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
Materials with high and 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
Less heat is lost from a building with the help of insulation (filled cavity in walls)
- 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
