Hemp wool vs Sheep wool insulation | Everything you need to know

Hemp wool and sheep wool are considered to be the “greenest” or most sustainable insulation materials. In this video, we’re going to look at how they are made, their main differences as well as their pros and cons.

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0:00 Introduction
0:17 Hempwool manufacturing
1:50 Sheep wool manufacturing
3:09 R value comparison
3:30 Cost
3:46 Dimensional stability
5:03 Van conversions
5:41 Installation
6:23 Workability
6:56 Noise Reduction Coefficient
7:17 Water repellency
8:39 Fire retardant test
9:50 Environmental impact
11:33 Conclusion

The outer layer of the hemp stalk is called bast fiber which has been used for centuries to make ropes, clothing, canvas and sails and now Hemp wool insulation batts. Let’s look at how sheep wool insulation is made. This pendulum swings back and forth to make multiple wool layers. The layers are bonded with a mechanically driven needle punch which stitches them together.

Hemp wool is sold by the pallet in various depths and widths. A 2” deep batt has an R value of 7 while a 7.5” deep batt is R28. The R value of sheep wool is exactly the same as hemp wool. A 2” deep batt is R7 and a 5.5” batt is R20. The 5.5” batts will fit in a standard 2×6 stud bay for an exterior wall. 5.5” thick Hemp wool costs $1.95 per sqft while the same sheep wool costs $2.25 per sqft.

Just like most insulating products, hemp and sheep wool operate on the insulating property of trapped air between the hemp and wool fibers. As you can tell, hemp is much stiffer, denser and heavier. It bounces back to its original shape after being compressed. Sheep wool on the other hand is very floppy, malleable, soft, lightweight. But the unique thing about wool is that you’re not only relying on trapped air for insulation, but the wool fibers themselves are good insulators. Each fiber is composed of protein molecules or keratin organized into five follicles.

Hemp wool friction fits into stud bays on walls and ceilings without any additional fasteners. Sheep wool has to be stapled to walls and fastened with a wire mesh or cables to the ceiling. Hemp is very tough and cannot be easily cut with an xacto knife. You have to use a table saw or a miter saw to get a clean cut. Sheep wool fibers are also surprisingly strong. You need to use a pair of sharp scissors or a proper insulation cutter.

Now, for the water repellency test. Hemp absorbed some water, allowed it to pass through to the other side and changed color when wet but it also dried up fairly quickly. It did not lose shape or disintegrate. Sheep wool is very similar to hemp in this aspect. When I poured water over the sample, it did absorb it but did not disintegrate. Sheep wool can also naturally absorb moisture while staying dry and retaining its high insulative properties.

Hemp wool is supposed to be a Class A fire retardant but it caught on fire very easily and released a lot of acrid smoke and fumes. On the other hand, sheep wool performed pretty well when lit. The flame didn’t spread even though it turned black and singed.

They are very environmentally friendly. The hemp plant requires very little water to grow and process, about a quarter of the water needed for cotton. Hemp wool contains no VOCs or volatile organic compounds. Sheep wool is also very eco-friendly. Wool insulation contains the least embodied energy of any insulation available, half that of cellulose and one-sixth that of mineral wool.

They are both excellent eco-friendly alternatives to traditional insulation but they need to be refined. For example, it would be great to use hemp wool as a fire-retardant continuous exterior insulation. Sheep wool either needs to have better dimensional stability or we just use it as loose fill insulation.
Rohit Sharma
Obelisk Farm
Havelock Wool
UK College of Agriculture, Food and Environment
RanchTV and Texas A&M
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Smith The Mister
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  1. My hope is that enough people in the coming decades will embrace the mindset that cost isn’t the most important thing to be able to really invest in these sort of technologies and lifestyles. Societies across the world are obsessed with economic metrics, like GDP, but largely ignore other, arguably more important metrics for human life, such as happiness and sustainability. America, for example, excels in the GDP metric, but is really low on metaphysical metrics, like quality of life. Does it really matter if your GDP outperforms that of other countries if your entire system has a shorter shelf-life? 200yrs from now, our descendants aren’t going to look back and be like, “Wow, they had a high GDP.” They’re going to view us through the same lens that we view our ancestors through: a more integrative analysis that transcends muh money.

  2. you know, ma'am. you are better than my college instructor. YOU EXPLAINED IT WELL, and I binge watch all of your videos. I am very sorry to discover you this late. THANK YOU VERY MUCH FOR SHARING YOUR KNOWLEDGE!! KEEP IT UP!! <3

  3. Organic wool may be fine in northern US and Europe, but in southern climates there are serious dampness and insect problems. Also, one feels better with inflammable insulation material.

  4. I do enjoy your commentary your direct to the point and noninvasive I appreciate the you look at pro and cons of products not who made it well done thank you for continuing to share

  5. Amazing content, it must be the fifth or sixth video I watch from your channel today and I am amazed at all the hard work and excellent content. I subscribed and I look forward to many more ! Thank you Belinda!

  6. My friend had a home insulated in hemp wool and unfortunately his home caught on fire. The firefighters got there pretty quickly but the house still burned down to the ground. He has video footage of this event and you can see all the firefighters trying to control the flames but they all appeared to be laughing and even at one point they all took a snack break and that's when the house ended up going down. They all just stood around and one of them said "Wow! Cool! Then they all laughed and went home.

    So I wouldn't recommend Hemp Wool

  7. Ms. Carr, I have a home recording studio in a 15×18 bedroom . I need acoustic sound absorption panels and plan to build them myself. I Learned from your videos the hazards of rock wool and fiberglass and therefore I prefer to use a material like hemp or wool( Havelock). Do have feedback on what the sound absorptions values would be on these materials in a 4 inch thickness? I plane to build about 8 or more panels. I appreciate your videos! Thanks

  8. Thanks for this valuable information. Hemp insulation has been something I have been very interested in but have not had, until this point, the question of fire proofing covered. I think for hemp insulation to be adopted mainstream it would have to have some fire retardant product applied/ incorporated.

  9. Question: We need to insulate our bedroom ceiling. There is no attic in the bedrooms. What would be a safe insulation we can place between the exposed beams? Love your videos by the way.

  10. Most pet owners wouldn't even notice the extra hairs around the house from sheep wool. Interesting video Belinda, I like that you bring an effort on objectivity when considering pros and cons of the materials you review, and also that you consider their possible use cases.

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