How does insulation work?

What does insulation mean?

Insulating is the process of covering something to stop heat from escaping, as well as sound and electricity. For example, an animal’s fur can be described as a good insulator, as it keeps them warm during winter. Insulation can be used around metal wires to encourage the electricity to travel in a certain direction without escaping and to soundproof a space, however the type of insulation that you use to do these two things will likely be very different. 

What is insulation?

Insulation is the type of material that’s used to do some of the jobs described above. It typically doesn’t conduct heat or electricity, and comes in all sorts of materials so that it can be used for a variety of purposes. There are certain materials that are known as ‘good’ insulators and others that are known as ‘bad’ insulators. A bad insulator isn’t very good at trapping heat, sound or electricity, however a good insulator can do this job easily, and includes plastic, rubber and wood.

How insulation works

So now that we know what insulation is and why we need it, how exactly does this material trap heat and sound?

Well, heat doesn’t stay still - in fact, it makes a number of movements.

Firstly, hot air rises because it is lighter, while cold air sinks because it is denser. This type of movement is called convection. Usually, you’ll find that your home is warmer upstairs than it is downstairs. This also explains why flats at the top of tall apartment buildings get very hot. As this heat continues to rise, it can exit your home through the roof, meaning your boiler has to work harder to maintain a constant temperature.

Secondly, heat moves naturally towards colder spaces. This is known as conduction. If you put a teaspoon in a hot cup of tea, for example, the heat will move up the spoon, making it as hot as the tea. In a similar way, the heat in your home will seek cooler spaces, meaning that it can flow into cooler lofts, garage and even outside.

In order to prevent these two movements of heat as much as possible, we need insulation. Insulation doesn’t work to keep the cold out, but instead traps the heat that’s in your home using the tiny pockets of air situated within the material itself. In materials such as fiberglass and foam boards (common insulators in homes), there are lots of these pockets, making them excellent insulators. As hot air becomes trapped in the material, it prevents any more heat from escaping, keeping your home nice and warm. A woollen jumper acts in the same way, whereby it traps your natural body heat to keep you even warmer.

You can use loft insulation to stop heat from escaping out of the roof, cavity wall insulation to reduce the amount of heat lost through the walls and even floor insulation. People don’t often think of floors as a source of heat lost, but this can often be the case in homes that have floorboards or wooden floors.

The effectiveness of insulation is measured by its R-value (Resistance-value). This value shows how good the material is at insulating and depends on the type of insulation, how thick it is and how dense it is. By installing more insulation in your home, you’re increasing its R-value.

Insulation can be just as effective in summer as it is in winter because it keeps our homes cool, too. During summer, heat can travel into our homes in the same way it travels out of them in winter. This is because, as explained above, heat travels to colder air. However, sufficient insulation can trap the heat that is coming from outside and prevent it from getting in, helping to keep your home nice and cool.  

How does loft insulation work?

Loft insulation can not only prevent heat from escaping out of the roof, but also stops heat from your home getting into the loft. The loft is an area that most people don’t need heating as it’s usually a storage space and nothing more, and so it would be a waste of money and energy to do so. You can  insulate your loft  in two ways. You can either insulate the floor of the loft, including under the joists and the floor itself, or you can insulate the walls. Doing both is also an option and the best material for the job is fibreglass wool. This man-made material is a combination of wool and glass that can trap the heat in an efficient way and prevent humidity.

The insulation under the joists acts as a barrier to stop heat travelling into the attic from the first floor and the insulation on the walls works to stop the heat from escaping out of your home altogether. No matter which option you choose, the insulation should be a thickness of at least 270 mm.

Why do houses need insulation?

Insulation is a requirement in UK homes in order to trap the heat that’s created by our boilers,  heat pumps  and other heating technologies. Without it, we’d be heating our homes and most of this heat would be escaping through the walls, floors and roof, leaving our homes almost as cold as they were before the heating went on, this is known as heat loss. This would be a huge waste of energy, and so at least some insulation is needed to prevent this from happening. Usually, it’s located in the loft and in the walls to stop too much heat from escaping. This is also the reason why we have double- or even triple-glazed windows and seals around doors.

Installing loft insulation could save you up to 15 per cent on your heating bills, or around £140 per year, and your house will be warmer for it.