Anti-Fogging Glass

Car windows, eyeglasses, camera lenses, even our bathroom mirrors are all victims of the frustrating effects of fogging. Fogging can pose hazard when it inflicts automobile windscreens; glass fogs up when warm, moist air comes into contact with it and cools to form thousands of tiny water droplets on the glass. The droplets scatter light, reducing the visibility through the glass.

Existing Technology

Fog is caused when steam condenses on a cool surface and then forms minuscule water droplets due to the water's surface tension. Water molecules are more attracted to each other than to air molecules and form a spherical shape to maximise contact between water molecules, which leaves as few as possible exposed to the air.

But water is also attracted to glass, and if this attraction is enhanced, it can overcome the surface tension. Previous anti-fog coatings have capitalised on this using titanium dioxide surfaces which increase the attraction between the water and glass. This overcomes surface tension so the water spreads out in sheets.

However, these coatings first need to be charged by UV light which means they do not work for long in the dark. And they tend to stop working altogether after three months.

Latest Anti-Fogging Glass

Super-hydrophillic

Super-hydrophillic - water loving - coating is composed of nano-particles made of silica, the same material that glass is made from, to create a coating with a rough surface, although it looks smooth to the naked eye. Polymer chains are used to assemble these very tiny particles of Glass onto a surface. A polymer chain is a long chain-like molecule with positive charge and the glass particles with negative charge are taken. So positive to negative attractive force can be used to build these layers up onto the surface. The net result is we create a very porous coating, that is, a coating that has lots of holes in it.

The silica particles form layers of tiny pores, each a thousand times smaller than the width of a human hair. The pores attract the tiny droplets of water that make up the foggy surface. Stacked ten to twenty layers thick, with air pockets in between, these pores create what's called a "wicking" effect, which forms the water droplets into a uniform sheet. When a droplet is dropped on that surface, the water is drawn into these pores instantaneously and wicked away into a uniform sheet. The result is no water droplets on the surface that can scatter light and a nice transparent lens in this case.

This cheaply produced technology added benefit of increasing the clarity of unfogged glass. It reduces the glare and allows more than 99 percent of light to pass through the glass, compared to untreated glass that scatters between four and eight percent of light. Because of the thin film coating that is filled with holes, it means that the coating also acts as an anti-reflection coating. That is, it will allow more light to pass through.

The super-hydrophilic materials with self-cleaning action are currently in use for side view mirrors of vehicles and exterior materials of buildings.

Super-hydrophobic

Super-hydrophobic - water-fearing – coating is made by adding a second, ultra-thin layer of water-repelling molecules. Then the large surface area created by the roughness of the surface has the opposite effect. It increases the repulsion between the water and glass, causing the water to form droplets.

These could be used to form self-cleaning surfaces, where water that lands on the surface is snapped up into droplets that grow larger and larger until they finally roll away, taking the dirt with them. This is the method a lotus leaf naturally uses to clean itself.

Application

• Windshields and windows

• Solar panels

• Lenses for cameras, endoscopes, laparoscopes, and other optical devices

• Eyewear – goggles and glasses

• Dental mirrors

Advantages

• Stable over time

• Inexpensive

• Does not require UV-light activation

• Excellent optical properties (high transmittance; low reflectance and refractive index)

Energy Conservation Building Code (ECBC)

The Energy Conservation Building Code (ECBC), launched on 28 June 2007, is a document that specifies the energy performance requirements for all commercial buildings that are to be constructed in India. The code is mandatory for commercial buildings or building complexes that have a connected load of 500 kW or greater or a contract demand of 600 KVA or greater. The code is also applicable to all buildings with a conditioned floor area of 1,000 m2 (10,000 ft2) or greater.The ECBC has been developed by India’s Bureau of Energy Efficiency, and is mandated by the Energy Conservation Act, 2001, passed by the Indian Parliament in September 2001.

ECBC is a set minimum energy efficiency standards for design and construction. ECBC encourage energy efficient design or retrofit of buildings so that it does not constrain the building function, comfort, health, or the productivity of the occupants and also have appropriate regard for economic considerations (life cycle costs i.e. construction + energy costs are minimized).

BEE would take suitable steps to prescribe guidelines for energy conservation building codes. Central Government can prescribe energy conservation building codes, and direct owners/occupiers to comply with them. State Government can modify the code in response to local climate conditions. ECBC provides a platform for the Broad stakeholders such as Building Industry, manufactures, professionals, Government Agencies etc to participate. ECBC addresses local design conditions and construction practices. It also emphasis on maximizing building envelope benefits – to encourage better designs.

ECBC defines the norms of energy requirement per sq. metre of area and takes into consideration the climatic region of the country, where the building is located. Norms have been developed to cater to 5 different climatic zones in India such as composite, hot and dry, warm and humid, moderate and cold.

The ECBC provides design norms for:

• Building envelope, including thermal performance requirements for walls, roofs, and windows, except for unconditioned storage spaces or warehouses.


• Lighting system (Interior and exterior lighting), including day lighting, and lamps and luminaries performance requirements.


