Report No. PA-96-1
TABLE OF CONTENTS
EXECUTIVE SUMMARY.............................................................................................................
i INTRODUCTION..........................................................................................................................
1.0...
CELLULOSE INSULATION...............................................................................................
1.1.. CELLULOSE USE IN CONSTRUCTION.....................................................................
1.2.. MASTIC CELLULOSE...................................................................................................
1.3.. PRODUCTION OF CELLULOSE INSULATION.........................................................
1.4.. ALTERNATIVE FIBER SOURCES................................................................................
2.0...
THE ALTERNATIVE CELLULOSE INSULATION PROJECT......................................
2.1.. FEEDSTOCKS................................................................................................................
2.2.. FEEDSTOCK PREPARATION......................................................................................
2.3.. PRODUCT TESTING.....................................................................................................
3.0...
THERMAL PERFORMANCE..........................................................................................
3.1.. THERMAL TESTING...................................................................................................
3.2.. TEST MATERIAL PREPARATION.............................................................................
3.3.. THERMAL TEST RESULTS.........................................................................................
4.0...
COST ISSUES.....................................................................................................................
5.0...
RECOMMENDATIONS...................................................................................................
5.1.. BETTER COLLECTION METHODOLOGY AT THE
PLANT....................................
5.2.. EFFECTIVE DRYING PROCESS................................................................................
5.3.. PROCESSING..............................................................................................................
5.4.. MIXING/QUANTITIES................................................................................................
5.5.. MANUFACTURED HOMES........................................................................................
6.0...
CONCLUSION....................................................................................................................
7.0...
ACKNOWLEDGMENTS...................................................................................................
8.0...
REFERENCES....................................................................................................................
25 APPENDIX A:............................................................................................................................
A-
The feedstock for the manufacture of cellulose insulation has experienced significant increases in cost and supply volatility during the past several years. This volatility has led to an interest in alternative cellulose feedstocks for the manufacture of cellulose insulation. Several materials have been experimented with or examined. This project primarily concentrated on the evaluation of paper mill screenings, a by-product of paper and paper production, as a feedstock for cellulose insulation manufacture. Paper mill screenings vary considerably in consistency, and must be sorted, processed, and dried before they can be used as a cellulose insulation feedstock. This project evaluated the feasibility of sourcing and drying the screening material and incorporating it into a manufacturing process for an acceptable cellulose insulation product. Despite difficulties in drying the material, enough cellulose feedstock was produced to test the thermal and flame-resistance characteristics of an alternative cellulose insulation product made from recycled paper mill screenings. Various grades of cellulose screenings were tested by an independent laboratory to determine their thermal performance relative to standard cellulose insulation. These tests indicated K-values for the cellulose screenings from 2.5 to 3.6, compared to a K-value to 3.8 for standard cellulose insulation. Furthermore, the product appears to perform similarly to typical cellulose insulation from the standpoint of flame spread resistance. The variation in these thermal tests is primarily the result of variations in moisture content, amount of sorting and processing conducted, and the time and location of collection at the mill. The results of this project suggest that effective methods for drying, sorting, producing, and installing the alternative cellulose insulation product can be developed economically with existing technologies. although effective drying and processing techniques were developed on a small scale for this project, these must be expanded considerably if development is to continue. The extent of drying and processing required could be reduced significantly by careful targeting of feedstock collection toward higher grades of paper mill waste. Beginning in the Fall of 1995, an evaluation was undertaken into the potential for the incorporation of alternative cellulose feedstock materials into the manufacture of cellulose insulation. This evaluation was motivated primarily by substantial increases in the cost of typical cellulose insulation feedstock: recycled newsprint. The cost of this material has fluctuated widely in the past several years, sometimes rising more than 300%. Although a number of sources of alternative cellulose feedstock were considered, the evaluation became focused primarily on paper mill waste, known as screenings. This material is routinely discarded or burned as hog fuel by paper mills, yet shows characteristics which suggest it might be appropriate as a component feedstock in the manufacture of cellulose insulation. The goals of the project were to collect alternative cellulose materials, then dry and utilize this material to make an appropriate insulation product. This product was then installed in typical building construction cavities using industry-standard installation practices to evaluate material consistency. Finally, test samples were evaluated by an independent test lab to determine the thermal performance of the alternative cellulose insulation product. 