Facade Glazing - Solar ControlIn a tropical country like India, glass facades can control the amount of heat that enters buildings. Therefore, solar control glass plays an important role in not just significantly reducing the incoming heat but also decreasing the cost on air-conditioning and blinds. Solar control glass has a microscopically thin coating on one side that reflects heat from the sun to the outside. In areas that are extensively glazed, glass helps prevent over-heating. It can also reduce the uncomfortable glare that comes from direct sunlight.  

Benefits

When using solar control glass for glazing large areas, the glass allows natural lighting whilst restricting the resultant heat from glazing. This is particularly useful in glass conservatory roofs or south-facing glazed areas. Glass facades with solar control glass are an energy-efficient way to reflect heat from the sun and keep interiors cooler. Solar control glass is well-suited for commercial glazing because of its ability to curtail excess heat whilst allowing optimum daylight and creating a larger sense of space. Saint-Gobain Glass offers a wide range of solar control glass. The different glass variants can be used in combination to create a multi-functional glazing that results in low-maintenance, noise reduction, aesthetic appeal and enhanced safety & security. 

SGG ENVISION is an advanced solar control glass and low-E glass. This green building glass is designed to give a spectrally selective solar control performance and comes with excellent thermal insulation properties. SGG NANO SILVER is manufactured by depositing a coating of metallic oxides by magnetically enhanced cathodic sputtering under vacuum conditions onto clear or body-tinted glass. It is this coating that gives the glass its solar control and thermal insulation properties as well as its distinctive appearance. SGG NANO is a high performance coated glass with advanced energy-efficient solar control and thermal insulation (low e) properties. It is ideal for modern architecture which demands exterior glazing solutions with a neutral appearance. SGG EVO is a solar control glass that is energy-efficient and has thermal insulation properties in a single glazing application. It is designed to be in conformance with the requirements of green buildings and ECBC (BEE) regulations and is the ideal choice for buildings that are going in for the LEED/IGBC rating and TERI-GRIHA rating. SGG PLANITHERM is an advanced thermal insulation glass manufactured by coating clear or body tinted float glass with metallic oxides through a process of magnetically enhanced cathodic sputtering under vacuum conditions. It also has a neutral appearance due to very low reflection. SGG COOL-LITE ST is an advanced energy-efficient reflective solar control glass that cuts excess heat and optimizes light transmission. The product has been specifically designed for countries like India which face tropical climate. SGG ANTELIO PLUS is a reflective solar control exterior glass that can be used to block the incoming heat radiation from

the sun, while allowing in natural light. It can be used in single glazing as protection from extreme weather. SGG REFLECTASOL is a reflective solar control glass that is best suited for buildings in geographies with tropical climate, where solar heat needs to be controlled in order to keep interiors cool. It reflects the right quantity of sunlight so as to limit glare, while allowing adequate amount of natural light and hence the need for artificial lights as well as air-conditioners is significantly reduced. SGG PARSOL is a body tinted glass manufactured by the float process. Specially designed for exterior applications, it is a tinted glass with a coloured appearance, and also has the properties of basic solar control glass.

