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US natural insulation comparison
This page describes natural insulation from recycled paper (Cellulose) to wool and cotton batts among other types which we define as containing less than 10% petrolium products (oils, resins, and plastics). We'll compare the differences, advantages, and disadvantages of each type. Our goal is to provide a comprehensive overview of natural in home insulation products that are free of formaldehyde and other toxic chemicals.
You're either starting your building from scratch and have a choice of insulation to use, or the desire to increase an already standing building while not increasing the amount of harmful VOCs coming from some traditional insulation. A natural insulator might be the an appealing option. Either way if you're considering your next type of insulation the Handbook of Sustainable Building will offer a range of preferred insulation materials. Starting with cork and cellulose (recycled newspaper), secondary options were listed as mineral wool and expanded polystyrene. Ending with a warning about polyurethane for health and environmental factors.
Why go natural/sustainable?
Here on Earth we have cyclical systems (which means there is truly no such thing as "waste"). Logically, we should avoid the use of harmful chemicals because they eventually end up in our bodies. There are a variety of options other than fiberglass or rockwool that can be installed in the walls of our homes providing a lower cancer risk and less lung irritation. Many types of natural insulation even have the added benefit of trapping energy which could be released through combustion  (though recycling is best whenever possible). Installing insulation can easily be done at home a How-To book, although contractors will gladly charge you $0.50 - $2.50 per square foot. 
Why use insulation? With out insulation your house would have no protection from the elements. Insulation can both keep heat out, when the outside temperature is higher than desired inside. As well as keeping heat in, when the outside temperature is lower than desired.
Reduced VOCs from phenol-formaldehyde, a binding agent used in traditional insulation.
To conserve our earths limited resources.
Recyclable at end of use.
Capture carbon instead of releasing it.
How it is made
These can be made from recycled blue jean material, thus their common name is Blue Jean insulation. With about 90% of recycled materials these cotton batts are very low in energy use, although recycling does require energy. For more information visit the cotton insulation page here.
The sheep are sheared and their wool is spun mechanically into batts that can be laid between. For more information visit the Wool insulation page here.
Made primarily of recycled newspaper with boric acid and ammonium sulfate. For more information visit the wool insulation page here.
The impacts of different types of insulation will be reviewed here. Impacts of materials will consider fuel consumption, water and/or land use to gauge sustainability and possible impacts.
Energy use of wool
Sheep are capable of living in many climates and are very versatile. With the simple requirement of grass and land sheep can be raised. If management is done correctly overgrazing will not occur, and waste will not adversely effect water bodies.
Energy use of cotton
Growing cotton is normally done in a warm climate, requiring sizable amounts of water to produce about 1.3 bale of cotton per acre.Although cotton is very land efficient, producing 36% of the world’s textile on only 2.5% of arable land. 
Energy use of hemp
Enough hemp to produce one house can be grown in just 14 weeks in one hectare of land. Although this value isn't for insulation, an alternative building material is Hemcrete which has a R-value of 5.2 not needing additional insulation in some areas. 
All impacts could be greatly reduced if building materials were reused, recycled, or otherwise not made from virgin materials. Also fuel consumption would greatly decrease if a locally available insulation is used.
For quick reference this chart will be useful.
|Material||Cost ($)||R-value (m2·K/W)/inch||Impacts||Embedded Energy||Advantages||Disadvantages|
|Cotton (Batts)||$12.50/m2||3.7||As a result of its recycled content, this product uses minimal energy to manufacture.||Natural Batts are easy to install because they come in strips ranging from 12 - 24 inches. Unlike fiberglass these batts aren't irritants.||May need topping off because of repeated moisture capture and release.|
|Cotton (Loose fill)||$8.50/m3||3.7||As a result of its recycled content, this product uses minimal energy to manufacture||Loose fill is easy to install because it can be blown into hard to reach attic spaces, or in finished and unfinished walls. (D.I.Y)||Any loose fill insulation has the risk of settling, resulting in a diminished R-value and may need topping off in one year.|
|Wool (Batts)||$12.5/m2||3.5 ||If properly managed sheep are a low impact way to raise wool. Although sheep are commonly 'dipped' in herbicides and anti fungal baths, occasionally accumulating arsenic, a toxin. ||[Medium]||Wool will self extinguish, will not melt, and is flame retardent.||In order to achieve proper insulation small spaces will not be sufficient because ample space is needed.|
|Wool (Loose fill)||3.5||If properly managed sheep are a low impact way to raise wool. Although sheep are commonly 'dipped' in herbicides and anti fungal baths, occasionally accumulating arsenic, a toxin.||[Medium]||Loose fill is easy to install in a wide range of applications.||In order to achieve proper insulation small spaces will not be sufficient because ample space is needed.|
|Cellulose (Loose fill)||$3.7/m3||3.0 - 3.7||As a result of its recycled content, this product uses minimal energy to manufacture. But the transportation of the newspaper before its use in insulation could be a considerable amount of fuel use.||[Low]||Loose fill is easy to install in a wide range of applications.||The major disadvantage of cellulose is that it absorbs more water than fiberglass or mineral wool.|
|Hemp||$7.75/m2||2.5-2.6||Majority is shipped from other countries.||[Unknown]||Helps naturally control humidity.||Often grown with the use of pesticides. Relatively untested.|
- Embedded/embodied energy:
These figures are determined using typical amounts of fuel for transportation and processing.
Cellulose – 46 MJ [Low]
Sheeps wool – 100 MJ [Medium]
Polyurethane – 424 MJ [High] 
- Handbook of Sustainable Building (Pg.25)
- S.V Joshi, L.T Drzal, A.K Mohanty, S Arora, Are natural fiber composites environmentally superior to glass fiber reinforced composites?, Composites Part A: Applied Science and Manufacturing, Volume 35, Issue 3, AIChE 2002, March 2004, Pages 371-376, ISSN 1359-835X, DOI: 10.1016/j.compositesa.2003.09.016.fckLR(http://www.sciencedirect.com/science/article/B6TWN-4B22XGW-2/2/1b44b7030199f4e8a08b090a81829327)fckLR
- Green Building & Remodeling. Hoboken, NJ: Wiley Publishing, 2008. 229-30. Print
By: Stuart Jones & Erin Haugen