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Sheep Wool Insulation - let's talk about it

 
R Ranson
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The act of using wool for insulation has been around for millennia. From yurt walls to palace tapestries, this has proven to be one of the most enduring traditions. It is fire retardant and can be made more so with some simple tricks. Wool is especially useful because it's portable. When properly cared for, wool goods can last for centuries.

That's not to say that wool is perfect, nor is it appropriate for every situation. It has it's draw backs - for example, it can start to degrade after exposure to 4,000 hours of direct sunlight. It is hydroscopic - meaning it absorbs water and holds water. It can absorb up to 30% it's dry weight in moisture before beginning to feel damp. As Jay White Cloud points out in This thread about converting a bus to a home it doesn't make it the most desirable insulation where condensation is likely. What's more, there is always the fear of the dreaded Mothra! ACHOO and ITCHY, some people are allergic to wool.

Moths and allergies may not be as big a problem as they first seem. There are simple ways to avoid moths, ones that don't use nasty chemicals. As for allergies, very few of the people who experience allergic reactions to wool are actually responding to the wool. Most commercial wool is processed with harsh chemicals which can cause allergic reactions and create a scratchy texture to the wool. They need these chemicals for large scale, industrial processing, but they aren't necessary for home processing.


So lets talk about wool insulation:
- when to use wool insulation
- when not to use wool insulation
- different types of manufactured wool insulation
- different methods for making wool insulation
- where to get free or cheap wool
- how to choose the wool - not all sheep are created equal
- other ways of using wool to create an insulating effect

...and any other questions that might pop up.

If you like, I can walk you through a lot of the different aspects of acquiring wool and the processes for making your own insulation. I only have a dozen years of fibre arts experience, but I have some gurus with a great deal more who I can call on for help if we get stuck on a process. There are a lot of tips and tricks to make wool processing an easy task.

 
Jami McBride
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The one aspect of wool as insulation that I have pondered is the cleaning part of the processing - I'll explain.... In the US wool is usually cleaned with detergents as part of the processing to remove dirt.
Not all wool contains the same amounts of lanolin to start with, and processing removes different amounts of lanolin along with the dirt.

So lets talk about lanolin: (from Latin lāna, ‘wool’, and oleum, ‘oil’) - Wiki says "Lanolin's waterproofing property aids sheep in shedding water from their coats. Certain breeds of sheep produce large amounts of lanolin." Lanolin in the wool greatly helps prevent the wool from absorbing moisture, as well as detouring some pests from calling it home.
Along this line of thought is the fact that Mongolian's making tarps for their yurts use un-cleaned wool (by US standards) they do give it a good beating. This helps to leave the wool of their yurt covers water-resistant/proof. Youtube Vid: https://www.youtube.com/watch?v=gJ0uojUHYdA

So if I were using wool as insulation - I've thought about felting it, un-cleaned, in large sections on the ground similar to the Mongolian's. This wool will of course have a much greater smell or musk which might be another factor that warrants discussing when considering wools application as insulation. As an after thought, lanolin can give wool a tacky surface, which may help in coating the wool with DE or some other type of pest deterrent.

Has anyone else wondered about wool's cleaning with regards to it's application . . . ?

 
Jami McBride
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One thing I forgot to mention is that I do know that felting wool will compact it and there by lower it's R value as insulation, by limiting the amount of air trapped between the fibers.

I was considering sandwiching an air pocket between two layers of felted wool as a possible insulation solution for a shed. I like the manageability of felted wool But felting wool may not be conducive for insulation purposes.
 
R Ranson
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Awesomeness - you dove right into the deep end.

Ah, lanolin. Where to begin? I'm going to go back to the very basics for those reading this thread who aren't familiar with sheep.

Sheep produce two main excretions through their skin, grease and sweat. Lanolin is the grease or oil produce by the sheep, and suint which is like sweat.