1. Cellulose INSULATION1.1 CeLLULOSE USE IN CONSTRUCTIONCellulose insulation accounted for approximately 5% of the two to three billion dollar annual residential insulation market in 1992. Although this is a relatively small percentage of the market, its popularity appears to be growing. In the northwest region, cellulose insulation is installed in approximately 6,000 site-built homes and 9,000 manufactured homes each year. In a very rough calculation, this represents about 22 million cubic feet, or more than 16,000 tons of cellulose insulation installed each year. Under current market conditions, the cost of insulating with loose-fill cellulose is competitive when compared to the cost of insulating with fiberglass. Various builders tend to prefer one or the other material; however, the market eventually responds to price fluctuations of insulation materials. Because of this, the relative cost of different insulation materials tends to remain at stable and related levels as different manufacturers try to remain competitive in this market, and some of the very large insulation manufacturers (particularly of rock-wool and fiberglass) are able to exert considerable price influence on the insulation market. Traditionally, cellulose insulation has been installed by blowing the loose cellulose directly into attics to a predetermined depth. Loose fill cellulose is typically installed dry, or it is slightly dampened at the time of installation (to reduce dust and improve loft). Loose fill insulation can also be used to retrofit existing walls by blowing the insulation into existing wall cavities. Because the insulation has no structure, it cannot be installed in open wall cavities. 1.2 Mastic CelluloseThe use of mastic cellulose insulation originated as an acoustical treatment on exposed walls, but eventually became valued for its thermal, as well as sound, insulating qualities. In recent years, improvements in the installation technique have greatly expanded the variety of applications for which cellulose insulation can be used, especially in new construction. The technique incorporates a mastic or glue into the cellulose at the time of installation. The mastic acts as a binder to prevent settling of the insulation (which has an adverse effect on insulation performance) and reduces the potential for subsequent damage to the insulation. More significantly, adding the mastic to the insulation allows the cellulose to adhere directly to vertical surfaces such as unfinished wall cavities. Mastic cellulose is installed by feeding dry cellulose stock into a large hopper. At the base of the hopper, an agitator moves the cellulose into an air stream fed by an air compressor. The compressor drives the material through a long hose to a nozzle, where the insulation material is mixed with a spray of water and mastic supplied by another hose. The air supply blows this mix into the building cavity, where the insulation adheres to the sides of the cavity or to the insulation already in place. The mixture of cellulose, air pressure, glue and moisture must be adjusted to account for the moisture content of the cellulose, glue consistency, desired density, and thickness of the installed insulation. In addition to the actual mixture, the configuration of the application nozzle affects the characteristics of the insulation product. The insulation is blown into a wall cavity between wall studs and over any installed plumbing and electrical wiring to completely fill the cavity. After the insulation has dried somewhat, the excess is scraped off flush with the stud face by using a rotary brush (called a scrubber). Excess insulation material can be reused by placing the material back in the hopper, reducing the generation of any waste product. Because widespread application of mastic insulation is relatively new, there is still a great deal of variation and experimentation with proper mixtures, installation techniques, and nozzle configuration. All of these variables allow for a great deal of flexibility in the installation process. 1.3 Production of Cellulose InsulationCellulose insulation has typically been made from recycled old newsprint (ONP), primarily collected from consumers. The newsprint is ground in a hammermill or similar grinding device, and boric acid or sodium borate is added to the material to provide fire resistance. The production process is relatively benign environmentally, and requires only a fraction of the energy required to produce fiberglass insulation. (These savings are somewhat offset by increased shipping costs.) Although the production process for cellulose insulation lends itself to smaller-scale regional production, the industry underwent substantial centralization in the 1970s and 1980s, as the number of cellulose insulation manufacturers dropped from over 700 to about 65. The cost of cellulose insulation is affected by the cost and availability of ONP feedstock, which can vary across different regions. During the last five years, the cost of ONP has increased significantly as it has become a replacement for virgin pulp in the production of new newsprint. ONP supplies, which were once inexpensive and readily available to cellulose insulation manufacturers, are now often expensive and difficult to obtain. In some areas, the cost of ONP rose 300% to 500% in 1994 alone. In this region, ONP prices had climbed to over $180 per ton for short periods in 1994 and 1995. Currently, prices have dropped to near $60 per ton, but remain volatile. 