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Figure 1.The atrium roof and the gable seen from above.
MicroShade™ MS-D is in the
larger tilted sections, while MicroShade™ MS-A is in the gable. Photo: DI
The
Headquarters of the Confederation of Danish Industries (“DI”) is situated right
in the center of Copenhagen at the Town Hall Square, and overlooking the famous
Tivoli Gardens at the rear. The building dates back to 1979 and over the past
two years it has been completely rebuilt, modernised and extended.
A prominent
feature of the new building is a large glazed atrium in the center. It rises to
the 7th floor level, and contains a conference facility, spacious lobby
and bridges which inter-connect the offices placed in the two wings of the
building.
The main
function of the atrium is to provide daylight to the core of the building and
at the same time provide a well balanced indoor climate in order for the atrium
to be used for conferences and meetings. The allowed temperature variation of
the atrium in the summer is in the range from 22 to 27°C, and in the winter
between 22 and 25°C. Temperatures above 26°C are accepted for 100 hours yearly,
and temperatures above 27°C must be limited to 25 hours yearly. In addition, it
was important to the client that the building was designed to be as energy
effective as possible, and that this was reflected in the choice of materials
and technologies used in the building.
The facade
area of the atrium is 1 700 m² of which 1 500 m² constitute
the roof and the remaining 200 m² the southwest gable. The roof is facing
southeast and features 7 segments that tilt between 0 and 46°. Because of the
orientation and tilt of the roof, heat gain from the direct sun is a major
issue in the summer period. Controlling solar heat gain in the atrium without
compromising daylight levels therefore became an important challenge. It was soon
recognized that a very efficient solar shading had to be implemented for the
atrium roof and gable.
Figure 2 below shows a model of the atrium.
Most of the triangular surfaces of the glazed roof (No. 3, 5, 7, 9 and 11) were
to be fitted with semi-transparent photovoltaics embedded in glazing. However, the
light transmission on these surfaces was reduced by 94%. On the remainding
surfaces No. 1, 2, 4, 6, 8, 10, 12 and the gable No. 13 a solution had to be found
which would provide the required level of daylight combined with high
performance solar protection.
Figure 2. Model
of the atrium with indication of the surfaces. Source: Rambøll
The initial
envisaged solution for the shading contained a combination of screen printed
glass and movable interior screens. The exterior screen print was designed to
vary between 0 and 75% density such that the surfaces with the largest tilt had
the most dense print. The movable interior screens featured an aluminum coating
to reflect the heat to the outside, but the optical transparency of the screen
was less that 10%.
The screen
print on the glass will reduce the heat flow to the building, but the specified
temperatures in the atrium only could be achieved by extensive use of the supplementary
interior screens. The disadvantages of using the interior screens were the
reduction in daylight below acceptable levels and blocking the view to the
outside. This combined solution was therefore rejected by the design team.
As an
alternative to the initial solution, MicroShade™ glazing was investigated.
MicroShade™
is a new generation of modern, energy efficient facade and roof glazing for new
and refurbished buildings.
MicroShade™ technology The
MicroShade™ technology is a progressive solar shading technology designed to
achieve a shading performance on a level with exterior shading solutions. The
progressive effect of the MicroShade™ ensures that most shading is provided
when most needed. MicroShade™ is a passive element which does not require any
maintenance, service or operation during use. MicroShade™
glazing provides a reduction of the solar heat gain up to 90%, while
maintaining visually transparency. The light transmittance is close to 50%
for 2 layer MicroShade™ glazing. |
MicroShade™
solar shading consists of a patented microscopic lamella structure built into
the glazing. The microscopic lamellas are angled to provide a shading of the
direct solar irradiation falling onto the window while allowing light from
other angles through the glazing. The advantage of these microscopic lamellas
is that they are invisible to the human eye even at close distance, and hence
allow a free view through the glazing at typical viewing angles. The
microscopic lamellas are made of metal and are built into the product during
the production of the MicroShade™ glazing. As the shading device is integrated
in the glazing and contains no moving parts it requires no service and is not
sensitive to the exterior climate.
Before the
decision was taken to use MicroShade™ glazing, a series of calculations and
simulations were made to compare the thermal and optical performance of
different scenarios and shading solutions. Initial calculations of the solar
heat gain in the atrium revealed that glazing fitted with MicroShade™ type MS-A
would lead to an unacceptable heat gain on a selection of the surfaces in the
atrium roof compared to the initial solution consisting of screen print in
combination with interior movable screens.
As a
consequence, PhotoSolar A/S, the Danish company which develops and produces MicroShade™,
manufactured a new version of MicroShade™ named MS-D. The MS-D differs from the
MS-A by having a steeper tilt of the microscopic lamellas. Accordingly, the
shading efficiency of the MS-D is higher than that of the MS-A, and the product
is better suited to the atrium roof of the DI building. The tilt of the
microscopic lamellas of the MS-D was optimized to provide the same energy
balance as the initial shading solution with screen print and movable screens.
Figure 3 shows a comparison of the total
solar transmittance through the different solutions – screen print in
combination with movable shades, MicroShade™ MS-A and MicroShade™ MS-D.
Figure 3. Total
solar transmittance on selected summerdays for the original solution with screen
print and movable shades, the traditional MicroShade™ MS-A and the modified MicroShade™
MS-D.
After that,
detailed CFD simulations of temperature and air currents in the atrium were conducted
in order to ensure the solution would live up to the indoor climate
requirements from the tender material. The simulations showed that the modified
MicroShade™ MS-D solution performed just as well as the original solution with screen
print and movable shades.
A simple
mock-up with a MicroShade™ glazing was made in order to test the view out
through a MicroShade™ glazing. The mock-up could be adjusted to the different
view angles, which exists in the atrium roof. Furthermore DI visited a MicroShade™
roof installation in Germany too see an installation of the product. In this
way the client got a first-hand experience of the MicroShade™ glazing before
the solution was finally decided.
There was a
great satisfaction with the MicroShade™ glazing, and this together with the
calculations lead to the final choise of MicroShade™ as the solar shading
solution for the atrium.
Table 1.
Technical properties of MicroShade™ solar shading for four standard types.
Type | Description | Tilt of
micro-lamellas | g-value1 | Light
transmittance2 |
Standard | ||||
MS-A | For facade and roof application | 16˚ | 0.10-0.33 | 0.49 |
MS-D | For facade and roof application | 23˚ | 0.10-0.30 | 0.43 |
MS-RS | For roof application | 0˚ | 0.09-0.28 | 0.49 |
MS-RW | For roof application | 40˚ | 0.09-0.28 | 0.32 |
1 The g-value varies with the position of the sun and depends
on the glazingtype, tilt and orientation.
2 The light transmittance normal to the surface according to
EN 410. The light transmittance varies with angle of incident.
The final
solution in the atrium roof became MicroShade™ MS-A Vertical in surfaced no. 1
and in the gable MicroShade™ MS-A was used. In the remaining surfaces (no. 2,
4, 6, 8, 10 and 12) the modified MicroShade™ MS-D was used.
It is not
possible to tell the difference between the different types of MicroShade™ with
the naked eye and thereby the entire atrium facade ended up appearing homogenous.
The MicroShade™
glazing was delivered by Glassolutions Scandinavia in the autumn of 2011 and in
January 2012 the atrium roof was finished. Even though some of the interior
works still remain before the building is ready for commissioning in May 2013,
it already now looks very promising for the large atrium.
Figure 4.
The atrium of the DI building during the construction. Photo: PhotoSolar A/S
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