I built a small adobe building and I had a LOT of empty 620ml beer bottles. They are almost worthless here to recycle so I came up with my own method: Cheap insulation for under the concrete slab!
Cheap floor insulation using free beer bottles provides an air gap between the earth and concrete slab floor. This air gap reduces the transfer of heat or cold from the earth through the concrete floor.
Steps For Free Bottle Insulation
Air and I did the following:
- Leveled the area where the building will be located.
- Marked out the approximate location of the concrete slab floor.
- Added soil to make the elevation of the floor higher to prevent flooding and loss of sand during rain storms.
- Added a couple of inches of sand for a level and soft base for the bottles.
- Used free lumber from Air’s father to build the forms to hold the sand, bottles, and concrete.
- As you can see below in the pictures we let the lumber run long where possible. This provided two benefits, including:
- No need to cut the lumber. We are off grid so this is a great benefit for us. Not to mention that I don’t have any power tools while I am here and the solar system was not installed at this point. Actually the electrical room is now in this building and the solar panels on the roof.
- The lumber was used for fascia boards on this adobe building.
- No need to cut the lumber. We are off grid so this is a great benefit for us. Not to mention that I don’t have any power tools while I am here and the solar system was not installed at this point. Actually the electrical room is now in this building and the solar panels on the roof.
- This wood is so incredible hard that I had to pre-drill the holes with a cordless drill. This allowed the nails to penetrate without bending during hammering!
I fastened each corner with a minimum of three nails. I did not drive the nails flush with the wood because it is much easier to remove the nails with the heads protruding by about a quarter of an inch. - Stakes driven into the ground flush with the wood forms within one foot of each corner and about every four feet along the forms.
- I used a four foot level to level the forms starting at a corner. Air held the form level while I drove two nails into the stake though the wood form.
TIP: Drive the nails into the stake with one as high as possible and the second one as low as possible. Separating the nails as much as possible adds vertical strength to the forms, reducing the chance of movement during the concrete pour. - Fill in the forms with bottles, starting at the narrow end and with the bottom of the bottles facing the wood form. Leave a two to three-inch gap between the bottom of the bottle and the concrete form. If the bottle was too close to the edge of the floor the concrete strength would be compromised.
- The second row will face the opposite direction so the necks of the bottles face each other and can lace together. This means that you can slide the second row a few inches in between the necks of the first row. This increases the total volume of air gap insulation in the floor.
- Dig trenches and install plumbing as needed before covering with the bottles, like I did lol. I had to remove some bottles to install the PVC toilet piping.
- Install plumbing pipes as needed.
- Add bottles around the stub ups for toilets, sinks, drains, clean outs, and ventilation stacks.
- Cover with sand to a depth that at least covers the bottles by half an inch. Be carefully walking on the sand once level as it will no longer be level.
TIP: Start adding the sand at one end and work side to side as you work towards the opposite end. This method should allow you to walk carefully on the bottles while adding and leveling the sand. We leveled the sand with our hands. This is the base for the concrete so you don’t want low areas as that will cost extra money for unneeded concrete. Raised areas compromise the strength of the concrete because it will be thinner here.
If you don’t have enough bottles you can see four other free or cheap materials you can use for floor insulation in my article here.
Scott Boyd
Advantages
- Free insulation materials. You can visit the local recycling center if you don’t drink a lot of beer as I do. You can also use two-liter and 500-soda bottles if they have caps. Without caps, the concrete can crush the plastic.
- No carbon footprint to build with this system. I regretted building with concrete, but I at least used bamboo for rebar. Also, as this building is a toilet and shower I could not build with an earthen floor.
- Easy DIY project for the whole family, no expertise required. Air’s nephew helped us, but I can’t seem to find photos with him included 🙁
Glass is an excellent material for thermal insulation, water proofing and energy conservation.
Building with bottles is quite an old technique. In 1905 Tom Kelly built a house in Rhyolite, Nevada (now a ghost town), using 30,000 beer bottles.
Evangelia Kyriazi
University of Peloponnese
Disadvantages
- ANTS! Pest control measures are necessary for this area as the ants love to remove the sand to make nests.
- Spiders and other pests like to make homes among the bottle insulation and sand too.
- Insulation value is not as high or effective as using foundation foam which is R5 per inch.
- A more effective insulation installation would include adding closed-cell foam insulation four feet wide around the perimeter of the building that is just under the ground. This insulation the ground around the building from the heat or cold that can come through the corners of the concrete floor slab.
See the last photo below to see the engineered concrete slab that I used when building houses and garages. It shows the insulation under the floor and around the perimeter under the ground.