1.4 alternative fiber sourcesCost increases and supply volatility have led to an interest in alternative fiber sources for the manufacture of cellulose insulation. One alternative which has been used as a supplement by some manufacturers is recycled old cardboard (OCC). This material has been used to replace up to 70% of the ONP previously used for cellulose insulation by some manufacturers. Other material such as office paper waste and mixed paper have also been experimented with, meeting limited success. However, the price of all of these recycled stocks has risen along with the cost of ONP. Another response to increased demand for limited fiber sources has been an increased interest in fiberization. As old newsprint is recycled, the fiber length of the material degrades with each use. It is estimated that newsprint can be recycled as newsprint approximately twelve times before the fibers are too short to be useful. Various technologies have been developed which can extend this life by improving the characteristics of the cellulose by combining or sorting the fibers, stabilizing the newsprint. This process is called fiberization. Cellulose feedstock which has outlived its usefulness as a paper stock can be fiberized to produce an insulation feedstock with greater loft, improving its thermal performance as an insulation material. There are a number of different fiberization technologies in use or under development. It is estimated that fiberization adds up to 30% to the cost of producing cellulose insulation. This cost is partially offset by increased coverage of the subsequent insulation material. Many of the available fiberization processes are capital intensive, and do not lend themselves to use in small plants. However, the technology represents a method of extending the useful life of recycled cellulose, and also a potential method to incorporate lower grades of cellulose fibers into existing manufacturing processes. 2. THE Alternative CELLULOSE INSULATION PROJECTThe goal of this project was to evaluate the feasibility of incorporating cellulose feedstocks recycled from construction debris and paper mill screenings into the manufacture of cellulose insulation. After identifying these cellulose sources, a good deal of time and effort was spent experimenting with processes to modify the consistency of the feedstock so that it could be installed in typical construction applications using standard installation techniques. During the course of this evaluation, the flame spread characteristics of the cellulose material was tested and compared to industry standards. A number of the more promising alternative cellulose insulation products were tested for thermal performance in order to evaluate their relative merits as an insulation product. During the course of this project, cost and process issues were identified and evaluated. 2.1 feedstocks2.1.1 Construction DebrisWood construction debris was obtained from a project under construction in Eastern Washington. The project was developed with strict environmental guidelines, and the owner was interested in recycling construction waste and generally reducing the landfill impact of the project. The owner purchased a tub grinder to deal with construction waste on site. The tub grinder was used to grind wood construction debris successively into smaller and smaller pieces until the final grind of 1/4-inch minus was obtained. The consistency of this material was similar to landscape bark mulch, with chunks of material up to 1/4-inch wide by 1/4-inch to 1/2-inch long in a matrix of smaller wood particles. Although this material could be mixed with cellulose insulation product and installed using the mastic cellulose installation process, the consistency of the construction debris material was far from ideal. When this product was installed as a component of mastic cellulose insulation, the result was an insulation material with higher densities and lower expected performance than typical cellulose insulation. Furthermore, the material required significant handling in order to grind, and only approximately 5% to 10% of the cellulose insulation could be replaced with the construction debris before significant impacts to the installation process were encountered. This suggests that while there might be some advantage to locating construction debris in wall cavities rather than landfills, from a practical standpoint the material tends to degrade rather than enhance insulation performance. 2.1.2 Paper Mill Screenings“Paper mill screenings” is a general term applied to cellulose waste from paper production which actually comes from several sources within the mill itself. As wood chips or other cellulose sources are processed by the mills, some of the feedstock is culled from the production process. The consistency of these screenings varies considerably, depending upon the stage of production. Traditionally, these different types of screenings are collected and disposed together, regardless of their characteristics or the stage in the process which generates them. At many mills, the screenings are burned as hog fuel. A single mill located in Port Townsend, WA estimates that it generates 30 tons of paper mill screenings as waste each week. This mill, Port Townsend Paper, was interested in the potential use of their cellulose waste as something other than hog fuel. The mill agreed to set aside an area for the collection of screenings for pick-up and use in this project. Throughout the project, the