Solar Gains Control Systems

Commercial Systems

OKALUX OKASOLAR 3D

By David Geisler-Moroder, Bartenbach GmbH, Austria, and Johannes Franz, OKALUX GmbH, Germany

Product Description

Brief Concept Description

OKASOLAR 3D is a three-dimensional, highly reflective sun protection grid embedded in the cavity between the glass panes that is used as sun protection and daylight management system. The transmission of direct solar radiation is blocked at all times, regardless of the height of the sun, so that the solar heat gain into the interior of the building is considerably reduced. However, a large amount of diffuse daylight can still enter the interior thanks to the structure of the grid, providing daylighting with a more homogeneous light distribution and a significantly lower fluctuation in brightness than with direct sunlight. The geometry of the sun protection grid has been optimised for roof applications. As shown in Figure 53, OKASOLAR 3D has two different functional areas:

Lock-out area, facing South in the Northern hemisphere:
- thermal sun protection with g-values ≥ 7%
- reduced glare
Area of transmission, facing North in the Northern hemisphere:
- diffused irradiation of daylight
- partial view-through

The main louvre of the system is made of aluminium with a reflectance (solar and visual) of about 95%. The cross bars are concave in shape, so that the sunlight is always reflected to the outside also at low solar altitudes. They are made of plastic with a highly reflective surface with a reflectance (solar and visual) of over 80%.

The sun protection grid, which is open to the North in the Northern hemisphere, enables partial transparency and admits diffuse irradiation. The thin cross section of the louvres enables to achieve high transparency level of the grid (up to 85%, depending on the direction of sight), and a diffuse light transmission of 60-70% in the area of transmission.

Figure 53. Functional principle of OKASOLAR 3D for installation in the Northern hemisphere.

Architectural and Technological Integration into the Envelope

The special feature of OKASOLAR 3D is that the sun protection grid is integrated into the cavity of an insulated glazing system. Hence, there are no special requirements with regard to installation, maintenance or repair, and the entire system can be treated just like standard insulated glazing. The thickness and type of glass depend on structural and building requirements. However, the bending radius is to be limited to 12 m under deformation for structural reasons. The system can be used in 2-pane configurations in the 24mm cavity between the glass panes as well as in 3-pane configurations. In this case, the sun protection grid is mounted in the outer cavity.

Figure 54. Sample of OKASOLAR 3D in a 3-pane insulating glazing unit, appearance as seen from outside.

Integration into the Building: System and Comfort

OKALUX OKASOLAR 3D is a static system integrated into the cavity of insulating glazing units. The special geometry of the sun protection grid always blocks the direct sun beam and thus needs no control nor movable parts. Proper design and installation of the system is however required by planner or architect and installer. Afterwards, the system is maintenance free and can be treated as any other insulating glazing unit.

Figure 55. Close-up view of the daylighting system OKASOLAR 3D on the left and appearance as seen from inside on the right.

SWOT Analysis

Strengths

The system provides a high-performance sun protection and an effective solar control: it blocks direct solar radiation reducing glare issues and heat gains, but high light transmission is possible for diffuse daylight
The brightness in the indoor space does not significantly vary comparing clear sunny sky or cloudy sky without sun
The daylighting is typically sufficient, and the use of artificial lighting can be reduced
Visual contact with the exterior is maintained thanks to a partial view through the area of transmission and the sun reflections
The appearance of the grid is homogenous when integrated in insulating glazing units
The system works without moveable parts and is maintenance free
The system does not need control and thus user operating errors are prevented
The materials can be easily recycled
The visibility for birds is enhanced

Weaknesses

Daylighting is reduced also when there is no sun
Direct sun beams cause high brightness patterns through reflection on the outer glass pane and slightly frosted glass is needed to avoid these sun reflections
The light transmitted to the inside is asymmetric: most light is pointed slightly to South
Proper design and installation are needed for a correct implementation, as a wrong orientation of the grid decreases or cancels the sun protection properties

Opportunity

Daylighting is reduced also when there is no sun
Direct sun beams cause high brightness patterns through reflection on the outer glass pane and slightly frosted glass is needed to avoid these sun reflections
The light transmitted to the inside is asymmetric: most light is pointed slightly to South
Proper design and installation are needed for a correct implementation, as a wrong orientation of the grid decreases or cancels the sun protection properties

Threats

Architects might not accept the appearance
Competitors provide solutions (e.g. screens) that cannot provide simultaneous sun protection and daylight provision but are cheaper in purchase
Standard key indicators (transmission and SHGC at normal incidence) do not describe the product well, thus it is not easy to understand and use for designers

Lessons Learned

OKALUX OKASOLAR 3D is an innovative daylighting system that allows simultaneous sun protection and optimal utilization of daylight.
As a static system integrated in the insulating glazing unit it does not require maintenance or controls and prevents erroneous user behaviour.
Proper design and installation of the system is required to allow optimal functionality of the system.

Product