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Advances in energy efficient architectural glazing

Finding ways to improve energy efficiency is one of the
greatest challenges facing contemporary architecture. Deploying highly
functional glass products and integrating energy-relevant products are
effective ways to achieve optimum efficiency even in large- format glass
façades. Façades have long moved beyond being just static shells
providing weather protection at the interface of building interior and
exterior. With good reason, they’re often compared to human skin, which indeed
does have a protective role to play, but also adjusts dynamically to external
conditions and thus maintains the body’s “ideal temperature."

Finding ways to improve energy efficiency is one of the
greatest challenges facing contemporary architecture. Deploying highly
functional glass products and integrating energy-relevant products are
effective ways to achieve optimum efficiency even in large- format glass
façades.

Façades have long moved beyond being just static shells
providing weather protection at the interface of building interior and
exterior. With good reason, they’re often compared to human skin, which indeed
does have a protective role to play, but also adjusts dynamically to external
conditions and thus maintains the body’s “ideal temperature.” Modern glass
façades are tasked with exactly this function – except in relation to indoor
climatic conditions. In light of significantly tightened energy efficiency
standards for buildings, the building envelope must play yet another crucial
role in achieving a reduced primary energy demand: Heating, air- conditioning
and lighting are among the most power-hungry systems in office buildings. And
the façade can directly influence these consumption factors. The goal must be
to optimise thermal insulation, protect interior spaces from overheating,
ventilate rooms in a controlled manner, use daylight to the fullest extent
possible and minimise the use of supplementary air-conditioning.

Keeping pace with ever higher expectations, façade
technology has been systematically improved in years past. One target pursued
in this development process is the multifunctional adaptive façade, a shell
that’s able to respond dynamically to changing environmental conditions. Glass
façades hold great potential in this area. Decentralised controls for
ventilation, heating and cooling via the building envelope enable significant
building technology reductions. At the same time, integration with building automation systems ensures that individual components can
work together in perfect unison to achieve maximum energy efficiency.

Opened in January of 2014 at 3,048 metres above sea level on top of Gaislachkogel peak in Sölden, Austria, the design restaurant “Ice Q” serves as a prime example for contemporary glass architecture right in the High Alps. The 900 m2 glass façade with its high-performance triple-pane insulation glass was designed and built by the Austrian façade specialist GIG Fassaden GmbH. Photo: GIG Fassaden

Efficient combination of components
Even today, the components needed for the multifunctional
façade of the future are already widely available. The challenge, then, for
architects, façade designers and façade manufacturers generally lies in the
optimisation of existing systems and in the individualised, demand-oriented
integration and combination of available technologies and products. Ambitious
targets have been set. In Europe, for example, the “Energy Performance of
Buildings Directive” (EPBD 2010) stipulates that all new buildings in EU member
states must be constructed as “nearly zero-energy buildings” from 2020 onwards.
This high bar can only be cleared by using highly efficient façades that
provide excellent insulation and smart indoor climate control – all while
harnessing the power of the sun.

Optimised system technology

The deployment of highly efficient, variable-use façade
systems is a prerequisite for the creation of energy-efficient glass façades.
Therefore, system providers aim at further improving the insulating performance
and application flexibility of their profile systems. Improved profile
geometries and the creation of the preconditions for the use of
high-performance triple insulating units are important aspects in this regard.
Despite significant progress, large-format glass façades continue to be left
behind, when it comes to heat transfer properties, by classic perforated
façades with insulation. At the same time, however, they also offer numerous
advantages over solid construction. Thanks to copious amounts of glass used,
they allow for visual contact with the outside world. What’s more, they create
enhanced lighting possibilities and ideal conditions for solar gain.

The E2 Façade by Schüco illustrates just how far system
technology has progressed in the direction of multifunctional glass façades.
It’s an energy-efficient complete system with a revolutionary combination of
façade and system technology that both saves and generates energy. Customised
solution packages can be created thanks to its four function modules
(decentralised ventilation, façade-integrated photovoltaics, façade-integrated
solar shading and integrated opening units).

The Schüco E2 Façade is an energy-efficient complete system that unites façade and system technology. Customised solution packages can be created thanks to its four function modules (decentralised ventilation, façade-integrated photovoltaics, façade- integrated solar shading and integrated opening units). Photo: Schüco

High-performance functional glass

The use of safety glass brings to the fore the extensive
structural possibilities and design advantages offered by glass (curved glass,
screen printing, digital printing, enamelling etc.) and thus provides
considerable flexibility in the design of customised high- performance glass
façades. However, large glass surfaces also allow for outside conditions to
strongly impact the indoor climate. As a result, the functionality of glass
products used is of considerable importance.

Excellent results are possible nowadays with
high-performance thermal- and solar-control glass. For example, double-pane
insulating glass filled with the noble gas argon and used with warm-edge spacer
systems currently achieves a thermal transmittance value of around 1.0 W/m2K.
This value drops to 0.6 W/m2K for triple-pane insulating glass used in standard
configurations. Even 0.5 W/m2K is possible if the space between panes is
increased. Even lower thermal transmittance values are possible in today’s
standard glass configurations by using the ultra-expensive noble gas krypton.

