Glass Buildings and The Environment


Here is another article from Thomas Hens on designing of glass buildings keeping in mind their impact on environment.

In our last issue, we discussed a number key factors to be taken into account when choosing facade glass. This issue will focus primarily on the environment and demonstrate that designers of glass buildings are also thinking about our planet.

We will be looking at three environmentally friendly construction methods:

  • Insulating buildings: cutting C02 emissions by reducing energy loss via glass.
  • Generating energy: cutting energy consumption by using glass as a construction component as well as to generate electricity.
  • Using sustainable materials and environmentally friendly manufacturing techniques.

Continue reading

Spray Hard Coat Glass Vs CVD Hard Coat Glass


If somebody tries to sell you cheap reflective glass saying it is “Hard Coated”, the first thing you should ask is “Is it spray hard coat or CVD hard coat?”. Spray hard coat could be termed as a primitive and is relatively cheaper, in this one the chemical composition is sprayed over glass which would be in a semi solid stage (online process). Most cases, the coating tends to be uneven and deposition rate would be poor. In most cases the coated side appears yellowish.

CVD (Chemical vapor deposition in atmospheric pressure) on the other hand is far superior and the latest. Here, the chemical composition is vaporised and then allowed to deposit on semi-solid glass (online coating) in a controlled manner, achieving high deposition rate and the coating would be even. In most cases, the coated side would have a silver appearance.

It would be a disaster if spray coated glasses which come at cheap rates are used (especially when it is mis-sold with the name “Hard coated reflective glass”) in buildings. Below are some pictures for reference.

Spray Hard Coat – Coating peel off

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Glass Types for Building Envelope Products


There are typically four different glass types used in glazing products: From weakest to strongest they are: Annealed, Heat Strengthened, Tempered and Laminated.

1. Annealed glass is your basic non-impact glass type. It is used in applications where the required wind load is not so high and safety requirements are not a concern. When annealed glass breaks, it breaks in sharp chards.

2. Heat Strengthened glass is also a non-impact glass. It undergoes a “heat treatment” that increases it’s strength to twice that of annealed glass. It is used in similar applications to annealed glass but where the required wind loads are much higher. When heat strengthened glass breaks, it also breaks in chards.

3. Tempered glass is your basic impact glass. It undergoes a more aggressive “treatment” that increases it’s strength to four times that of annealed glass. It is used in “small missile” impact applications typically installed 30 feet or higher above ground and in safeguard applications. When tempered glass breaks, it breaks into very small cubes.

4. Laminated glass is your typical impact glass. It is a combination of two (usually) of the three previously mentioned glass types that are “laminated” together with an interlayer between them. It is typically used in “large missile” impact applications installed up to 30 feet above ground. When laminated glass breaks, it breaks based on it’s glass type make-up but is held in place by the interlayer…similar to a car’s windshield.

By,
Rick DLG

Designing Safely With Glass

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Here’s an interesting article by Rick De La Guardia on how to design safely with glass for today’s threats. This article was featured in US Glass Magazine. (Click on the article image to read more and download the entire edition)

Is Glass Really A Green Building Material?


If somebody says that Glass is a green building material, the straight and honest answer would be a big No! Just because in many high rise green rated buildings, glass has been used extensively, it doesn’t make it a green product in itself. One might have encountered with many architects and glass industry professionals who bluntly promote glass as a green product, then why is this article contradicting that belief? Here is an explanation on why glass is not a green product by itself, but why it is essential for a green rated building. This article is in context of float glass only, which is the most widely used in buildings.

Glass could earn a few green points for the fact that it could be recycled. Broken pieces of glass are added along with the raw materials while glass is manufactured so as to bring down the boiling point and there by reduce the energy consumption. Also if the manufacturing facility is near to the building in construction, that could also fetch a few points for green rating, as the material is locally sourced. Local sourcing of material means less energy consumed for transporting the material.

Glass is extensively used in green buildings to harvest maximum light inside and to reduce energy consumption for internal lighting requirements. When more natural light enters a building, equal amount of heat also enters the building. 50% of the Visual Light Transmittance (VLT) is direct solar energy (ER or DET). So when you are asking for 100% light transmittance, you are getting 50% of heat along with it! If in a building, which is centrally air-conditioned, and if it is clear glass which is being extensively used, energy consumption for internal lighting might get reduced to a significant level, but at the same time energy consumption by the air-conditioner would be enormously escalated. This is where solar control and thermal insulating glasses play a major role.