The suint is water soluble and tends to make an unpleasant smell to the wool. Lanolin being grease is not water soluble and produces a pleasant smell - or unpleasant if you don't like it. Wool moths are attracted to both suint and lanolin, but more to the suint than the grease. Both suint and lanolin are a bit tacky, lanolin more so, and attract dirt particles to the wool. Moths are attracted to dirt particles on wool. Lanolin can become hard over time as it oxidises.

The biggest advantage to lanolin is that it repels water.

Some people also like the feel of it on their skin and use it in skin care products, other people are allergic to lanolin.

As Jami says, different breeds of sheep, and different individual sheep, produce different amounts of lanolin. A great many of the modern (aka, those breed to make wool that works well with mechanical processing) produce more lanolin than the old (pre 1700s) breeds. There are exceptions, but it covers the general theme. So, for example, an Icelandic sheep produces very little lanolin whereas a southdown produceses a fair amount. Merino sheep produce a great deal more. It's complicated and relates to individual follicles, &c. Basically, in real life what it means is that sheep not breed for producing wool for industrial scale mechanical production (tend to) produce far less lanolin than those who are. Traditional cultures are possibly using a sheep that does not produce much lanolin.

Most of us in the West don't have access to wool from these traditional breeds of sheep as those fleeces are usually gobbled up by handspinners. Unless of course you have the financial means or are raising your own sheep, let's pretend that we are working with modern sheep breeds.


Washing wool:

We wash wool to remove one or more of three things: the lanolin, the suint and/or the dirt. Dirt can also be removed through mechanical means such as picking. Picking is a process where we pick apart the wool (by hand, by a machine called a picker, or by beating the wool with sticks).

Mechanical processing uses chemicals to remove suint, lanolin and dirt - often using chemicals that simply dissolve away the plant matter. Then, because the lanolin is removed, they have to apply carding grease to the wool to make it work with their machines. Depending on the processing, other things are added or subtracted from the woo (ie, superwash wool).

When washing wool at home we have a lot more options than mechanically processed wool.

We can merely pick the dirt and vegetable matter (ie, hay) out of the wool - leaving in essence a raw, unwashed wool that has been picked. This is what they were doing in the video. With a particularly dirty fleece, this is sometimes done prior to washing, but not usually as the tackiness of the lanolin and suint make it difficult to get the dirt out.

In the video, it looks like they are layering washed wool on the outside to create a moth barrier. Some of the wool they are beating look washed, others obviously not. Great video, thanks for linking to it.

We can wash the wool in water with soap/detergent. This removes a great deal of the dirt and suint, but as we know lanolin is not water soluble so it remains. This also removes most of the things that attracts moths and other wool munchers.

Or, we can scour the wool. Scouring wool is a way of washing wool that subjects it to a temperature hot enough to melt the lanolin. Aka, very hot, don't put your hand in it, water. hot water melts the grease with aid of soap/detergent, we rinse with water of the same temperature, repeat until the lanolin is gone.

Very seldom do we scour wool at home. It's a lot of work, and quite often we have to add grease back into the wool to be able to work with it.

What usually happens is we wash in very warm water so that the suint, dirt particles and some of the lanolin is removed. Some of the lanolin remains. We can adjust the temperature of the water depending on what our final desire for the wool is.


There is another way of washing wool that takes advantage of the suint and lanolin. You put the wool in water, and allow it to ferment. The suint combines with the lanolin to make soap (actual soap as in alkali and grease) somehow, and you can use the subsequent water to wash more fleeces. It does stink and takes a lot of water to rinse out the smell.

Once the wool is dried, it is picked which also helps to loosen the fibres and prepare them for the next stage in the processing.