mill gathered screenings from throughout the mill, representing material from different stages in the manufacturing process. When these screenings were collected, their consistency was found to vary considerably. One of the collection points occurred where the feedstock fibers are aligned for paper production. A percentage of the feedstock fiber does not align with the rest of the material and must be removed from the process. The removed material tends to have longer fiber lengths and retains the characteristics necessary for use in insulation. At another stage in paper production, material which does not retain enough fiber length to be used in paper production is collected. This material is essentially sludge, and seems virtually worthless as an insulation feedstock. Between these collection points are a number of others which generate cellulose with varying fiber, moisture, and composition characteristics. Unfortunately, the mill did not discriminate in its collection process, and all of the different screening types were mixed together for use in this project. One particularly problematic aspect of the collected material was the presence of “clinkers”; small hardened chunks of the screening material which are periodically scraped off of a stack in the production line and end up as part of the general screening stock. After finding several batches of screenings contaminated in this manner, collection was timed to occur before the stack cleaning generates clinkers. Although the mill was able to target certain types of screening stock for use by this project over time, they did not necessarily have the time or resources to sort out the different types of paper mill screenings most appropriate for use as an insulation feedstock. A good deal more effort would be required in order to identify and collect the most appropriate feedstock material from the mill. By working more closely with the mill operation, these screenings could be identified and separated from the production process in order to improve the collected stock for a recycled cellulose insulation product. 2.2 FEEDSTOCK PREPARATIONDue to the slurry nature of paper production, most of the collected screenings had a very high moisture content. Moisture contents as high as 60% were common in the batches collected from the mill. Since cellulose insulation is installed at 5% to 15% moisture content, the screenings had to be dried before they could be used as an insulation product. This turned out to be a much more significant problem than was anticipated at the inception of this project. 2.2.1 Passive DryingOriginally we had anticipated that the screenings could be air dried at shop facilities and outdoor areas in Wenatchee, WA. Unfortunately, the project was not initiated until after the end of the warm season, so outdoor facilities could not be used. Even indoor facilities were problematic as humidity rose in the wet season. Other drying process problems were also soon encountered. As the screenings were dried on the concrete floor of a heated shop, they required constant turning to expose wet surfaces. By this passive method, the screenings dried into a chunky substance which was difficult to use in the insulation installing equipment, and resulted in a less than ideal insulation product. To resolve this, a number of firms with different drying technologies were approached to try to find an alternative drying method. 2.2.2 Active DryingA number of firms involved in the drying of various agricultural products for production use were contacted. These firms were given samples of paper mill screenings and asked to evaluate the feasibility of their drying process on these materials. Several firms in the Midwest indicated a willingness to dry the material, however most of the prices we were quoted (up to $800/ton of dried material) were well above what could reasonably be afforded for an insulation product. With shipping added, these costs became quite prohibitive. A firm in Milton-Freewater, Oregon experimented with tumble drying equipment for the screenings. The result of this experiment was a baked mass rather than a soft fibrous insulation material. Eventually, two drying technologies allowed the project to move forward. The first was the identification of a firm in New York state which had developed an effective method for drying paper mill screenings. This firm was just getting started, and operated only seasonally. Although they agreed to provide us with samples of their dried screenings, they were very hesitant to discuss their drying process itself. The factory was also hampered by a spate of bad weather which shut down their operation for several months in early 1996. The factory sells the dried screenings for $10/ton, well below the market rate for ground newsprint cellulose. However, this price may not reflect the actual production cost of the material, because the drying plant also collects tipping fees from the mills that produce the screenings as waste in the first place, thus subsidizing the drying process. The operators of the factory were unwilling to provide many details about the economics of their production process, making our evaluation of the cost of the material difficult. After about three months of delay, the NY mill sent a sample of their dried screening product for experimentation. This product seemed appropriate for use in cellulose insulation, and Western Fibers has been experimenting with its incorporation into insulation products. Unfortunately, the material produced by this firm does not seem to have a reliable consistency from one batch to the next, apparently due to the fact that they are drying material from a variety of different sources. Currently, the dried material is primarily marketed as animal bedding. As we continued to express interest in their drying process, the firm became less willing to