Thermal conductivity

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Thermal conductivity of solid, powder, liquid & paste

We are a Singapore-based third-party test laboratory, providing lab test services of thermal conductivity. Our lab is SAC-SINGLAS (ISO 17025) accredited and our customers are from around 30 countries.

We provide a wide range range of thermal conductivity testing services, for various material types and applications.

Material types

  • Solid (e.g. rock wool, concrete, wax)
  • Powder (e.g. sand)
  • Liquid (e.g. lubricating Oil)
  • Paste (e.g. silicone grease)

Test methods

  • Heat flow meter (ASTM C518)
    • SAC-SINGLAS accredited
  • Transient hot wire (ASTM C1113, D5930, D5334 or D7896 with manufacturer’s instructions)


  • Thermal resistance and U-value rating
  • New material development
  • Material characterization

Online ETTV U-value calculator

Interested in performing your own U-value calculations based on BCA ETTV code? We have a user-friendly online calculator:

Online ETTV U-value calculator

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(+65) 6908 0126

More information

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Test methods

For thermal conductivity testing, the selection of test method is dependent on the sample type.

If you are not sure of the test method to be used, please contact us with your sample information or read the Samples section below.

Steady state method with heat flow meter

The steady state method is mainly applicable to thick insulation materials with two parallel flat surfaces, e.g. mineral wool board.

  • ASTM C518-17 Standard test method for steady-state thermal transmission properties by means of the heat flow meter apparatus

This method is SAC-SINGLAS accredited

Transient method with hot wire thermal conductivity meter

The transient method is mainly applicable to general solid (e.g. plastics), powder (e.g. sand), paste (e.g. silicone grease) and liquid materials (e.g. lubricating oil).

Depending on the material type, one of the methods below will be used:

  • ASTM C1113/C1113M-09 Standard test method for thermal conductivity of refractories by hot wire (platinum resistance thermometer technique)
  • ASTM D5930-17 Standard test method for thermal conductivity of plastics by means of a transient line-source technique
  • ASTM D5334-14 Standard test method for determination of thermal conductivity of soil and soft rock by thermal needle probe procedure
  • ASTM D7896-19 Standard test method for thermal conductivity, thermal diffusivity, and volumetric heat capacity of engine coolants and related fluids by transient hot wire liquid thermal conductivity method

There are two instruments available at OTM for thermal conductivity testing.

Heat flow meter (for steady state method)

OTM uses Thermtest HFM-100 heat flow meter for the steady state method. The NIST standard reference material (SRM) 1450d Fibrous Glass Board is used in the lab for heat flow meter calibration.

Heat flow meter for thermal conductivity testing
Heat flow meter

Hot wire thermal conductivity meter (for transient method)

Transient hot wire meter for thermal conductivity testing
Transient hot wire meter
Detailed view of the thin film probe of the transient hot wire meter
Hot wire sensor

There are different sample requirements depending on the test method.

Steady state method based on ASTM C518

  • Typical sample types:
    • Insulation materials, e.g. mineral wool, polystyrene foam, polyurethane foam
    • Bulk solid materials, e.g. concrete block, fiberglass reinforced board
  • Thermal conductivity range: up to 2.5 W/(m K)
    • External thermocouple kit will be used for non-insulation materials
  • Temperature range: -15 to 65 °C
  • Sample size:
    • Preferred size: 300 mm x 300 mm
    • Maximum size: 300 mm x 300 mm
    • Minimum size: 200 mm x 200 mm
    • Maximum thickness: 100 mm
  • Sample requirements:
    • Parallel and flat top & bottom surfaces
    • Non-parallel and non-flat surfaces result in smaller results, due to contact resistance

Transient method based on ASTM C1113/D5930 (solid)

  • Typical sample types
    • General solid materials, e.g. concrete, brick, plastics, ceramics
    • For homogeneous materials only
  • Thermal conductivity range: up to 10 W/(m K)
  • Temperature range: room temperature only
  • Sample size:
    • minimum size: 30 mm x 30 mm x 1 mm
    • Size requirement is dependent on material type
  • Sample requirements:
    • Two samples are required, to sandwich the thin film probe in-between
    • The surface touching the probe shall be flat and smooth
      • Customer may machine or sand the surfaces to flat
      • OTM can only do sanding, but not machining
    • Non-flat surfaces result in smaller results, due to contact resistance

Transient method based on ASTM D5334 (soil)

  • Typical sample types:
    • soil and soft rock in tube form
  • Thermal conductivity range: up to 5 W/(m K)
  • Temperature range: room temperature only
  • Sample size:
    • Preferred soil tube size: 200 mm long and 100 mm in diameter
  • Sample requirements:
    • In soil tube form
    • In the intact form, i.e. with moisture level and density as close to the original state as possible

Transient method based on ASTM D7896 (liquid)

  • Typical sample types:
    • Liquid, e.g. lubricating oil, coolant, water
  • Thermal conductivity range: up to 10 W/(m K)
  • Temperature range: room temperature only
  • Sample volume:
    • Minimum volume: 100 mL
  • Sample requirements:
    • The liquid shall be non-toxic and safe to handle in general laboratory environment without special protection
Extended results

More than thermal conductivity

On request, the following extended results can be calculated and reported:

  • Thermal resistivity
  • Thermal resistance (R-value)
  • Thermal conductance
  • Thermal transmittance (U-value)

The calculations are based on:

  • ASTM C1045-19 Standard practice for calculating thermal transmission properties under steady-state conditions
Cost, lead time & procedures


Please contact us for the testing fee.

Lead time

The typical lead time is 5 working days.


Our sales personnel will guide you through the necessary procedures.

Upon your request, the following three documents will be emailed to you:

  1. Official quotation
  2. Standard terms & conditions
  3. Test request form

The client needs to return us the following documents:

  1. Official purchase order (PO) or signed quotation
  2. Completed test request form

The client needs to submit the test samples to our laboratory. The test will commerce as soon as possible after the test samples are received.


Frequently Asked Questions (FAQs):

Q1. Can you test thermal conductivity of metals, e.g. aluminium?

No. The thermal conductivities of metal materials are too large to be measured by our instruments.

Q2. Can you test thermal conductivity of paint

No. As paint is typically a very thin layer, the thicknesses of typical paint layers are insufficient for our lab testing.

Q3. How accurate are your results?

The measurement uncertainties are stated in the test reports. They are typically ±5% with the steady-state method and ±8% with the transient method.
However, as mentioned in the Samples section, the accuracy is also dependent on the samples. Non-parallel and non-flat samples result in smaller results, due to contact resistance.

Q4. Can you test thermal resistance or U-value

For the steady-state method with heat flow meter, the thermal resistance (R-value) can be directly measured.
For other cases the thermal resistance cannot be directly, we can do calculations based on the thermal conductivity measured and the thickness declared by you, according to ASTM C1045.
For U-value, it cannot be directly tested and the calculation method based on ASTM C1045 is always used. We can use the boundary conditions specified in this BCA code or declared by you.
We can calculate a range of extended results on your request.

Q4. How much is the cost?

Please contact us for the price.

Q5. How long is the lead time?

You will receive the results within 5 working days, after sample submission.

Q6. What are the procedures?

Please contact us with your sample size and quantity. We will provide you the relevant documents and the sample submission instructions accordingly.

Q7. Can I visit your lab?

Sure, we welcome you to visit our lab to understand our testing procedures and assess our quality system. Please contact us if you wish to visit our lab.

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