Our instrument: UV/VIS/NIR spectrophotometer

We are a Singapore-based third-party test laboratory, providing lab test services of material optical & thermal properties. We use PerkinElmer Lambda 950 UV/VIS/NIR spectrophotometer, with the following key information.

PerkinElmer Lambda 950 UV/VIS/NIR spectrophotometer
PerkinElmer Lambda 950 UV/VIS/NIR spectrophotometer

Specifications

  • With 150 mm integrating sphere
  • Wavelength range: 250 nm – 2500 nm
  • For both transmittance & reflectance measurement
  • With option to exclude the specular component
    • Total, diffuse & specular transmittance/reflectance
Interior of the 150 mm integrating sphere

Related lab services

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Work with the expert in Optical & Thermal Measurement solutions.

OTM Insights Newsletter: Issue 4

Our newsletter OTM Insights Issue 4 was sent to our customer on 27 Apr 2020. We are sharing some technical insights of optical & thermal property test of glasses from existing buildings in the newsletter. Click the image to read the full newsletter.

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OTM Insights Newsletter: Issue 3

OTM Insights Issue 3

Our newsletter OTM Insights Issue 3 was sent to our customer on 03 Feb 2020. We are sharing some technical insights of partially fritted glazing optical & thermal property testing procedures in the newsletter. Click the image below to read the full newsletter.

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New release of lab profile 2020 edition

We are pleased to release our 2020 edition of laboratory profile, which is a 56-page comprehensive document, with rich information on our capabilities and many technical insights.

What are in the laboratory profile?

  • A comprehensive overview of the laboratory
  • Detailed introduction of 10 popular tests
  • 14 informative technical insights articles

You may download a soft copy of our lab profile.

Free gift: OTM Inflatable Travel Pillow

OTM Inflatable Travel Pillow

All local customers will receive a travel pillow as free gift delivered together with the test report.

How to use the inflatable travel pillow

To inflate:

  • Step 1: Open the anti leak valve of the air pump
  • Step 2: Cover the rear air valve
  • Step 3: Press the air pump repeatedly until the pillow is fully inflate
  • Step 4: Cover the anti leak valve of the air pump

To deflate:

  • Step 1: Open the rear air valve
  • Step 2: Press the pillow to deflate

Daylight reflectance, color and gloss

Color and gloss are commonly used quality check quantities by material suppliers and construction companies, whereas daylight reflectance are relatively new to the industry. This article aims to explain the relationship between the three quantities.

Daylight reflectance and color

The total and diffuse daylight reflectance is directly related to color. Materials with light color are with high total or diffuse daylight reflectance; materials with dark color are with low total or diffuse daylight reflectance. Our eyes cannot quantify daylight reflectance, but they can assess daylight reflectance qualitatively.

Most color instruments with integrating sphere geometry can measure color in the SCI (specular component included) mode or the SCE (specular component excluded) mode. Color measured in the SCI mode is equivalent to the total daylight reflectance; color measured in the SCE mode is equivalent to the diffuse daylight reflectance.

The closest color scale is Yxy scale. Of course, due to various technical constraints, color measurement instruments cannot accurately determine daylight reflectance, but the results are sufficient for internal use.

Daylight reflectance and gloss

The specular daylight reflectance is directly related to gloss. Materials with high gloss are with high specular daylight reflectance; materials with low gloss are with low specular daylight reflectance. Our eye can qualitatively assess if a surface is with high gloss or with low gloss.

Gloss meters can measure material gloss level. However, the relationship between gloss meter readings and specular daylight reflectance is qualitative. It is not possible to quantitatively coorelate them.

Notes to applications

For projects where low specular daylight reflectance is required, materials with low gloss level are preferred.

For projects where low total daylight reflectance is required, materials with dark color are preferred.

