Thermal conductivity of thin materials (paint, coating, metal sheet)

We are sometimes requested to test the thermal conductivity of thin materials, such as paint, coating and metal sheet.

Negligible thermal resistance of thin materials

For a wall (or a roof) system, the influence of such thin materials to the overall wall system U-value is negligible.

Shown below is an example calculated with our online ETTV U-value calculator. it is obvious that the thermal resistance of a 0.2 mm thick paint layer with 0.2 W/(m⋅K) thermal conductivity is only 0.001 (m2K)/W, which is negligible comparing to the thermal resistances of other layers (e.g. concrete, plaster, or insulation wool).

For thin metal sheets, e.g. 0.7 mm thick aluminium plates, the thermal resistance is further smaller, as the thermal conductivity of metal is much larger.

Thermal resistance of thin material

The reason is that thermal resistance is dependent on both thermal conductivity and thickness, with the following relationship:

Thermal resistance = Thickness / Thermal conductivity

In practice, due to the small thickness of thin materials (typically less than 1 mm), it is not practical to reduce the thermal conductivity of thin materials to achieve better insulation.

In wall/roof U-value calculations, the thin materials can be simply ignored. It is not meaningful to get the thermal conductivity of thin materials.

Thin material thermal conductivity testing

It may be still necessary to determine the thermal conductivity of thin materials. For example, the thin material is not used in a wall/roof system, but in a system with low thermal resistance.

For such scenarios, we can test the thermal conductivity of thin materials according to ASTM D5930, with the following practices:

  • For low thermal conductivity paint and coating, the paint/coating can be applied onto flat substrates for testing.
    • There is no specific requirement on the substrate type, as long as the substrate surface is flat. We recommend flat metal plates or glass plates.
    • The preferred substrate size is 50 mm x 50 mm (minimum size: 30 mm x 30 mm; maximum size: 100 mm x 100 mm). There is no requirement on the substrate thickness, as long as it is strong enough.
    • The thickness of paint or coating should be thick enough (3 mm or thicker preferred, 1 mm minimum)
    • 2 pieces of painted/coated samples are requried
  • We cannot test materials with large thermal conductivity [i.e. > 10 W/(m⋅K)], for example, aluminium or stainless steel.

Please refer to our thermal conductivity page for more details.

Online glass U-value, SHGC & shading coefficient calculator: V2.0.0

We are pleased to introduce our upgraded online glass U-value, SHGC & shading coefficient calculator. The current version is V2.0.0. Click the screenshot below to access this online calculator.

Online glass U-value, SHGC & shading coefficient calculator

Refer to this early post for the features of the V1.1.0 version.

New features added in V2.0.0

  • SHGC and shading coeffcient calculations
    • Note: limited to single glazing systems; this is due to the restriction of the mathematical model in ISO 9050/EN 410
  • More compact user interface
  • Tooltips on glass configuration schematics

Feedback and comments

We will improve this calculator regularly. If you have feebback and comments, please let us know.

Online ETTV U-value calculator: V1.1.0

We are pleased to introduce our online ETTV U-value calculator. The current version is V1.1.0. Click the screenshot below to access this online calculator.

Online ETTV U-value calculator

Features:

  • No download or installation required.
    • The calculator works in all mainstream browsers with javascript enabled.
  • User friendly and responsive
    • In fact, you don’t need to click the “Calculate U-value” button and the results are updated instantly after your changes.
  • Full compliance to BCA ETTV code
    • With built-in ETTV material library and standard conditions for air gaps and surface film resistances
    • Accuracy has been validated with other independent codes.
  • Flexible and powerful
    • User materials can be added and edited conveniently
    • The thermal resistance of each layer is listed clearly
    • Informative tooltips are displayed when the curve is moved over the schematics

Feedback and comments

We will improve this calculator regularly. If you have feebback and comments, please let us know.

Online glass U-value calculator: V1.1.0

We are pleased to introduce our online glass U-value calculator. The current version is V1.1.0. Click the screenshot below to access this online calculator.

Features:

  • No download or installation required.
    • The calculator works in all mainstream browsers with javascript enabled.
  • User friendly and responsive
    • In fact, you don’t need to click the “Calculate Glass U-value” button and the results are updated instantly after your changes.
  • Full compliance to ISO 10292 or EN 673
    • Accuracy has been validated with other independent codes.
  • Flexible and powerful
    • Major factors influencing glass U-value are supported: insulating glazing units, low-e coating, gas fills, laminated glasses.

Future developments

It is planned to include US NFRC U-value calculation in the future. SHGC and shading coefficient calculations may be included too.

Feedback and comments

We will improve this calculator regularly. If you have feebback and comments, please let us know.

Online solar reflectance index (SRI) calculator: V1.1.0

We are pleased to introduce our online solar reflectance index (SRI) calculator. The current version is V1.1.0. Click the screenshot below to access this online calculator.

Online SRI calculator

Features:

  • No download or installation required.
    • The calculator works in all mainstream browsers with javascript enabled.
  • User friendly and responsive
    • In fact, you don’t need to click the “Calculate SRI” button and the results are updated instantly after your changes.
  • Full compliance to ASTM E1980
    • Accuracy has been validated with other independent codes. Eq. 1 of ASTM E1980 is solved iteratively.
  • Informative
    • Surface temperatures and SRIs of all 3 conditions are displayed side-by-side and with options of 3 temperature units

Feedback and comments

We will improve this calculator regularly. If you have feedback and comments, please let us know.

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

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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.

View past issues:

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.