We LOVE the look of the colored glass walls used in earthships. But did you know that it’s more difficult now to find the bottles you need in multiple colors? Recycling has made things better, unless you happen to be looking for cool materials for your glass bottle wall. So many earthship builders spend months and sometimes even years scavenging for and collecting the “right” bottles, or, they *whispering*...they BUY the bottles in the colors they want them in.
While beautiful, the glass bottle walls are poor insulators. So, many people now only use them on the south or west exterior walls... if they are leeward (the direction the wind normally GOES), and on the interiors of the home. Don't use bottle walls on the north unless you live in Mexico or parts south where winter is pretty much "summer-lite." Basically, you only want bottle walls where the need for insulation is minimized.
Maintenance-wise, the glass bottles of yore pose another concern: grossness. The open ones that were originally used in earthships collect bugs and dust, they are ugly on the “cork” side, and they break easily. Cleaning them can easily be a full time job.
Many people, including EB, now take the bottoms of two bottles and to tape them together and make what is referred to as a “bottle brick”. You will need about 2000 bottles, a means of cutting them, and ducttape to make the standard 1000 bottle bricks. You’ll want to remove the labels by soaking the bottle in water with dishsoap and then using a putty knife to remove what remains. Using gloves, to keep from getting cut, etch the bottle 4” above the base using a sharp glass blade cutter and dip the etched bottle into hot but not boiling water for 10-12 seconds, then dip it in a ice cold bath for a few seconds, and the hot again... until this cuts the glass through. Alternately, a high quality tile saw works well to do this quickly. Wash and dry the bottle ends completely. Using a clear glass end and a colored glass end for the most light transmission, tape the bottles together with duct tape, painting tape, or two layers of packing tape. Here's a GREAT Step-by-Step Guide to Making Bottle Bricks from Manitoba Earthship Project!
Another trick for not using glass bricks but getting the same effect which many builders already know and are using: use pretty colored and shaped glass blocks. Which kindof moots the point of the walls “recycling benefit”. But it works. For the long-term. Maintenance is minimized, thermal performance is maximized, and privacy is maximized. Plus you can get EXACTLY the look you want.
Glass blocks and bottle walls should not be used as loadbearing walls, and they should be laid not in concrete but in Type S mortar or cob of not more than 3/8” in thickness. For stability, especially if used on the exterior, these walls should not extend more than 15 feet in any direction and should be limited to an area less than 140 square feet overall. Curved wall sections are possible, but require an expansion joint at each change of direction. The radius of the curve should be limited to no less than 4 feet.
Expansion joints, an expansion strip between the glass and the regular wall and sealed with a sealant either side, should be installed at the heads and sill of exterior glass block and bottle walls, especially, to allow for movement and settling. Use recycled content expansion joint filler for these locations.