Control climate

http://www.metroglasstech.co.nz/catalogue/093.aspx  minh hoa

https://www.google.com.vn/search?q=facades+with+glazing+thermal+solutions&biw=1600&bih=756&tbm=isch&tbo=u&source=univ&sa=X&ei=z4NkVKuaL6eNmwWTqYDgAg&ved=0CDwQsAQ#facrc=_&imgdii=y5vIcMQi3dwbFM%3A%3Bg-t9faaEXi4HPM%3By5vIcMQi3dwbFM%3A&imgrc=y5vIcMQi3dwbFM%253A%3BPMt_gNV8rbI6hM%3Bhttp%253A%252F%252Fwww.glassforeurope.com%252Fimages%252Fcont%252F199_58133_image.jpg%3Bhttp%253A%252F%252Fwww.glassforeurope.com%252Fen%252Fissues%252Ffaq.php%3B502%3B397

~~~~~~

Understanding thermal performance of Glazed Facades

Mr D E V S Kiran Kumar

30 November 2012

Buildotech

Recent developments in glazing systems provide optimized

solutions for daylighting as well as heat gain. They are

manufactured to transmit an adequate amount of light in the

visible portion, while excluding unnecessary heat gain from the

part of the radiation spectrum. Near-IR radiation should get

reflected through low solar gain coatings especially in case of hot

climate. Double glazed-reffective coated glass gives the best

performance in these situations. They provide almost 10% better

energy performance compared to single pane clear glass for a

commercial building located in warm-humid climate.

Dark tinted glass absorbs considerable amount of visible light and

changes its colour. Whereas if they absorb ultraviolet (UV) or near

IR, there will not be any change in visual appearance. There are

some heat-absorbing glasses to lower down the heat gain and

control the glare. Tinted glass is used to absorb the radiation and

reduce the heat transmission but more heat absorption by a tinted

glass causes rise in its surface temperature. However, the

absorption is not the most efficient way to reduce the heat gain.

Absorbed solar energy from the glazing emits back as long-wave

far infrared energy. The emission of radiant heat is one of the

most important heat transfer pathways especially in case of

double glazed system. For example, coating a glass surface with

low emittance (Low-E) material and facing that coating into the

gap between the glass layers prevents significant amount of this

radiant heat transfer and reduces the total heat flow. Due to its

energy efficiency, daylighting and comfort benefits, low-e glasses

are now widely used in the facade construction.

The three thermo physical properties of the glass that are usually

given by manufacturers are; conductance (U-Value), solar heat

gain coefficient (SHGC) and visual light transmittance (VLT).

Depending on the climate, U-value becomes important for energy

savings and for comfort. When considering U-value of a window

as a whole, it refers to the centre of glass, edge of glass and

frame respectively. Buildings with low U-value windows/ facades

bring down the conductive heat gain in to the buildings. SHGC is

the fraction of solar radiation that hits the glazing and passes

through the glazing and heats the room.

The lower the SHGC the greater it shows its shading ability. VLT

is the percentage of transmitted visual light through the glazing.

When a good daylight is desired, high VLT is advisable. But the

lower SHGC (eg. tinted-glass) will bring down the visual light

transmission (VLT). So, proper combination of these two

properties is required for a good selection of glazing materials.

The best performing glass is with VLT 0.66 and SHGC 0.33 as

specified by the manufacturer but the physical theoretical limit is

roughly VLT 0.6 and SHGC 0.25. The performance of the facade

doesn't depend on the glazing properties given by the

manufacturer alone. The overall heat gain will increase when a

glass is fixed on a metal frame. However, the glazing properties

specified by the manufacturer always do not match with its

performance in actual conditions. SHGC of the glazing has more

importance than U-value in the determination of cooling load.

Effect of glazing on energy systemsWhile calculating the

cooling load we consider several external and internal heat

sources. A building with 10m2 floor area and with commonly used

concrete construction gets 35-40% of heat gain through walls and

windows. Solar heat gain through window tends to be the single

most significant factor in determining the cooling load of a

building. However, there are other parameters related to window

design to be considered for optimizing its impact.

The HVAC equipment has to be selected carefully. Especially in

fully glazed buildings, proper combination of control set points,

glazing and solar shading are crucial for energy performance.

Past research shows that for every 10C drop in set temperature,

about 10% of additional energy is required. So, it is necessary to

create comfortable indoors with optimal energy consumption.

There is a chance of overheating near fully glazed areas which

causes non-uniform distribution of temperatures across the room.

So, it is important to select an air-conditioning system that works

to satisfy the demand using less amount of energy. Sizing of the

system is also very important which is done through estimating

the correct amount of heat gain. Lower SHGC glazing reduces the

peak demand which leads to the smaller size equipment. An

integrated approach is required to get benefits because of the

interrelationship between window glazing, mechanical systems

and lighting systems.

Issues related to facade designVarious parameters that

influence the facade design are - the outdoor environment;

building form and orientation; properties of opaque and

transparent materials used; scale and surface properties of the

surrounding buildings; window size and geometry. New

technologies and some design guidelines are described below.

Modern glazings control radiation by addition of various thick

coatings and colour tints that influence the absorption, reflection,

transmission and emission as functions of radiation frequency.

Gas fillers (argon, krypton, xenon) and special materials (poly

carbon, fibre glass) are used to control conduction. These

