TestLab Solar Façades

Testing, development and evaluation of façades

The services of TestLab Solar Façades at a glance:

 

Accredited Optical and Thermal Characterization of Façade Components

 

Notified Testing for Energy Conservation and Noise Reduction in Construction Products

 

Daylighting and Glare Studies

 

Development and Optimization of Facade Components

 

Testing of Building Products for the North American Market

 

Comprehensive Energy Assessmentb of Passive and Active Building Envelopes

In TestLab Solar Façades, we characterize transparent, translucent and opaque materials, test façade components and evaluate the energy, thermal and optical properties of complete façades. We assist manufacturing companies, building planners, architects and construction managers in optimizing building envelopes and developing new façade components.

We have extensive experience for the following applications:

  • Architectural glazing
  • Solar-shading systems
  • Building-integrated photovoltaics (BIPV)
  • Building-integrated solar thermal (BIST)

Our TestLab Solar Façades is accredited and notified:

  • Our measurements and calculations of transmittance, reflectance, g value and U value are accredited according to DIN EN ISO/IEC 17025:2018
  • We are a notified testing laboratory for the German Institute for Building Technology (DIBt), in the field of energy conservation and noise reduction. We have specialized in architectural glazing
  • We support German and European manufacturers who wish to address their products to the North American market in the testing of building products. Fraunhofer ISE is the European Regional Data Aggregator (RDA) for the US National Fenestration Rating Council NFRC.

Our tests are also used in areas that are not related to façades.

 

Spectrophotometer and Integrating Spheres

Vertical cross-section through the TAUWIN integrating sphere
© Fraunhofer ISE
Vertical cross-section through the TAUWIN integrating sphere for angle-dependent transmittance measurements.

We use spectrophotometers of different types to determine the transmittance and reflectance of glazing, solar-shading products and other materials. For many years, we have focused on measuring light-scattering and light-deflecting materials such as screen-printed or etched glass, solar-shading textiles and slats for blinds.

Our laboratory is equipped with large integrating spheres with large sample apertures, TAUWIN and RHOWIN, with which spectra can also be measured for obliquely incident radiation. For non-scattering samples, a high-end laboratory benchtop spectrophotometer with a customized integrating sphere completes the suite of spectrometric equipment.

From the measured spectra of the single components, we calculate many other parameters such as the light and solar transmittance and reflectance, the g-value (or SHGC: solar heat gain coefficient) and the color rendering index CRI of multi-pane glazing units according to EN 410 and ISO 9050, parameters for combinations of solar-shading elements and glazing according to EN 14500 and ISO 15099, color coordinates according to CIE 15 and the Solar Reflectance Index (SRI) according to ASTM E1980-2011.

3D Scanning Photogoniometer

3D scanning photogoniometer
© Peter Apian-Bennewitz, pab advanced technologies Ltd.
The 3D scanning photogoniometer measures the light transmitted or reflected by a sample, using a detector which moves mechanically at a constant radius around the illuminated spot of the sample. Radiation transmitted or reflected by the sample can be measured at almost all emergent angles.

Information on the spatial distribution of transmitted or reflected light is required to evaluate the daylighting and glare control performance of solar-shading systems and other building envelope technology.

Light scattering is characterized by measurements of the bidirectional scattering distribution function (BSDF). For these measurements, we use a 3D scanning photogoniometer (pab-pgII, pab advanced technologies Ltd.), which offers several combinations of detectors, light sources and sample holders for different purposes.

Spectral or polarization-dependent BSDF measurements are available on request.

Calorimetric Facility With a Solar Simulator

Teststand zur kalorimetrischen g-Wert-Bestimmung
© Fraunhofer ISE
The test stand for calorimetric g-value determination essentially consists of a water-cooled absorber inside an air-conditioned measuring cabin and a solar simulator. The measurement sample is mounted in front of the absorber.

We use a calorimeter facility with a solar simulator to determine the g value (or total solar energy transmittance TSET or Solar Heat Gain Coefficient SHGC). This test facility is suitable for measuring individual components, such as glazing units, as well as for fenestration systems combining a glazing unit and a shading device (external or internal) and for entire façade elements such as double façades and closed-cavity façades. This test facility is also used to characterize façade-integrated PV or solar thermal technology.

Our calorimeter also enables angle-dependent g-value measurements, as the angle of incidence of the irradiation can be varied both by adjusting the height of the solar simulator and by rotating the measurement setup and absorber around a vertical axis. The spectrum of our solar simulator generated with the help of metal halogen lamps is almost identical to the standard solar spectrum according to EN 410.

