fire hazard in using wood duff for insulation?

Maybe this is a really ignorant question, but I don't really know much about flammability risks in construction in general.

I'm wondering if the pressure on the insulation in a wofati roof is enough to compress it to a point where it's non-burnable in the same way they say straw bales in straw bale construction are less flammable than conventional construction.

If that's not so, what is the best fire-resistance factor about a wofati? how does it compare with a conventional wood house?

I searched for "fire hazard" and "wofati" and didn't find anything.  

I guess not having a fuel or electrical heating system in the house makes things less risky, and whatever you cook with you're going to pay more attention to.

(Also, is it safe to just put sawdust in a wall in a conventional house for insulation?)

Thanks much!

Joshua Myrvaagnes wrote:
I'm wondering if the pressure on the insulation in a wofati roof is enough to compress it to a point where it's non-burnable in the same way they say straw bales in straw bale construction are less flammable than conventional construction.

One thing I do know is insulation works by having tons, like millions, of tiny little air pockets, and if insulation is compressed, it no longer insulates. The fluffier an insulation can be, the better the thermal qualities it has on preventing heat loss or transfer.

(Also, is it safe to just put sawdust in a wall in a conventional house for insulation?)

I think that depends on who you ask but I doubt the fire marshall would recommend it, and if something like that which may not be to codes is done it could possibly make a house unsaleable until it's replaced.

Putting sawdust in the walls of an old house was common practice back in the old days, but it was hardly ideal. I helped keep the house warmer...for awhile. Fire was actually the least of the problems with this type of insulation. The greater problems were with settling. Over a very short period of time, the sawdust would compress, and leave gaps at the top of the walls. Since heat rises, this just let the heat out.

Another problem was with the lathe that they used back in those days. Any tiny hole would cause the sawdust to come billowing out...from say a mouse or rat.

Rats and mice burrowed through the walls and loved the sawdust to make rats nests in as well.

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Today...cellulose is used, which is just paper which of course comes from wood. The difference is, today they have machines that blow it in to a certain pressure so there is no settling. The cellulose also has borax in it which makes it fire resistant, as well as mice and rat resistant. And of course construction methods have got to the point where we have much more air tight walls that keep the cellulose in them.


A person could certainly make their own sawdust insulation, but for rat and fire resistance, they probably should add borax.

I don't have experience in using wood duff for insulation. But people should have a look a this youtube vid featuring Beau and his homemade mycellium insulation. There is no doubt as to whether it will burn or not!

I think the risk is minimal.  Little of the insulation is wood duff, and it is in an envelope with almost no oxygen flow through.  The wofati as a whole would resist a wildfire flowing over it better than any conventional house.  An electrical fire inside would have a hard time getting anywhere near the wood duff, nor would roundwood be very flammable (that's why you have to split so much wood.

If the insulation (wood duff, sawdust, leaves, straw) is encased or sandwiched within a layer of dirt or clay it should be pretty darn safe.  Just like strawbale home construction is.  This subject is definitely a concern,  but also not the biggest deal imo.  There are tons of things inside our homes that will easily go up in flames.  Carpet, beds, clothing, curtains, to the very wood in the walls the house is built from.  Houses dont catch on fire very often, but shit happens and that's life.  Personally, I'm not wearing a helmet all day because I might fall and bump my head.  But to each their own, if it's to concerning choose a different insulation.  The foam that would usually be used for insulation here burns pretty good too.  I'm more concerned with the big wood rot potential in these designs than the fire hazard.