Science Loft Insulation

Heat energy is transferred from homes by conduction through the walls, floor, roof and windows. It is also transferred from homes by convection. For example, cold air can enter the house through gaps in doors and windows, and convection currents can transfer heat energy in the loft to the roof tiles. Heat energy also leaves the house by radiation through the walls, roof and windows. http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/energy_home/1_keeping_homes_warm2.shtml Visited 28/01/13
All objects give out and take in thermal radiation - also called infrared radiation. The hotter an object is, the more infrared radiation it emits. This infrared radiation can be reflected by shiny surfaces. Infrared radiation is absorbed best by black, dull - not shiny - surfaces.
Infrared radiation is a type of electromagnetic radiation. It involves waves, rather than particles. Unlike conduction and convection, radiation can even work through the vacuum of space. This is why we can still feel the heat of the Sun even though it travels through a vacuum for 150 million km to reach the Earth. http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/energy_home/1_keeping_homes_warm1.shtml Visited 28/01/13
Pay-back time

If some heat escapes from the house, it costs money and wastes resources. In deciding how cost-effective an energy-saving measure is, we need to know what its pay-back time is. In other words, taking the example of double-glazing: how long will it take before the cost of having the double-glazing installed will be recovered by what we save in fuel bills? The calculation is: pay-back time in years = cost of energy-saving measure ÷ money saved each year http://www.frankswebspace.org.uk/ScienceAndMaths/physics/physicsGCSE/reduceHeatLoss.htm Visited 28/01/13
Loft insulation or under floor insulation reduce heat losses by conduction. The insulation material traps air. Air is a poor conductor of heat. The fibres of the insulation also prevent the trapped air from circulating and causing a convection current to be set up. http://www.bbc.co.uk/bitesize/standard/physics/energy_matters/heat_in_the_home/revision/1/ Visited 28/01/13
Probably the most cost effective method of insulation is loft insulation. Heat passes through the roof by conduction through the plasterboard ceiling, by convection in the loft space, then by conduction through the roof tiles. If thick insulation is placed over the base of the loft, then the rate of heat conduction is much reduced. Convection currents cannot then easily form in the loft and heat loss is much reduced. http://www.astarmathsandphysics.com/gcse_physics_notes/gcse_physics_notes_insulating_buildings.html Visited 28/01/13

Heat always flows from a warm region to a cooler region. An un-insulated house loses heat at a faster rate during cold climates than an insulated one. Insulating a loft reduces the amount of heat loss from the roof by means of installing insulating materials such as fiberglass matting, which reduce the U-value of the loft. http://wiki.answers.com/Q/How_does_loft_insulation_save_heat_energy Visited 28/01/13
Your house is standing on cold soil or rock, so heat flows down directly into the Earth by conduction.
Heat travels by conduction through the solid walls and roof of your home. On the outside, the outer walls and the roof tiles are hotter than the atmosphere around them, so the cold air near to them heats up and flows away by convection.
Your house may seem like a big complex space with lots going on inside in but, from the point of view of physics, it's exactly the same as a camp fire in the middle of vast, cold surroundings: it constantly radiates heat into the atmosphere.
The more heat escapes from your home, the colder it gets inside, so the more you have to use your heating and the more it costs you. The more you use your heating, the more fuel has to be burned somewhere (either in your own home or in a power plant up-state), the more carbon dioxide gas is produced, and the worse global warming becomes. It's far better to insulate your home and reduce the heat losses. That way, you'll need to use your heating much less. The great thing about home insulation is that it usually pays for itself quite quickly in lower fuel bills. Before long, it's even making you money! And it's helping the planet too.
Since warm air rises, plenty of heat escapes through the roof of your home (just as lots of heat escapes from your body through your head, if you don't wear a hat). Most people also have insulation inside the roof (loft area) of their homes, but there's really no such thing as too much insulation. Loft insulation is generally made from the same materials as cavity-wall fillings—such things as rock wool and fiberglass.
Wall and roof insulation cuts down on heat losses by convection and conduction, but what about radiation? In a vacuum flask, that problem's solved by having a reflective metallic lining—and the same idea can be used in homes too. Some homeowners install thin sheets of reflective metallic aluminium in the walls, floors, or ceilings to cut down on radiation losses. Good products of this kind can reduce radiation losses by as much as 97 percent. http://www.explainthatstuff.com/heatinsulation.html Visited 28/01/13