandings. We direct reader’s attention to the current lawsuit “Gifford v. USGBC.” before the U.S. District Court Southern District of New York.



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Daylight AnalysisDaylight FactorValue Range: 0.0 - 22.0 %© E C O T E C T v 5

pretty, illuminating renderings, to allow for early design tweaking.

The credit asks for the minimum 2% Daylight Factor (DF) in 75% of all occupied space for critical visual tasks. The daylight factor (DF) is a measure for expressing the daylight availability in a room. DF is a percentage ratio of the instantaneous illumination level at a reference point inside a room to that occurring simultaneously outside in an unobstructed position. DF is calculated under an overcast sky, excluding any direct sunlight. Once the model is built, it's fairly easy to analyze glare as well as natural and artificial illumination.

How architects can use the analysis?

We recently helped an architect who asked us to justify a desired substitution of skylights by window walls in order to add an extra floor. Skylights can provide copious and diffuse illumination, far superior to vertical windows; therefore, the task prove challenging but not overwhelming.

The Upper Threshold.

How about an upper window size limit? We often see office spaces glazed over 50% window to floor ratio, and fully glazed exterior walls are nothing unusual, often over 80% window to wall ratio. The design is left up to the architect, with the miscellaneous performance requirements placed as an engineering lid, prompting Dr. Lstiburek 's and other building scientists' jokes.

Glass Basic Characteristics

The story about an angry Northerner discovering his architect designed almost opaque glazing should warn us about the simplest glass characteristic which affects the human comfort:

Vision

The visible light transmittance (VLT) is defined as glass transmittance in range from 380nm to 780nm, as shown on the chart below. This is the only glass characteristic which can be verified by the traditional way architects chose a glass: comparing glass samples. What VLT should an architect specify? The VLT should be derived from the daylight factor (DF) analysis described above and correlated with other necessary physical glass characteristics. We will answer this question in the following discussion.

Daylight Factor Analysis



Long-Wave Heat

We were recently approached by an architect who specified and designed a large window replacement project in his condominium building complex in Long Island, NY.

He had the same new windows installed in his condominium unit and described them as unbearably cold, drafty, and covered with water condensation. Apparently, this was how he specified them. Understandably, his wife, kids, and condominium board were pissed off on him.

The secret of success is to know how to pass the blame; therefore, his primary interest and the reason he approached us was to prove that the contractor provided wrong windows. (We get it a lot.) We suggested relevant field testing which could be used to verify whether the specs were met.

In our experience, much field testing is performed just to confirm the inferior specs were met. A lot of money and aggravation would be spared if owners verified the adequacy of the architectural specifications before embarking on the expensive testing.

It was freakishly cold in January 2011 when he told his story, so we felt sympathy for him. Experience is the name we give to our mistakes.

We tried to help him as much as we could, so we privately suggested he used rolled towels to pick water, duct tape to stop drafts, and thick blankets as curtains, and offshore tax heavens to fend off plaintiffs, but we could not stand the terrible cold for long, so we quickly returned to the sunny Florida.

We never heard back from him, so we cannot tell whether it worked out for him. Please, let us know if you survived the winter and happen to read this article.

As this architect and his family and clients experienced on their own skin, the heat transmittance is also easy to detect. There are heat receptors in our skin which detect rate of heat loss, making it easy to tell a good window from a bad window. For benchmark purposes, it's described as a U factor illustrating thermal transmittance in range from 2,500nm to 50,000nm (which we feel as heat). This way we can compare windows without standing next to them, which makes the process of writing architectural specifications much easier.

The energy conservation codes generally tie the U factor with the glazing ratio for prescriptive compliance method.

The typical chart reproduced from ASHRAE

Picture by AGC



90.1 is shown below. It ends at the 50% window-to-wall ratio and 5% skylight-to-roof ratio. There is nothing wrong in jumping off these charts as long as a designer knows what he or she is doing. It's called a performance path, and is observed to quickly widen the gap between architects and mechanical engineers, in spite of the "green" educational courses taken by both. This is why these "off the charts" projects are often found very uncomfortable by occupants, and seldom code compliant when carefully examined.