• Mechanical systems and equipment, including ventilating, and air Conditioning.


• HVAC system, including energy performance of chillers and air distribution systems.


• Electrical system and motors.


• Water heating and pumping systems, including requirements for solar hot-water systems.

The code provides three options for compliance:

1. Compliance with the performance requirements for each subsystem and system;


2. Compliance with the performance requirements of each system, but with tradeoffs between subsystems; and


3. Building-level performance compliance.

Simulation exercises indicate that ECBC-compliant buildings use 40 to 60% less energy than similar baseline buildings.

ECBC development Process

1. An extensive data collection was carried out for construction types and materials, glass types, insulation materials, lighting and HVAC equipment


2. Base case simulation models were developed


3. The stringency analysis was done through detailed energy and life cycle cost analysis.


4. A stringency level for each code component was established


5. Code was finalized after consideration of comments on a draft version.

ECBC Scope

1. Mandatory Scope Covers commercial buildings


2. Applies to New Construction only


3. Building components included
   
   
   
   • Lighting (Indoor and Outdoor)
   
   
   • Building Envelope (Walls, Roofs, Windows)
   
   
   • Heating Ventilation and Air Conditioning (HVAC) System
   
   
   • Solar Water Heating and Pumping
   
   
   • Electrical Systems (Power Factor, Transformers)

ECBC Compliance Approaches

1. Component-based (prescriptive)

• Requires little energy expertise


• Provides minimum performance requirements


• No flexibility

2. System-based (trade-off)

• Allows some flexibility through the balance of some high efficiency components with other lower efficiency components

3. Whole building design analysis (performance)

• Allows flexibility in meeting or exceeding energy efficiency requirements (as compared to a baseline building)

Building Envelope Design

Impact of Energy Codes

1. Market Development for EE products

• Building Insulation


• Energy Efficient Windows (Glass and Frames)


• High-Efficiency HVAC Equipment

2. Improved Design Practices

• Lighting and Day-lighting


• Natural Ventilation/Free-Cooling Systems

3. Lower Energy Use and Reduced Electricity Bills

4. Reduced connected load and Improved Power Factor

Body-tinted Glass

Body-tinted glass is normal float glass into whose melt colorants are added for tinting and solar-radiation absorption properties. This tinted glass saves energy and reduces heat penetration into buildings and gives a striking visual effect. Coloured glass is an important architectural element for the exterior appearance of façades.

Tinted glass refers to any glass that has been treated with a material such as a film or coating, which reduces its ability to transmit light. Glass can be tinted with various types of coating, which block and/or reflect different amounts and types of light, according to the needs and preferences of the consumer. Glare reduction is another important property of tinted glass. Glare

The production process of body-tinted glass is similar to that of float glass. The only variation is in the colorants mixed at the beginning with the standard raw materials. Body-tinted glass is produced when colorants and iron are introduced during the glass manufacturing process. Different additives may produce differently coloured glasses. Bronze, dark grey and green are the commonly used tints.

The end product does not affect the basic structure of the glass itself, but does enhance its performance in relation to the (solar) electromagnetic spectrum. The colour is homogenous throughout the thickness of the glass. The solar energy transmission, shading coefficient and visible light passing through the tinted glass will vary according to the colour selected.

During the float glass melt process, chemical colorants can be added which tint the colour and increase absorption from the sun. This helps minimize the solar radiation that enters a building, keeping it cool from the inside and protecting furniture from fading. As an example of the colorants used - to create a purple exterior, manganese is added, while pinks and reds can be produced from selenium.

Colorants and colors

Some of the most-used colorants and the colours they produce are listed below:

Iron – Green, brown, blue
Manganese – Purple
Chromium – Green, yellow, pink
Vanadium – Green, blue, grey
Copper – blue, green, red
Cobalt – blue, green, pink
Nickel – yellow, purple
Titanium – purple, brown
Cerium – yellow
Selenium – pink, red
Gold – Red
Cadmium-Sulphide – yellow
Carbon & Sulphur – amber, brown

Double-Glazed with High-Performance Tinted Glass

Tinted Glass is intended for universal application. Either as single or double glazing for a basic level of solar control, and even in furniture, interior design, partitions, etc. It is also the base glass for many high performance comfort glasses.

Doubly-glazed tinted glass reduces solar heat gain to below that of bronze or gray tint but has a visible transmittance closer to clear glass. High-performance or spectrally selective tinted glass products are typically light green or light blue. The tint has no effect on the U-factor but reduces solar heat gain. Doubly glazed tinted glass allows 51 percent of solar heat gain and 69 percent transmission of visible light.

Advantages

• Saves energy, controls solar heat and gives a striking visual effect
• Meets the increasing demands for light in workplaces, creates attractive interiors and gives a feeling of spaciousness
• Offers a practical, stylish alternative to traditional materials when used in screens, partitions and furniture at home or in the office
• Gives designers the freedom to create attractive modern environments that are also economical and easy to maintain
  

Body tinted glass gives the added benefit of making a building look unique and contemporary, creating a lasting impression for business HQs.
Applications

The range of available thicknesses enable glass to be used where superior strength, greater spans, reduced deflection, higher daylight transmission and enhanced noise suppression are required.