Today’s argon-filled and Low-E-coated triple-pane insulation glass can reach Ug values of up to 0.6 W/m2K. In order to achieve optimum thermal insulation, it is necessary to deploy modern warm-edge seal systems such as the spacers made by Swisspacer. Combining a highly insulating profile consisting of plastic composite materials, a gas-tight foil and desiccants as filling materials, the spacer system minimises heat loss and ensures long-lasting serviceability of the insulation glass by. Photo: Swisspacer

Another option exists for pushing down even further the
thermal transmittance coefficient while using argon – quad-pane insulating
glass. Even though these products achieve a U-value of 0.3 W/m2K, they’re not
any heavier than conventional triple-pane glass because they’re made using hardened thin glass. Another
option, vacuum insulated glass (VIG), would make stacking window panes an
easier-to-manage task for window and façade manufacturers. Glass of this kind
is already available in Asian markets, but despite focussed research efforts,
Europe is still waiting to see equivalent products for façade applications
become ready for mass production.

Solar control and light directing

Besides heat insulation, large-format façades must also
master the challenge of providing reliable solar and glare protection. Solar
control glass alone – while efficient and easy to integrate – is often not
sufficient to reliably prevent undesirable heat gain in interior spaces during
the summer. Alternatives to shading systems installed on the inside or outside
of the façade are available, including special solar control glass featuring
electric voltage- based automatic tinting to minimise the impact of sunlight.

In autumn of 2013, the University of Giessen presented an
intriguing development in this area. Led by Prof. Bruno Meyer, the Physical
Institute there developed and filed a patent application for an
energy-efficient glass coating that allows for temperature- dependent thermal
transmittance. Using this passive (i.e. non- voltage), transparent glass
coating allows for the straightforward control of sun-induced heat gain in
interior spaces. At 20 degrees Celsius, the material autonomously switches from
semiconductor (permeable to light) to metal (reflective).

The synergy of active light directing and variable solar control in insulating glass: DLS Ecklite Evolution by the Austrian company Eckelt Glas integrates two separate, electrically driven louvre

Insulation glass with integrated solar and/or light directing
control is another frequently used alternative. These systems are integrated
into the glass and can be controlled manually or electronically to align with
individual insolation and light conditions. Thanks to integrated slats with
variable adjustment angles, daylight can be directed into the interior of the
room. The Austrian company Eckelt Glass offers DLS Ecklite Evolution, for
example, an insulation glass product with two separate, electrically driven
louvre blinds integrated into the glass, featuring a concave section for active
light directing in the upper part of the glass and a convex section for
efficient solar and glare control in the vision area. Depending on exterior lighting
conditions, users can choose to open either the vision area only or both the
vision area and the upper area for an unobstructed view. Other effective
solutions for targeted daylighting and balanced illumination of rooms besides
these louvre systems include glazing with engraved louvre structures, rigidly
mounted reflective blinds and integrated prism structures.

Energy from the façade

Seeing that the amount of available solar energy is 3,000
times greater than total global energy consumption, it would seem smart to
harness the sun to generate eco-friendly energy right in the façade.
Photovoltaic modules can be incorporated in nearly any kind of glass
installation. Solutions with integrated PV can easily be implemented even with
multi-pane insulating glass with thermal and acoustic protection properties and
with overhead and walkable glass. Set up correctly, the solar control
functionality of a PV façade can even make additional shading systems obsolete.
Moreover, solar energy from collector systems integrated into the façade can be
used for heat production. Glasstec 2014 in Düsseldorf will show just how innovative
the glass industry really is, including in this market segment, what product
solutions the sector has in store to help make glass façades more energy
efficient and how architects and façade builders envision the future. From 21
to 24 October, the leading international trade fair of the glass industry will
present the latest developments revolving around the energy-efficient building
envelope at the trade fair stands, the special show “glass technology live” and
the

Façade Center. This range of offerings is further enhanced
by the scientific conference “engineered transparency,” which focusses on
“Glass Construction,” from 21 – 22 October 2014 and by the International
Architecture Congress, entitled “Glass 5.0 – Design, Function, Emotion,” on 22
October 2014.

The triple-pane solar control glass ipasol neutral by AGC Interpane delivers excellent thermal insulation and ideal protection from the sun in this office building, which is superimposed upon an air-raid shelter in Bochum, Germany. Partially coating the glazing with ipachrome design helps to provide additional glare and solar control, especially on the building’s south-facing side. Photo: Fotodesign Andreas Braun, AGC Interpane

The building envelope as multiplayer
Thanks to continuous construction, technology and product
advancements, plenty of development potential remains for large- format glass
façades. Regardless of any temporary façade design trends, topics such as
energy efficiency and improvement of indoor climatic conditions will dominate
architecture and façade construction in future, with additional attention paid
to the sustainability of materials and products used.

Stronger multi-disciplinary cooperation will be critical on
the path to energy-optimised glass façades and buildings. “Architects,
engineers, builders and façade specialists must and will aim to meet political
imperatives regarding the optimisation of energy consumption, without
neglecting architectural and quality-related aspects or ecological and economic
considerations. The building envelope turns into a ‘multi-player’ with the
ability to coordinate and control light, air and energy flows simultaneously,”
says Rudolf Locher, the Managing Director of the Swiss Centre for Windows and
Façades (SZFF) in summarising the future challenges awaiting façade
professionals.

For more information

glasstec-online.com