Natural wool insulation is a form of insulation often used in construction for the purpose of maintaining temperature and or increasing the energy efficiency of a building. "Thermal insulation is any material that is added to a building assembly for the purpose of slowing the conduction of heat through that assembly." Although natural wool insulation is primarily used for thermal purposes, it can also function to dampen or preserve acoustics. Natural wool serves as a sustainable source of insulation because it's efficient, non-flammable, non-toxic, renewable, recyclable, and prevents condensation and mold.
This page describes natural wool insulationW, as shown in fig. 1, as a potential component of United States of America home construction. There are several types of wool insulation available, this page will specifically address natural wool insulation which is made of sheep wool fibers.
Reasons for product[edit | edit source]
Nearly one-third of the energy consumed in the United States is from residential heating, cooling, and lighting. Through the use of insulation an increase in a building's energy efficiency can be achieved,which cuts down on energy costs and overall consumption. Natural wool insulation offers an alternative to conventional insulation products available in the market such as fiberglass, mineral (rock or slag) wool, cellulose, and foam. Aside from requiring a great deal of energy in its production, possessing a relatively quick rate of deterioration, and creating a toxic material difficult to dispose of, fiberglass wool has long been thought to have negative effects on human health. "Glass wool (respirable size) is reasonably anticipated to be a human carcinogen based on sufficient evidence of carcinogenicity in experimental animals." Natural wool insulation can have less of an environmental impact, depending upon the process in which it is made. Natural wool insulation requires less energy in its production and lasts longer than conventional man-made insulation products[verification needed]. Additionally, organically produced natural wool is non-toxic and threatens neither human nor environmental health regarding use and disposal. Natural wool insulation is comparable to conventional insulation in regards to efficiency and is often produced at a lower cost. Sheep's wool is naturally flame retardant, wool only chars when exposed to fire (similar to human hair). If a fire occurs in a home with natural wool insulation, the insulation itself will not ignite. Additionally, natural wool is breathable and absorbent allowing the insulation to retain its thermal properties under both dry and wet conditions. The ability for wool to absorb and breath adds to its durability as a product and is less likely to breakdown overtime unlike synthetic insulation materials which degrade more quickly [verification needed]. Lastly, natural wool insulation's capacity to breath reduces the chance for issues pertaining to mold due to moisture. this means the sheep is moist.
How it's made[edit | edit source]
Natural wool insulation can be made using one hundred percent wool fiberW, sheared off of sheep, which is mechanically woven and shaped in rolls, batts, or ropes. Each form has specific applications; the rolls and batts are used between studs inside wall cavities or laid down between rafters in the attic. Ropes can be used between logs in a cabin. Also available is unbonded fibers which can be used as loose fill and blown into cavities. Depending on the thickness and density, a variety of R-values are available.
The R-value of a material refers to its resistance. "Resistance (R) is the reciprocal of the thermal conductivity." The equation for resistance is as follows:
where htc= thermal conductivity
Refer to both Fig 2a and 2b for Department of Energy recommendations of R-value levels for insulation in regions of the United States.
Impacts[edit | edit source]
The potential environmental impacts resulting from the production of natural wool insulation is often dependent upon the practices employed by the rancher in rearing the flock. Wool from sheep raised on a pasture based system with on site forage production that excludes the use of fertilizers and herbicides will have much less embedded energy associated with it. This is due to less energy used in the importation of feed and exportation of waste. Lower methane emissions can also be expected and overall soil fertility of the land is increased. Wool from sheep reared without sustainable practices would have associated with it the problems of high energy requirements, harmful waste emissions, and watershed deterioration from overgrazing. Additionally, wool is often treated both before and after it is harvested. In a process called 'dipping', sheep are submerged in a liquid containing a pesticide and a fungicide(See Figure 4). Though the chemicals can be removed from the wool after it is harvested, the wastes associated with this process have been found to contaminate soil and groundwater. Finally, there are few producers offering natural wool products, therefore it is possible that the materials will be required to travel great distances when distributed.
Fig 4. Sheep dipping process. (Photo from Gooreen Collection)
Product and/or DIY instructions[edit | edit source]
There are several types of wool insulation products available for construction as outlined in Table 1 (below). Not all products can be used for the same purpose, and depending on the product type and resistance (R-value) prices may vary per square foot. In comparison to conventional insulation such as fiber glass, which is often used in building construction, natural wool insulation is slightly higher in cost per square foot, but contains significantly less chemicals and poses less risk to the installer.
|Table 1. Wool Insulation Product Types and Uses|
|Product Types||Product Description||Common Uses||Ideal Project Use|
|Loose Fill||loose sheep wool fibers, that are either poured or blown into an attic or cavity||attics or vertical cavities i.e. wall frames||remodel or retrofit project|
|Batting||semi-rigid blocks of wool material varying in width||loft, rafters, internal wall, and inter-floor||new and existing wood frame buildings|
|Roll||wool material similar to batt, but not rigid, formed into a roll to cut desired lengths||loft, rafters, internal wall, and inter-floor||new and existing wood frame buildings|
|Rope||wool material formed into ropes to insulate between logs in a log cabin structure||notches and laterals in log cabins||new and existing cabins|
Advantages and disadvantages[edit | edit source]
Advantages of natural wool insulation:
- Low energy input
- Absorbs VOCs
Disadvantages of natural wool insulation:
- Few producers
- Maybe treated with pesticides, fungicides, and flame retardants
- Poor ranching practices
[edit | edit source]
See also[edit | edit source]
References[edit | edit source]
- Woolpic. Photograph. File:Woolpic.gif. Wikimedia Commons, 25 May 2008. Web. 24 Sept. 2010. <https://commons.wikimedia.org/wiki/File:Woolpic.gif>.
- Allen, Edward, and Joseph Iano. Fundamentals of Building Construction: Materials and Methods. Hoboken, NJ: J. Wiley & Sons, 2004. Print.
- Davis, Mackenzie Leo, and Susan J. Masten. Principles of Environmental Engineering and Science. Boston: McGraw-Hill Higher Education, 2009. Print.
- IARC. 1988. Man-made Fibers and Radon. IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Humans, vol. 43. Lyon, France: International Agency for Research on Cancer. 300 pp.
- Ludwig, Krickl. Insulating Element for Building. Patent 5,246,760. 21 Sept. 1993. Print.
- "Energy Savers Tips: Insulation." EERE: EERE Server Maintenance. Web. 23 Sept. 2010. <http://www1.eere.energy.gov/consumer/tips/insulation.html>.
- Hale, Margo, and Linda Coffey. Sheep: Sustainable and Organic Production. NCAT: ATTRA, 2010. Print.
- "Managing old sheep dip and footbath sites: a guideline for landowners" (PDF). January 2003. http://web.archive.org/web/20150128222927/http://ecan.govt.nz/publications/Reports/sheepdip.pdf. Retrieved 2010-05-22
- Sheep Dipping. 1950. Photograph. Gooreen Collection. File:Sheep Dipping.jpg. Wikimedia Commons, 10 Feb. 2008. Web. 24 Sept. 2010. <http://commons.wikimedia.org/wiki/File:Sheep dipping.jpg>.
- Simmons, H. Leslie. Olin's Construction: Principles, Materials, and Methods. Hoboken: J. Wiley & Sons, 2007. Print.