Research on the Thermal Conductivity of Korean and US Cellulose Insulation

Cellulose insulation was introduced into Korea in the 1980s when several small companies started production. The cellulose industry in Korea is still in an early stage of development with current production of about 1000 tons a year. The Korean equipment used to produce cellulose insulation was imported from the United States and installed by U.S. technicians. A typical cellulose manufacturing plant includes facilities for storing and moving large quantities of waste paper, chopping and shredding, milling or fiberizing, adding chemicals, and packaging. For broader use of cellulose insulation in buildings in Korea, it is necessary to establish its thermal performance. To this end, the effect of density and temperature on the thermal conductivity of loose-fill cellulose insulation manufactured in Korea and U.S. was reported. The apparent thermal conductivity of a particular type of spray-applied cellulose insulation was also determined and compared with previously published data. Apparent thermal conductivity (ka) measurements of Korean-made loose-fill cellulose insulations were completed using equipment that was built and operated in accordance with ASTM C 518. Korean loose-fill cellulose has thermal conductivity about 5% greater than the corresponding U.S. product at the same density. This is likely due to differences in the recycled material being used. Both spray-applied and loose-fill cellulose insulation lose about 1.5% of their thermal resistivity for 5.5°C increase in temperature. Introduction Cellulose insulation for use in building applications is primarily manufactured from recycled newsprint or cardboard using shredders and fiberizers. Cellulose insulation as a product is about 80 wt.% cellulosic fiber and 20 wt.% chemicals, most of which are fire retardants such as boric acid and ammonium sulfate[1]. Cellulose insulation was introduced into Korea in the 1980s when several small companies started production. The cellulose industry in Korea is in an early stage of development with current production of about 1000 tons a year[2]. Its current market share as building insulation is only about 0.3%. Organic insulations such as polystyrene foam board and polyurethane foam represent about 71% of the total Korean insulation market, and inorganic insulations such as fiberglass and rock wool make up about 29%[3]. On the other hand, in North America, cellulose insulation has been used since the 1940s and many studies have been done to improve its physical properties and performance. About 750,000 tons of paper has been recycled as cellulose insulation annually early 2000s in the U.S. That would imply a production volume of about 940,000 tons of cellulose insulation per year. The market share for cellulose insulation in residential buildings is 8-10 % and it claims 20-25% in the commercial spray-insulation market[4]. Cellulose insulation in the U.S. generally conforms to one of three ASTM Standard Specifications. ASTM C 739[5] is the Standard Specification for loose-fill cellulose insulation commonly used in attics or similar horizontal applications. ASTM C 1497[6] is the Standard Specification for stabilized cellulose generally intended for horizontal applications. Stabilized cellulose is made by adding an adhesive to loose-fill insulation to reduce post-installation settling. Self-supported sprayapplied cellulose insulation described in the ASTM C 1149[7] is commonly used in commercial