discuss its drying process due to concerns about the loss of proprietary information without compensation. Eventually we decided that we would concentrate on local suppliers of cellulose material, rather than shipping the waste product from the other side of the country to demonstrate a local recycling technology. Concurrent with these discussions with the New York plant, Mike McGuire of Western Green Construction developed a method of drying small batches of the paper mill screenings. Mike used a propane fired blower/heater to blow the screenings through a length of duct with an interior grid. The grid breaks up and fluffs the screenings as they are carried in the warm air stream. Although development of the process was both time consuming and small scale, Mike was able to dry a quantity of the screenings sufficient for installation and thermal testing of the cellulose product. 2.3 PRODUCT testing2.3.1 InstallationAlthough drying the screenings to an ideal consistency proved problematic, the installation process turned out to have a great deal of flexibility. Using the mastic cellulose installation process, virtually every cellulose product we examined could be blown into a wall cavity. Even the ground up construction debris could be combined with other cellulose stock and installed in a wall cavity. However, the initial density and moisture content of the feedstock had a significant impact on the characteristics of the installed insulation product. The installation process turned up a significant challenge to the use of alternative cellulose as an insulation product. Many of the combinations of cellulose feedstock ended up significantly more dense than ideal once installed. The expectation was that this would adversely impact the thermal performance of these samples. The higher installed density is caused in part by the moisture retention characteristics of the alternative cellulose feedstock, and partly by the density of the cellulose screenings themselves. Also troubling in the use of the screenings is the fact that the moisture they contain at the time of installation seems to be retained for a much longer time period than typical cellulose insulation. Typically, cellulose insulation can be blown damp to improve application and reduce settling. Mastic cellulose is blown damp to distribute the mastic evenly in the insulation. Within a few days of installation, cellulose insulation tends to dry out into its more permanent state. With the screenings however, the moisture is retained for a much longer period. Apparently, despite extensive efforts at drying, the screenings still retained higher levels of moisture at the time of installation. This poses a problem both for the thermal testing, since moisture reduces thermal performance, and for the wider prospects of using the material in actual construction applications. Once again the drying issue arose as the critical factor in the use of paper mill screenings. Installation testing using the dried screenings from New York was also undertaken. This material worked well as a mastic cellulose feedstock with little or no additional processing. This suggests the feasibility of using screenings as a feedstock is good, once the drying issue is resolved. 2.3.2 Flame Spread TestingFire resistance in cellulose insulation is accomplished by the addition of a fire retardant consisting primarily of boric acid or sodium borate. These substances are commonly available and have relatively little impact on human health. They also provide the additional advantage of discouraging termite and ant infestations. Each cellulose manufacturer seems to have their own recipe for a fire retardant additive, and this information is not commonly shared. Nevertheless, there does not seem to be wide variation on the fire resistance characteristics of cellulose from different manufacturers. Resistance to combustion in cellulose insulation is measured by two standard tests; the critical radiant flux test (ASTM-C-739-86), and the smolder test (ASTM E-84) . These test results are compared with the Underwriters Laboratory (UL) rating required for cellulose insulation to be installed in buildings. On an experimental basis, these tests can be replicated to determine the relative flame-resistant performance of various test samples of cellulose insulation. However, in order to qualify for a UL listing, specific tests of insulation must be conducted in conjunction with a specific manufacturing process and location. For this project, flame resistances of experimental cellulose insulation products were tested using the critical radiant flux test protocol. In this test, a sample of the insulation product is placed in a calibrated heated test chamber. Heat is applied to the sample by a sloping plate at 450°F. Because the plate is sloping, the heat applied to the sample diminishes along the length of the sample. The sample is ignited at the hot end and allowed to burn. The extra heat applied by the panel accelerates the flame near the hot end, but as the flame moves away, the resistance of the material to flame increases, and the flame is extinguished. The burn distance is measured, and compared to the accepted standard for cellulose. Because the testing device is calibrated, the burn distance can be converted directly into critical radiant flux (CRF); the amount of radiant heat necessary to support surface flame spread. Cellulose insulation must have a CRF of 0.12 w/cm2 or higher. The tested samples indicated CRF ratings of 0.16 or higher. Installed samples of paper mill screening cellulose were subjected to the smolder test (ASTM E-84) at various densities and combinations with other cellulose feedstocks. Significant variations in flammability from standard cellulose insulation were not observed in any of the flame spread tests. This leads to the conclusion that the use of alternative cellulose feedstocks in insulation manufacture would not adversely affect the flammability of cellulose insulation. 