We’ve decided to go back to basics and explain just how insulation works. In this article, we are looking at how thermal insulation helps to control heat flow.
Heat moves from warmer to colder areas. This is what causes buildings to get colder in winter and hotter in summer. It happens through one or more of the three heat transfer mechanisms.
Thermal insulation works by restricting how heat moves via conduction, convection and/or radiation.
Conduction
Conduction is how heat moves along or through a material. The ability of a material to conduct heat depends on the material itself. For example, metals are a good conductor of heat. Think how hot your seatbelt buckle can get during the summer months! A low lambda value (which measures how well an insulation conducts heat) is important for insulation materials to reduce heat loss through conduction. The lower the lambda value of an insulation, the better it can resist heat transfer through conduction.
Convection
You know how we say “heat rises”? Well, this is applicable here. When the molecules that make up a gas or liquid heat up, their density will change. So warmer air will become less dense and rise. This is called ‘natural convection’, but it can also be sped up by wind or artificial means known as ‘forced convection’. Closed-cell insulation with small cell sizes inhibits convection within the cell, making it less prone to affecting neighbouring cells.