Using sawdust as insulation

I've got access to tons of sawdust from clean non treated wood. Is there a process I could use this to insulate my barn? I would like to close in an old barn and reuse it as a aquaponics facility. The biggest challenge to doing this is keeping the place at a temp greater than 70 degrees...all year long and I live in north central wisconsin. I plan to use multiple rocket mass heaters to heat the place as wood is not a problem. If I can find a way to use free sawdust it would be a real touchdown.

Thanks,
Damian

Same process they use for cellulose (shredded paper) insulation--boric acid (or borax) is used for mold/pest/fire proofing.

It takes a LOT of borax to do it, like so much it may be cheaper to buy cellulose. There is also the problem that there is more food left in sawdust compared to paper (which is pretty much pure cellulose) for bugs to eat.

A clay slip can be made for almost nothing. It provides suitable fireproofing. Search out wood chip clay. It's the same process. Sawdust from conifers is unlikely to be attractive to vermin. Mix in as much cedar as you can get. Bugs don't like it.

What ever you do be sure you have it dried down solidly before it goes in the wall. Fungi love sawdust and it is often high moisture and it traps moisture solidly.

Both air leaks and interior humidity would make a big difference in how well the sawdust resists rot. Cellulose insulation is dirt cheap.

So cellulose isnt flammable?
Did not know that.
About the clay slip, I would have thought that the insulative properties of sawdust came from the air trapped between the pieces and that the clay would occupy that.

The cellulose is much better. Fire spreads more easily in homes that have fiberglass. It melts away like candy floss, to provide a chimney for the flames to follow. I'm currently watching a house burn near the corner of Bay and Cook. The roof is fully engulfed.

Clay slip locks the sawdust together and gives some air seal while also filling some of the insulative holes.

William Bronson wrote: So cellulose isnt flammable?
Did not know that.
About the clay slip, I would have thought that the insulative properties of sawdust came from the air trapped between the pieces and that the clay would occupy that.

As soon as winter breaks I will experiment with a small out building I have on the farm. I read this article on making your own clay and my wife says this area is loaded with it. So it will be a three-fer; clay extraction, clay-sliped sawdust insulation (installation) and making my first rocket stove. The outbuilding (wolf) was originally slated to be a wood working workshop and with these additions I use it year round.

Thanks everyone!

Sawdust is very fine and not very porous, I would look up the r-value first but I guess it is lower than other materials. Both cellulose and sawdust have one problem. They sit down over time and create uninsulated areas, if you are unlucky you can create mold there. My guess is that mixing the sawdust with clay brings further down the insulation value but this is much preferable to having a part of the wall completely uninsulated after some year. My guess is that wood shavings would be far better than the sawdust. And I would compost the sawdust all you can get with some bags of blood and bone.

Angelika Maier wrote:Sawdust is very fine and not very porous, I would look up the r-value first but I guess it is lower than other materials. Both cellulose and sawdust have one problem. They sit down over time and create uninsulated areas, if you are unlucky you can create mold there. My guess is that mixing the sawdust with clay brings further down the insulation value but this is much preferable to having a part of the wall completely uninsulated after some year. My guess is that wood shavings would be far better than the sawdust. And I would compost the sawdust all you can get with some bags of blood and bone.

High R-value is good. Low is bad. The finer dust insulates better than coarse stuff. Shavings allow convective currents and are much less effective. They are one of the worst options due to flow issues, convective issues, and tendency to catch on obstacles and create voids. Vermin love to nest in shavings.

I've insulated hundreds of homes, mostly with cellulose. It settles less than fiberglass and most other materials.

I've demolished over 200 houses by hand. When cellulose is done right, with a hole at the top and bottom of each wall cavity, it barely settles in 30 years. Sawdust usually settles 2 or 3 inches in an 8 ft. cavity. Blown fiberglass and rock wool can settle a foot and voids are created when obstacles block the flow. Vermin like fiberglass. Drafts blow through fiberglass much easier than through cellulose.