Advantages of keeping lanolin in wool:
- it has antibacterial properties
- it repels water (as in water droplets - not the same as preventing moisture absorption - see The Big Book of Handspinning for an overly in depth analysis on this)
- it possibly repels moths (my experience says no, other's experience say yes - jury's still out on this one)

Disadvantages of leaving lanolin in the wool:
- it oxidizes and thus hardens and colours over time
- it adds weight to the wool
- it makes processing the wool more difficult


If I were making a felt for a yurt, I would be inclined to wash but not scour the wool. It would keep some of the lanolin in the wool, but remove most of the stuff that attracts moths. Beating the wool with sticks helps to fluff it up and pick out the dirt, however, it's more labour intensive than other methods I've tried with a less consistent result. Perhaps for the filler - aka, wool in the middle of the felt - it would be useful. Although doing it on the ground, with the lanolin in the wool, would probably pick up more dirt than it released. Perhaps I would go for the medieval European method of beating the wool over a screen raised up at about waste height.


 
R Ranson
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Good thought.

Wool traps air two ways, one between the fibres, and two... we get into the structure of wool. Each wool fibre has little scales on it, like our human hair. Air can trap under these scales. (not including superwash and certain other industrial wool based creations).

If we want to go for even more insulating, alpaca and llama have hollow fibres and are reported to be 4 times more insulating than wool.

By lowering the R value when you felt wool... lowering from what state?

I imagine that people using wool for insulation would use batts, felt or cloth (woven/knit/&c.). A wool batt is wool that has been carded by specific machines. You can card by hand or by drum carder or by machine, each produces a similar but different result which isn't important to this discussion. At it's simplest, carding is a way to fluff up and semi-organize the wool so that it is easier to use for the next step. Carded wool compacts nicely - which may or may not be what you want in insulation. For example, a modernday wool mattress is made from compacted carded wool. It takes a lot of wool to make a mattress.

The advantage of carded wool is that it's lofty, there is lots of air in it. It can also be very light weight. Air can flow freely through the batt, which may or may not be an advantage. For the volume of the wool batt, there isn't much wool in it. A 1 foot square, 1 inch thick section (usually) weighs less than an oz. There are different ways of making batts, so I say usually.


Felted wool, like you say, has less air trapped in between the fibres. Those little scales I talked about on the individual fibres, latch onto each other in a way that holds together remarkably well. Felt is made by agitating wool with moisture. There are other things you can do to speed up and simply the process of felt making, but at it's most basic, it's agitated wet wool.

Because there is more wool in felt, and the fibres are closer together, it allows less air to pass through. It still holds a lot of air inside it, but not as much as the batt. More than (most) cloth however. Felt is considerably heavier than wool batts for the volume. Felt can be very tightly compacted or lightly affixed together, depending on what you want it to do. So if you want the advantage of felt being more stable than a batt, but the loftiness of a batt, you could slightly felt the batt. Or if you want hardwearing felt for shoes, you would felt it a lot.

Felt will usually not compact unless it is subjected to moisture plus agitation.


Fabric, for the purpose of this thread, is usually made from yarn that is interconnected in some way: knitting, crochet, weaving, tatted, &c. This can be very lofty or very smooth - having lots of air trapped in it, or virtually none. It depends on the yarn you use, the method you use to make the fabric, and your finishing techniques. Fabric is usually lighter than felt by volume, but heavier than batts.

I know both felt and fabric have historical precedent for using as insulation. Many times in history people had other options, but people still chose wool.

My question, given this very basic overview of fabric, batts and felt, which would make a better insulation? What situations would you use each kind? What qualities are lacking that are desirable in insulation?
 
Jay C. White Cloud
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Hey R. R....thanks for starting this post!!!

I would really like to pick your brain on the other aspects of yurt building too.


Should we do that here? I don't want to detract from this great conversation? Perhaps another thread? Let me know and I will start it. I had a student a few years back from Uzbekistan. He and his son stayed with me several summers to learn timber framing and on the last summer there Erikin wanted to build a yurt/ger as he had seen in his youth. I suggest Ash as the best local wood to perhaps use and there begins the story...If I can get it back from him, I will assemble and take photos.

Good point about the wool and moisture condensation. I would definitely put good ventilation high on my list for any small living space. I wonder how other natural insulation materials would hold up with that problem?