U Value Test Stand

Guarded hot-plate apparatus, type TLP 800 S
© Fraunhofer ISE
Guarded hot-plate apparatus, type TLP 800 S, Netzsch Taurus Instruments GmbH.

For the metrological determination of the heat transfer coefficient or U-value, a guarded hot-plate apparatus is used to determine the thermal conductivity of the component under test.

The guarded hot-plate apparatus, of the type TLP 800 S from the manufacturer Netzsch Taurus Instruments GmbH, measures according to the two-plate method specified in the ISO 8302. The test specimens are placed in the system between an electrically heated plate with a surrounding protective heating ring and two external cooling plates. The measurement stack is integrated into an insulated measurement chamber. The measurement chamber with the samples can be tilted for testing in both horizontal and vertical orientations.

The U-value of glazing units is determined with the guarded hot-plate apparatus in accordance with EN 674. In this case, the dimensions of the glazing samples are larger than those of the heating plate and protective heating ring. Hence, the results obtained with this method apply to the central area of ​​the glazing without edge effects, the so-called COG value (center of glazing).

Scientific-Grade Luminance Camera

The evaluation of luminance and color under real operating conditions is used for daylighting, glare protection and material characterization.

We use a scientific-grade luminance camera to generate luminance images and determine color coordinates (TechnoTeam LMK 98-4 color). Our luminance camera is equipped with a filter wheel for color measurement, which is adapted to the CIE color sensitivity functions of the 2° standard observer (CIE 1931).

The filter wheel allows the installation of a total of 6 filters, whereby 4 filters are required for color measurement. In addition, the measuring system can also be equipped with filters for scotopic luminance V' (λ), the circadian effect function C (λ), part of the NIR spectral range (only 780 nm - 1000 nm), BLH (blue light hazard) or with a clear glass filter.

High resolution and the evaluation of luminance and color images are available in combination with the LMK LabSoft software package. 

Rotatable Two-Room Test Facility

Tageslichtlabor auf dem Dach des Fraunhofer ISE
© Fraunhofer ISE
Daylighting laboratory on the roof of Fraunhofer ISE.

The effects of façade technologies and their control strategies on thermal and visual comfort must be evaluated in laboratories with typical room dimensions.

For thermal and visual comfort investigations, we use an office-like facility consisting of two identical rooms. This test facility is mounted on a rotatable platform that allows different orientations to be analyzed. The room dimensions are 3.65 m x 4.60 m x 3 m. Each room has a glazed façade (3.65 m x 3.00 m), which can be removed and replaced entirely.

Our rotatable two-room test facility is equipped with sensors to quantify the thermal and lighting conditions in the rooms. In addition, comfort conditions can be evaluated subjectively on the basis of user surveys. The Daylight Glare Probability metric, which is used for glare evaluation according to EN 17037, was developed using this facility.

 

Spectral Reflectance and Transmittance

EN 14500 defines the direct-direct, direct-diffuse and direct-hemispherical reflectance as the ratio of the directly or specularly, diffusely and hemispherically reflected radiant flux to the directly incident radiant flux. Likewise, the standard defines the direct-direct, direct-diffuse and direct-hemispherical transmittance as the ratio of the directly, diffusely and hemispherically transmitted radiant flux to the directly incident radiant flux. For energy and daylighting applications, the spectrally resolved reflectance and transmittance of fenestration and façade materials are aggregated into broadband optical characteristics, representing properties for the solar spectral range (wavelengths from 300 nm to 2500 nm according to EN 410) and the visible spectral range (wavelengths from 380 nm to 780 nm).

Bi-directional Scattering Distribution Functions

BSDFs describe the spatial distribution of light scattered by a sample in reflection and/or transmission. A BSDF value (BSDF_j) at a certain position with respect to a sample is given by the sample radiance as seen by a sensor located at that position and directed towards the center point of the sample (L_j), divided by the incident irradiance on the sample (E) for a uniformly illuminated and uniform sample:

BSDF_j = (L_j / E) [sr-1]

Solar Reflectance Index (SRI)

The Solar Reflectance Index (SRI) is the relative temperature of a surface with respect to standard white (SRI = 100) and standard black (SRI = 0) surfaces under standard solar and ambient conditions [ASTM E1980-11(2019)].  It is determined from an energy balance between the surface and its surroundings under steady-state conditions, taking the radiative and convective heat exchange into account.

