Warm homes
Look around the room you are in. How is it heated? If you are at school, you may see a radiator. If you are at home, you may see a convector heater, a central heating radiator or a gas or electric fire. They all provide warmth to keep you comfortable.
If it is cooler outside than in your room, heat will try to escape.

Heat always moves from a warmer place to a cooler place. If a door is open, the warm air will mix with the cooler air by convection or if a wind is blowing, the warm and cool air will simply mix. When all the windows and doors are closed, the main way the room will lose heat is through its walls, floor and ceiling.

Look at the floor. Is it covered in hard, smooth tiles or a thick, soft carpet? If it is covered with tiles, heat will pass quite quickly into it by conduction. Besides being comfortable to walk on, the carpet also provides a layer of insulation to the floor. The material from which the carpet fibres are made is a poor conductor and there are air spaces between the fibres, which also prevent heat loss by conduction.

Look at the walls. If you can see bricks or concrete blocks heat will pass through them quickly by conduction. If you are looking at wallpaper the wall will be a better insulator. Wallpaper needs a smooth surface to hold it in place. This is provided by plasterboard. The main material of plasterboard is wood. This is a good insulator. In some older houses the inside walls are covered with wood panels. They form an attractive wall covering and also help to keep the room warm.

Look at the windows. Are they single or double-glazed? You can tell the difference by looking for a bright grey strip of metal in the sides, top and bottom. If it is present the windows are double-glazed. The metal strip separates the two planes of glass, which may be difficult to see. Glass is a good insulator and so is air. A double-glazed window is a sandwich of insulation. The two panes of glass are separated by a layer of air.

Close the doors and hold your hands close to the door and the doorframe. Can you feel a draught or cold air? If you can, the door is badly fitting and heat is being lost.

Look at the ceiling. If it is covered in plaster it will have plasterboard underneath it which also forms a layer of insulation. Some ceilings have even more insulation. They have plastic tiles stuck on top of the plasterboard.

If you have tried all these tests, you should now be able to think how well the room holds onto its heat. Is it a heat holder or a heat loser? If it is losing a lot of heat, what could be done to keep the room warmer?

When Stone Age people lived in caves, how did they keep warm?
Caves are not as cold as many people think. Deep in a cave can be much warmer than outside. Caves also hold their heat more steadily than buildings and some may remain at almost the same temperature in both winter and summer. The first people who lived in caves lit a fire at the entrance to keep themselves warm, cook their food and keep away dangerous animals such as lions. In the summertime Stone Age people moved away from the caves and lived in tents made from animal skins. Some of these people set up these tents inside caves in winter for extra warmth. They also set up a windbreak made from animals' skins across the mouth of the cave. This reduced draughts and kept in the warm air from the fire.

Have people always used glass in windows?
No. In fact, people have not always used windows. In the past many people lived in huts which had just a door and no windows. The first windows were small and set high in the wall to keep out animals and burglars. They did not have glass or any other material in them to keep out the draught. In time people began to use oil-soaked linen or waxed paper stretched across the window. This reduced draughts, kept out rain and let in a little light. In many places, shutters were put up round windows. When they were closed they kept out some of the draughts but also kept out light. The Romans were the first people to use glass in windows. The window glass was only used in the homes of rich people. By about 1600 glass was cheap enough for ordinary people in most countries to have it in the windows of their homes.

How long have people used curtains?
Curtains were first used about six hundred years ago. Most of them were not used around the windows. They were used around beds! At that time many houses had wooden shutters to close their windows because cloth was considered too expensive to drape over them. Instead, the draughts were allowed to blow through a bedroom and the people put the curtains round their four poster beds to keep themselves warm. It was not until about three hundred years ago that people put curtains around their windows. Cloth blinds were brought into use at about the same time and by the 1750s people could set up spring-loaded roller blinds on their windows.

What is central heating?
It is a way of heating a whole home from one source of heat. The first central heating system was invented by the Romans. It was known as the hypocaust. In a room below a Roman house, a furnace was set up which burnt wood or charcoal. The hot air from the furnace passed under the floor of the house and warmed the rooms above. There were also pipes in the wall through which the hot air could also pass to make the house warm. The central heating systems used in homes today have a boiler, which is usually placed in the kitchen. Hot water from the boiler passes through pipes under the floor to radiators in each room. When the water has lost its heat through convection and radiation it returns to the boiler to be heated again.

Why can it get very hot in a conservatory in sunny weather?
Waves of heat energy pass out from the Sun in all directions. When they reach a conservatory or other glass building, such as a greenhouse, they pass through the glass. In the conservatory, the heat energy is absorbed by the floor and furnishings then some of it is radiated back into the room. These waves of heat energy cannot pass through the glass so they stay in the conservatory and heat it up.

What is solar heating?
A solar heating system uses heat from the Sun's rays. The Sun's heat is collected by a solar panel on the roof of the home. There is a black board in a solar panel. It has a water pipe zigzagging across it. Above the pipe is a piece of double glazing which forms the front of the solar panel. When waves of heat energy pass through the glass in the solar panel, they are absorbed by the black board. New waves of heat energy are radiated from the black surface but they are held in the panel by the double glazing. This trapped heat is conducted through the pipe into the water. As the water heats up it moves down to the hot water tank in the home. It passes through a coiled pipe in the hot water tank and warms the water there. The water circulates between the solar panel and the hot water tank to provide the home with hot water.