Most earth structures such as adobe are located in hot, dry climates. But what if you live in a cold climate and want the benefits of low-cost earth building techniques? 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 could all be used for insulation.
One possibility is to add a seam lengthwise down earthbags or polypropylene tubes to divide them into two compartments. The outer part could be filled with insulation; the inner part with soil. This would create an insulated wall with thermal mass on the interior. For many situations, this is an ideal wall system.
The placement of the seam could vary, depending on the climate. In a mild climate like New Mexico, I would add about 4”-5” of insulation on the outside. This would provide about R-10 insulation. In a slightly colder climate the seam could go down the middle (50% insulation/50% soil). In extremely cold or extremely hot climates I would fill the bags with 100% insulation (or all earth in a hot climate if insulation wasn’t available).
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Earthbag Building Blog 
What a great idea!
Is this only practical on the larger size bags? I’d like to hear how awkward it gets to fill them. I suppose you might want to load lightweight gravel in first, so it was still easy to handle and pass down to the soil filling station.
I’d also like to hear how much more time this takes to fill.
Good questions. This is a new idea I’ve just started experimenting with and there’s still more to learn. The one bag I filled wasn’t difficult or awkward, but then again I wasn’t balancing on top of a wall… Total fill time is about double that of using one fill material. I recommend using bucket chutes (one for each side) to make it easier. This system will work on typical 18″ wide bags. I think adding the insulation first is the easiest method. Perlite is highly recommended for it’s light weight and high R-value.
No need to make a seam. Your chute idea will work fine. Just have two removeable long chutes (pieces of AC ducting or possibly a short length of downspot). Have the chutes reach all the way to the bottom of the bag. Fill each side accordingly. remove the chutes from the bag. Each chute is nothing more than a long square or rectangle tube and should slide out of the bag/soil. You may have to build special sized tampers to compact each side a bit. Or you can can tamp the bag after you put it in place.
interesting idea :)
H