Okay, so the uses and advantages of radiant barriers over existing insulation have been exaggerated by many. When people go around claiming that radiant barriers save close to 40% of your energy which is completely untrue. Now one does see a significant 10-20% energy saving from radiant barriers, but a radiant barrier isn't for everyone. Here are a few reasons why radiant barriers work:-
Number one, if you're living in a place that experiences a hot climate, you'd want to install a radiant barrier and it will work. The second reason is if you're living in an area of high humidity. The reason high humidity is mentioned is because of the use of foam spray and a radiant barrier between rafters is very common. Now there's a drawback to foam barriers as one needs to remove all the existing insulation from the house to install the current foam barrier. This doesn't need to be done in place of a radiant barrier. Instead of getting rid of the old insulation, it works with the existing products to accomplish one thing, to keep your attic cool.
Another thing is that a radiant barrier would be great if you have a one-story home, larger the roof the more energy it saves. If you have a one-story home it's a great idea to consider a radiant barrier as part of your heat management system. The last reason to get a radiant barrier is if it's installed correctly, proper installation of radiant barriers requires an airspace gap.
Also, there's an actual R-value associated with radiant barriers. To know more about under roof insulation blanket just search the internet.