Solar control glasses let in maximum light and also cuts DET down to a great level. Since 80 to 90% of heat entering a building is solar heat, maximum energy could be saved on lighting and air-conditioning. Apart from direct solar energy, non-solar energy or indirect energy, could also be controlled by using double glazed/ Isulated glass units(DGU / IGU), and thermal insulating glass. A DGU cuts down the heat entering a building due to conduction (glass is a good heat conductor) and convection. A thermal insulating or a low emissivity (Low-e) coated glass can reduce the non-solar heat by cutting down the transmittance of Long Wave Infra Red Radiation (LWIR). LWIR is emitted by objects like trees and furnitures during the night time, which absorb the Short Wave Infra Red Radiation (SWIR). In moderate to cold climate conditions, where heaters are used in buildings, it is better to go for a very low u-value glass, so as to prevent heat loss from the building. In tropical climates, it is better to have a moderate u-value range.

In short, it is not an isolated pane of glass that is green rated or that helps you gain green points, it is the configuration of glass units installed in your building, based on the window to wall ratio, orientation of the building, total glazing area, energy efficiency of the building, and hours of operation of the building occupants.

(Originally written for Associatedcontent.com)

News on Glass & Refractory World: week# 07


° Corning predicts for 2011 increased demand for special glass installed in tablet computers and smartphones, which employ scratch-resistant Gorilla Glass for touch screen devices. This will also drive increased utilization of platinum components used in these glasses specialties production.

° Cabot Corporation/US and China National Bluestar (Group) Corporation have initiated expansion of fumed silica production capacity Jiangxi Province, PRC. It will be a USD 43 million investment at Cabot Bluestar Chemical (Jiangxi) Co. Ltd. First phase will increase capacity from 5000 to 20000 TPY, second phase is aimed to a final 20000 TPY capacity.

° Guangdong Orient Zirconic Ind. Sci. and Tech. and DCM DECO Metal (DCM) won the approval of Australia authorities to jointly acquire Australia Zircon NL; in May 2010, the Chinese company announced it would invest 40 million Australian dollars to set up the joint venture with DCM, giving itself a 51-percent stake in the scheme to acquire all of Australia Zircon NL’s assets. This is a significant move to control Australian zircon sources, made by Chinese entities.

Hard Coated Reflective Glass


Espace rolin fortis, Brussels- Stopsol Silverlight

Hard coated or pyrolytic coated reflective glasses are those in which the coating is applied when the glass is manufactured,i.e. it is an online coating process. In this process of coating, the glass is fused into the glass at 650-700 degree celcius, and on cooling, the coating becomes a part of the glass.

Primary advantage of hard coated glass is the durability, it could also be handled like normal/annealed glass, could be easily heat strengthened, toughened, laminated or curved. These glasses could also be used in single glazing without any fear of losing the coating. Soft coat glasses (to be discussed in the next post) are susceptible to scratch and degradation over time, and requires special handling, hard coated glasses were invented just to counter this problem. Only disadvantage is the variety of colors available when compared to off line coating. Continue reading

Non-Solar Heat Control Glasses

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Solar and Non-solar heat transfer- IGU

In the previous post, types of heat entering a building was discussed, of which solar heat comprises around 80% and the rest is non-solar heat. It becomes very important to control non-solar heat as well even though it contribute to only 20% heat entering a building, especially in buildings where there is 24 x 7 operations and households, so as to bring down the energy consumption during night time. In this post, non-solar heat and how all to control it will be discussed in detail.

Non-solar heat is mainly transferred in three ways- conduction, convection and radiation, and is measured in terms of U-value (W/m2.K). Continue reading

Solar and Heat Control Glasses

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solar and non-solar heat

Glass is used in a building to harvest natural light inside it and there by reducing the internal artificial lighting requirements, in turn saving energy. The two major sources for heat entering the building is solar heat and non-solar heat; solar heat is nothing but the direct solar heat entering the building through visible light, non solar heat is caused by various factors like conduction, convection and radiation. Out of the heat sources, solar heat is the major one and requires more attention, even though the effects of non-solar heat could not be ignored as well, as it plays a major role in certain structures. Continue reading

Thermal Breakage in Glass


There are many instances where the glass panes in a building tends to crack for itself. This could be attributed to various factors like poor quality glazing, but there is also another factor which causes such breakage and is called thermal breakage. Thermal breakage in glass mainly happens due to the high difference in temperature between two points in a single glass pane, resulting in expansion and contraction in the same pane.

