The treatment of sawdust insulation for protection against decay, insects, animals and fire


Material Information

The treatment of sawdust insulation for protection against decay, insects, animals and fire
Series Title:
Report ;
Physical Description:
4 p. : ; 27 cm.
United States -- Forest Service
Forest Products Laboratory (U.S.)
University of Wisconsin
U.S. Dept. of Agriculture, Forest Service, Forest Products Laboratory
Place of Publication:
Madison, Wis
Publication Date:


Subjects / Keywords:
Insulation (Heat)   ( lcsh )
Wood waste -- Protection   ( lcsh )
federal government publication   ( marcgt )
non-fiction   ( marcgt )


General Note:
Cover title.
General Note:
At head of title: Memorandum.
General Note:
"January 1944."
General Note:
"In cooperation with the University of Wisconsin."

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 029608123
oclc - 757825622
System ID:

Full Text

January 1944


No. I1092

I(( F .-, ^ ;.*

Madison, Wisconsin
In Cooperation with the University of Wisconsin




Dry ssardust or planer shavinCs proi-erly yaclked in the woall aIn.d attics of
buildings afford, excellent heat insulation. They have long been use-. for
the purpose although apparently not vert extensively. The Forest Products
Laboratory is frequently asked by prospective users of such insulation to
si:--'est methods of treatment to prevent it being used as a nesting -nice for
rats, mice, Pnd insects, or to increase its resistance to decoy or fire. So
far as known, no experiments have been published to sup-nly the ....'.-. e to the
questions about rodents and insects but a few experiments on t!he effective-
ness of fire-retarding chemicals in sawdust have been reported-!-.

"r-om a consideration of the character of the insulation and the habits of
mice, rats, and insects, it seems improbable that a wall packed "ritP, either
sawdust or planer shavin- s would prove more attractive than hollow walls to
any of these pests, but it is known that they rill nest in insulatc-! w;alls
if other conditions are favorable. Although termites could build their
runways through insulated walls and use the sawdust and shavin.,s 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 providedd
by hollow walls. For these reasons it is believed that sawcust or ,laner
shavings need no treatment for protection a.-ninst insects and verm,. If
t'-e walls of a. uildinL, remain damp for any considerable period of t.i:e they
,,.y decay and if they remain dry they will not doc-ir, whether or not they are
filled with saw'ust.

Thi-s memor',--u2, i7 not for publication, It .as. been rre-nrfA in orc'er
to anqs,-er the numerous requests of corresron.4ent7 for information
about the subjects discussed. It is subject to revision from t.ine
to time as ne', information is ot-inE<.
-"Decreasin the Coibustibility of Sawdust." by Joseph L. 'cCarth,
I-c. and En -. Chem. Vol. 32, p. I)94-96, ( 1.ov. !9O).



Condensation may develop in walls during cold weather and the more efficient
the insulation the more likely condensation is to occur. Most building
materials, such as plaster, wood, brick, and concrete, are permeable to
vapor. Condensation takes place when outside temperatures are below the
dewpoint of the inside atmosphere and the moisture passing as vapor through
the plaster and insulation reaches some surface that is below the dewpoint.
The same principles of v:-ror movement apply to unventilated attics. The
relative humidity in a house of normal occupancy and without air condition-
ing will avera.-e about 20 percent when the outside temperature is zero. The
dewpoint for 70 F. and 20 percent humidity is 28L F., and laborAtory tests
on insulated walls show that the inside face of the sheathing will be con-
siderably below 20g during periods of zero weather and possibly even with
temperatures as high as 150 above. Conditions are then favorable for con-
densation. Obviously, the higher the inside humidity the higher the dewpoint
temperature, and the greater the amount of water that will condense in the
wall in cold weather.

Attics can usually be protected a.-airst condensation by ample ventilation.
Protection against condensation in side walls is obtained by increasing the
resistance of inner wall surfaces to vapor transmission. For new houses,
the use of asphalt-coated sheathing paper applied over the inside face of
the studs before plastering is recommended. For buildings already con-
structed, suitable raint coatings on the plaster or interior finish should
give ample protection for most cases. Aluminum paint followed by other
finishing paints gives excellent protection over plaster. Primer and sealer
paints also make good base coats. Glue size, kalsomine, and cold water
paints offer practically no protection. For further details on the subject,
see the publication "Condensation Problemrs in modernn Buildings," which may
be obtained from the Forest Products Laboratory upon request.

If a wall containing sawdust or shaving insulation became thoroughly damp
it would take a long time for it to dry out, anl considerable trouble might
result. The insulation should, of course=, be thoroughly dry when place in
the walls, the walls should be dry and thy construction should be such that
they will remain dry. If this can be accomplished no disadvantage from the
standpoint of decay should result from the use of untreated sawdust or
planer shaving insulation.

