MEMORANDUM 
THE TREATMENT OF SAWDUST INSULATION FOR PROTECTION AGAINST 
DECAY, INSECTS, ANIMALS, AND FIRE* 
NOT FOR PUBLICATION 
Dry sawdust or planer shavings oroperly packed in the walls and 
attics of "buildings afford excellent heat insulation. They have long 
been used for the purpose although apparently not very extensively. 
The Forest Products Laboratory is frequently asked by prospective users 
of such insulation to suggest methods of treatment to prevent it being 
used as a nesting place for rats, mice, and insects, or to increase its 
resistance to decay or fire. So far as known, no experiments have been 
published to supply the answers to the questions about rodents and in- 
sects but a few experiments on the effectiveness of fire-retarding 
chemicals in sawdust have been reported—. 
From a consideration of the character of the insulation and the 
habits of mice, rats, and insects, it seems improbable that a wall 
packed with either sawdust or planer shavings would prove more attrac- 
tive than hollow walls to any of these pests, but it is known that 
they will nest in insulated walls if other conditions are favorable. 
Although termites could build their runways through insulated walls 
and use the sawdust and shavings for food if they so desired, they 
probably prefer solid wood. The presence of the insulation in the 
walls should be of no advantage to them. Similarly it does not seem 
probable that sawdust or shavings in a wall would offer any attraction 
to bedbugs, cockroaches, silver fish, ants, or other household insects 
or provide any more favorable conditions for them than are provided 
by hollow walls. For these reasons it is believed that sawdust or 
planer shavings need no treatment for protection against insects and 
vermin. If the walls of a building remain damp for any considerable 
period of time they may decay and if they remain dry they will not 
decay, whether or not they are filled with sawdust. 
-This memorandum is not for publication. It has been prepared in order 
to answer the numerous requests of correspondents for information 
about the subjects discussed. It is subject to revision from time 
P to time as new information is obtained. 
-"Decreasing the Combustibility of Sawdust," by Joseph L. McCarthy, 
Ind. and Eng. Chem. , Vol. 32, p. 1U9U-96, (Nov. I9U0). 
R1092 
