Thermal Properties of Materials
Thermal conductivity, specific heat, density, and emissivity values that govern heat transfer through building materials
Thermal properties of building materials determine how heat flows through walls, roofs, and floors. Four core properties: (1) Thermal conductivity (k or λ) — heat conducted per unit thickness per °C, in W/m·K. (2) Specific heat capacity (c) — heat required to raise 1 kg by 1 °C, in J/kg·K. (3) Density (ρ) — mass per volume, kg/m³. (4) Emissivity (ε) — radiative heat-loss factor (0-1). These properties drive U-value (transmittance), R-value (resistance), and thermal mass calculations that govern ECBC compliance and HVAC sizing.
Typical k values for Indian construction materials (W/m·K): RCC = 1.74; brick masonry = 0.81; AAC block = 0.16-0.22; concrete block (hollow) = 0.55; lime mortar = 0.72; PCC = 1.28; cement plaster = 0.72; glass = 0.78; steel = 50; aluminium = 211; timber (sal) = 0.17; gypsum board = 0.16; rockwool = 0.038; EPS = 0.035; XPS = 0.030; PUR foam = 0.025. The lower the k, the better the insulation. Most masonry materials are 20-50× worse insulators than rockwool — which is why dedicated insulation layers matter on roofs and walls.
Source standards: IS 3346:1980 (Method of determining thermal conductivity), IS 11239 series (Building materials thermal performance), NBC 2016 Part 11 (Approach to Sustainability — thermal envelope), ECBC 2017 (Energy Conservation Building Code).
- U-value and R-value calculations for ECBC compliance
- HVAC heat-load estimation for cooling/heating sizing
- Roof and wall insulation thickness sizing
- Thermal mass design for passive cooling
- Comparison of alternate masonry materials (AAC vs brick vs hollow block)