The temperature difference as mentioned above could be a result of many factors, such as difference of temperature between inside and outside, solar intensity in the region where building is located, type of glass (whether it is tinted, reflective, etc.), thickness of the glass, internal ventilation, type of glazing done, partial shade on glass, etc. Of all these factors, solar intensity plays a major role and it differs with geographical location, building orientation, seasons, etc. Continue reading

Optical Distortion in Tempered or Toughened Glass


In my previous post on Glass Tempering or Toughening Process, I had mentioned how the process is executed and the physics involved (Refer Back). Also a brief mention how the toughened glass quality is assessed after it breaks, this is very important because safety is the reason for we spend on tempering. There are also other issues in terms of quality when glass is tempered. These are mainly optical distortion, roller marks, waviness and bend, edge strength, coating burns, fragmenting, burns, spontaneous breakage, etc.

High Optical Distortion

Quality of tempered glass mainly depends on the quality of equipments used and the quality control procedures adopted. Optical Distortion , is mainly a blurred appearance in images when seen through the glass, as well as on the reflection on the glass. This quality issue in tempered glass is common to all types of glasses. Even though minor levels of optical distortion is present in most of the tempered glasses, but it gets magnified when the quality is that poor and the glass is applied on high rise building facades. The minor level optical distortion is inherent on tempered glass, considering the fact that glass nearly reaches it’s softening point as it is heated up to a temperature of 726 degrees, and also the fact that this glass moves in rollers, therefore it is also called roller wave distortions. Such distortions could be easily identified in reflective and low-e coated glasses. Roller wave distortions could be easily controlled by adopting suitable technology and quality control procedures (use of forced convection furnaces instead of radiation furnaces). Continue reading

Laminated Glass: Myths and Facts


There are major defects happening with laminated glass, if the process is not executed properly. Most prominent of such problems is de-lamination. This happens mainly due to the poor bonding between the glass and PVB sheet. In my previous post on laminated glass basics, I had mentioned about the clean facility requirement for lamination process, if this is not followed in the facility, there are chances for dust to stick on to the PVB and at a later stage, resulting in de-lamination. Waviness in the glass is also another reason for de-lamination: waviness in the glass can happen mainly due to poor quality tempering and even in annealed glass which has high amount of  inherent waviness. De-lamination mainly occur at the edges where chemical bonding is weaker. De-lamination may also happen when the unit is over exposed to water, mason errors (like improper cutting), applying poor quality sealants, etc. Continue reading

Laminated Glass Basics

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Laminated glass is made by sandwiching Poly vinyl butryl (PVB) sheet in between two pieces of glass. Laminated glass offers more safety because when the glass breaks, it keeps sticking on to the PVB sheet in the middle. Apart from … Continue reading

A Glass Is a Glass Is Not Just a Glass!!!

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To be honest, my exposure to glass and glazing industry is brief, and the same was my knowledge about glass. Glass never had more than a decorative value in my mind, as it had to be for me since I was from a decorative product segment (paints). It was just after I got inducted into this industry that I had to invent this statement- “A Glass is a Glass is not just a Glass!!!”.

At first, I realized that there are different types of glasses being manufactured, each with different chemical properties and functions. But I could superficially assimilate the knowledge and as a new comer, it was enough for me to classify them as Soda-lime glass, lead glass, borosilicate glass and glass fibre. Since I’m only concerned with glass as a building material, I would be writing only about flat glass. Flat glass industry includes both float glass and sheet glass manufacturers. Basic difference between these two are the process by which they are made. Sheet glass is made by using iron rolling pins to flatten the molten glass and to get it into desired shape, and further grind and polish it to make it clear. Float glass on the other hand is flattened by making the molten glass to float over molten tin. I also learned that the float glass manufacturing process was invented by Alastair Pilkington and Kenneth Bickerstaff in 1957. Continue reading