Insulating glass units (IGU) are hermatically sealed, multiple-

pane assemblies consisting of two or more glazing layers held

and bonded at their perimeter by a spacer bar and with a cavity

space filled with air or argon gas.

Other recent smart window technologies include electrochromic,

thermochromic, photochromic, liquid crystal device and

suspended particle device windows. Frit glass enables the

designer to use patterns on the facade They can help in reduce

heat gain by using high performance ceramic coatings. Frames

are also available with different materials and composites. They

are manufactured with thermal breaks to bring down the heat

enter into the buildings.

Window geometry and size are key factors which can influence

the indoor mean radiant temperature (MRT). A large window area

implies a large hot surface. Tall and narrow windows are better

than square windows; they should preferably be located apart at a

distance not less than one half of the smaller window dimension.

The high intensity of direct sunlight in the tropics provides a very

significant potential of utilizing natural light without glare and

excessive heat gain. Avoiding glare is the main challenge of

daylight design with glazed facade. Although buildings with high

VLT values are susceptible to glare, it can occur even with a small

windows and very Low VLT values. Full glazing causes too much

daylight at least in the perimeter areas.

A well designed building will provide natural lighting in to the deep

floors. In this context, window geometry and percentage of area

on facade are very important factors. Taller windows give greater

penetrations, and the broader windows give better distribution of

light. For a given penetration, a number of small windows properly

positioned along the same or the opposite walls will give better

distribution of illumination than a single large window. Buildings

with small punctures/ openings can be a source of glare due to

excessive contrast between the bright window and adjacent dark

wall.

Bringing the natural light into the building will reduce the lighting

energy consumption. The area of the opening/size is important for

that. Numerous studies have shown that there are no daylighting

or energy benefits with window to wall ratios over 60%, and in

most cases an area of between 25 and 40% is optimum. Natural

light can be integrated with electrical lighting using controls in

achieving optimal lighting as well as energy savings. According to

a model study done by Lawrence Berkeley National Laboratory

(LBNL), Berkeley, higher window to wall ratios (WWR), with

sunshades and daylighting controls requires less energy than

lower WWR without daylighting controls.

When a tinted glass is selected for less heat gain, the visual light

transmission value will also come down. In such cases, the whole

window can be divided into two shelves a daylight window and a

view window. Thus, lighting and thermal requirements can be

balanced with good light transmission properties for daylight

window and low heat transmission for view windows. Another

practice is that use of different glazing for window and spandrel

separately. Spandrel glazing will be insulated from inside to cut

down the overall heat gain of the facade.

Surrounding surfaces also influences the facade design. For

example, when reflective glazing is used on any neighbouring

building, it will act like a mirror and intensifies the sun's effects

and over heat building patios. Green cover around the building

will reduce such affect where as large water bodies again can

cause reflective glare. Solar heat gains vary by orientation which

influences the energy use in hot climates. It is important to follow

a few basic rules in design when determining perimeter areas like

avoiding the East and West facing zones. Shading is necessary in

the South facing zones and the North facing is acceptable even

without shading. As the heat gain comes down, orientation has a

lesser impact. Differences in energy use due to orientation can be

minimized not only by selecting proper glazing but alsoby external

shading Overheated spaces near the unshaded windows lead to

non-uniform distribution of temperatures inside the building and

cause thermal discomfort to the occupants. Shading should be

considered as an integral part of facade design in order to

balance the daylight requirements and reduce solar gains.

In this context, fully glazed buildings where the above discussed

problems are prominent, sun control films are the one of the

possible retrofitting options. Recent developments in solar film

coatings for window glass show substantial solar heat reduction

due to the direct beam and diffuse components. These films when

stuck on window glass provide a substantial heat reduction; which

indicates the lesser energy expenditures while people enjoy the

natural light and maintain the goodvisual contact with outside

environment. However, care hasto be taken when one wants to

apply film on glass. Film, when stuck on the glass will increase

the absorption of the glass and cause discomfort due to the

surface temperature.

Tags: thermal power, enery systems, thermal performance,

glazed facades

@@@@@@@@@@@@@@@@@@@@@@@

Climate control: intelligent façades2 September 2011

Share on facebookShare on twitterShare on emailShare on printMore Sharing Services0

Why shouldn't building façades be smart enough to adapt to the weather?

In recent years, architects and consultants have been coming up with an array of designs for digitally controlled sunscreens that move in response to shifting environmental conditions.One leading expert in the field is New York City-based designer Chuck Hoberman, who has helped develop a variety of responsive sunshading systems for buildings around the world. The recent wave of concern about sustainability and reducing buildings' carbon footprints has spurred interest among architects in such systems, he says.With a traditional static façade, designers have to "come up with a best fit to all of the conditions that the building will see," Hoberman remarks. "But if you're in a zone where you have a hot summer and a cold winter, or intense solar gain at certain points during the day but not at others - that 'best fit'... entails compromises on its performance and on the occupants' experience within the building."By contrast, with a responsive design, "the building will optimise itself to changes in the environment," he says. "That optimisation results in improved energy efficiency and environmental performance but, equally importantly, in enhanced comfort."

