P2.5 Revision

What is cavity wall insulation and how does it work?

By pumping insulation into the cavity, it replaces the air that's in the cavity, and with this insulation between the walls there is a reduced rate of heat transfer, and the air that is trapped in the fibre further reduces the rate of heat loss

How does aluminium foil between the radiator panel and the wall reduce the rate of heat transfer?

The radiation reflects off the surface, away from the wall and so reduces the rate of energy transfer by radiation

What is loft insulation and how does it work?

Loft insulation is a material, either made from a foam coated with a silver surfaced film, or made from fibreglass, they are very good insulators, they are very thick, they have low thermal conductivity, and the air trapped in the fibres also reduces heat loss

How do external walls reduce the rate of heat transfer

The outer walls have thick bricks and low thermal conductivity, this means the rate of heat transfer from inside to outside will be lower

What are double glazed windows and how do they work?

They have two panes of glass with air or a vacuum between them, the thick glass and the trapped air reduces the rate of heat loss by conduction, a vacuum gap would also stop heat loss by convection