Hay bale insulation

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Spent years thinking I'd try this, but straw is an expensive commodity around here (not much grain.) Straw, not hay (less food value, less interesting to things that eat.) Stucco or plaster over it keeps critters and fire risk under control. Makes a nice R50 wall, but it takes up a lot of space, and if straw isn't cheap, the building isn't either. Where straw is cheap or a nuisance, it's a great material.
 
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Did some work in a house constructed like that which is heated with a radiant slab in the full basement and tube suspended under the floor for the main level. The walls are indeed 2' thick.


The main level did not heat well at all. Maximum of about 60* in moderately cold weather (10*F).
The condensing gas fired boiler was set to 130* and there was no provision for two temps in the system piping. Huge mistake.
Even so, I would have thought that given the supposed R-value of the walls the main level would have been OK with the 130* water. Apparently this was not the case. We had to bump the water temp up to 160* to get it to heat. The problem obviously at this point is the inability of the boiler to drive water temps up that high when the basement slab is calling also. Only solution is to hack the piping and install a mix valve for the basement zone.
 
You lose a lot of interior space with 18"thick walls. And window and doors openings must be a challenge as well.
 
Straw costs more than the best quality hay here. Seems odd considering that it's a waste byproduct of the grain.
 
I've built a few places with strawbales. the short of it is that if you hire real construction labor, the cost is about the same as any high qualty performance house. if you are a homeowner with a little help you can build it yourself, but it's not quite slapping plastic--- sorry, vinyl-- siding on, 51/5" fibreglass insulation, 10 year asphalt shingles, OSB and 1/2" drywall, 1.5" of stucco will last 150 years, and offer huge thermal mass benefits.

they have a really cool feel, heat and cool really easily. they also allow for a little of your artistic expression to show. for small places, the cost for the square footage eaten up by the thick walls is expensive, but if you stick with a regular rectangle to simplify the details and are building a "normal" sized house, the marginal cost is not really that much. non-bathroom and kitchen space: $80 a SF. Kitchen and bathrooms: $200-250/SF.

athough with most places that well insulated there's no point having a fancy wood boiler. we would put in a masonry or wood stove and a high mass solar thermal system and shallow floor tubes heated off the water heater for extended absences.

other than the solar themal tax credit, no tax $ needed. Don't get me started on 100 years of tax subsidies for the oil industry.

around here straw is a byproduct of grain, which there is some, but it's in high demand for animal bedding, what with all us newbie hobby farmers around. our chickens have a strawbale passive solar igloo coop.

karl
 
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I would think if you pour 18" of just about anything between 2 walls you would get good r Value. ICFs may be a smarter way.
 
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I would think if you pour 18" of just about anything between 2 walls you would get good r Value. ICFs may be a smarter way.

They were originally developed as a response to people needing housing, and strawbales which were a novelty after mechanization late in the 19th century. I've seen pics of places in nebraska and kansas that had walls opened up and looked good after 100 years.

ICFs may have many plusses, but low embodied energy or non use of non-renewable resources isn't one of them. I live in a house with 6" of foam in the walls and roof, and if I ever had to build again, I'd do strawbale and cellulose all the way.

the other cool thing about strawbale is you get your envelope, siding, insulation, and drywall in one shot. not too shabby.
 
A new friend of mine has one, unconventional yes, but after 30 yrs building "conventional" track houses I was impressed. He used some kind of straw from Canada that was better for the straw bale const. I'm not sure if the straw is special or the bale (density?) itself. Very comfortable with only a small central coal stove.
 
Bugs, varmints, and rot potential (induced by rain or other moisture) make straw insulation absolutely out of the question for *ME* in northern Michigan.
 
Rot and insects etc are not a problem in clean straw much more than wood / fiberglass construction. If it still has much grain on it then watch out.

We have had trouble keeping mice/squirrel out of our conventional framed place, I'd love a nice continuously cementitious layer to keep those bugger out. We are in a wet climate and stucco exterior needs a rain screen as it doesn't dry so some type of siding is required rather than just stucco.
 
I looked into a straw house it looked all right but nobody would insure it,the excuse was something about the possibility of a wolf huffing and puffing and blowing the house down.
 
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So, you're insurance provider was calling your family 'lil pigs'?? ;)
 
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Well one larger pig (myself) and some smaller ones.

Just remember what the second house was built from, and it didn't fare too well either.

the critters LOVE fibreglass insulation. cellulose not so much.
 
The critters would like cellulose better if it didn't have boric acid in it for fireproofing.
 
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TI live in a house with 6" of foam in the walls and roof, and if I ever had to build again, I'd do strawbale and cellulose all the way.
the other cool thing about strawbale is you get your envelope, siding, insulation, and drywall in one shot. not too shabby.
You mean to say the straw bale is the only material in the wall? How does it hold up the roof? Keep from shifting/moiving. How do you install electric outlets inside ? i could go on.
 
You mean to say the straw bale is the only material in the wall? How does it hold up the roof? Keep from shifting/moiving. How do you install electric outlets inside ? i could go on.

2 ways of doing it: load bearing bale walls. really only done in the SW where rain during the building process isn't a concern. there is a perimeter beam built around the top to hold everything together and usually threaded rods pre-compressing the bale walls.
most places use timber frame, post and beam, modified post and beam or Studs and headers to hold up the roof/provide building code compliance etc. these things do go on a foundation and still have to meet building codes y'know.

outlets can be done a lot of ways. I prefer smurf tube (ENT) or NM between the first and second course of bales, and boxes either screwed to stakes or 1'x1' pieces of plywood. once there's 1.5" of stucco around the whole thing, it's not going anywhere.
 
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