Why insulation reduces heat loss

Take a look at this thermogram of a house. The roof and windows are the hottest, showing that most heat is lost from the house through those parts. Heat energy is transferred from homes by conduction through the walls, floor, roof and windows. It is also transferred from homes by convection. The common construction issue that can be detrimental to the performance of your ceiling insulation.

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Bradford helps you avoid these top 5 renovation regrets. As heat energy flows from the hot object to the cold object, the heat energy from your hot water will be transferred to the surrounding cold air inside the fridge once you put the glass jars inside.

The most significant mechanism of heat transfer in this case is convection, which means that the air just next to the hot jar is warmed up by the hot water. Then, the warm air is replaced with cold air, which is also warmed up. At the same time, the cold air cools down the water inside the jar. The heat of the hot water is transported away by the flow of cold air around the cup.

If you left the jars in the fridge long enough, you might have observed that the temperature changes until the hot water reaches the temperature inside the fridge.

Without a temperature difference between the water and the fridge, the heat transfer will stop. Heat from the water is also lost through conduction: the transfer of heat through the material, which is dependent on the thermal conductivity of the material itself. The glass jar can conduct heat relatively well. You notice that when you touch the glass jar with the hot water the glass feels hot as well.

What effect did the different wrapping materials have? You should have noticed that with wrapping materials, the temperature of the water after 10 minutes inside the fridge was higher compared to the unwrapped control. Wrapping the glass jar reduces the heat transfer from the hot water to the cold air inside the fridge.

Using wrapping materials that have a very low thermal conductivity reduces the heat loss through conduction. At the same time the insulator can also disrupt or reduce the flow of cold air around the glass jar, which results in less heat loss via convection. One way of reducing convection is creating air pockets around the jar, for example, by using insulators such as bubble wrap, fabric or wool, which have a lot of air pockets. Air in general is a good thermal insulator, but it can transmit heat through convection.

However, if the air pockets inside the insulating material are separated from each other, heat flow from one air pocket to another cannot happen easily. This is the reason why you should have measured the highest temperature in the bubble-wrapped jar and fabric-wrapped jar. This also explains why most of our clothes are made of fabrics and why you stay warmer when you put on an extra jacket.

Paper and foil make it easier for the heat to escape because they don't have many air pockets. This activity brought to you in partnership with Science Buddies. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options.

Discover World-Changing Science. Key concepts Physics Heat transfer Insulation Material science Introduction What do you do when it gets very cold in winter? Materials Five glass jars with lids Scissors and adult to help with cutting Tape Aluminum foil Bubble wrap Wool scarf or other wool clothes Paper Hot tap water Thermometer Fridge Timer Paper for writing Pen or pencil Preparation Cut a piece of the aluminum foil, the bubble wrap and the paper have an adult help if necessary.

Each piece should be large enough to fit three times around the sides of the glass jar. The use of more loft insulation can reduce heat loss by reducing the movement of air upwards. The fibres of the insulation can also prevent the trapped air from circulating and causing convection currents.

Any cracks or breaches in walls or ceilings especially around ceiling hatches or floors should also be filled to reduce heat loss. Installing roof insulation helps keeping the heat generated in. You may also be eligible for free roof and loft insulation through an energy supplier.

Generally, the gaps between the panes of glass are filled with air. Heat loss is reduced as air is a poor conductor of heat. The use of caulking materials around window and door frames can also reduce heat loss.

Draught excluders around doors can save energy too. The installation of a draught excluder is easy and you can do it yourself, making these a great investment when reducing heat loss. In addition to minimising heat loss, investing in an efficient heating method will also reduce your energy consumption. The lower your heat loss, the less heating you will require and the less it will cost you.

The less heating you require, the more likely a comfortable, low temperature underfloor heating system will work for you. You should also pay attention to opening the windows. Leaving windows open is one of the major sources of heat loss as people usually open the windows then the indoor air feels stuffy or is simply too hot. All this wastes energy and money so getting a heating system that does not overheat makes sense. Floor heating is ideal for low heat loss areas where it provides gentle and energy efficient heat, without contributing to a stuffy atmosphere.

There are other simple ways to reduce the overall heat loss, including fitting carpets, underlays, and curtains.