Automobiles

One of the most common applications of tinted glass is in automobile windows. Almost all cars come with tinting at the top of the windshield to reduce solar glare when the sun is low in the sky. Apart from this, the windows of several cars are tinted either at the factory or as an aftermarket add-on by the consumer, to provide privacy to the car’s occupants, as also to reduce the build-up of heat in a car while it is parked outdoors.

Dwellings

Another popular use of tinted glass is in windows of homes and commercial buildings. Residential glass tinting is much easier to do than automotive tinting. It can even be done by the homeowner himself, with some practice. Tinted glass in homes serves many practical purposes, such as limiting ultraviolet light transmission through windows, and reducing overall heat gain inside the home by reflecting solar heat energy, thereby saving the homeowner money on air-conditioning.

Commercial Buildings

Tinted glass is also used in commercial buildings. Apart from keeping the interiors cooler, it gives the outside of a building a more uniform, aesthetically pleasing appearance. Depending on the creative use of different colours of tinted glass, the building can also take on a unique and interesting appearance while being insulated from the sun at the same time.

Bullet Proof Glass

Bullet proof glass or bullet resistant glass refers to any type of glass that is built to stand up against being penetrated by bullets. Although the public uses the term ‘bullet proof glass’, generally within the industry itself it is referred to as bullet-resistant glass, because there is no feasible way to create consumer-level glass that can truly be proof against bullets.

Bullet proof glass is usually constructed using a strong but transparent material such as polycarbonate thermoplastic or by using layers of laminated glass. The desired result is a material with an appearance and light-transmitting behavior of standard glass but offers varying degrees of protection from small arms fire.

The polycarbonate layer, usually consisting of products such as Armormax, Makroclear, Cyrolon, Lexan or Tuffak, is often sandwiched between layers of regular glass. The use of plastic in the laminate provides impact-resistance, such as physical assault with a hammer, an axe, etc. The plastic provides little in the way of bullet-resistance. The glass, which is much harder than plastic, flattens the bullet and thereby prevents penetration. This type of bullet proof glass is usually 70–75 mm (2.8–3.0 in) thick.

Bullet proof glass constructed of laminated glass layers is built from glass sheets bonded together with polyvinyl butyral, polyurethane or ethylene-vinyl acetate. This type of bullet proof glass has been in regular use on combat vehicles since World War II; it is typically about 100–120 mm (3.9–4.7 in) thick and is usually extremely heavy.

Working Principle of the Bullet Resistant Glass

In the bullet proof glass, the Laminate-layers of tough plastic called polycarbonate sandwiched in between the pieces of toughened glass make the glass ten times thicker than the ordinary glass and it is very heavy. If someone fires a bullet at an ordinary piece of glass, the glass can't bend and absorb the energy. So the glass shatters and the bullet carries on through with hardly any loss of momentum. That's why ordinary glass offers no protection against bullets.

But when a bullet strikes bullet proof glass, its energy spreads out sideways through the layers. Because the energy is divided between a number of different pieces of glass and plastic, and spread over a large area, it is quickly absorbed. The bullet slows down so much that it no longer has enough energy to pierce through—or to do much damage if it does so. Although the glass panes do break, the plastic layers stop them flying apart.

Advances in bullet resistant glass have led to the invention of one-way bullet resistant glass, such as used in some bank armored cars. This glass will resist incoming small arms fire striking the outside of the glass, but will allow those on the other side of the glass, such as guards firing from inside the armored car, to fire through the glass at the exterior threat.

One-way Bullet Proof Glass

One-way bullet proof glass is usually made up of two layers, a brittle layer on the outside and a flexible one on the inside. When a bullet is fired from the outside it hits the brittle layer first, shattering an area of it. This shattering absorbs some of the bullet's kinetic energy, and spreads it on a larger area. When the slowed bullet hits the flexible layer, it is stopped. However, when a bullet is fired from the inside, it hits the flexible layer first. The bullet penetrates the flexible layer because its energy is focused on a smaller area; the brittle layer then shatters outward due to the flexing of the inner layer and does not hinder the bullet's progress.

Advancement

The field of bullet proof glass is constantly developing, and there are a number of military projects underway to create lighter-weight, more defensive forms of bullet proof glass. One of the most promising is the use of aluminum oxynitride in the outer layer, in place of a polymer layer.

U.S. military researchers are moving quickly to develop this new class of transparent armour incorporating aluminium oxynitride (Trade name: ALON) as the outside "strike plate" layer. It performs much better than traditional glass/polymer laminates. Aluminium oxynitride "glass" can't defeat threats like the .50 caliber armor piercing rounds using material that is not prohibitively heavy. This more resistant-glass that can be used in military assault vehicles and aircraft.

Applications

Bullet Resistant glasses have a wide range of applications as follows:

• Banks
• Government Buildings
• Convenience Stores
• Churches
• Schools
• Check Cashing Stores
• Liquor Stores
• Post Offices
• Jewelry Stores
• Art Galleries