Insulation, construction and engineering materials (-20 °C to 70 °C)

This guarded hot-plate is an NPL designed and built national standard for thermal conductivity (or thermal resistance) of insulation and medium thermal conductivity materials (e.g. plastics, masonry, timber, composite boards). As well as normal measurements in air, it can be used with a reduced pressure or specified gas atmosphere. Measurements of total hemispherical emittance can also be carried out, by having a small gap between the specimen surface and the surface of the cold plate (with known emittance) in a vacuum environment.

Specification

• Thermal conductivity range: up to 2 W/m·K
• Thermal resistance range: greater than 0.025 m²·K/W
• Mean specimen temperature range: -20 °C to 70 °C
• Conforms to ISO 8302:1991, EN 12667:2001 and EN 12664:2001

Accreditation

• UKAS accredited test service (UKAS 0002)
• Transfer standards to ISO Guide 34 (UKAS 4002)
• Accredited under 89/106/EEC: Construction Products, Notification id: 1146
• Registered laboratory in CEN Keymark scheme for Thermal Insulation

Specimens dimensions

A single specimen is required.

• Thickness: 25 mm to 50 mm
  (The thickness is within 2% of its mean thickness over its whole area)
  Note: Thinner specimens can be measured, if it is the thickness that they will be supplied to the end user
• Length and breadth: 305 mm x 305 mm
  (Within range 302 mm to 315 mm)
• Flatness: The 305 mm square faces are flat to better than 0.2 mm.
  (Flatness criteria do not apply to compressible or fibrous insulations)

Note 1

Although 'thermal conductivity' is a property of a homogeneous material, it is generally accepted that the term can still be used for insulation/construction products that contain a continuous mixture of two or more materials (e.g. air and glass fibre or air and concrete) providing the size of any particles is less than a tenth of the specimen thickness. However, if your samples have either discrete layers or large particles, then 'thermal resistance' would be quoted on the Test Report, rather than 'thermal conductivity'. However, the thickness of the product during the test would be quoted in the Test Report, allowing an 'effective' thermal conductivity to be calculated by dividing the thickness (in metres) by the thermal resistance.

Note 2

If you do not have a specific temperature at which you would like the measurements made, then we would suggest a mean specimen temperature of 10 °C, as this is most commonly used for certification and comparison of construction products.

Contact

Customer Services tel: +44 20 8943 6245
E-mail: thermal_enquiries@npl.co.uk