3. Thermal PerformanceThe thermal performance of building insulation is evaluated by comparing the resistance of the material to heat transfer across the insulation. This value is expressed as a K-value in resistance to heat flow per inch of material, or as an R-value expressing the resistance of a given thickness. For example, typical fiberglass insulation batts for installation in a 2x6 wall have an R-value of 19. The higher the R-value of an insulation, the more the insulation will resist heat transfer, reducing heating energy loss through the building envelope. Thermal performance of insulation is affected by a number of factors, including thickness, material density, the presence of air spaces within the material, and moisture content. In general, the thicker the material, the higher the R-value, or resistance to heat flow of the material. In wall construction, the possible thickness of the insulation material is limited by the thickness of the wall. However, there can be significant variation in other insulation characteristics within the same wall thickness. Although less widely evaluated, different insulation types can also affect the rate at which air passes through the building envelope (infiltration). “Tight” construction allows air movement to be controlled, and potentially reduces heating bills. “Loose” construction results in uncontrolled drafts through the building envelope, increasing heating loads and causing drafts. Fiberglass and loose-fill cellulose insulation tend to leave gaps for air movement through wall and ceiling cavities. Mastic cellulose insulation can be very effective at sealing potential gaps to reduce air movement. For practical purposes, the performance of a given thickness of cellulose is controlled by the density of the installed insulation. The ideal installed density for loose fill cellulose insulation ranges from about 2 lbs/ft3 to 3 lbs/ft3, depending on manufacturer and insulation characteristics. Mastic insulation tends to install at higher densities of 3 to 5 lbs/ft3, due to the added moisture and mastic used for installation. Moisture content at the time of installation will affect installed density, with material which is high in moisture going in at relatively high densities. Cellulose insulation which is installed too densely will not perform as well, because the cellulose itself conducts heat more readily than the air which is entrapped in the matrix. On the other hand, cellulose which is not installed with enough density will also not perform as well, because the material tends to settle, reducing its coverage or thickness (not a problem with mastic cellulose) and because at lower densities there is a greater possibility for air movement within the insulation, which increases the heat loss rate of the material. 3.1 Thermal TestingInsulation is typically tested using an ASTM C236 test, known as a steady-state thermal performance of building assemblies, by means of a guarded hot box test method. The test is conducted by constructing a sample wall panel containing the insulation material to be tested. This test panel is placed in a hot box test chamber, which maintains a specified temperature on one side of the wall and measures changes in temperature over time on the other side of the wall. By this method, the rate of heat transfer through the test panel can be determined. From the results, the heat loss rate anticipated for the stud framing members and the sheathing can be calculated and the K-value derived. 3.2 Test Material PreparationFor this project, the test panels were constructed with 2x4 stud framing in a 4 ft. by 6 ft. wall panel, then filled with the experimental insulation product. Each test panel was constructed with interior studs to replicate the construction of a framed wall. The first thermal test was conducted on a panel containing 100% paper mill screenings. The second test was conducted on a panel containing 50% paper mill screenings and 50% Wallkote IIâ, an insulation material made from recycled old cardboard (OCC). In both cases, the screenings were blown into the test panel using the mastic cellulose installation equipment. The panels were allowed to dry for about a week prior to thermal testing. After the completion of the thermal tests, the panels were dismantled and the density of the insulation was measured. The results of the tests (see Appendix A) were evaluated, and converted into standard K-values to determine the relative performance of the insulation product compared to other insulation materials currently available. The K-value is obtained by calculating the contribution for the cellulose to the overall thermal resistance of the tested sample using a parallel heat flow evaluation as follows: The calculation is based on the overall thermal resistance of the section excluding interior and exterior surface resistance (R or Rpanel). From this value, the thermal resistance of the sheathing (Rsheathing) is subtracted, leaving only the thermal resistance of the cellulose and the wood studs in the R-value being considered (call this Rfill). Based on the construction of the panel, the percentage of the cross-section composed of wood studs is calculated compared to the percentage of panel composed of cellulose insulation. (The wood occupies 18% of the cross-sectional area in the test panels.) Since the thermal resistance of the wood studs at the tested thickness is known (Rstuds), the thermal resistance of the cellulose (Rcellulose) can be calculated. These steps are described by the following formula: Rcellulose = [[(Rfill)
