Chicago Window Expert

Mark Meshulam is an expert witness and consultant for architectural glass and glazing.

Chris Dolan is director of commercial glass markets at Guardian Industries. Guardian is one of the top players in the manufacture of float architectural and fabricated glass.

Q: What can you tell us that will help put the array of Low-E glass choices into an understandable framework?

Guardian: We organize our products into Commercial and Residential lines: the SunGuard® and ClimaGuard® series of products respectively. Guardian markets SunGuard and ClimaGuard products globally with local production and distribution capability.

For most commercial buildings, the most important attribute for energy savings is blocking direct and indirect solar radiation. Guardian’s SunGuard product line is specifically designed to reduce building cooling costs while letting in plenty of light and providing the aesthetic appearance desired by architects worldwide.

Most commercial buildings in North America have high cooling loads, so SunGuard commercial coatings are used on the #2 surface. Guardian SunGuard products are categorized by the following groups:

• SuperNeutral® Series — High light transmission, double silver layer Low-E coatings with the highest amount of spectral selectivity.
• High Performance Series — Medium light transmission, single silver layer Low-E coatings with high spectral selectivity and varying reflectivity.
• Solar Series — Lower light transmission, metallic reflective coatings with medium spectral selectivity designed for lowest solar heat gain coefficient (SHGC).

The best product for a particular market can vary based on location and project type. In Chicago, commercial buildings generally have a high cooling load, so reducing solar gain is a big concern. Our most popular coating for this situation is Double Silver Low-E SuperNeutral 68. It has 68% visible light transmittance and blocks 62% of solar radiation with the coating on the #2 surface of an insulating glass unit.
For high-rise residential buildings in Chicago, where the desire is to have more privacy yet block glare and the solar heat gain, AG 43 from the high performance series is often specified. It is a reflective Low-E hybrid product with low indoor reflectivity allowing better outdoor views at night.

For the Southern U.S. with extreme hot climates, we have SunGuard SuperNeutral 54, for use in commercial projects and ClimaGuard 55/27 for low-rise residential. In these climates in coastal regions, we often see single glazed laminates for hurricane resistance. The SunGuard SuperNeutral 68 can be used on the #2 surface embedded against the PVB interlayer combined with tinted glass to greatly reduce the solar heat gain.

However, in Canada and Northern Europe where there is little residential air-conditioning, ClimaGuard is often used on the #3 surface of the insulating glass unit. It allows maximum visible light plus low emissivity for reduced heat loss during winter nights and maximum solar gains during winter days for free heating. In this case, summer cooling relies on operable windows for ventilation and not on a low SHGC coating on the glass.

Q: Is Guardian involved in self-heating glass, glass that warms itself with the application of electricity?

Guardian: No, Guardian is not involved in self-heating glass.

Q: Is Guardian involved in the PV (photovoltaic) market?

Guardian: Yes, in fact, Guardian has several products on the market today that were specifically designed and developed to meet the needs of the global photovoltaic industry. The applications span crystalline silicon, thin-film, concentrating PV and BIPV (building integrated photovoltaic) applications and systems, and our global manufacturing capability allows us to offer these products to customers throughout the world.

Under the Guardian EcoGuard® collection of products, we currently offer very low-iron EcoGuard Float (smooth) and EcoGuard Pattern glass in a variety of solar transmission or performance levels, thicknesses and strengths (e.g. heat-treated options). Leveraging Guardian’s traditional expertise in mirror, glass bending and lamination technologies, we also offer EcoGuard Solar Boost mirrors in monolithic or laminated configurations for concentrating PV or solar-thermal applications.

In addition, the Science and Technology Center at Guardian is in the process of introducing specialized glass coatings that provide additional solar transmission gains and long-term performance when applied to our EcoGuard glass products. Examples include anti-reflective and anti-corrosive coatings to allow these PV systems to perform at peak levels over long periods of time.

Finally, we are also introducing a series of conductive coatings for a variety of thin-film photovoltaic applications including Amorphous Silicon, Cadmium-Telluride and CIS/CIGS. These transparent and non-transparent conductive coatings, which are applied to the base of EcoGuard low-iron glass, are designed to maximize the output and conversion efficiencies of these thin-film PV technologies.

A great example of an application where these technologies are being integrated into other products currently offered by Guardian is our SunGuard BIPV thin film modules for commercial façade applications.

When looking at everything going on in the solar power markets today, it’s an exciting time and Guardian is absolutely dedicated to continually working to keep pace with our customers’ ever-evolving needs in the PV market.

Q: Is Guardian involved in “vacuum glass”, glass with R-values close to that of an insulated wall, by using a vacuum in the airspace?

Guardian: Yes, Guardian is developing vacuum insulating glass using proprietary technology. This exciting technology will offer a substantial improvement over standard insulating unit U-Factors, with a target of 0.10 achievable in the near future, a vast improvement over current insulating glass technology without the weight, IGU thickness, low light transmittance and potential gas loss issues of comparable triple glazed units.

In this unit, two pieces of glass are held apart from one another by tiny “pillars,” the edges are hermetically sealed and a strong vacuum is pulled to create a barrier to thermal conductivity and convection. Radiation is controlled with the use of a high performance Low-E coating. The pillars are generally not visible from distances of 1 meter or more. The challenge is to space them from each other for optimal strength, appearance and thermal properties. In addition to the high thermal insulation value, this product will provide exceptional acoustical performance.

The development focus has been a design that can be easily mass produced with high yields, thereby providing the lowest possible cost structure and lowest risk. This is being achieved with a combination of innovation and adoption of existing process technologies from other markets and industries, such as the television CRT market and computer electronics industry.

Q: Are there any other exciting technologies coming up at Guardian?

Guardian: Guardian has recently launched ClimaGuard 63/31 high performance low-E for residential applications. This new product will help many window manufacturers meet the new ENERGY STAR® and Energy Efficiency Tax Credit criteria (30/30 standards). A commercial version will be available in the near future as well.

Guardian is also developing products with electro-chromic capabilities for decorative, privacy and solar control applications. Guardian’s resources as a global manufacturer provide the capability to develop and launch multiple new products on several continents which will reduce the time to market for new products in the future.

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