4.8 Explain how insulation is used to reduce energy transfers from buildings and the human body.

Objects/materials that are insulators are bad conductors. They often "keep" the heat, reflect it, etc and are usually non metals. Examples of insulators include:

• Bubble wrap
• Lids
• Foam
• Duvet covers
• Wool

If an object is surrounded by an insulator, it will lose less heat by conduction. If there is little or no space for particle movement in a liquid or gas, less heat will be lost through convection. Shiny materials can be used to reflect radiation, while black, matt surfaces will absorb the most heat (but, because the hotter the object the more infrared it radiates, will also radiate the most heat)

In cold environments, you'd want to keep your body or your house nice and warm :) and lose as little heat as possible.

In buildings (let's say a house, as an example), much of the heat is lost through the roof and un-insulated walls.

Figure 1: Heat loss in a house

How insulation can help:

Figure 2

• Heat loss through the roof: fit loft insulation. An insulating material is used to reduce heat loss through conduction and convection, as there is no space for air to circulate and therefore no convection currents can be created within this gap. It works similarly to cavity wall insulation.

• Heat loss through walls: fit cavity wall insulation. Insulating material is blown through the gap between the bricks and the wall, stopping heat loss through conduction and convection as, again, there is no space for air to circulate.

•  Heat loss through windows: double or triple glaze. This helps reduce heat loss through conduction as air (between layers of glass) is a poor conductor and convection is unlikely to occur because the gap is very small. Curtains also help reduce heat loss.

• Heat loss through doors: cover the gap between the floor and the door with a draught excluder (see figure 3). This stops heat from escaping through convection and conduction. If the door has glass or a window, see heat loss through windows.

• Heat loss through floor(s): lay down carpets. This stops heat loss through conduction as cloth used for carpets is a very poor conductor.

Figure 3: Draught excluder example

In humans, heat loss occurs mainly from the torso, as can be seen in Figure 4.

(Source: BBC Bitesize)
Figure 4: A thermogram of a man, woman and child

To reduce heat loss in the human body, you could do the following:

• Use insulating clothing (eg socks, scarves, hats) because warm air is often trapped in materials such as wool. 
• Wear insulating jackets - some jackets are a bit puffy, meaning they have air pockets that stop heat loss through conduction

The more layers you wear, the warmer you'll be!