Is it a good idea to install a radiant barrier to save energy in a home?

There is nothing new about this, has been around for a very long time. IF you are trying to keep a house cool, then you are better off with an attic fan that has a thermostatic on/off switch, set to about 85 degrees. IF you are trying to save heat in the winter, better to spend the money on insulaltion (insulation will also keep the house much cooler if in conjunction with the attic fan). You do not want to reflect heat back out of the attic (once through those shingles, reflected heat back onto them will greatly shorten their expected life!...they are getting pelted from both sides!). The time to install a radiant barrier is when the house is being built...Aluminum sheeting is used as a vapor barrier, and acts as a reflector for heat Inside back to the inside, and outside, back to the outside...usually installed before insulation is put in attic. IN northern states with cold climates, this is used in walls also. I would NOT install as an after fit! Good luck, Goldwing