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# How your home loses heat through windows

By Sirena Rubinoff, Networx

But before you turn the thermostat up to accommodate the colder weather outside, you might want to learn a little bit about how the heating in your house actually works. Sometimes turning up the heat dial will only turn up your bill if your home is experiencing extreme heat loss. So, read on to find out how heat travels through your home and what you can do to keep it where you want it.

#### Conduction

One of the laws of physics is that energy always flows from warmer to colder areas. This is called conduction: Heat is conducted away from hot objects and towards cold objects. For example, when you sit down on a chair, heat flows from your body into the chair. Then if you stand up and touch the chair cushion a few minutes later, it will feel warm. This happens because of molecular movement. When you sit down on the chair, your body heat causes the molecules in the chair to start moving faster. Once they start moving, they hit other molecules nearby until all of the molecules near the top of the seat are moving and transferring heat throughout the entire object. Heat conduction only works through direct contact of solid objects. An example of this in your home would be in your flooring. If your floors are warm or heated, they will help warm up any furniture, carpets, or other objects touching the floors, which will in turn stabilize the heated temperature you've set for your rooms.

#### Convection

When we conduct heat to air or water, it is called convection. This is how we heat our homes. Our heat sources (boiler, furnace, etc.) conduct heat into the air, which then moves away from the heat source towards cooler areas in the room. This phenomenon is called a convection current. If your room is sealed properly, the convection current will work in your favor to heat up your room quickly and cozily. If you have air leakage to the outside, convective heat loss will occur as your warm air seeks to flow out towards the cold air. This may occur through air leaks around windows, doors, floors, ceilings, and walls.

The third form of heat transfer is radiation, whereby a hot object emits infrared radiation at the speed of light. The radiation is absorbed by anything nearby that is cooler than the hot object and the absorption causes temperature to rise, without heating the air in between the hot and cold objects. You can feel heat radiation when you hold your hand near your stovetop burner or electric heater. In your house, heat radiation is often lost through the wall immediately behind a radiator if that wall is not insulated.

#### Main Forms of Heat Loss in a Home

If your home is not properly maintained to keep heat in, your heaters will have to work much harder and longer to keep you warm. This will result in a waste of energy and money. So, if you want to do something that's good for your wallet and the environment, check your home for ways to reduce heat loss. You'll want to start by looking for any air leakage near your windows, doors, floors, walls, and ceilings. If you can feel or see drafts coming in around plumbing vents, electrical outlets, window frames, baseboards, or recessed lighting, apply caulk or weather stripping to seal the leak. Also be sure to close the chimney damper, or else it acts like an open window sucking air up and out through the chimney. You could lose up to 30 percent of your heat through an open damper. If you have an attic that you access through a folding stair, check around the edges of the opening to see if warm air is leaking into the attic from the house. An easy way to test for this is to switch on the attic light with the door closed and then look for specks of light around the door. If you can see light, this means there is space for warm air to escape. Cover these spaces with weather stripping to keep heat inside where it belongs.

Once you've checked to make sure air is not leaking out of your home unnecessarily, you might want to consider adding extra insulation to keep even more heat inside. You can do this by simply adding wall hangings, thick curtains, and carpets. You can apply a double glazing to your windows and if you want to take on a bigger project, you might consider adding better insulation to your walls and attic. But be sure to check your home for air leaks before you take on any expensive projects. A few extra carpets and a little caulk and weather stripping can go a long way towards keeping you warmer and your energy bills lower.

Source: http://www.networx.com/article/the-physics-of-heat-loss