Sawdust insulatioin

[damhik]

I recently put up my 30foot diameter yurt. made the wall & cieling insulation out of Reflexix,which seems to work prety good. It gets a little cool in the mornings due to poor planning on insulation the floor. Since it's on pier & beam, I can get under there & blow something into the space between the beams, then seal it up. I have access to all the sawdust I can haul away, for free. Has anyone used it for insulation? I assume that there are chemical(s) hat have to be mixed with it to act as a fire retardant. I seem to revall borax as a fire retardant? or is age creeping up on me? Any thoughts or suggestions, even other materials, would be welcome.

Thanks,

Damhik

[rotornuts]

Sawdust was used as an insulation material for years until materials like vermiculite, rock wool and fiberglass took over. I have personally removed sawdust from many walls and attics to replace it with fiberglass or cellufiber and I would not recommend using it anymore as the drawbacks out way the low cost. Most if not all sawdust will be too moist unless you get planer shavings as soon as they are produced.

Solid wood has an insulating value of R1 per inch of thickness so we can maybe assume an R value of 1.5 ish for loose sawdust. this means that in a 4 inch thick wall (3 1/2 actual) you would have an R value of 5.25. Fiberglass insulation will give an R value of  12 in the same space.

If it's all you can afford or have access to than I say go ahead but see if you can dry the sawdust somewhat, somehow, before you blow it in. If your just trying to save a few bucks I would say it's a really poor way to save money.

Standard just my opinion disclaimers apply.

Mike

[Mary B]

look into making a pellet machine and make an extra heater that burns the sawdust pellets. Not sure if it can be burned by injecting it with air, might be worth a try.

[gale]

3 years ago, I tore down a ice house.  The walls were filled a foot thick with saw duct.  I was totaly surprised by the lack of mice nests.  I then smelled the sawdust, even after 100 years, you could still smell the cedar.

As long a the sawdust is kiln-dryed and not of green wood, you should be fine.  They are building houses with straw walls, and they don't treat them for a fire hazard.  The best, I think like the old ice house, if you can find cedar sawdust, that should eliminate any insect or rodent problem you might have.  I have been using sawdust around the farm since the mid -1980's, mostly for bedding, But I have insulated water tanks, well heads and misc. buildings with it for years.  One prblem is spontaneous combustion, but the saw dust has to be soaking wet or made from green wood.  Saw dust like most loose insulation will settle over time, you may want to be able to reload the walls later.

One particular thing about sawdust, especially kiln-dried sawdust.  It absorbes moisture.  The neighbors' cattle barn, used to have the walls dripping wet in the winter from the expiration from the cows, when he used straw.  When he used sawdust,  all of the wetness disappearred.  His cows suddenly became much healthier.  

[chadking]

I've seen mixed reviews on the R-factors on sawdust insulation, but it is used by a lot of people.  If you look up 'cordwood construction' you will see a lot of people use sawdust for insulation because it's a by-product of the construction process.  

To ward off pests, and possibly add some fire retardant qualities, it is commonly mixed with builder's lime. I've seen anything form 1:1 ratios to 9:1 ratios.  People also mix it with other insulative materials, vermiculite, styrofoam peanuts, etc.

I do not have any experience with it myself, but you might be able to find out some more specifics by doing a couple searches.

Have a great one!

Chad

[luv2weld]

As others have said it will work. Sawdust was used for years, most notably

in icehouses. Critters will not tunnel into it because they don't burrow in

anything that has the possibility of collapse. (Guess they're smarter than people.)

So if you fill it all the way to the top, you won't have uninvited guests.

One of the main things you would need to do is put a layer of plastic under

the sawdust. If you can find plastic sheeting at least 6 mil thick, that would

be great. It will keep it from absorbing moisture from the ground.

I would also use hardware cloth (also called rat wire by some folks) 1/4 or 1/2 inch

mesh. Dig a trench around the perimeter about 12 inches deep. Then wrap the mesh

around the bottom of the yurt. With the bottom of the wire in the trench, which

will be backfilled, even if something tries to tunnel under it they will give

up. The mesh will also keep critters from moving in on top of the sawdust after it settles.

As far as the fire threat, saw dust will smolder. It will not burst into raging

flames. If you don't believe me, put a pile of it in an ashtray and try to

light it with a match.

There are fire retardants on the market that you can buy. Or you can

search for an old time treatment that our grandfathers may have used. I don't

remember any right off except for the borax you already mentioned.

