fleece scrap fabric as insulation?

Greetings.

There is a lot to be said about sheep wool as insulation. I may have a source for fleece scrap fabric (I don't think it's wool, likely synthetic). They say it is new material, completely clean, from sewing production. / That the fleece is inherently flame resistant. . They manufacture clothing to protect people from fire so the fleece will not burn, perfect for insulation....

Any thoughts? This is for a laundry room/tiny house. No one living in there right now.

Doesn't sound right.  Fleece is flammable.  

Maybe look into rice hulls (if you can source them) or aerated concrete (if you can make a foam generator).  

Fleece isn't flammable, but it melts.  That may be worse.

Well, there are many different kinds of "fleece".  Rather than wool, it's more likely "Polar fleece", which is a type of polyester fabric.  Polyester, is most commonly the plastic called "polyethylene terephthalate" (PET) , which is what soda/pop bottles are made of.  Recycling code #1.  It's essentially a carbohydrate polymer like wood.  Over 250 °C it  "melts" and turns to liquid, and at 350 °C  it decomposes, pyrolyzes, volatilizes.  

A fire-safety engineer in a lecture at a top engineering institute told me that molten plastic in a fire is "like gasoline".  It's volatile, contains a lot of energy, and can flash-over very quickly.  That's why it's generally kind of dangerous to say that plastic has any kind of fire-safety rating.  It's probably more flammable than wood.  Maybe some plastics don't catch fire quite as quickly, so maybe in some sense it is "fire retardant",  but that is so misleading.  It's kind of dangerous to wear fleece around fire.  I think that guy was either putting you on, or he was talking about some other material besides polyester.  I don't believe that a wooly polyester fabric is used in a fire proof garment.  

I have to agree with P Mike on this.
fleece that is used for clothing (that isn't wool) will not only melt and then flash into a gasoline type accelerant but  it will gas off many toxic fumes which will be incapacitating to anyone inhaling this "smoke".
While the idea sound good, without having the complete specifications of that material, which includes the hazmat statements, it would be a crap shoot. In a fire event or even if it just got very hot, it could end up a deadly choice.
Some of the fire retardants are also not so great for humans to breathe and these can also become part of the toxic fumes in a fire event.

There are several polyester-based insulation products available; Bradford makes polyester based "Polymax" batts which were formulated to reduce the dust and skin irritation produced by traditional fiberglass batts.  The garment industry has a regulating body that, among other things, classes apparel fabrics according to ignition hazard.  Polyester has a high rating which makes it safe in relative terms.  ASTM E84 tests interior building finishes for flame spread after ignition, and polyester fabrics are often rated Class A, which means relatively low flame spread.  Most large drapes you might see in hotels are polyester or have a generous amount of polyester fiber to allow them to hang with good sheer and little wrinkling.

Almost all building insulation is required to be covered by an ignition barrier, like gypsum board, in conventional light frame or steel frame and infill.  It is far more likely that ignited room contents, furnishings and interior finishes will reduce occupant escape probability than insulation located within a stud bay due to this fact.

The two issues I see with using scrap fabric for stud cavity insulation are lack of homogeneity and consolidation.  The fabric scraps will have to be spun or ground to create a homogeneous, air-entrapped material to provide an efficient insulation, and then supported to avoid consolidation at the bottom of the stud bay and air gaps at the back of the interior wall finish.  I have witnessed the removal of interior finishes on hundreds of walls during my career, and every single loose-fill application and most of the batt applications were in support failure at the time of removal.  Many failures for loose-fill occur after only 2-3 years; batts fail usually after 5-8 years if improperly supported.

The three best practices for insulation design are continuity, support and location within the wall section.  So, for example, low R-value well-supported continuous insulation installed dead tight against the back of interior wall board will provide more comfort and energy savings than discontinuous high R-value poorly supported insulation installed with an air gap between the interior wall board.  If you decide to use the scrap fabric, I'd be interested to hear how you end up installing it.

I agree with your post Brett, but there are a lot of people who don't follow proper construction methods to the letter when building their own off grid buildings. That can create issues not usually thought of by those who are in the construction trades.

I build walls with two sets of fire blocks but I've seen people build their house with stud walls and no fire blocks at all.
I've also seen undersized lumber used for roofs and floors in owner builds off grid.
When things like that happen, the codes and regulations aren't followed and are thus out the window.

At the end of this thread https://permies.com/t/40/64494/fiber-arts/love-woolen-industry-rise-ashes  there is a link to a BBC discussion on what to do with wool and mention a company that is making insulation out of wool :-) so it can be done .

David