- (% wood studs) x (Rstuds)] / (% cellulose)] - (Rsheathing) The resulting value, Rcellulose, represents the thermal resistance of the full 3.5-inch thickness of the cellulose insulation. The K-value is obtained by dividing this value by the thickness of the cellulose insulation to find the thermal resistance of the material per inch of thickness. 3.3 thermal Test ResultsAlthough not terribly out of line with typical insulation thermal performance values, the first two thermal tests were somewhat disappointing. The thermal performance indicated by the testing for these panels suggests a lower performance than would be expected from typical cellulose insulation. The tested screening samples also failed to perform as well as a comparable thickness of fiberglass, even though typical cellulose outperforms fiberglass in an inch per inch comparison. When the panels were dismantled, it was found that the installed densities of the cellulose in these panels was much higher than ideal. This was assumed to be the primary cause of the poor performance of these test panels. The high density of these test panels seemed to be the result of two factors: 1. Despite repeated attempts to dry the material with a variety of experimental methods, the screenings material still contained more moisture at installation than was ideal. In addition to increasing the density of the installation, the moisture was also likely to adversely affect the thermal performance by its presence alone. 2. The fiber characteristics of the screenings themselves varied greatly. The results from these two tests led to a re-evaluation of the approach for the use of paper mill screenings. In particular, despite extensive efforts to dry and sort the material, the performance was still not up to par. This suggested that some additional processing was needed to improve the consistency of the screenings and allow for a lower installation density. Mike McGuire set out to develop a fiberization apparatus to improve the loft of the screenings. He developed a process to clean, fluff, and sort the material. The process he developed was time consuming, and only produced a small amount of material at a time. Nevertheless, the results of the process were interesting and informative. The process consisted of a series of grinding and filtration devices which both fluffed the material and sorted the screenings by fiber length through a series of filters. Mr. McGuire estimates that at the conclusion of processing, he had sorted out and discarded 30% of its weight in the form of dirt and ash. At the same time, the volume of useable material had increased by about 15%. This suggests that the raw screenings include a substantial amount of contamination, and that processing can remove this contamination and improve fiber quality at the same time. After processing a quantity of the material, a third test panel was constructed and filled with 50% processed screenings and 50% Wallkote IIâ. Thermal testing of the third test panel yielded thermal performance results much more in line with the expected performance of cellulose insulation. At the conclusion of testing, the installed density of the material in the third test panel was found to be more consistent with typical densities for cellulose insulation. Table 1 below shows the thermal performance of the tested insulation products and the densities of the insulation product. For comparison, standard cellulose and fiberglass insulation performance and densities are also shown. Table 1: Thermal Performance of
Tested Insulation
4. Cost IssuesDespite various setbacks in the processing of paper mill screenings into cellulose insulation during the course of this project, the third thermal test results suggest that the use of paper mill screenings in the manufacture of cellulose insulation is a viable option, and that a more careful review of the economic considerations is in order. Standard cellulose insulation in this region costs an installer approximately $400 to $500/ton for the insulation product, including shipping. Breaking this number down is somewhat challenging because many of the costs to the manufacturer are considered trade secrets and are not readily available. The critical costs for this discussion are the cost of the feedstock and the cost of processing. Processing costs are a closely guarded trade secret. Our best estimates suggest that material processing runs in the neighborhood of $100 per ton of material. This represents approximately 20% to 25% of the cost of the finished insulation product. Raw material acquisition costs have proven to be quite volatile in the last few years, but currently are about $60 per ton. The feedstock cost therefore represents 15% of the manufactured cost of cellulose insulation. Neither of these figures include markups. By comparison, Port Townsend Paper has suggested that if the material becomes useful, they might expect to charge about $10/ton for the screenings feedstock. (Under current conditions, it is estimated to cost the mill about $40/ton to handle and dispose of the material as compost or hog fuel.) This represents a decrease of 85% in the cost of the feedstock (at current prices), but only an 11% decrease in the total cost of finished and installed cellulose product. If we assume that paper mill screenings would require the same amount of processing as current feedstocks, we can evaluate the cost of the feedstock alone. A reduction in traditional feedstock cost to $50 or less does not leave much room for any additional processing costs which might be associated with paper mill waste. On the other hand, traditional ONP feedstock cost has been volatile, as much as three times its current cost within the past year. As the costs and volatility of traditional feedstocks increase, the cost of paper mill waste becomes much more attractive. These costs are illustrated in Table 2. Table 2: Comparison
of Estimated Costs of Cellulose Insulation Production Using Standard
and Alternative Cellulose Feedstock.
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