Solar Heat

Human body generally cannot directly and instantaneously detect solar radiation other than the visual (VIS) light range, but the near-infrared NIR radiation is absorbed by objects such as human skin and re-radiated in the thermal range which we can feel as heat (see the paragraph above). The NIR radiation stretches from 780nm to 2,500nm, as shown on the chart above.

This phenomena contributes to “greenhouse” effect. An example of a car windshield below illustrates such condition.

Unless your intention is to experiment with the passive solar design, the heat gain via windows is generally undesirable, particularly in the South, where we don't care much about the letter "H" in the HVAC acronym.

This is best illustrated by the recent case.

A famous, award-winning, and green Miami architect specified the VLT lower than SHGC for the glass in a fully glazed office tower, with a 50% window-to-floor ratio. Both were in mid 30's. It means the glass coolness factor of the glass was less than 1, which is considered a serious error. Why? The ultimate results is the occupants are hot, and the cooling bills are high. Were the daylight analysis performed, the lower VLT would result. Let's

Picture by AGC



assume a 15% VLT would be just enough, given the high window/floor ratio and a good window access. Were the more spectrally selective glass (at exactly the same initial cost) specified, the SHGC could be theoretically five times lower. The building elevations are fully glazed; therefore, the solar heat gain correlates well with the cooling energy costs. Imagine energy bills two times lower and occupants two times happier. Nowhere else so much could be wasted by so few.

What is SHGC?

Solar Heat Gain Coefficient (SHGC) (or Solar Factor) is one of the glass benchmarks allowing comparison of different glass types. It illustrates glass transmittance of solar radiation, as opposed to the U factor illustrating thermal transmittance.

Americans have not developed any good standards in this respect; therefore we have to again rely on Europeans. According to the European Standard ISO EN 410 "Glass in building - Determination of luminous and solar characteristics of glazing" cited by American NFRC standards, SHGC is the glass transmittance in range from 300nm to 2,500nm, as shown on the chart on page 6. This range embraces ultraviolet (UV) rays, visible (VIS) range, and near-infrared (NIR) range called also “solar range,” or “short infrared."

UV, Structural Strength, Condensation Resistance Factor, Opening Protection, Safety, Roller Wave Direction, Fire Resistance, Air Tightness, Noise Resistance, Reflectivity, etc.

We purposefully left out a number of glass and glazing performance characteristics in this article, concentrating our attention on the most overlooked and ironically the most important solar aspect: the glass coolness factor. The interested reader may want to register and attend one of our glazing seminars available via the http://www.b-e-c.us webpage to learn about other aspects of glass design.

What Kind of Glass?

The quick development of the modern sciences and technology brought us a glass short only of a miracle. However, the "chopper rule" holds true. Wonders of modern engineering are often found squandered to achieve aesthetic architectural goals, or senslessly misused.

Vision

There are many ways the modern glass helps us to harvest the natural light:

Dirt: The most important light obstruction is the dirt; and the deferred maintenance became a norm in the welfare-burden economy. We sometimes observe opportunities for doubling and tripling the VLT, were the glass washed regularly. Therefore, a self-cleaning glass was developed with a Titanium hydrophilic surface. Self-cleaning glass needs a water flow to clean. We see this glass used on flat skylights where it serves no useful purpose, except for allowing building enclosure consultants showing off their skills by demonstrating to owners how much money they could have saved, if the glass were specified properly.



The best way to the clean glass is to design the permanent window-washing access. We direct the interested reader to our article titled "Facade Access Manual," available free-of-charge on our webpage http://www.b-e-c.us.

Reflections: Another important way to improve the visibility is the reduction of reflections; therefore, antireflective glass was developed, particularly useful for showroom and retail storefronts, where it can better expose the merchandise on display. This way you can gain around 3-4%, and significantly improve the subjective perception of transparency. Glass reflectivity, on the other hand, may be desired in some applications demanding privacy, such as residential buildings.

