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GB/T 31389-2015 English PDF (GBT31389-2015)

GB/T 31389-2015 English PDF (GBT31389-2015)

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GB/T 31389-2015: Technical requirements and evaluation methods of solar reflective materials for exterior walls and roofs

This Standard specifies the terms and definitions, classification, requirements, tests, and evaluation methods of comprehensive solar reflective performance of solar reflective materials for exterior walls and roofs. This Standard is applicable to the evaluation of the solar reflective performance of solar reflective materials for exterior walls and roofs.
GB/T 31389-2015
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 91.100.01
Q 10
Technical Requirements and Evaluation Methods of
Solar Reflective Materials for Exterior Walls and Roofs
ISSUED ON: FEBRUARY 04, 2015
IMPLEMENTED ON: NOVEMBER 01, 2015
Issued by: General Administration of Quality Supervision, Inspection
and Quarantine;
Standardization Administration of PRC.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 5
4 Classification ... 6
5 Requirements ... 6
6 Test and Comprehensive Reflective Performance Rating Methods ... 7
Appendix A (Normative) Determination of Total Solar Reflectance and Near Infrared Reflectance ?€? Relative Spectrometry ... 12
Appendix B (Normative) Determination of Total Solar Reflectance and Near Infrared Reflectance ?€? Radiation Integration Method ... 16
Appendix C (Normative) Determination of Hemispherical Emittance ?€?
Radiometer Method ... 18
Appendix D (Normative) Instructions of Weight Coefficient of Solar Reflective Performance Index ... 20
Technical Requirements and Evaluation Methods of
Solar Reflective Materials for Exterior Walls and Roofs
1 Scope
This Standard specifies the terms and definitions, classification, requirements, tests, and evaluation methods of comprehensive solar reflective performance of solar reflective materials for exterior walls and roofs.
This Standard is applicable to the evaluation of the solar reflective performance of solar reflective materials for exterior walls and roofs.
2 Normative References
The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) are applicable to this document.
GB/T 1865 Paints and Varnishes - Artificial Weathering and Exposure to Artificial Radiation - Exposure to Filtered Xenon-Arc Radiation
GB/T 3181-2008 Color Standard for Paint Film
GB/T 9780-2013 Test Method for Dirt Pickup Resistance and Stain Removal of Film of Architectural Coatings and Paint
GB/T 11186.2 Method for Measuring the Color of Paint Films - Part 2: Color Measurement
GB/T 11186.3 Method for Measuring the Color of Paint Films ?€? Part 3: Calculation of Color Differences
GB/T 16422.3-2014 Plastics - Methods of Exposure to Laboratory Light Sources - Part 3: Fluorescent UV Lamps
JG/T 235 Architectural Reflective Thermal Insulation Coatings
JG/T 402-2013 Roofing Products from Metal Sheet with Reflect Thermal Coating 3 Terms and Definitions
For the purpose of this document, the following terms and definitions apply. 3.1 Solar reflective materials for exterior walls and roofs
Materials that are applied to the exterior wall and roof, and have a high total solar reflectance, near infrared reflectance and hemispheric emittance.
3.2 Solar reflective coating for buildings
Paint that is applied to the surface of building with higher total solar reflectance, near infrared reflectance and hemispherical emittance.
3.3 Solar reflective metal sheet for roofs
The metal sheets with surface coated with a solar-reflective coating for building roofs. 3.4 Lightness
The visual perception characteristic value that indicates the brightness of the surface color of the object; gives division on the basis of absolute white and absolute black; and is expressed by L*. (one of the three attributes of color).
[GB/T 3181-2008, definition 3.14]
3.5 Total solar reflectance
The ratio of solar radiation flux BEWTEEN the visible light and near-infrared band reflection in 300nm ~ 2500nm AND the incident in the same band.
3.6 Near infrared reflectance
The ratio of solar radiation flux BEWTEEN near-infrared band reflection in 780nm~2500nm AND the incident in the same band.
3.7 Hemispherical emittance
The ratio of the radiant exitance BETWEEN the thermal radiator in the direction of the hemisphere AND the full radiator (black body) at the same temperature.
3.8 Thermal insulation temperature difference
Under the specified test conditions, the difference of the surface temperature facing away from the heat source between the heat insulation test plate and the standard blackboard.
3.9 Comprehensive reflective performance rating
The L* value is measured according to the provisions of GB/T 11186.2; the total solar reflectance and near infrared reflectance are measured according to the provisions of Appendix A or Appendix B. Refer to Appendix A for arbitration inspection. 6.1.2.3 Hemispherical emittance
It shall be carried out according to the provisions of Appendix C.
6.1.2.4 Change rate of total solar reflectance after contamination
Test the initial solar reflectance according to the provisions of 6.1.2.2; then carry out the contamination treatment according to the method A specified in GB/T 9780-2013; and then test the total solar reflectance after contamination according to the provisions of 6.1.2.2. For coatings that require ultraviolet light irradiation, the test panels that have expired shall be irradiated for 4h by ultraviolet light before contamination treatment (UV light irradiation is carried out according to the provisions of the GB/T 16422.3-2014 standard, exposure method A, cycle number 1, The light source adopts UV-A340 lamp). The result is calculated according to Formula (1):
Where:
c1 ?€? change rate of total solar reflectance after contamination, in %;
??0 ?€? initial solar reflectance;
??1 ?€? total solar reflectance after contamination.
6.1.2.5 Artificial weathering aging
Test the initial solar reflectance according to the provisions of 6.1.2.2; and then conduct the artificial weathering aging test according to the provisions of GB/T1865. According to the type of coating and the corresponding product standards, the artificial weathering aging time shall meet the requirements of Table 4.
Appendix A
(Normative)
Determination of Total Solar Reflectance and Near Infrared
Reflectance ?€? Relative Spectrometry
