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.

5 certainties amid uncertainties: our COVID-19 strategy

COVID-19 has brought in many uncertainties to the business environment and will bring in more uncertainties in the future. As OTM’s COVID-19 strategy, we remain committed to the following 5 certainties:

  • Certainty 1: our long-termism principle
  • Certainty 2: consistent efforts on innovation
  • Certainty 3: consistent efforts on branding
  • Certainty 4: consistent efforts on global opportunities
  • Certainty 5: consistent efforts on customer loyalty

Certainty 1: our long-termism principle

We will stay focused on optical & thermal testing.

Certainty 2: consistent efforts on innovation

We will consistently develop our own instruments, tools and methods for optical & thermal testing.

An instrument under active development at OTM
One of the online optical & thermal calculators developed by OTM

Certainty 3: consistent efforts on branding

We will consistently update our website, newsletter and lab profile, with rich information on optical & thermal testing.

Certainty 4: consistent efforts on global opportunities

We will consistently support global customers to improve the utilization rate of our resources.

Our customers are from more than 20 countries

Certainty 5: consistent efforts on customer loyalty

We will consistently reward our loyal customers, with loyalty vouchers issued to all customers to nurture long-term relationship.

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.

COVID-19 update 2: office open as usual from 02 June

Business activities in Singapore are gradually resumed after the “circuit breaker” period between 07 April and 01 June. At OTM, we will also transit to the normal operation gradually.

Office open as usual

From 02 June onward, our office will be open as usual, according to our normal office hours (10 am – 5 pm, Monday to Friday).

It allows sample delivery and report collection more conveniently.

Nevertheless, we prefer customers to reduce unnecessary person-to-person interactions, e.g. using third-party courier services for sample delivery or using electronic modes for payment.

Additional 2 days of lead time

The lead time of all testing services are still 2 days longer than our usual practice, as we are working on alternate shifts to reduce commuting to the office.

Based on our practices during the “circuit breaker” period, most orders are processed within the normal lead time, without delay.

SafeEntry digital check-in/out system

We’ve also implemented the SafeEntry digital check-in and check-out system, according to the government guidelines. All visitors need to scan the QR code prominently displayed at the entrance to check-in or check-out. Additionally, face-to-face meetings are not encouraged in this special period.

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

Choose OTM.

Work with the expert in Optical & Thermal Measurement solutions.

COVID-19 update: lab testing services as usual while working from home as much as possible

It is the “circuit breaker” period in Singapore (07 April – 01 June 2020), in response to the current COVID-19 situation.

Below are the updates from OTM on our operations. Please also refer to this attachment for details.

Lab testing services as usual

Testing labs are classified as an essential business, exempted from suspension.

OTM is able to perform all lab testing services as usual, without interruption.

Please feel free to contact us for your lab testing needs.

Work from home as much as possible

During this special period, it is everyone’s social responsibility to maintain safe distancing. In our case, it is to reduce commuting to and from office and to reduce gathering in office.

We are working from home as much as possible during the “circuit breaker” period, unless for genuine essential activities.

Non-contact delivery of test samples

As most of the time our office is unmanned, non-contact delivery of test samples is required, without our presence.

Please refer to the appendix in the attachment for the instructions.

Please be assured that the test samples will be safe and we will acknowledge you the receipt status via email in due course.

Additional 2 days of lead time

Due to the measures mentioned above, additional 2 days of lead time is required to complete the test jobs.

The typical lead times are 5 working days for optical tests and 7 working days for thermal tests, during the “circuit breaker” period. In practice, we will shorten the lead time whenever possible.

Stay safe

Last but not least, we sincerely wish all our customers and suppliers are safe during this crisis.