The differences between EN, ISO and NFRC glazing system test methods

Some example calculations were conducted to illustrate the possible differences between EN, ISO and NFRC glazing system test methods. The three standards are widely used, but specific national standards may exist for respective countries (e.g. JIS R3106:1998 and JIS R3107:1998 for Japan).

Sample glazing systems

Two sample glazing systems were selected:

  • Double glazing unit with high spectral selectivity: AGC Stopray Clearvision 60T
    • 6 mm Stopray Clearvision 60T with coating on #2 (IGDB #4383) + 12 mm air space + 6 mm generic clear glass (IGDB #103)
  • Single glazing with hard low-e coating: AGC Sunergy Clear
    • 6 mm Sunergy Clear with coating on #2 (IGDB #4210)

The two representative examples were selected because relatively large discrepancies can be expected based on our experiences.

Calculation methods

Glass material optical data available in IGDB were used in the calculations (accessed through Optics).

WINDOW was used for NFRC calculations.

Proprietary calculation tools developed by OTM was used for EN and ISO calculations.

Results

The tables below list calculation results obtained according to the three methods:

  • For the double glazing unit
MehodENISONFRC
Visible light transmittance (VLT)  0.605 0.605 0.605
Visible light reflectance, front (VLRf) 0.151 0.151 0.151
 Visible light reflectance, back (VLRb) 0.198 0.1980.198
Solar transmittance (ST) 0.349 0.344 0.317
 Solar reflectance, front (SRf) 0.374 0.384 0.424
 Solar reflectance, back (SRb)  0.2900.296 0.323
Solar heat gain coefficient (G)  0.393 0.390 0.365
Shading coefficient (SC) 0.452 0.448 0.419
 Thermal transmittance, winter (Uw) 1.57 1.57 1.63
 Thermal transmittance, summer (Us) N/A N/A  1.57
  • For the single glazing system
MethodENISONFRC
Visible light transmittance (VLT)   0.677 0.6770.677
Visible light reflectance, front (VLRf) 0.086 0.086 0.086
Visible light reflectance, back (VLRb) 0.102 0.1020.102 
Solar transmittance (ST)  0.538 0.5350.517
Solar reflectance, front (SRf) 0.0920.0920.094
Solar reflectance, back (SRb)  0.103 0.1030.105 
Solar heat gain coefficient (G)  0.600 0.6030.599 
Shading coefficient (SC)  0.690 0.694 0.688
Thermal transmittance, winter (Uw) 4.104.114.12 
Thermal transmittance, summer (Us) N/A N/A 3.36

All quantities are unit-less, except the thermal transmittance (U), with the SI unit of W/(m2K).

Observations and interpretations

  • The visible light quantities (VLT and VLR) calculated by the three methods are the same
  • There are relatively large discrepancies among the solar related quantities (ST, SR, G and SC) calculated by the three methods, particularly for the double glazing unit with high spectral selectivity
    • The reference solar spectrum in EN 410 is based on the AM1 global spectrum (direct + diffuse) defined in CIE 085:1989
    • ISO 9050 uses AM1.5 global spectrum (direct + diffuse) defined in ISO 9845-1:1992
    • NFRC 300 uses AM1.5 direct normal spectrum defined in ISO 9845-1:1992
  • There are some discrepancies among the thermal transmittance quantities (U) calculated by the three methods, particularly for the single glazing system with hard low-e coating on surface #2 (summer condition U-value is significantly lower)
    • The internal and external surface heat transfer coefficients defined in the three methods are different
    • There is no separate summer condition thermal transmittance in the EN and ISO methods

Which test method shall I use?

  • All methods are widely accepted and fair comparison can be made only if the results are from the same method
  • It is not appropriate to compare results obtained with different methods
  • It is at the end user’s discretion on method selection. Your end user could be internal staffs, project owners, certification bodies or government agencies.
  • If the end user has no preference, NFRC method is recommended due to the availability of a suite of software tools. The summer condition thermal transmittance is also more relevant for summer condition applications

Please feel free to contact us for any enquiries.