___A i I - - -■':" "-'- i.:-t: aiiqn for protection acai:'. : V., INSHCTS, RODENTS, AIID FIRE Forest Products Laboratory,— A Forest Service U. S. Department of Agriculture OSITORY Dry cavdusi or planer shavings properly packed in the rails and attics of LI i : s afford excellent he vt insulation. They have Ion*- been used for the urpose, although apparently not very extensively. The Forest Products Lab- oratory is frequently asked by prospective users of such insulation to suggest methods of treatment to prevent its being used as a nesting place for rats, nice, and insects, or to increase its resistance to decay, mold, or fire. As far as knorn, no test results have been published to supply the ansrers to the questions about rodents and insects, but a few experiments on the effective- ness of fire -retarding chemicals in sawdust have been reported.fi From a consideration of the character of the insulation and of the habits of mice., rats, and insects, it seems improbable that a wall packed v.ith either sawdust or planer shavings would prove more attractive than hollow Trails to any of •' :-. e pests , but it is known that they rill nest in insulated walls if other conditions are favorable. Although termites could build their run- ways through insulated vralls and use the sardust and shavings for food if they so desired, they probably prefer solid wood, '."he presence of the insulation in the vralls should be of no advantage to them. Similarly, it does not seem probable that sardust or shavings in a wall would offer any attraction to bed- bugs, cockroaches, silver fish, ants, or other household insects or provide r more favorable conditions for then than are provided by holler: vails. For these reasons it is believed that sardust or planer shavings need no treatment for protection against insects and vermin. If the rails of a building remain damp for any con rider able period of time, they may decay; and if they remain dry, they i ill not decay, rhether or not they are filled rath sardust. Condensation may develop in vralls during cold weather; and the more efficient the insulation, the more likely condensation is to occur. Lost building mate- rials, such as plaster, rood, brick, and concrete, arc permeable to vapor. Condensation takes place vrhen outside temperatures are below the dew point of the inside atmosphere .and the moisture, passing as vapor through the plaster and insulation, reaches some surface that is below the dew point. The same principles of vapor movement apply to attics and roof spaces. 1 -Llaintained at Madison, "■ is., in cooperation rath the University of Fisconsin, 2 """ lecreasing the Combustibility of Sawdust," by Joseph L, McCarthy. Indus. & Eng. Chen., Vol.32, p.lh. 1 - I , Nov. 15 UO. Rept. No. R1092 (revised) -1- September ±9h9 Conditions favorable for condensation are likely to be present v-hen humidi- ties are 30 percent or higher inside of the houses during periods when out- door temperatures are 15>° F. or lover. Attics and roof spaces can usually be protected against condensation by ample ventilation. Protection against condensation in side walls is obtained by increasing the resistance of inner vrall 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 constructed, suitable paint 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 sise, calcimine, and cold-rater paints offer practically no protection. For further details on the subject, see the publication, "Condensation Problems in Modern Buildings," which may be obtained from the Forest Products Laboratory upon request. If a vrall containing sawdust or shaving insulation became thoroughly damp, it would take such a long time Tor it to dry out that considerable trouble might result. The insulation should, of course, be throughly dry when placed in the walls j the walls should be dry, and the construction should be such that they will remain dry. If this can be accomplished, no disad- vantage from the standpoint of decay should result from the use of untreated sawdust or planer-shaving insulation, A vrall properly filled with sawdust or planer shavings is more resistant to flame spread up through the vrall space than a similar hollow wall, for the insulation prevents drafts and thus retards the spread of flames, A smoulder- ing fire in a sawdust-filled wall might be difficult to get at and to put out, but the very slow rate of burning should more than offset this disadvantage allowing plenty of time for extinguishing it. If one side is burned away from a sawdust-filled vrall, loose sawdust will, of course, run out. For the foregoing reasons, treatment of the insulating material does not seem very important, Nevertheless, it is possible by suitable treatment to in- crease the resistance of planer shavings and sawdust to fire, decay, and insects. The following treatments are suggested for the benefit of those ••■ho may be rilling to bear the expense and inconvenience of treatment for the additional insurance of satisfactory performance that treatment will provide. It is not known that these treatments will have any effect on rats. and mice, but they include chemicals known to be highly effective Inst decay, insects, and fire. Treatment A For Pro te ction \ r a ln; .t iiold , ,7, and Ins ects I Lx thoroughly with each 100 pounds of air-dry sawdust or planer shavings, by sprinkling and stirring, a hot-water solution (approximately 1$ gallons) Rept. Ho. R1092 (revised) -2- containing 3 pounds of sodium fluoride and £ pounds of borax. A clean con- crete mixer could be used if available. Sodium fluoride is a fine y-hite powder that is poisonous to hum an and animal life. Car e should be taken to avoid brea thing or swa llow ing the d ust. Since sodium fluoride nay resemble sugar, trblo sal t, or baking soda so closely that it may be mistaken for them , it is be st not t o have .a i r/ left over af'te r the treating job is done . After the chemical is mixed rdth the wood particles, the mixture should be dried very thoroughly before being put into the walls of a building. Treatment 3 For Prote cti on Against Flame Spread Mix with each 100 pounds of air-dry sawdust or planer shavings, in the same manner as for treatment A, a solution containing $ pounds of monoammonium phosphate -and $ pounds of borax in about 1$ gallons of water. If, from the standpoint of cost or availability of materials, it is desired to substitute another chemical for monoarnmonium phosphate, diammonium phosphate, ammonium sulphate, or boric acid may be used. Monoammonium phosphate is preferred to the others, horever, because it is less hygroscopic than either diammonium phosphate or ammonium sulphate and, therefore, is less likely to lead to moisture -condensation problems, and because it is a better fire-retardant than ammonium sulphate or boric acid. Fire-retarding chemicals of high hygroscopicity, such as zinc chloride and calcium chloride, are not recom- mended because they may cause undue dampness in the wall cavities. After the insulation has been treated, it should be dried thoroughly before being used. Treatment C For Protection Agni nst Flame Spread ho ld. D e cay, and Insect s Fix with each 100 pounds of air-dry sawdust or planer shavings, in the same manner as for treatment A, a solution containing 5 pounds of .monoammonium phosphate, £ pounds of borax, and 3 pounds of sodium fluoride. After the insulation has been treated it should be dried thoroughly before 1 eing used. Kept. No. R10g2 (revised) T r et Treatment Preferable UNIVERSITY OF FLORIDA 3 1262 08927 9128 For treating insulation vdth the formulas given under treatments A, B, and C, the chemicals can be mixed in the dry form if circumstances are such that the solution method cannot be used. The treatment by solution is preferable, however j oecaiise it insures a permanent, even distribution of the chemical, vft ereas vith the dry treatment, there is a tendency for the. fine chemical to sift through the coarser sawdust or shavings • No specific information as to cost can be given, for labor and chemical costs vary ridely vdth tine and place. Both transportation charges and quantity purchased have an important bearing on the cost of the chemicals. Attention is called to USDA Farmers Bulletin No. 1635, "Rat Proofing Build- ings and Premises," and to Conservation Bulletin Uo, 8, "Pat Control," which can be obtained for 5^ each from the Superintendent of Documents, Government Printing Office, Washington 2^, D. C. (stamps or personal checks not accepted). Rept. T Io, R1092 (revised) -h-