Here's a big negative for fiberglass that I only learned of a couple years ago. During really cold weather, it becomes far more conductive which reduces it's R-value when you need it most. I found out that they were conducting tests at very moderate temperatures and the Canadian government tested at sub zero temperatures and got much worse results than what industry testing produced.

If you have an attic that has fiberglass batts, blow some cellulose over them. Convection will be reduced and a thousand cracks will be filled. The coldest temperatures will be against the cellulose, so that the fiberglass will perform a little better at more moderate temperatures. You get the added value of the cellulose plus some remediation of the problems inherent with fiberglass batts.

I can't really believe that fiberglass bats sits down. We had to replace the cellulose in our attic with bats because it was not doing the job properly. It is simply not very logic that a mat goes down more than a loose material.

Dale Hodgins wrote:[quote=

I've demolished over 200 houses by hand. When cellulose is done right, with a hole at the top and bottom of each wall cavity, it barely settles in 30 years. Sawdust usually settles 2 or 3 inches in an 8 ft. cavity. Blown fiberglass and rock wool can settle a foot and voids are created when obstacles block the flow. Vermin like fiberglass. Drafts blow through fiberglass much easier than through cellulose.

Is it feasible to tear down the roof and sides of this barn, keeping the frame for support and build in greenhouse on the 2nd floor? My wife and I were throwing around ideas last night..

Angelika Maier wrote:I can't really believe that fiberglass bats sits down. We had to replace the cellulose in our attic with bats because it was not doing the job properly. It is simply not very logic that a mat goes down more than a loose material.

I hope they went over top. Unless there has been a moisture or vermin problem, pulling any insulating material out and replacing it seems like a waste. I could see a salesperson selling that idea. It's nonsense. The sensible thing and the much less expensive option would have been to add more cellulose or if there is a bias against cellulose, use blown fiberglass. In a properly built house that is adequately ventilated, there's no way for it to not work. Batt over loose fill is an extreme rarity. The gap and air sealing qualities of the loose material can't help the inferior batt system if the batts are on top. Glass on top exposes the glass to the coldest temperatures. As temperature drops, the R-value of fiberglass drops.

I've never seen glass batts over cellulose. Cellulose over glass is common for the good reasons stated in my earlier post.

I haven't said that batts settle. They don't, unless the vermin nests get too heavy. Batts don't settle, they allow convective currents within the material and in gaps between them. Once it reaches a certain point, cellulose doesn't either. Blown fiberglass will settle too much some times and it is prone to compaction if walked on. Cellulose is much more forgiving in this regard. On many occasions, I've had to install wires in attics. A simple brush with a corn broom puts cellulose back where it belongs after disturbance. Loose glass leaves compacted prints similar to when damp snow is walked on.

Fiberglass batt and poly systems are an antiquated technology which I hope will soon be relegated to the scrap heap of history. Better choices abound.

If I were to combine first a sawdust layer to fill in the huge seams and then use spray insulation...I've been looking online for that, any know a good source?

Damian Jones wrote:

Dale Hodgins wrote:[quote=

I've demolished over 200 houses by hand. When cellulose is done right, with a hole at the top and bottom of each wall cavity, it barely settles in 30 years. Sawdust usually settles 2 or 3 inches in an 8 ft. cavity. Blown fiberglass and rock wool can settle a foot and voids are created when obstacles block the flow. Vermin like fiberglass. Drafts blow through fiberglass much easier than through cellulose.

Is it feasible to tear down the roof and sides of this barn,

keeping the frame for support and build in greenhouse on the 2nd floor? My wife and I were throwing around ideas last night..

The roof and gable end walls represent about 3/4 of the work in building a structure like this. It would be like starting over. Quite often, old barns are held together quite a bit by the sheeting. If this building were being framed, half of the work would be in creating the gambrel roof. I would reinforce the existing framework and remove sheeting where glazing is desired.