One of the biggest challenges I see with wool insulation (particularly when used in the "tin cans" that trailers, buses and related are) is the issue with condensation. I love wool insulation...I also only know of one manufacturer (in the U.K.) that has any that I would recommend to clients. Perhaps after this conversation I will learn of others..... Wool is (as are many natural insulations) great but it has to "breath freely"...completely free permeability of the thermal diaphragm when used in architecture...no house wraps or related barriers or other condensing surfaces.

I do hope I'm allowed to both agree and disagree at the same time.


From the other post, by all means challenge me on any point I make about wool. Without query and friendly discourse we shant learn as much, and I may not have all my facts strait, so question away...please!

I know this subject more from a "crafters and artisan" perspective having spun, woven, felted (my favorite form of the stuff) hand knotted, crocheted, and played with the stuff on and off for the last 40 years...be it sheep, bison, dog, yak, or a myriad of other "wooly wee beasties" including some absolutely incredible "qiviut" (simply the warmest in the world in my view) from muskox...That stuff will give Arctic fox fur a run for the money in warm and durability and sheeps wool doesn't even have a chance...but...it is rare, expensive and hard to come by...

I wonder if the method you use to process wool isn't the most efficient thus making it seem like a difficult task when it needn't be?


I would say...probably yes. So that is why when folks bring up "using wool" I listen first and only interject when they talk about "raw wool" being the same as "commercial wool insulation." Two different things entirely, as you have clarified yourself...Thanks for doing that...

A 5 pound fleece can be washed, picked, carded, and spun in under two weeks - on about an hour a day. I once did two fleeces washed, picked, carded, blended, re-carded, spun and knit in under 10 days, but I had two hours a day to work on it, so it doesn't count. This is all using hand tools, not even a drum carder.


Now that sounds like what my Grandmother would say (she was my teacher) and I agree...

Felting takes a different concentration of effort so we can ignore the spinning and knitting bit. It also doesn't require the fleece be carded - but that does help. Basically, the prep work and time requirements for felting is usually considerably less.


Agree again 100%...so many ways and styles from so many cultures...we could chat for days!!

(Orvus isn't perfect however, but that's a topic for another thread).


Hmmm...I will look into this...sounds interesting. We started with a fermented suint bath when I did this with my grandmother...Have you (do you) ever use it?

Once you know the tips and tricks, processing a fleece is fast and easy.


I agree, and some make it much harder than it needs to be...but I will own that is subjective...on my part...

But (a 'but' to negate what I just wrote, not a 'yes...but' intended to negate anyone else) felting for insulation is not one fleece. It is a lot of fleeces.


LOTS, and LOTS...and lots...and lots of fleeces...

I have been told up to 150 to over 200 for just the average family Yurt/Ger...so your numbers of 60 to 190 are in exactly the same range...

To be continued...

 
Jay C. White Cloud
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As I read the thread (and dig through old notes) I can add little bits of info.

Here is one, and why I am just "silly in love" with felt...

Wool batt insulation (commercial) has about R value of ~ 3.5 to 3.8 per 25 mm...Now lets compress it...!!...

Felted carpet padding has an R value of ~ 2.8 to 3.4 and that is for polyester/wool blend...not pure wool...

You would think that this "compressing" (a.k.a. felting) would send the R value way down...guess what...it doesn't! (and if we think about it that kinda makes sense)

And...if you take other consideration into account about "proper insulation" and other factors about "thermal envelope diaphragms" of architecture...perhaps felt (though more work and expensive) is a better way to go as it actually is draft proof unlike the batt insulation. Soooo....working in concert with each other, if I was to use a commercial wool batting it would be combined with wool felt as well. I will state for the record that my preferred "go to insulation" for most projects over the last 15 years has been "rock wool" (or mineral woo) which is a repurposed wastes steam product that has been around for over 100 years and has an R value of 3.5, without many of the drawbacks that wool has. We have played with ideas of how to get it to work on a superinsulated yurt with both wool felt and mineral wool board and batt so we can achieve a roof R value of 60+ and walls that are R 30...

more to come...
 
R Ranson
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Jay, you are fantastic.

