[l2ridehd]

This is just my opinion and how I would tackle this issue.

If you look at the cost of a radiant barrier vs the cost of insulation, the cost to hire someone to install it if you choose not to do it yourself, there is no comparison. Insulation wins every time. And extra insulation helps with summer cooling and winter heating. And insulation savings beat a Radiant Barrier by a huge margin. So take the attic insulation over the entire home including the garage to a minimum of R-34 or even to R-40 before spending anything on a Radiant Barrier. The cost is usually lower and the payback is always much faster. If your insulation is already at that level and you want to save a little more, insulate the garage door. Very easy to DIY. Next step is to use a smoke pencil and seal every crack, outlet and switch cover, door and window. Eliminate every leak possible. Even with that done your air will still change 3 times a day in the home. After doing all of this, and you still need to save a few pennies at the cost of $$$, consider a Radiant Barrier.