Low Iron: The third way, used by some seriously involved architects and historic-conservation people, is the elimination of iron from the glass melt. Iron makes glass slightly greenish, which is the more easily detectable, the larger thickness of glass is viewed. The 2-4% gain is justified in some thick, high-end applications, requiring numerous plies of laminated glass to achieve the necessary structural redundancy, where the low-iron glass is a real saver.

Long-wave Heat

Contradictory to claims of some glass-addicted designers, glass doesn't come close to the opaque insulation, but several ways were developed to reduce the heat transmittance, such as gas cavities, warm spacers, etc, marking the significant improvement over the historical glazing.

This effort was largely squandered by architects, as described by Joe Lstiburek and John Straube in their famous comparison of the average building envelope R-value over the ages.

Long-wave heat characteristics are so well described by the publicly available media, that we are not going to spend any space on their description here. The interested reader may also want to register and attend our thermal energy seminars available via the http://www.b-e-c.us webpage to learn about thermal aspects of facade design.

Solar Heat - Glass Coolness Factor

Much effort is expended by the architectural glazing industry to increase so called “coolness” of glass illustrated by the proportion of the SHGC to the visible light transmittance (VLT).

This is the most important characteristic of the modern architectural glass, and part of the

Glass Coolness Chart Picture by AGC



historical quest to bring the natural light deeper into the buildings while avoiding discomfort of perimeter occupants.

The low-emissivity (Low-E) coating is one of the most important developments in this quest. It reduces the portion of heat absorbed and radiated by the coated surface.

Part of the transmitted short wave infrared radiation is absorbed by the glass itself and re- radiated as heat. Therefore, generally speaking, tinted glass should be positioned closer to the exterior because it absorbs more radiation than a clear glass.

A useful tool for visualization of the infrared glass performance is the simple table demonstration, in which different glass samples are compared by placing between an IR lamp and NIR sensor. Seemingly identical glass samples would exhibit different solar performance. Similar comparison could be done outdoors, using sun in lieu of IR lamp. The NIR sensor could be substituted by an inexpensive pyrometer. These elementary demonstrations would allow participants visualize the performance described by so-far meaningless to them acronyms and numbers placed on glass labels.

Picture by AGC

Table demonstration of solar transmittance

with IR lamp and NIR sensor

Outdoor demonstration with $25

pyrometer



How To Design a Window.

As soon as the floor plans are developed, pick the worst-case layout and run the Daylight Factor (DF) analysis to optimize the size and Visible Light Transmittance (VLT) of the glazing and shading. On basis of the VLT obtained from Daylight Factor (DF) analysis, and using the chart reproduced above, a designer should pick the SHGC range. The SGHC should be verified againts energy code requirements, which in case of many large buildings is met by the performance path. Therefore, the total SHGC of a window should be coordinated with the mechanical Basis of Design (BOD), obtained from the mechanical engineer, and re-calculated to receive the nominal glass SHGC, by removing projections, shading, framing, screens, etc. The necessary glass thickness, affecting the solar characteristics, can be estimated using ASTM E1300 "Standard Practice for Determining Load Resistance of Glass in Buildings" The result should be the glass thickness and nominal SHGC. Then, using the free Windows and Optics software developed by Lawrence Berkeley National Laboratory (LBNL), a designer should be able to pick the optimum glass before ordering glass samples for comparison purposes. The typical project uses roughly 20 types of glass to optimally address their performance aspects. Therefore, at this point, it'd be better to leave the further refinement of the glass specification to the delegated design teams. We never saw an architect following the good practice and picking the glass this way; therefore, we would kindly ask the readers to report any observed instances. We will fund a private award to honor them and encourage others by the good example. Unfortunately, the average architect visually picks the glass and then leaves the design entirely up to the contractors, ending up sometimes unpleasantly surprised with the results in the field.

Use of Insulated Glass in The South.

