Conductive: Direct contact. If you touch a pot on the stove, this is conductive heat transfer.
convective Convective: Steam, moisture. If you put your hand above a boiling pot, you will feel heat in the form of steam. This is convective heat transfer.
Radiant: Electromagnetic. Step outside on a sunny day and feel the sun’s rays on your face. You are feeling radiant heat transfer. All objects above absolute zero (-459.7 degrees F.) emit infrared rays in a straight line in all directions.
A radiant barrier reflects radiant heat energy instead of trying to absorb it. What does this mean in your home or business? During the winter, 50-75% of heat loss through the ceiling/roofing system and 65-80% of heat loss through walls is radiant. In the summer, up to 93% of heat gain is radiant. If you are depending on R-value (resistance) alone to insulate against heat gain and loss, remember that thin layers of fiberglass are virtually transparent to radiant energy and are affected by changes in humidity (moisture levels). A 1-1/2% change in the moisture content of fiberglass insulation will result in a 36% decrease in performance (referenced from HVAC Manual 10.6; McGraw-Hill).
A pure aluminumized film radiant barrier is unaffected by humidity and will continue to perform at a consistent level no matter how humid it may be.