For those new to earthbag building, please read my Step-by-Step Earthbag Building Instructable . Also, my new Earthbag Building Guide and Earthbag Building DVD are now available.
Energy performance on most buildings can be improved with insulation, including those made of earth such as adobe and earthbag structures. Although most earthen structures are located in hot, dry climates, there is increasing demand for low-cost, eco-friendly earth building techniques in cold climates. This article explores four innovative methods for insulating earthbag buildings, which extends their building range to cold regions.
Most earthbag buildings use polypropylene grain bags or mesh bags filled with soil. Bags or tubes can be used. We demonstrate bags, because they’re often available recycled for very low cost. The bags or tubes are filled in level courses and then tamped solid. There are typically two strands of barbed wire between courses to bond the bags to each other and add tensile strength. The building process for insulated earthbag houses is nearly the same, although the materials would weigh significantly less and speed construction considerably.
Unlike other earth building methods, earthbag building has the unique advantage of providing either thermal mass or insulation, and therefore can be adapted for cold climates with an insulated fill material. Scoria, pumice, perlite, vermiculite or rice hulls are all suitable insulating materials. These materials are natural, lightweight, easy to work with and non-toxic. Most (all but rice hulls) will not burn or rot and do not attract insects or vermin. In addition, all but rice hulls are not adversely affected by moisture and can be used as part of earth-bermed or earth-sheltered structures. Recycled polystyrene (Styrofoam) is another good possibility. Another possibility is adding foam board or foam insulation on the exterior of earthbag walls, as explained in the 4th option.
The table below compares the approximate R-values of five low cost insulating materials that could be used in earthbags. (The first column in the table is the insulative value per inch; the second column shows the R-value for a typical 15" thick earthbag wall.)
Material -- R-value/inch -- R-value/15"
Rice hulls -- R-3 -- R-45
Perlite -- R-2.7 -- R-40
Vermiculite -- R-2.13 -- R-32 to 36
Extruded polystyrene -- R-3.6 to R-4.7 -- R-54 to R-70
Molded polystyrene (low density) -- R-3.85 – R-58
(Source: Wikipedia Encyclopedia.) http://en.wikipedia.org/wiki/R-value_(insulation)
Tools and supplies:
Shovel, bucket, garden hose, tamper, slider, gravel, soil and/or insulation, earthbags (poly sand bags), barbed wire, wire cutters, level
The following pages discuss four low cost methods of building insulated earthbag houses.
For more information, my You Tube Channel has dozens of short videos showing every step of earthbag building. And our Earthbag Building Blog , the number one blog on the subject, covers every aspect of building with bags in detail.