The Florida Building Code (FBC) 2007 introduced the requirement for insulated glass, which illustrates the widespread misunderstanding of the physical glass properties expanding into the area of law. In the South Florida, the improvement of the U-factor of the glass will only exacerbate the thermal comfort challenge and energy waste. Why? Let us illustrate with typical measurements. The temperature of the interior glass surface in the direct sun often exceeds 100 degrees, chiefly due to its absorption, while the exterior ambient air temperature seldom raises above 90 degrees at the same time. The average exterior air temperature is in mid-seventies, and the solar heat gain is the prevailing cooling load. Therefore, the transmission of the long-wave heat should be encouraged in order to dissipate the excess heat from the interior to the exterior environment. With the new requirements in place, the heat is trapped inside buildings, adding to the cooling peaks, and increasing energy expenditures. If the code increased the glass coolness factor instead, than some serious energy savings would follow, meeting the original intent of the code.



2007 Florida Building, Appendix 13-D, Effective March 1, 2009:

BUILDING ENVELOPE REQUIREMENTSBuilding Element Mandatory Requirements

Roof: Absorptance U-factor

≤ 0.22 ≤ 0.027

Wall: Absorptance U-factor

≤ 0.3 ≤ 0.089

Raised Floor Insulation: U-factor

≤ 0.052

Windows: U-factor Window Area SHGC 0-40% WW Ratio SHGC 40-50% WW Ratio Overhang Projection Factor (PF)

≤ 0.45

≤ 50% window to wall area ratio 0.61 North

0.25 all others 0.44 North

0.25 all others 0.5 (projection half the distance of window height)

Skylights: SHGC Skylight U-factor Maximum percent of roof area

≤ 0.19 ≤1.36

5 percent Opaque Door U-factor Swinging Non-swinging

≤ 0.70 ≤ 1.45

Not Just Glass - Other Items to Consider

Shading: Many aspects besides glass performance affect the VLT and SHGC of your window. Their calculation is described in ASHRAE Handbook of Fundamentals. External shading, louvers, framing to glazing ratio. as well as opening projections, printed and screen media, insect screens, etc. affect the physical glazing characteristics, such as VLT and SHGC. How does it affect buildings? For example, in Moscow, Russia (a very shady

place), the printed advertising media used by greedy landlords to cover entire building elevations lowered the daylight factor significantly below 2% causing occupants' complaints.

Source ‐Willmark



The same solution, ironically, is often suggested by this author to owners of new, over-glazed office towers in the Southeastern U.S., to cover the entire building façade with advertising media, limiting the sun access and generating revenue, improving occupants 'comfort, and collecting funds for a proper glazing replacement in case their architects proved insolvent. The similar solution was used by this author to improve performance of the large east window adjacent to his desk in his office. He installed a dense exterior insect screen, purchased from a home-improvement store. The combination of the interior shades and the exterior screen made the heat manageable.

Light Not Always Good. Many projects are challenging for glass-addicted designers. The primary example are museums, where light access is generally limited to protect the exhibited artifacts from fading. In one case, this did not stop one architect from designing over one acre of sloped glazing over the museum building, but this glazing remained wisely hidden behind the ceiling, creating a large, inaccessible, and very expensive to cool and heat attic space. This was almost one century ago. The American-designed sloped glazing is generally observed to be very leaky, and this one was no different; therefore, after many decades of leak-fighting, the hidden skylights were replaced following a re-design by another glass-addicted designer. At this time, equipped with the modern day lighting analysis clearly indicating the glass visible light transmittance (VLT) should be brought down to zero, the new architect paradoxically specified the expensive, ultra-transparent low-iron glass, instead of replacing the glazing with an opaque roof or metal panels (at the fraction of the cost). Nobody could tell the difference anyways, because the glazing is again hidden behind the new ceilings, to protect the interiors from the damaging light. We were told that the new sloped glazing leaks profusely, keeping up with the tradition.

Harvesting The Sun: In some cases, the excess glazing can be used for environmentally conscious design. A thin-film photovoltaic coating can be applied to vision glass at the minor loss of visible transmittance. Curtain walls of this kind are sold off-the-shelf for a decade or so in Europe.

Other example of an ecological design is a mur vegetal, which self-adjusts to the season: shading the facade during sunny months and shedding leaves before the dark winter.



Many Suns: The world-famous "Ray of Death" building in Las Vegas is not a lone example.

We recently investigated a building facade affected by three very strong reflections from the surrounding environment. These reflections have been present before the design begun; therefore, it would be reasonable to expect the designers to address them.