To determine it, initially the spectral reflectance of material samples in the solar and IR spectral ranges is measured in the laboratory.  Then, the solar reflectance, the solar absorptance, the thermal emissivity and finally the Solar Reflectance Index (SRI) are determined according to the method specified in ASTM E1980-11(2019).

U Value

In the building sector, the U value (or thermal transmittance) describes the heat transfer across a component (e.g. through a wall or glazing) due to a temperature difference between the adjacent air layers. As a result, the thermal transmittance not only takes the heat conduction within the solid body into account, but also includes the heat transfer at the interfaces between the body and the adjacent gases. It thus represents a measure of the insulating effect of the component (SI unit is W / (m² · K)). The larger the U-value, the worse the insulating effect. Conversely, a small U value indicates that the component is a good thermal insulator. 

G Value

The g value or total solar energy transmittance (TSET) or Solar Heat Gain Coefficient (SHGC) is a measure of the proportion of the solar energy incident on a building envelope that is transferred into the interior of the building. The g value is a ratio with a value between 0 and 1. A g value of 0.3 means, for example, that 30% of the incident solar energy enters the interior of the building, either as short-wavelength radiation or as heat. The total solar energy transmittance thus provides the basis for calculating solar heat gains in buildings, especially in the case of transparent façades and building envelopes. These solar gains contribute to the heating of the building, which leads to a reduction in the heating energy required, especially in winter, but often also to unwanted overheating in summer.

For simple cases, there are calculation methods for determining the g value, for example according to DIN EN 410, but these can be used only for optically simple systems such as clear glazing. For more complex geometries, such as venetian blinds or light redirecting systems, experimental determination is required.

Delivery Address

Fraunhofer ISE - Central Goods Entrance
TestLab Solar Façades 
Berliner Allee 30
79110 Freiburg (Germany)

Delivery / collection times

Monday to Friday from 7.30 a.m. to 12.30 p.m. and from 1 p.m to 2.30 p.m.

Postal Address

Fraunhofer Institute for Solar Energy Systems ISE
TestLab Solar Façades 
Heidenhofstraße 2
79110 Freiburg
Germany    

Kontakt

Bruno Bueno

Contact Press / Media

Dr. Bruno Bueno

Head of TestLab Solar Façades

Fraunhofer ISE
Heidenhofstr. 2
79110 Freiburg

Phone +49 761 4588-5377

Ulrich Amann

Contact Press / Media

Ulrich Amann

G Value Testing, U Value Testing

Fraunhofer ISE
Heidenhofstr. 2
79110 Freiburg

Phone +49 761 4588-5142

Helen Rose Wilson

Contact Press / Media

Dr. Helen Rose Wilson

Spectrometry, Goniometry, SRI and Color Measurement

Fraunhofer ISE
Heidenhofstr. 2
79110 Freiburg

Phone +49 761 4588-5149

Accredited Optical and Thermal Characterization of Façade Components

Illuminated sample at an aperture of the integrating sphere for spectral transmittance and reflectance measurements
© Fraunhofer ISE / Photo: Dirk Mahler
Illuminated sample at an aperture of the integrating sphere for spectral transmittance and reflectance measurements at normal incidence.
We make optical and thermal measurements of transparent, translucent and opaque materials as well as façade components for manufacturing companies, building planners, architects and construction managers. Special emphasis is placed on testing objects that can often be only insufficiently characterized with conventional measurement methods (e.g. due to angle-dependent behavior, light-scattering and light-redirecting materials, thick elements). Accompanying simulations with realistic consideration of the users offer maximum reliability for façade planning.

Our tests are also used in areas that are not related to façades.


Accredited Tests

TestLab Solar Façades is accredited for measurements and calculations of transmittance, reflectance, g-value and U-value according to DIN EN ISO/IEC 17025:2018.

  • Transmittance and Reflectance
    Spectral measurements as well as light and solar characteristics, also angle-dependent and to characterize scattering and light deflection behavior (bidirectional)
  •  g Value
    Calorimetric determination of the g value (or total solar energy transmittance or solar heat gain coefficient), also angle-dependent; realistic testing also with solar-shading systems as well as with rear ventilation
  • U Value
    Testing of glazing, thermal conductivity measurement of insulation materials or panels


Standards and Specifications

  • Accreditation according to DIN EN ISO/IEC 17025:2018
  • Transmittance, reflectance and g value according to DIN EN 410, ISO 9050, DIN EN ISO 52022, DIN EN 14500, DIN EN 14501
  • Thermal conductivity and U value according to ISO 8302, DIN EN 673, DIN EN 674
  • Solar Reflectance Index (SRI) according to ASTM E1980

TestLab Solar Façades has been awarded "flexible accreditation" as the highest accreditation level. This entitles us to develop and apply new test methods as well as modify existing ones.