A.1 Principle
Use an ultraviolet spectrophotometer with an integrating sphere, a visible light spectrophotometer, a near-infrared spectrophotometer, or a spectrometer to accurately measure the reflectance of materials at different wavelengths. According to the relative energy distribution of sunlight in the wavelength range of heat rays, calculate the total solar reflectance and near infrared reflectance of materials within a certain wavelength range through the weighted average method.
A.2 Testing device
A.2.1 Spectrophotometer or spectrometer
The wavelength range is 300nm~2500nm or above; the minimum wavelength interval is 5nm; the wavelength accuracy is no less than 1.6nm; and the photometric measurement accuracy is ??1%.
A.2.2 Integrating sphere
The inner diameter is no less than 60mm, and the inner wall shall be highly-reflective material.
A.2.3 Standard whiteboard
Pressed barium sulfate or Teflon plate is used for baseline calibration. A.3 Preparation of test plate
Solar reflective coating for buildings shall be conducted in accordance with the provisions of 6.1.2.1; and solar reflective metal sheet for roofs shall be conducted in accordance with the provisions of 6.1.3.1.
A.4 Test process
A.4.1 Preheat to a stable state after booting.
A.4.2 Set the instrument parameters and use the instrument configured standard whiteboard for baseline calibration.
Appendix B
(Normative)
Determination of Total Solar Reflectance and Near Infrared
Reflectance ?€? Radiation Integration Method
B.1 Principle
Use a number of detectors with different wavebands to measure the radiation reflection with an incident angle of 20??. Through the detector-configured filter device, obtain the electronic induction consistent with the specific wavelength band of the sunlight spectrum; and get the total solar reflectance and the near infrared reflectance after being processed by the reading module.
B.2 Testing device
B.2.1 Portable reflectance tester
B.2.1.1 Measuring head
It is composed of tungsten halogen lamp, filter and detector with multiple different wave bands. The tungsten halogen lamp is used as a radiation source for irradiation. The filter is used to adjust the radiation reflection to adapt to a specific wave band. And the detector is used to sense the radiation reflection of different wave bands. B.2.1.2 Reading module
The reading module is connected to the measuring head and is used to process the signal of the measuring head, the digital output signal of the reflectance, and display the input parameters or calibration information. The digital display resolution of the reading module is 0.001.
B.2.2 Calibration device
It contains black cavity and standard plate; black cavity is used for zero adjustment of the instrument; and standard plate is used for instrument calibration.
B.3 Preparation of test plate
Solar reflective coating for buildings shall be conducted in accordance with the provisions of 6.1.2.1; and solar reflective metal sheet for roofs shall be conducted in accordance with the provisions of 6.1.3.1.
B.4 Test process
Appendix C
(Normative)
Determination of Hemispherical Emittance ?€? Radiometer Method
C.1 Principle
Heat the thermopile in the detector to cause a temperature difference between the detector and the test plate. The temperature difference has a linear relationship with the emittance of the test plate. By comparing the temperature difference between the high-emittance standard plate, the low-emittance standard plate and the test plate surface, obtain the emittance of the test plate.
C.2 Testing device
C.2.1 Portable radiometer
C.2.1.1 Differential thermopile radiant energy detector
It consists of a controllable heater, a high-emittance probe element and a low- emittance probe element. The controllable heater ensures that the detector temperature is higher than the test plate temperature or the standard plate temperature. The emittance probe element can produce an output voltage proportional to the temperature difference. Detector repeatability is ??0.01.
C.2.1.2 Reading module
The reading module is connected to a differential thermopile radiant energy detector and is used to process the output signal of the thermopile. The digital display resolution of the reading module is 0.01.
C.2.2 Heat sink
The heat sink platform is used to place the test plate and the standard plate. The heat sink shall have good thermal conductivity to ensure that the temperature of the test plate and the standard plate is stable and consistent.
C.2.3 Standard plate
It is composed of low-emittance polished stainless-steel standard plate and high- emittance black standard plate.
C.3 Preparation of test plate
Solar reflective coating for buildings shall be conducted in accordance with the provisions of 6.1.2.1; and solar reflective metal sheet for roofs shall be conducted in Appendix D
(Normative)
Instructions of Weight Coefficient of Solar Reflective Performance
Index
D.1 Overview
This appendix gives instructions of the process of determining the weight coefficient of the solar reflective performance index by the Analytic Hierarchy Process (AHP). D.2 Principle
The overall evaluation objective of comprehensive solar reflective performance is decomposed into different component factors; and is divided into a criterion layer and an index layer according to the interrelationship and subordination of each factor; and form a three-level analysis structure model. Give judgment to the relative importance of the factors in the criterion layer and indicator layer; write the judgment matrix by the 1~9 scale method. Through calculating the maximum feature root of the judgment matrix and its corresponding feature vector to calculate the relative importance weights of factors in criterion layer against the target layer, as well as index layer against the criterion layer. Weighting and synthesizing by the weights of the factors in the criterion layer and the index layer to obtain the relative importance weights of the index layer factors against the comprehensive solar reflective performance, that is, the weight coefficient.
D.3 Determination process of weight coefficient
D.3.1 Solar reflective coating for buildings
D.3.1.1 Establish analysis structural model
The analysis structural model of comprehensive solar reflective performance rating is shown in Figure D.1.

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