One issue is to avoid sending a death of ray in harms way. The other is to mitigate the rays already present on the existing site. Some reflections are well known, such as from the water surface, affecting buildings located along the shorelines.

There is a growing tendency of using highly-reflective facade surfaces, e.g. high albedo roofing, which would foreseeably exacerbate the challenge for future designers. We can already see this phenomena, scanning surroundings of tall buildings in urban areas with a thermographic camera: modern roofs and facades strongly reflect infrared radiation.

HVAC And Interior Design Coordination: We often enter a room only to discover that the largest load (windows, and generally building enclosure) is not addressed by the HVAC system. In the North, it leads to damage of moisture-sensitive materials by water condensing on windows. In the South, lack of air conditioning in part of the room adjacent to hot windows renders this area unhabitable, not meeting the ASHRAE 55 “Thermal Environmental Conditions for Human Occupancy "criteria. This also illustrates the interior design coordination challenge: we recently found a large media conference room of this kind in a freshly designed building. The half of the room adjacent to the south-west elevation featuring large strip windows was not air-conditioned. The room was re-arranged, with the speaker podium in front of the window. The speaker was literally placed in a hot spot and the attendants' glare discomfort would hardly match his.

The excessive window to floor ratio is sometimes caused by the lack of coordination between building shell and core designs. Tenants often design and build the spaces long after the shell is constructed.



Internal Shades: While the building enclosure performance is typically the last thing interior designers would ever have in mind, they can affect it by choosing the right sun shades. We find that the vast majority of sun shades are roller shades rolling down from a window head. Therefore, any mid-position leaves a horizontal strip of light above a sill, incidentally where it hurts eyes the most, and least lights the room. Were the shades operated upside-down, a bright strip could be left at the top, providing some useful day lighting, saving artificial lighting, and preventing the glare discomfort.

LEED Certification Ramifications: Many modern buildings are LEED certified, and we would venture a guess that most of them have incorrectly specified glazing, affecting their performance. Dr. Lstiburek once joked he sends unsolicited proposals for forensic services to owners of new LEED-certified buildings appearing in media headlines. USGBC recently introduced revocation procedures in response to critics pointing out the abysmal actual performance of some LEED certified buildings in comparison to their designed performance. We direct reader’s attention to the current lawsuit “Gifford v. USGBC.” before the U.S. District Court Southern District of New York. These ramifications should be investigated and understood by owners before embarking on any investigations.

Cheap Fixes: There is always a strong temptation to use a band aid approach. However, in some cases a band aid may hurt more than help. This is the case with glass. We have many friends in the glass-tinting business, but we do not recommend interior-applied items that increase the temperature of the glass, such as the common aftermarket tint films or translucent insulation panels. Sorry folks. They may induce a glass breakage because the edge of the glass would stay cool, chilled by its framing. It may be compared to pouring a hot water on a center of a glass dish freshly removed from a fridge. It may break due to the thermal stress. For the same



reason, such an approach often would void the glass warranty; therefore, the manufacturer should be consulted first.

Conclusion

The glazing is the most advanced and the most expensive part of many facades; therefore, it warrants a good, more than a skin-deep design. Nowhere else so much could be wasted by so few. A design is only as good as the research that went in its preparation. While it's true that the wonders of the modern engineering are often squandered to achieve architectural goals, it's even more depressing to observe when they are misused to aggravate it even more. Multiple examples illustrate the compliance with the building codes may not warrant an adequate design. Glazing can be engineered to both provide the natural light and limit the occupant discomfort and energy use, while maintaining the appearance desired by architects. The glazing coolness factor remains the most important and ironically the least known performance characteristic of the architectural glass.

About the author Karol Kazmierczak (Kaz), CSI, CDT, AIA, ASHRAE, NCARB, LEED AP, is the Senior Building Science Architect and President at Building Enclosure Consulting, LLC and the leader of the BEC Miami. He has 15 years of experience in building enclosure technical design, engineering, consulting, and inspection. He can be contacted via e-mail at [email protected].

When You Need A Window - Solar Design - Bec

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