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IS 10754:1983 is the Indian Standard (BIS) for method of determination of thermal conductivity of timber. This standard specifies the method for determining the thermal conductivity of timber using a guarded hot-plate apparatus. It covers the principle, apparatus, specimen preparation, test procedure, and calculation method. The resulting thermal conductivity value (k-value) is essential for the thermal design and energy performance analysis of buildings.
Method of determination of thermal conductivity of timber
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Moisture content is the most critical variable affecting timber's thermal conductivity. Ensure specimens are conditioned to the specified state (e.g., oven-dry) for accurate and repeatable results.
! The direction of heat flow relative to the wood grain (parallel or perpendicular) significantly impacts the result and must be recorded and reported.
! The test is highly sensitive and requires a stable laboratory environment and a properly calibrated guarded hot-plate apparatus as per IS 3346.
Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus
Provides the detailed methodology for the guarded hot-plate test, applicable to timber among other materials.
EN 12667:2001CEN (European Committee for Standardization)
HighCurrent
Thermal performance of building materials and products - Determination of thermal resistance by means of guarded hot plate and heat flow meter methods - Products of high and medium thermal resistance
Specifies the guarded hot-plate method for building materials, which directly covers timber.
ISO 8302:1991ISO (International Organization for Standardization)
HighWithdrawn
Thermal insulation — Determination of steady-state thermal resistance and related properties — Guarded hot plate apparatus
A foundational international standard for the guarded hot-plate method, whose principles align with IS 10754.
JIS A 1412-2:1999JSA (Japanese Standards Association), Japan
HighCurrent
Test methods for thermal resistance and related properties of thermal insulations -- Part 2: Guarded hot plate apparatus
Japanese national standard detailing the guarded hot-plate method, very similar in principle and application.
Key Differences
≠IS 10754 is specific to timber, whereas modern standards like ASTM C177 and EN 12667 are general methods for a wide range of (mostly insulating) materials.
≠Modern international standards mandate detailed uncertainty analysis and reporting, which is not a requirement in the 1983 Indian standard.
≠Apparatus specifications in IS 10754 are less stringent regarding temperature uniformity, flatness, and guard gap imbalance compared to the detailed requirements in ASTM C177.
≠The standard pre-test conditioning environment in IS 10754 (27 °C, 65% RH) differs from the common international norm (e.g., 23 °C, 50% RH in ASTM C177).
Key Similarities
≈All standards are based on the same fundamental physical principle: applying Fourier's Law of heat conduction under steady-state, one-dimensional heat flow.
≈The core apparatus design, a guarded hot-plate assembly sandwiched between two specimens and two cold plates, is conceptually identical across all standards.
≈The requirement to achieve thermal equilibrium (steady-state) before taking final measurements is a critical and common procedural step in all listed standards.
≈The fundamental formula for calculating thermal conductivity (λ) from measured heat flux, specimen thickness, and temperature difference is the same.
Parameter Comparison
Parameter
IS Value
International
Source
Primary Apparatus
Guarded Hot-Plate
Guarded Hot-Plate
ASTM C177-19
Standard Conditioning Temperature
27 ± 2 °C
23 ± 2 °C
ASTM C177-19
Standard Conditioning Humidity
65 ± 5 % RH
50 ± 5 % RH
ASTM C177-19
Specimen Thickness
12 mm to 25 mm
Varies; defined by apparatus size and material type, often limited to < 1/3 of metering section width.
EN 12667:2001
Typical Temperature Difference (ΔT)
At least 20 °C
Sufficient for precision, typically 20 K or more.
ASTM C177-19
Typical Mean Test Temperature
27 °C
10 °C or 23 °C are common, but depends on product application.
EN 12667:2001
Measurement Uncertainty
Not explicitly required to be calculated or reported.
Mandatory to be calculated and reported as part of the test results.
EN 12667:2001
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Specimen Thickness25 mm to 50 mm
Specimen Size (for 30cm apparatus)300 x 300 mm
Specimen Size (for 60cm apparatus)600 x 600 mm
Test Equilibrium ConditionSuccessive readings differ by < 1%
Standard Test ConditionOven-dry condition
Time Interval for successive observationsNot less than 30 minutes
Key Formulas
λ = (Q * d) / [A * (t1 - t2)] — Calculation of thermal conductivity, where Q is heat flow, d is specimen thickness, A is area, and (t1-t2) is the temperature difference.
The test establishes a steady, one-dimensional heat flow through a pair of identical, flat timber specimens using a guarded hot-plate apparatus to measure the heat input and temperature gradient (Clause 4).
What specimen thickness is required?+
The thickness of each specimen should not be less than 25 mm nor more than 50 mm (Clause 6.1).
How is the end of the test determined?+
The test is considered complete when thermal equilibrium is reached, defined as when thermal conductivity values from successive observations (at >=30 min intervals) do not differ by more than 1 percent (Clause 7.6).
What key apparatus is needed for this test?+
A guarded hot-plate apparatus conforming to IS 3346 is the primary equipment required (Clause 5).