Topic Free Electricity - Does it Really Exist?
If you DO have it in the attic, then consider the staple-up Smart Energy Box Review method. When you think about it, putting it in the attic is like making ice cream in the oven. Not really smart. By stapling the foil to the bottom of the rafters you will get the benefit of reducing radiant heat gain into the attic insulation AND reducing the attic temperature. By reducing the attic temperature, less heat will be transferred INTO the duct work by conductive heat flow. Plus, it's very cool to walk into your attic on hot Summer day and it feel tolerable compared to being inside of an oven.
Either install method works well. In colder climates, laying across the attic insulation is the way to go. In warm/hot climates it's a decision of what's easiest verses what is best. Putting the foil over existing insulation is usually the easiest and works great. Stapling to the bottom of the roof rafters will create a cooler attic, put the air flowing through your ducts in a less hostile environment AND reduce radiant heat gain into the home. For this reason, the staple-up method results in the least overall heat gain into the home. Both installation methods will make your home more comfortable and save you money on your utility bills.
It's something that anyone who pays bills will want to know, how to reduce home energy bills. Those costs seem to rise up and at the worse times. But with very simple ways you will be able to cut those bills down a lot.