If it were a demolition, removal of the roof would be about half of the total work. I took the sheeting off of the walls of a similar barn and pulled it down with a truck with the roof intact. It was a shaky structure that I didn't trust. You've seen the YouTube videos. It's more dramatic when you're there to feel the wind and the ground tremors. Pulling a barn over with a truck is a truly satisfying feat. Get er Done.

Dale Hodgins wrote:The roof and gable end walls represent about 3/4 of the work in building a structure like this. It would be like starting over. Quite often, old barns are held together quite a bit by the sheeting. If this building were being framed, half of the work would be in creating the gambrel roof. I would reinforce the existing framework and remove sheeting where glazing is desired.

If it were a demolition, removal of the roof would be about half of the total work. I took the sheeting off of the walls of a similar barn and pulled it down with a truck with the roof intact. It was a shaky structure that I didn't trust. You've seen the YouTube videos. It's more dramatic when you're there to feel the wind and the ground tremors. Pulling a barn over with a truck is a truly satisfying feat. Get er Done.

Just found out the barn is on a North / South lie, guess I lucked out there. So now I think removing a portion of the siding and replacing the area with a greenhouse skin and perhaps a clayslip sawdust then using some sort of foam insulation, then covering it all with plywood would be a good bet. The foam insulation will be a bit costly but much cheaper then doing a whole greenhouse structure on the 2nd floor.

Chasing my tail? Thoughts please.

Hi Damian,

My thought would be it might be easier to just build a greenhouse extension on the south facing side and install a door into the barn at the back of the greenhouse, rather than take out the whole wall.

Good luck with your project whatever road you choose.

Daniel

Yes Daniel, I thought an addition to the barn also and I may go that way. To me it seems putting the AP directly about the stock tanks and RMH's would be more efficient. I will explore both options. Right now I'm really just trying to collect enough data to make a good informed decision.

Thanks for the well wishes..It is a new adventure for me.

Daniel Clifford wrote:Hi Damian,

My thought would be it might be easier to just build a greenhouse extension on the south facing side and install a door into the barn at the back of the greenhouse, rather than take out the whole wall.

Good luck with your project whatever road you choose.

Daniel

Bonjour!
I stumbled on this forum while looking for information on wood shavings for insulation. Some interesting replies. I'm actually in the process of putting up a yurt for a small school in southern France. We have already put up several yurts the underfloors being insulated with wood-shavings mixed with lime, the idea being that the lime discourages insects and vermin. Personally I'm not sure of the usefulness, certainly the ants don't seem to be put off. Anyone got any first-hand experience of this? Is it actually effective or are there other more practical solutions?
Thanking you in advance for the advise.

My experience with blown in cellulose has been excellent.

Every insulation system has strengths and weaknesses.

Yes, cellulose can settle. I have used two approaches to solve this.

1. Go back a year later and fill up the voids at the top.


2. Make sure your blowing machine is up to the task. If you blow in the cellulose to the preferred density, it won't settle at all. In a typical stud bay, I put one hole at 4' and another at the top of the bay, or let's say 7.5'.

For in-wall cellulose, they usually give you this funnel device that reduces the 4" hose down to 1.5". That restriction makes if very difficult to get good installed density. I solved that by cutting great big 4" holes and just stuffing the whole unrestricted hose in the wall. In addition, I also go through and manually compact the cellulose with my hand/arm. You can reach through a 4" hole pretty well. Now I have zero issues with settling.

You won't get quite as much coverage as they say you're supposed to, but you will end up with a better install.


Cellulose, per say, is certainly flammable. Proper cellulose insulation with borax mixed in is very fire resistant.

And yes, fiberglass insulation does not perform nearly as well as they say it does, except in the lab. For my heat loss calculations, I reduce the stated r-factor by 40%. Cellulose has been, in my experience, a far better performer in cold climates.


Of course, my house and shop are not normal framing. The walls of the shop are a foot thick. That's ~r-50 with cellulose, and the double framing gives a thermal break to reduce heat loss through the wood. Highly highly effective.

troy