Mark Meshulam is an expert witness and consultant for architectural glass and glazing.
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).
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.
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 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.
Need new approaches to your insulated glass?
Hello Mark,
With all of the interest in meeting the new energy star numbers a lot of residential window manufacturers seem to be turning to the double low-e product. Our company has been researching it and the product does appear to get the U values necessary to bring most aluminum clad products under the .30 U value needed. There appears to be concerns with this product and I was wondering what your thoughts were on it.
The items of concerns: Hard coat low – e on # 4 surface can scratch easily. Even sticker residue or paint clean up could possibly damage it. We found simple rubbing on the surface can mar it.
The interior surface of this product shows only a 3 degree gain in temperature over a clear / clear insulated IG unit which would make it more susceptible to interior condensation considering the product would be used primarily in the northern zone.
In the interview Chris Dolan mentioned a product Clima Guard 63/31 but did not elaborate on it. Is that a dual low-e product or is it something new? With all that is going on in the glass industry we are anticipating a lot of new things to meet future demands.
Thank you in advance for any comments or information that you may forward.
Dennis Krueger
General Manager
Lincoln Wood Products/Timeline Vinyl Products
Hi Dennis,
Thanks for writing.
Your point:
Hard coat low – e on # 4 surface can scratch easily. Even sticker residue or paint clean up could possibly damage it. We found simple rubbing on the surface can mar it.
My comment:
Totally agree. I would not be comfortable putting either hardcoat or soft coat low-e on #4. I do know that it is not uncommon to put a hardcoat on #1. Nonetheless, my general preference is to put coatings on #2 or #3, and that you can do both provided the heat buildup issues are addressed by heat strengthening per manufacturer’s instructions.
Your question:
The interior surface of this product shows only a 3 degree gain in temperature over a clear / clear insulated IG unit which would make it more susceptible to interior condensation considering the product would be used primarily in the northern zone.
My response:
Using Window 5.2, a free software provided by the Lawrence Berkeley Laboratory, we compared the following as measured with 0 degrees F exterior, 70 degrees F interior, 12.3 mph exterior wind:
A. 1″ overall, two lites 1/4″ clear, no coating
Center of glass temperature: 44 degrees F
B: 1″ overall, two lites 1/4″ clear, (1) low-e coating
Center of glass temperature: 54 degrees F
As you can see, this is a 10 degree, not a 3 degree benefit and will have a positive effect on condensation resistance.
Your question:
In the interview Chris Dolan mentioned a product Clima Guard 63/31 but did not elaborate on it. Is that a dual low-e product or is it something new?
My answer:
ClimaGuard 63/31 has only one coating, and it is on the #2 surface. It is called “double silver” because the coating has two layers of silver within it.
Thanks to Jason Theios at Guardian for support in answering this question.
Hello Mark:
It was good talking with you to follow-up on the questions to the Guardian interview on your site. Attached is some basic information on the glass temperature of a glazing in winter conditions. With no Low-E coating, the indoor glass temperature is about 44 F, and with the Low-E coating it increases to about 54 F (Please see pdf files showing the calculated temperatures). See the reports:
Thermal analysis: 1″ insulated unit with 2 lites clear glass
Thermal analysis: 1″ insulated unit with 1 Low-E coating
Another method to determine temperatures is by measuring with a thermal imaging camera. Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California made some of these photographs. Once again these confirm the two temperatures of about 44 F & 54 F. Please note in the photos that the temperature actually varies from near the top of the lite to the bottom. While we are on the topic of VIG (vacuum Glass) notice the thermal image photos of the VIG unit.
Best regards,
Jason
Jason Theios, P.E.
Applications Engineer
Carleton, MI
Thanks, Jason, for some great information. The thermal images you provided are being presented in a new article entitled “Thermal Images of Insulated Glass Types”.