I think if I had access to all the saw dust I could haul, I would be tempted

to do as Mary said. I would get a pellet stove for my house, and I'd build a

hydraulic press to make pellets. Once you recover the cost of the pellet making

machine, you have free heat for the rest of your life.

Ralph

[Slingshot]

Maybe a little off topic, but what are good places to get free sawdust?  

[luv2weld]

A sawmill, high school or VoTech that has a wood shop, cabinet shop, furniture

makers and probably a lot more that I can't think of right now.

Ralph

[gale]

Sawdust from different sources are much different.  A sawmill cuts green wood, it produces a very wet sawdust, locally you can get a truck load for a $25 loading charge.  and the mills have a pile out back big enough to ski down.  Dust from a factory, is generally a pine sawdust, but kiln dried.  descent for animal bedding and insulation. a furnature factory will generally have kiln dried hardwood sawdust.

  Fifteen years ago, I worked at a processing mill.  We took rough cut kiln dried hard wood boards, planed them on 2 sides and either cut them to dimensional or into strips to be glued into panels.  between the planers, hoggers and wide belt sanders, we sent out about twice as much sawdust as actual product.  A local man had a contract with the mill to keep the sawdust silo empty.  He sold the dust to the local farmers for bedding at $150 for 15 yard load.  We even sent the walnut to a special bin.

If you can find a reasonably priced pellotizer, more power to ya.  The cheapest I have ever seen in working condition was $7000. and it ran on 440 3ph.

In europe the had special sawdust stoves.  It had a sawdust fuel mold.  It looked like a 10 gallon bucket witha 5 inch tube in the middle, you packed the sawdust in, then carefully pulled the tube out.  The entire tub fit down into the stove and the sawdust burnt from the inside out.

[ghurd]

Walnut sawdust will kill a horse.

Farmers would not take sawdust with walnut in it for free.

G-

[damhik]

Thanks for all the comments. As further illumination: the sawdust is comes from a Douglas fir flooring factory, is kiln dried to less than 6% moisture, then the boards are run through the moulder that puts the tongue, groove & stress relief grooves on it. The sawdust is the byproduct of all this machining. I like the idea about using plastic sheeting held in place by 1/4 inch hardware cloth.I am thinking about turning a commercial shop vac around somehow & using it to blow rather than suck; or perhaps a leaf blower. I can get under the yurt so tacking up the hardware cloth & plastic would not be a problem. Great ideas & comments. Thanks all! When I get it done I'll do another posting.

Damhik

[SteveCH]

I lived for ten yr. in an old mine cabin that was insulated with sawdust. The cabin was probably at least 75 yr. old, but I couldn't testify to it. It was old. The sawdust was packed in the walls and attic. There used to be sawmills in the area making both mine timbers and lumber, so local supply of sawdust was no problem.

There were some problems I noted over the years. For one--and by the way, this was a wood-frame cabin--ants set up nests in a couple walls. It didn't cause me too much trouble, they were apparently not the type of ants that cared about kitchen foodstuffs. Then, one wall became damp inside due to a leak I never found, and the sawdust swelled just enough to bulge the walls out a little. Once smoke began to come from the area that the woodstove pipe went into the ceiling. I crawled up to find that rodents had scattered the sawdust around enough to where some came in contact with the stovepipe and was glowing red. Good, insulated stovepipe would've prevented that, of course. I did find evidence of insect life at various times when I had reason to cut into a wall here or there.

[winddreamer]

there is better things to use but sawdust will work. I have just spent a week shoveling it out of my 100 year old home I have re done it with two layers of r 14  fiberglass

one thing i found interesting is that there was lime powder mixed in with the sawdust I guess it helps to preserve it  must work because the sawdust still smelt good

[TimV]

There is a ton of info on sawdustburners (sawdust fired pottery kilns)

Air injection...burning in suspension...yes...commercial burners use this method.

If you seaarch Yahoo, MSN, and others not ruined,excuse me,run by google...you will come up with a lot of info instead of ads for everything you never wanted in the first place.

As far a pellet make it takes thousands of pounds of pressure to make pellets (pug mill) and sawdust is a medium used as well as small wood chips. There is a place in Idaho that casts a simple set of grates used to burn sawdust using only the natural draft of a chimney in suspension. I have link someplace for them.

I can be reached at (minus the J's) JJweldingrodd at JJhotmail.JJcom