 

Notified Testing for Energy Conservation and Noise Reduction in Construction Products

g-value test facility
© Fraunhofer ISE / Photo: Dirk Mahler
g-value test facility with absorber plate inside a climatic chamber (left) and solar simulator (right). A scanning device is being set up to measure the irradiance distribution over the test area.

TestLab Solar Façades is approved by the Deutsches Institut für Bautechnik (DIBt) as a Testing Laboratory (AVCP System 3) according to Annex V No. 2.(3) Regulation (EU) No. 305/2011 for the construction products listed in the Annex, i.e. glass in building, in the field of energy conservation and noise reduction.

Standards and specifications

  • Notification for the following harmonized product standards: EN 1096-4:2018, EN 12150:2004, EN 1279-5:2018, EN 14179:2005, EN 14449:2005, EN 1863:2004, EN 572-9:2004

Notification notice [PDF]

Daylighting and Glare Studies

Tageslichtlabor auf dem Dach des Fraunhofer ISE
© Fraunhofer ISE
Daylighting laboratory on the roof of Fraunhofer ISE.

To support product development and building planning, we simulate and investigate daylighting and glare, e.g. for offices with complex window and solar-shading systems. Detailed angle-resolved transmission and reflection measurements of complex materials are often required for this purpose, for which a photogoniometer is available at Fraunhofer ISE. The instrument can be used to determine BSDF (Bi-Directional Scattering Distribution Function) data sets as a basis for simulation programs. In addition, Fraunhofer ISE has a rotatable daylighting test facility. With this, we can conduct studies on usage preferences and visual comfort.

Development and Optimization of Façade Components

Mounting of a glass sample at a photogoniometer
© Fraunhofer ISE / Photo: Dirk Mahler
Mounting of a glass sample at a photogoniometer for angle-dependent optical measurements.

With our expertise, we support building planners, architects, construction managers and manufacturing companies in the optimization of building envelopes and in the development of new façade components. Based on differentiated models, simulation and measurements, we support the development of elements of the building envelope holistically from energy-relevant and visual perspectives.

Research Topic »Building Envelopes«

 

Testing of Building Products for the North American Market

Large integrating sphere
© Fraunhofer ISE / Photo: Dirk Mahler
Large integrating sphere for spectral, angle-dependent transmittance of e.g. light-scattering samples.

Fraunhofer ISE is the European Regional Data Aggregator (RDA) for the National Fenestration Rating Council NFRC. European glazing manufacturers who wish to address the North American market with their products must have their spectral data sets reviewed by the European RDA and entered into a database in collaboration with the Lawrence Berkeley National Laboratory LBNL, Berkley, USA. Fraunhofer ISE advises and supports the European manufacturers in this process and accepts the documents to be submitted. This applies not only to transparent glass panes but also to light-scattering glazing.

Comprehensive Energy Assessment of Passive and Active Building Envelopes

Seminar room with building-integrated photovoltaics (BIPV)
© Fraunhofer ISE / Photo: Guido Kirsch
New laboratory building at Fraunhofer ISE: Seminar room with building-integrated photovoltaics (BIPV), partly transparent PV module with angularly selective transmission (PV-Shade®).
Manufacturing companies must prove the advantages of their innovations in the multifunctional building envelope sector to building managers and architects and make the interaction between the building envelope and the building interior plannable. Fraunhofer ISE offers support here based on its extensive research experience in the areas of:

We specialize in mathematical and physical modeling of optical, thermal, and PV-electrical processes in solar irradiated façades, as well as analysis of their effects on the energy-relevant properties of the building.

 

The TestLab Solar Facades is accredited according to DIN EN ISO / IEC 17025: 2018.

The TestLab Solar Facades was awarded »flexible accreditation« as the highest level of accreditation. It is thus authorized to develop and use new test methods and to modify existing ones.

The TestLab Solar Facades is approved by the German Institute for Building Technology (DIBt) as a test laboratory (AVCP system 3) in accordance with Annex V No. 2. (3) Regulation (EU) No. 305/2011 for the construction products listed in the annex.

 

The TestLab Solar Façades is Regional Data Aggregator (RDA) for IGDB data sets from European glazing manufacturers on behalf of the National Fenestration Rating Council (NFRC) .