Advantages & Disadvantages
of Glass as a Building Material
ADVANTAGES
Adds beauty to the building
Supply of natural day light
Weather resistance
Does not Rust
Easily Cleaned
Allow natural light to enter the house even if door/window is
closed
An excellent insulator against electricity
Available in varieties of colours
It can be blown, drawn and pressed to any shape
It provides an ideal way to showcase a product
Glass is 100% recyclable and can be recycled endlessly without
loss in quality or purity
No problem with UV degradation
Excellent abrasion resistance
Stable over a wide range of temperature
It is unaffected by air, water and most of the acids
Its use fulfils the architectural view for external decoration
By using glass in interior, it saves the space inside the building
Conserves heat and protects against outside barriers
DISADVANTAGES
An expensive Material. So, increase the cost of building
Breaks Easily, Very Rigid and Brittle
When broken, the pieces may be sharp, injuries
Less impact resistance
It is affected by some alkalis
It is affected by hydrofluoric acid
Use of glass also enhances the cost of security
Glass is also unsafe for earthquake proven area
Glass is poor in terms of heat preservation, leading to higher
costs in the operation of air-conditioners
Glass absorbs heat and hence act as a greenhouse and hence
not suitable in warm and hot climates. It will increase A\C load
and more energy consideration for air conditioning.
Though many feel that once you provide glass in a building
façade, you are free from painting expenses for ever but this is
not fine. You may have to spend equally for cleaning of glass.
Sometimes it is as costly as external painting. Again, you may
paint building once in a 5 years but for glass you have to clean
every year
Glare is a major problem in glass façade.
INSULATED (DOUBLE-GLAZED,TRIPLE-GLAZED):
Insulated glazing refers to glazing units consisting of two or more
panes of glass. Insulated glazing can be double glazed or triple
glazed. The glass panes are spaced apart and sealed to form a single
glazed unit with an air space between each pane of glass. The glass
layers and the air space resist heat flow. As a result,insulated glazing
lowers the U-factor and solar heat gain coefficient.
GAS FILLED GLAZING:
To improve the thermal performance of glazing the space between
the glass panes is filled with inert gas.Because these gases have a
higher resistance to heat flow than air,they are sealed between the
window panes to decrease the glazing’s U-factor.
Gas filling can bring down the U-value by 0.2-0.3W/m20k.The
most common types of gases include argon and krypton.
HEAT ABSOBING TINTS:
Tinted glass absorbs a large fraction of incoming solar radiation
and glare thus reducing the solar heat gain coefficient. However
they reduce visible light transmittance.
Gray-and bronze-tinted glazings reduce the penetration of both
light and heat
Blue and green tinted windows offer greater penetration of
visible light and slightly reduced heat transfer compared with other
glasses of tinted glass.
Tinted glass reflects only a small percentage of light , so that it
does not have the mirror like appearance of reflecting coatings.
LOW-EMISSIVITY COATINGS:
Low emissivity coatings are microscopically thin, virtually
invisible, metal or metallic oxide layers deposited on a window or
skylight glazing surface primarily to reduce the U-factor by
suppressing radiative heat flow.
In general, low –E coatings are designed to reduce heat transfer
caused by long wave radiation.
Clear glass has an emissivity of 0.84 which means that it absorbs
84% of long wave radiation and reflects 16%.
Low-E coatings typically have emissivity ranging from 0.35 to as
low as 0.04, which means 65%-96% of the long wave radiation is
reflected back to the atmosphere.
SPECTRALLY SELECTIVE GLASS:
Spectrally selective glass also blocks long wave radiation , but they
have another important function. The multiple layers of silver in the
coating allow the glass to selectively transmit and reject wavelengths
of solar radiation.
Spectrally selective glass is very similar to Low-e glass in the sense
that it restricts heat ingress but the difference lies in the capacity to
transmit visible light.
REFLECTIVE COATINGS:
Reflective coatings usually consist of thin, metallic layers which
come in a variety of colors including silver, gold, and bronze.
Reflective coatings are applied on the outer surface of glazings i.e.
the surface exposed to rain.
Reflective coatings on window glazing or glass reduce the
transmission of solar radiation, thereby blocking heat. However they
also reduce a window’s visible light transmittance.
Reflective window glazing is commonly used in hot climates
where solar heat gain control is critical . Reflective glazing is used by
many architects because of its glare control and uniform exterior
appearance.
TYPES OF GLASS
Float Glass: Float glass is also called soda lime glass or clear glass.
This is produced by annealing the molten glass and is clear and flat.
Its modulus of rupture is 5000-6000 psi. Stronger than Rocky Balboa
taking punches from 2000 psi punches man Ivan Drago. It is available
in standard thickness ranging from 2mm to 20mm. and has weight
range in 6-26kg/m2. It has too much transparency and can cause
glare. It is used in making canopies, shop fronts, glass blocks, railing
partitions, etc.
Tinted Glass: Certain additions to the glass batch mix can add color
to the clear glass without compromising its strength. Iron oxide is
added to give glass a green tint; sulphar in different concentrations
can make the glass yellow, red or black. Copper sulphate can turn it
blue. Etc.
Toughened Glass This type of glass is tempered, may have
distortions and low visibility but it breaks into small dice-like pieces
at modulus of rupture of 3600 psi. Hence it is used in making fire
resistant doors etc. They are available in same weight and thickness
range as float glass.
Laminated Glass: This type of glass is made by sandwiching glass
panels within a protective layer. It is heavier than normal glass and
may cause optical distortions as well. It is tough and protects from
UV radiation (99%) and insulates sound by 50%. Used in glass
facades, aquariums, bridges, staircases, floor slabs, etc.
Shatterproof glass: By adding a polyvinyl butyral layer, shatter
proof glass is made. This type of glass does not from sharp edged
pieces even when broken. Used in skylight, window, flooring, etc
Extra clean glass: This type of glass is hydrophilic i.e. The water
moves over them without leaving any marks and photocatylitic i.e.
they are covered with Nanoparticles that attack and break dirt
making it easier to clean and maintain.
Double Glazed Units: These are made by providing air gap
between two glass panes in order to reduce the heat loss and gain.
Normal glass can cause immense amount of heat gain and upto
30%of loss of heat of air conditioning energy. Green, energy efficient
glass can reduce this impact.
Chromatic glass: This type of glass can control daylight and
transparency effectively. These glass are available in three forms-
photochromatic (light sensitive lamination on glass),
thermochromatic (heat sensitive lamination on glass) and
electrochromatic (light sensitive glass the transparency of which can
be controlled by electricity switch.) It can be used in meeting rooms
and ICUs
Glass wool: Glass wool is a thermal insulation that consists of
intertwined and flexible glass fibers, which causes it to "package" air,
and consequently make good insulating materials. Glass wool can be
used as filler or insulators in buildings, also for soundproofing.
Glass blocks: Hollow glass wall blocks are manufactured as two
separate halves and, while the glass is still molten, the two pieces are
pressed together and annealed. The resulting glass blocks will have a
partial vacuum at the hollow center. Glass bricks provide visual
obscuration while admitting light.