A wall properly filled with sawdust or planer shavings is more resistant to
flame spread up through the wall space than a similar hollow wall, for the
insulation prevents drafts and thus retards the spread of flames. A
smouldering fire in a sawdust-fillid wall might be difficult to get at and
extinguish but this disadvantage should be more than offset by the very slow
rate of burning which should allow plenty of time for extinguishing. If one
side is burned away from a sawdust-filled wall, of course, loose sawdust
will run out.

For the foregoing reasons given, treatment of the insulatiri- material does
not seem very important. Nevertheless, it is possible by suitable treatment
to increase the resi-,ance of planer shavings and sawdust to fire, decay,
and insects. The following treatments are suggested for the benefit of


thc'r who .a be wil l 1inc- to undergo ,he expense and incoenience o treat-
ment n or tIe addIticnal insurance of sati"factoryeoa that treatment,
rsa o'oranc tho noreatmenth--e tt
w111 provide. 't i3 not known that hee tretments will have an. efect on
ratsv a' mice, "bt 1-,he include chem-icals known to b> hihl:y effective ,.G.a.t..
decay, in" c tus, and fire.

:Yre:atzment A

For Decay, and Ins-octs
'o e, rounds

To ea ...,i rounds of air-dry sawdust or planer sha,.:ins add d pounds of
sodium The addition may be :, made by spreadinry the sawvdust on a
floor, ..prcadinr te sodium fluoride over it, and then mixing 'he t'vro to-
,etl'jr by repeated shoveling and stirring. A concrete mixer could be sed
if availa le, Sodium fluoride is a fin-e ,.:hie orderr that is po isoious to
h-in ..:i..c animal life. Care should he t... to avoid breathing or swallowving
tLe du st. Since sod-ium fluroide resenibles sogcar, tabl salt, and 1- .'.. .
......t .t n,{ay b)e mistakenn for thenr, it s I es-- nct 'o0 e:ava a-ny left
o .':er a'tor ho trea';i n jot is done. Damienin-r the sar-.rdust :bh wate-r before
sJr-adtn 'luor de on s': should a'vo1d. dustin : troi :les. A still better
m' ho( o0 a r1liati0on !.: to dissolve the sodium. fluoride in 12 to Ir -alions
of hot r'.iar and mix the waterr vith the swcvdust.

After the che-ical is mixed ,:ith the 'rood, the mixture should bo dried very
t orou -:hy before putting it into the walls of a building.

iTreatment B!

For Fireproofing

'oh 0 ounclzd o dr01 s&r-dust mi:. thorou.hlyv (by sprinkling and stirring )
"",, .! ~~~~~~~ t- nd' poundso r .. ~' m' .
a"'. ."',er soul .on contaminT- 3 prlounds of no.noamonium phosphate a 5 pounds
o cr: (yo 1r to 1 *allons of vra;.r should be su"fIVKt). If insect
a nd lee resl st .ance are desired as well as firepuroofing, bohn Tr.-a.,,.,_nt A
a,'. Tre.....ent I- can bo ,hsame time, dissolvin- a!l the- che-mcals

S.... ''raion as to cost can be given for labor and chemicals
cc ;:: v-"': -del, KIn different localities. Both tr-ansortatioa cdirces and
7.., .r.-'a ',ae ha've an important bearing on -he cost of the chemic'is.
-orre. 2'e 'jlotation: in tra"Ide journals (Juily i.)'W) for considerable
'Y; w, Cre 1 : follows: sodium lon -ideC, cents per pound, mo'oammonium
ho::h'e, to .-1/2 cents pc- pound; borax, 3 to 4 cents :er pound. Retail
r '<., vhj, wou'I include ,hi :in.' co:ts mihht b e considerably 3, '. *r.

S ecial Treatment Agninst Rats

The folloin' is quoted from a memorandum from the Fish an. 'i!l'.1'c service
(formerly -.uro'u of Biological Survey):

"It is found that rats are prone to nest in -i'e
v,'lls filled i-ith sawdust or wood shvi'ri', -ovie1, o-" c-C
the nearby environment is other.'ie famorable. It s-es reot!.
been learned that it may be possible to prevent thi isturo'wce
to sawdust to a considerable extent b:' b'lenAinf ,it'- it + 0o -r
co' carbonate, using 12 )oun-s in each 100-pounc" rixt'-re.
"This ",re:-oration may be mixnd -:yith treatment A he- it
is either wet or dry. It may mix more unif-r l-:, ho,'"Rvc"r,
folloi,,n- the drying -'rocess."

Attention is called to Farmers' Bulletin 163S, "tRat Proofinm' ili" :: .-
Premises," a'xe Conservation Bulletin S, "Rat Control," Tich cd'r e ct'ined
for 5 cents each from the Suoerintcnde7t of Document -"overn."'eet F .ritinr3
Office, '.ashington, D, C. (stamr.: not accented).

Date Due

R! .12


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