There has been an energy savings product on the market for quite some time called radiant barrier. The main concept behind this product is that it is put up in your attic rafters. In the summer, it reflects the warm air out, and in the winter, it helps keep the warm air in. It has been an adequate product for many years.
However, there has been a newer product emerge called reflective insulation. This newer product often has some type of energy efficient interlayer sandwiched between the reflective surfaces.
Through much research, I found a reflective insulation product that has a polyethelene interlayer. The great thing about this type of interlayer is it doesn't attract or hold moisture. It also is core perforated. Having the product 'cored' instead of simply 'perfed' is an advantage because the holes can never be sealed up by dust and dirt. The advantage here is you don't have to worry about moisture being trapped.
Finally, if you are looking at radiant barriers or reflective insulations, make sure you find a product that works for your specific use. Many times with inexpensive radiant barriers or reflective insulation, you get one product that is supposed to be used in all parts of the house. It is more or less a 'one size fits all' mentality and not very customized for your home.
It is best to look for a reflective insulation product that has a family of products. Using this philosophy, you will find a product that is designed specifically for the use your home requires. It will also make your home more energy efficient.