Packing Peanuts Attic Insulation

Good insulation works by trapping air.

Packing peanuts attic insulation.

The older kind might work okay. Plastic peanuts hold air that helps cushion whatever is being shipped. I m not convinced that it s effective or even safe. Air with very small temperature gradients will start to float through the peanut pack and transfer heat from the warm surface to colder zones with little resistance.

Another problem is that newer environmentally friendly cornstarch peanuts dissolve when wet. We found millions of packing peanuts loose in the attic presumably intended to function as insulation. In a wall cavity they would offer little resistance to air movement so they would be of limited r value. The problem comes from the large interstitual spaces between the pieces.

Osborn a former associate editor replies. The r value of polystyrene is about 4 0 per inch. Most packing peanuts are made of polystyrene. The very reason why plastic peanuts work well as packing makes them a bad choice for wall insulation.

If they get wet they ll dissolve and they re made to be highly biodegradable so they ll break down pretty quickly anyway. But the problem with using packing peanuts for attic insulation is that while the individual peanuts may have an r value of about 4 0 per inch the peanuts have large air spaces between them which allows air currents to easily flow through a layer of packing peanuts.