Thank you for not minding my overly introductory posts - it's difficult to write both to someone who has experience and for the random person who reads this thread and is totally amazed that wool comes from sheep.

I'm most definitely in favour of a yurt thread. I'm still gathering materials for my first yurt, but focusing on refurbing an old door I 'found'. Actually I stole it from the chickens - it was acting as a ramp to the henhouse. Fantastic, solid wood, TARDIS style door... how could I resist?

This summer is focused on building my yurt, next summer I hope to rebuild an old canned ham trailer... so glad I found you. Yours is exactly the brain I need to pick.


Going to write more later, but got a sheep in labour, so I'm off to see if I can help her pop a new life into the world.
 
Jay C. White Cloud
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Hmmm...this could be a scary union...??

You love wooly animals...

You love felt...

You would repurpose a "chicken door" because it has good wood...

You think staying in a Yurt sounds like a grand idea..

And...

You know what the Tardis is...

This combination characteristics among friends could lead to all manner of adventures...

 
R Ranson
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Stayed up all night, checking on the ewe every half hour... fell asleep for an hour as the sun began to shine her first rays on the world. Silly ewe had her lamb without me. Healthy baby boy and a rather shell shocked first time momma sheep. Not to mention a shepherdess in dire need of coffee.

Made me glad to see someone recognize my TARDIS reference.


Fermented Suint Wash: For those of you new to this, it's a way to wash wool without using any additional soap or detergent. The raw, uncleaned wool is placed in water for about a week where it begins to ferment. Through a magic process involving enzymes and friendly bacteria and stuff, the Suint (sweat) and Lanolin (grease) combine to create their own soap. The wool is then rinsed and the dirt, grease and sweat just wash away. You can use the fermentation water time and again, submerging a raw fleece in it for about three days. Each time you use it, it is suppose to get better at cleaning the wool

This method of washing wool is said to work best with moderately greasy fleeces, though others say it's only for traditional breeds with low lanolin. The general consensus is that the starter fleece is best if it's a high grease (and therefore high sweat).

The fermented wool bath STINKS. There is no nice way to say this. It's part of the process.

For me, the biggest advantage of this process is not using any outside inputs. No soaps or detergents which may be made from ecologically damaging stuff, may or may not biodegrade, and supports the big industrial capitalist complex. What's more, when finished, the liquid from this can be used to fertilize (and possibly deter pests from) your garden. Dilute it at least 10 to one (10 parts water, one part stink juice) or better still 20 or 50 to one.

I've only tried this on a few fleeces so far, and perhaps not the best fleeces for the method. That's maybe why I'm not super-impressed with it yet.

I tried several methods of rinsing, both hot and cold water. Rinsing by hand took a lot of water to get the smell out - a lot more water than my normal washing method and we have a limited water supply here. Leaving the wool draped over a screen and letting a few days of rain rinse the fleece for me worked much better and only took one hand rinse to feel and smell clean.

When the wool dried, it felt pretty good. No smell left over. I thought maybe this is the method for me so long as I time it right to catch the rains. But then stuff happened and life took over, keeping me from my wool for about 8 months. When I came back to it, the wool I washed with this method was far more tacky than the wool from the same fleece I had yet to wash. I don't know why or what I can do to improve this.

This is something I would like to try again but maybe not for a year or two. With a better setup, I think the results can be improved. I know other fibre artists have had great results with this method. But their well didn't break twice while they were fermenting their wool.

What was your experience like with this method?


R Value of Wool: Thank you so much for posting this.

Please forgive me if this is a completely daft question - is the R value of something for a set thickness or does it change depending on how thick the substance is?

That's amazing about the R value of wool not changing much from batt to felt.

Thinking about yurt and using felt for the walls/insulation. I wonder if multiple layers of felt would be useful. For example, if I had two 1/4 inch thick layers of wool felt instead of one 1/2 inch thick layer. It would drape better I imagine - because it's all about looks when using felt on a yurt. The two layers may catch air between them and help add more insulation than one layer alone - or not, I might be thinking this through wrong due to lack of sleep. I could add or subtract layers depending on the time of year, maybe even have a thin layer of alpaca/llama wool felt which is suppose to be 4 times as insulating as wool.