"Digitally controlled sunscreens can move in response to shifting environmental conditions."At the Simons Center for Geometry and Physics by Perkins Eastman in Stony Brook, New York, a kinetic sunscreen along the southern glazing of a lobby creates an effect like "dappled sunlight coming through leaves," says Hoberman, who helped design the system. It uses a technology called Tessellate, which is made of multiple overlapping layers of perforated metal panels, the movement of which creates kaleidoscopic patterns.In 2008, Hoberman's eponymous design studio teamed up with engineering firm Buro Happold to form the Adaptive Building Initiative (ABI), a company devoted to researching and developing responsive façades like this one. Tessellate is part of ABI's line of 'intelligent surfaces', technologies that are highly customised for each building project. Using Tessellate in a building envelope can lower overall energy consumption by 6%, and it can reduce the cooling load by 15%-20%, when compared with fixed shading. The shifting geometries are also designed to be appealing to the eye, creating a kind of 'functional artwork', Hoberman says.For a competition-winning design for the new headquarters of the Abu Dhabi Investment Council, Aedas came up with its own bespoke shading screen with engineering help from Arup. The screen will shield the building's two 25-storey glass towers from the city's often-scorching sun. Aedas is aiming for an LEED Silver rating for the project, known as the Al-Bahr Towers, which is under construction and slated for occupancy in early 2012.Modern mashrabiya

In searching for a sustainable, culturally appropriate form of sun protection, the architects "struck upon the mashrabiya, which is the traditional Islamic perforated screen," says Aedas deputy chairman Peter Oborn. But they gave the design a modern update

"by making it dynamic. That would allow us, then, to reduce the glass specification to provide better views and more natural light."The screen is made of a mesh of thousands of umbrella-like devices that cover the towers on all sides except the north. Controlled via a combination of preprogramming and live data from light, wind and water sensors, the 'umbrellas' open and close as needed to protect the inside from the sun's heat and glare, according to Abdulmajid Karanouh, an associate in Aedas's research and development group, who specialises in system design.Each unit of the screen is triangular, divided into six smaller triangles. Made of duplex stainless steel, aluminium and fibreglass fabric coated with PTFE, an electric screw jack system drives the movement, forcing the point of intersection of all the triangles backward when the fabric needs to unfurl. Because the sunscreen will reduce the need for air-conditioning and artificial lighting, it is expected to lower energy use by 20% for the building as a whole; even higher in the towers alone, Karanouh says.The design might evoke comparisons to the responsive sunscreen at Jean Nouvel's l'Institut du Monde Arabe in Paris, but the Aedas architects were careful to avoid the mechanical failings of that early example from the 1980s.

"The screen is made of a mesh of thousands of umbrella-like devices that cover the towers on all sides except the north."To ensure the system's reliability, during design development, "the first thing that we put on our agenda is testing," Karanouh says. He recalls how, at a facility in Basel, the mashrabiya was tested by through 30,000 cycles (the equivalent of 84 years of operation) while being sprayed with salty water, dust and sand from Abu Dhabi.

"Jean's Nouvel's building is an obvious precedent," says Oborn, "but he designed that, in fairness, quite some time ago now, and the technology that he used was considerably more primitive than that which is available today, both in terms of design and operation. So I think that the market and world has moved on a long way since his initial work at the institute."Featherlike façades

Cologne-based JSWD Architects and Parisian firm Chaix & Morel et Associés designed the building, known as Q1 ThyssenKrupp in Essen, which received a DGNB (German Sustainable Building Council) Gold certificate. Unlike the fabric of Aedas's design, Essen's smart sunshading system is made of stainless steel slats in a featherlike pattern. It is one of many sustainable features of an 11-storey office building in the corporate campus of ThyssenKrupp.The shading system helps reduce solar gain while often leaving gaps that allow external views and let natural light enter, reducing the need for artificial light. "This is very important, because the greatest energy use in a building is electric energy, especially for lighting," says Jürgen Steffens, a partner at JSWD Architects. Because of the shading system and other green features, the building uses less than 120kWh/m² of energy a year, a low amount for a glass high-rise.Of course, energy savings of smart sunscreens are only part of the equation. The benefits to occupants' comfort, morale, and health are less easily quantified but equally significant. With the project in Abu Dhabi, Karanouh notes. "Really our selling point was... it will improve the health and working environment of your employees and, ultimately, their performance. The more natural sunlight they get and the less mechanical air ventilation they're subject to, the healthier and more energised they're going to be." After all, human energy is an important resource too.