Packing Peanuts Attic Insulation

Plastic peanuts hold air that helps cushion whatever is being shipped.

Packing peanuts attic insulation.

Good insulation works by trapping air. Most packing peanuts are made of polystyrene. 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. The r value of polystyrene is about 4 0 per inch.

We found millions of packing peanuts loose in the attic presumably intended to function as insulation. I m not sure when they switched to the new kind but it wasn t more than five years ago or so. New packing peanuts are made from a type of corn starch. The problem comes from the large interstitual spaces between the pieces.

The older kind might work okay. Osborn a former associate editor replies. The very reason why plastic peanuts work well as packing makes them a bad choice for wall insulation. In a wall cavity they would offer little resistance to air movement so they would be of limited r value.

Another problem is that newer environmentally friendly cornstarch peanuts dissolve when wet. 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.