I'm off to spend my dedicated google time discovering what Rock Wool is. Then it's a day with my sheep, I may have to teach this ewe the ins and outs of being a mum. Sometimes the first timers think that it's just a huge, overly demanding poo, and get fed up with their new creation. Or maybe she's just grumpy from me keeping her up all night by checking on her.
 
Jay C. White Cloud
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Hey R.R., et al,

Sounds like you have a new member to the flock...congratulations!

"The Doctor" and his travels are big topics of conversation with my Son. I have been a fan of all the Doctors and my Son and I just was trying to decide who we like best and least of them...

The fermented wool bath STINKS. There is no nice way to say this. It's part of the process.


Well that is a subjective view ...(no it isn't...but...) I have seen folks drop to one knee from the wonderful aroma...and when I (and my family from stories) was kids...it was a rite of passage to see who could take ten deep breaths over a freshly removed lid and not gag or pass out...I always won, but my mother said I was "dog" when it came to food and smelling out things...

For me, the biggest advantage of this process is not using any outside inputs. No soaps or detergents which may be made from ecologically damaging stuff, may or may not biodegrade, and supports the big industrial capitalist complex. What's more, when finished, the liquid from this can be used to fertilize (and possibly deter pests from) your garden. Dilute it at least 10 to one (10 parts water, one part stink juice) or better still 20 or 50 to one.


Ah, yes...someone else down on the entire "big industrial capitalist complex." I'm standing with you on that one till the end!!

As for on the garden...Grammy used it 60:40, and also had a way of adding it to "bone sauce" that I haven't taken the time to rework...

She said the stuff she used back on the homestead was like the "hearth coal" it had been burning (brewing) for over 100 years...

I tried several methods of rinsing, both hot and cold water.


We always took it out of the "bath" and let it dry completely first in the sun before rinsing...(the aroma seems to lesson quite a bit as well with drying)...I will admit that rinsing was a cheated game for us..(me)...as it is with tanning leathers. We would at worse use a pond, but most often a wood "rinsing trough" set not to far from a spring fed stream. Here the fleece would have fresh clear water run over it for as long as two days (or until Grammy was pleased.)

Another trick to "up the oils" in the mix is to add some olive oil to the batch if the fleece to start it doesn't have enough lanolin. Grandma would also add a dusting of hardwood ash to the top ever batch but said there was more to it, and I haven't ever gotten around to experimenting with that one either...just so much got handed down to me that I am just now getting around to writing things like this post reply about such subjects...

Please forgive me if this is a completely daft question - is the R value of something for a set thickness or does it change depending on how thick the substance is?


Yes in deed...R value is always for a determined thickness (usually 25 mm or 1 inch) is the standard determination. As for does it change? Well now that is a topic of debate among building science "geeks." As some of us think it can and others don't believe so. Yet there is still a great deal to learn about "thermodynamics" and insulative qualities of materials and how they behave. Log homes have a low "R value" yet can be very warm and snuggly if built well...Why? There are those of us that "think" (its hard if not impossible to quantify with current testing methods) that a materials ability to hold an retain water, as well as air and its "thermal mass" all working in concert with each other is part of the determining factor. Who knows for sure, but I can tell you that well build log structures are warm and cozy when built well, and combined them with other methods and they can reach a "net zero" state.

That's amazing about the R value of wool not changing much from batt to felt.


Yeah...just one more reason for me to love felt so much...I sleep outside almost year round, and a gifted (from my Usbeck friend) "Black Goat Felt" cloak, has kept me warm for many years. Combined with some modern synthetics (because of weight) and I can get down to about 40 below and still sleep straight through the night quite warm...Even wet it does a good job of it...Wool felts are truly amazing and little that man has come up with competes as "outdoor wear and equipment."

Thinking about yurt and using felt for the walls/insulation...


