Insulating Earthbag Walls with Tube Sandbags

My earlier post about Earthbag Building in Cold Climates on January 17, 2009 piqued some interest. Since energy performance on most buildings can be improved with insulation, including those made of earth — adobe, earthbag, etc. — I decided to pursue this idea further.

Insulation-filled tube sandbags on exterior of soil-filled earthbags creates a superinsulated wall with high thermal mass.
Insulation-filled tube sandbags on exterior of soil-filled earthbags creates a superinsulated wall with high thermal mass.

So here’s another method for insulating earthbag buildings using tube sandbags, also called traction tube sand bags, typically used to improve automobile traction on snowy/icy roads. (The bags are sold to add weight for vehicle traction.) This method involves stacking tube sandbags filled with insulation on the exterior of earthbag walls, thereby creating a double wall. One benefit over the other method just mentioned is ease of filling.

Filled tube sandbags provide about 10” of insulation, which is perfect for many climates – not too much, not too little. Again, scoria, pumice, perlite, vermiculite or rice hulls could all be used for insulation. Perlite would be my first choice due to its high R-value (R-2.7×10”=R-27), although the final decision needs to be weighed against other locally available and inexpensive natural materials.

21 thoughts on “Insulating Earthbag Walls with Tube Sandbags”

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    • Yes. but perlite is more expensive than sand and the dust is very bad (the course grade is better). Use what’s most appropriate for your area. This may be the best option in this case.

  2. I will stay away from vermiculite because of the asbestos contaminated type. The USA mine from Libby Montana produced as much of 70% of the Asbestos vermiculate sold in the country. Asbestos is not something you can see with your naked eye or smell it is only detectable if you take a sample to the lab for analysis.
    Within the USA asbestos is regulated under legislation not the same situation for Canada, India or Mexico and is required to show on the bags the content and percentages.
    So if you are buying from suppliers from another countries just be savy about reading your labels and make sure it doesn’t say any of the following minerals, Vermiculite, Amosite, Crocidolite,Tremolite, Anthophyllite, Actinolite and Chrysotile which is the most common.

    • I’ve heard that problem has been cleared up with US companies. Not sure how closely they regulate imported products. Judging by all the hazardous things in the news (imports from China, etc.), it’s prudent to be careful.

  3. I’m no building expert, but if I were building an insulated wall, I’d use plastic temporary fencing as a means of binding the bags filled with insulation to the bags filled with earth. Lay down five courses of earth-filled and insulation filled bags on top of the fencing and then pull it up and over and “nail” it down with another course of earth-filled bags. Repeat the process to the top of the wall. This would work for walls with earthen or lime plaster finishes, which breathe. For walls with a cement stucco finish, I’d use 1″ metal mesh with the edge of the mesh ending half-way on the earth-filled bag, to prevent thermal bridging. Secure the metal mesh with short pieces of #3 rebar driven into the earth-filled bags.

    My two cents …

    • I like the first idea of joining the insulated bags to the soil-filled bags. Thanks for sharing.

      Thin wire mesh shouldn’t be a major concern for thermal bridging. Maybe use plastic mesh if someone is concerned.

  4. How are the two layers of bags connected to each other? If they aren’t secured to each other, what prevents the outer layer from falling away? Could you use one-inch steel wire cloth starting mid-way in the earth-filled bag layer (to prevent thermal bridging) laid horizontally and then bent vertically to secure, say, five layers of bags before terminating mid-way again? The wire cloth could then be coated with shotcrete, as is done with structural concrete insulated panels (not the same as SIPs, by the way!). It might be a good idea to drive short pieces of #4 rebar vertically through the mesh and into the earth-filled bags to make sure the wire cloth doesn’t pull out.

      • I’m sorry, but with all due respect, your answer doesn’t inspire confidence in me. You have two wythes here (one filled with earth and one filled with insulating material) and you would tie them together with baling twine? When moisture penetrates the wall (and it will) and the twine disintegrates, then what? Even if you use a plastic twine, your method isn’t very sturdy. I wouldn’t build a wall like this, knowing that one day, I might go outside to see the outer wythe separating from the inner one, with very expensive consequences.

        • Use good building practice and you won’t have a lot of moisture in the walls. Baling twine is tough stuff. It’s well proven in strawbale construction. I’ve never heard of it rotting in walls.

          But if you think you have a better idea, then I recommend testing, developing and marketing it to the world. There are lots of people in cold climates who would benefit. If we think it works, we’ll promote it on our site just like we do all the other ideas people are coming up with (hyperadobe, mortar sprayer, new house designs, reinforced earthbag, etc.).

  5. Owen,

    You might think twice about recommending vermiculite – do a Google search on “vermiculite asbestos” – you will find that a W.R. Grace mine in Libby, Montana and another mine in Louisa, Virginia both mined deposits contaminated by asbestos. The W.R. Grace mine stopped operation in 1990, according to what I read, but the Louisa mine is apparently still in operation. Perlite might be a better choice.

  6. Owen,

    What will you say about building with bags filled with ex-clay ( ) ?

    It looks like:

    Ex-clay is small round pellets made from extruded thermal treated clay with very small cavities filled with air.
    It requires energy to produce (which is not very sustainable), however it is not very expensive. And alternatives such as vermiculite, pumice, perlite and scoria are not produced in our area and thus would be expensive if I can found them.

    Will the wall built with bags filled with such material alone be strong enough to support its own weight and the weight of the roof?

    Seems that scoria and pumice have sharp edges helping the material to hold together. Ex-clay, to the contrary, is round. That causes some doubts.

    I can mix the ex-clay with earth or with clay+sand mix to make sure it will hold together, however this will reduce the R value.

    Another thing I worry about is that some of ex-clay pellets may break while tamping the bags.

    • Expanded clay has good potential for numerous applications, but it would compress during tamping and so you’d lose the air spaces. It might also make it difficult to achieve strong compact.

      I’ll be blogging about vetiver and hempcrete soon. These look more promising.

  7. hi, I would like to know if the second bag could be filled with straw instead of perlite. I’m afraid of the cost of perlite for the quantities needed and I would have to get it from a big city since it’s not local.

    And what about adding either straw or perlite in the earthbag ( the interior row) instead? what would be the R value of this?


    AMélie from Mont-tremblant, quebec

    • Loose straw would be vulnerable to moisture damage and a fire hazard. Best to look for something better like vermiculite, pumice or scoria.

      For best performance you want insulation on the outside, mass on the inside.

  8. I live in Northern Canada (Prince George BC) and I would love to build a permanent earthbag house here in the city. The 3 big problems I face are: how to insulate, how to get code approval, and who can give me advice and assistance. I’m accepting all input from anyone who knows anything! Thanks!

    • I’ve written several posts and articles on this. You can search this site and our site for articles. Or you can use Google and do a search for insulated earthbag Geiger or something similar.

      In short, insulated earthbag building is an exciting new development that opens this building method to far more people. The key breakthrough was Kelly Hart’s house made with bags of scoria (lava rock). His house stays comfortable year round in a very cold climate.


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