Packing Peanuts Attic Insulation

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

Packing peanuts attic insulation.

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. I m not sure when they switched to the new kind but it wasn t more than five years ago or so. Good insulation works by trapping air. 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.

Another problem is that newer environmentally friendly cornstarch peanuts dissolve when wet. The r value of polystyrene is about 4 0 per inch. I m not convinced that it s effective or even safe. New packing peanuts are made from a type of corn starch.

The very reason why plastic peanuts work well as packing makes them a bad choice for wall insulation. The problem comes from the large interstitual spaces between the pieces. Most packing peanuts are made of polystyrene. In a wall cavity they would offer little resistance to air movement so they would be of limited r value.

The older kind might work okay. If they get wet they ll dissolve and they re made to be highly biodegradable so they ll break down pretty quickly anyway.