YES, yes...and layers are the way to do it properly, just as you described. That is why we had been toying with the idea of wool felt, mineral wool, and other materials as well for more permanent designs.

Till later...I look forward to your view of mineral wool...and hope the new mum takes to her lessons on being a good one from you...

Regards,

j
 
Frank Dugan
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Wool is (as are many natural insulations) great but it has to "breath freely"...completely free permeability of the thermal diaphragm when used in architecture...no house wraps or related barriers or other condensing surfaces.


J.C., this is actually an answer to a question I have been trying to determine on my own. A little more detail regarding your statement would be greatly appreciated.

The end of about three years of research on tiny houses is coming to a close, and I have plans to begin a minimally toxic house on a trailer soon.

Cutting a longer post short and staying on topic, the walls will be 2x4 framing on 5" plates with diagonal 2x4 bracing to give it shear rather than plywood with its adhesives. 1x8 shiplap siding will be installed horizontally on the exterior (directly on the studs) and similar shiplap or tongue and groove vertically on the interior. The plan is to use 3.5" batts between the studs and 1.5" of loose fill around the bracing and interior nailers. This should yield close to R-21, with a 1.5" thermal break on most of the wall.

The roof will be 2x6 rafters, shed style, with 1x4 bracing and purlins with metal roofing directly on top. For this, I was thinking of using 5.5" batts and allowing the remaining 3/4" as a breathing space and to avoid direct contact with the metal as a potential condensing surface.

Sheep's wool seems the best choice, but I've never used it before.

The following questions remain:

1) I want my house to breath, but not be overly drafty: will this arrangement be tight enough for better than average heat retention?
2) Will it breath enough to keep the wool dry?
3) Is there a concern with condensation with this design?

Time will prevent the processing all my own wool, and the three manufacturers of sheep's wool insulation that I've found do put in a a little borax and, from what I can tell, a bit of plasticizer in the batts.

I suppose that leads to a fourth question:

4) Would all loose fill in this design be too drafty?

If you have specific recommendations for a supplier of sheep's wool insulation, I'm interested to hear them! I'm currently in Connecticut, so a northeastern supplier would be ideal.

Also, your high regard for rock wool insulation has me a little curious. I've always assumed it was laden with several kinds of toxic gick; is this not true? Further, is it less toxic than sheep's wool that has borax and plasticizer?

Thank you for a great discussion.
 
Rhys Firth
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There has been some post maintenance with rock wool/mineral wool now having it's own thread, so I'll just move a part of one post there back here as it is a bit more wool related then mineral related.



NZ has an advantage of having many sheep per capita and while we have no direct agricultural subsidies like the US or EU, the government does have tax funded "primary" research unit which look for ways to increase profitability and add value to our exports, generally carrying out initial research to the point a future profit solution is visible, at which point a private organisation takes over and drives it to marketable state. Higher export value = higher NZ trade revenues = richer NZ companies + better farm product prices = more taxes without rising taxes. Not really a subsidy as it has been calculated that the govt receives $8 back for every $1 spent on "unprofitable" primary research in the long run.


One quick look, no big search, and three wool batting manufacturors show up, using low NZ wool scraps to make higher value insulation.

http://www.terralana.co.nz/

http://www.naturalwoolproducts.co.nz/

http://www.ecoinsulation.co.nz/insulation-solutions/ecofleece/


Older NZ homes like my mothers on the farm which was built prior to the Murchison earthquake, (We don't know WHEN it was built, but do know it survived the quake in 1929, so it is older than that) used simple dead air space insulation. Wooden lapped weather boards outside, usually 4x2 framing giving a 4" deep dead air space, butted rough sawn interior walls with scrim tacked over and plaster applied (cheap) or wallpapered (posh houses). Old shepherds huts and miners shanties used many different methods, on sheep stations wool was plentiful and was often used as insulation, Quilted into old flattened wool bales and nailed to the interior of the huts.
Up to around 1980 insulation was not mandated by building codes...
 
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