Thermal conductivity

• Thermal Conductivity

   

  • Thermal conduction is the process where energy is transferred by vibrating particles in a substance
  • The vibrating particles transfer energy from their kinetic store to the kinetic store of neighbouring particles
  • The direction of energy transfer is always from hot to cold
  • The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material
  • Materials with high thermal conductivity heat up faster than materials with low thermal conductivity
• Insulating a Building

  • Insulating the loft of a house lowers its rate of cooling, meaning less energy is lost to the outside
  • The insulation is often made from fibreglass (or glass fibre)
  • This is a reinforced plastic material composed of woven material with glass fibres laid across and held together
  • The air trapped between the fibres makes it a good insulator
  • It has a much lower thermal conductivity than the roof material
  • Several layers of insulation make it very thick and therefore decrease the rate of cooling
• • Another aspect that affects the cooling of buildings is the walls
  • Houses in cold countries are fitted with cavity wall insulation which is made from blown mineral fibre filled with gas
  • This lowers the conduction of heat through the walls from the inside to the outside