Building the Largest Underground and Off the Grid Farm on the Planet Part 9

Building the Largest Underground and Off-The-Grid Farm on the Planet—Part 9

Welcome back for Part 9!

There are many things that have to be figured out ahead of time if you work with concrete. Once concrete sets up, putting holes in the concrete or adjusting concrete is very difficult and time consuming. One of the many things that had to be determined before we could shotcrete the earth shelter domes was ventilation and where those ventilation tubes would come out of each of the five earth shelter domes and various connector tunnels. I decided that we would run the ventilation for bathrooms, cooking vents, dryer vents, and air exchanger vents out the sides of the domes. Luckily the founder of the earth shelter dome company was watching our weekly videos on this project and noticed the episode where we were running the tubes out the sides of the domes. He emailed me and told me that all ventilation has to come out the front wall or the top of the domes near the ridge of the dome structure. He told me that the way we had the ventilation pipes was not right and that as the earth settled around the domes, anything coming straight out of the sides of the domes would be broken off from the pressure of the settling earth. Because of this email, we delayed shotcreting so that we could reposition our ventilation ports to the top of the domes.

I studied a great deal about earth tubes and passive ventilation for this project because the homeowner and I felt that non mechanical ventilation would be a good fit for this project. The more I studied about the earth tube ventilation idea, the more I found that there was a very distinct line right down the center of the people who believed the earth tubes worked and those who didn’t think that the earth tubes would work. Briefly, earth tubes are a passive ventilation system which includes pipes of a specific diameter run underground for certain distances with the idea that the ground would pre-condition the air as it comes into a building. I questioned if this system would remove the high humidity that Michigan gets in the summer time, and I wondered how introducing humid air into a structure which is constantly battling humidity would work. I created what I thought was a good solution and we will cover that in a future installment of this series. We will also discuss the low voltage Panasonic Whisper Green bathroom fans which we used on the project in a future installment of this series.

We spent the time to rerun the ventilation pipes in each of the five domes. We made the pipes coming out of the top of the domes just long enough to shotcrete around without the pipes hindering our need to walk around on top of the domes to shotcrete. The plan was to connect the pipes during the backfilling of the domes which would occur several months from the time the domes were shotcreted.

Around this time, our friend Pam from out west emailed me to let me know that the burlap on her earth shelter domes had been exposed to the sun for less time than what the burlap material on our project had been exposed to the sun and they found that her burlap was deteriorating from the exposure to the sun. The next day after that email, I went to random spots on each of the five earth shelter domes on our project and checked for deterioration of the burlap. In some spots, the burlap was very weak and in the areas that were covered with the tarps all winter, the burlap was in great shape still. I emailed Pam back and asked her how they dealt with the bad areas of the burlap when they shotcreted her domes and her response was that they used cardboard as a backer in the areas that had deteriorated burlap. The burlap is what stopped the shotcrete from passing through the rebar and wire mesh. She offered another piece of advice and that was that the spray from the shotcrete left an incredible mess all over her concrete floors and the clean up was very difficult. Pam recommended moving tarps around as we sprayed the shotcrete, which we did and I still thank her til this day for that piece of advice.

The value of videoing our project and putting it online was paying off. If I didn’t receive the emails I mentioned above, the shotcreting of the domes and the cleanup following the shotcreting would have been a real game changer on the project. Filming the project and putting up a video every week on Vimeo allowed many people to follow along and those people often caught something that I missed or suggested a course change as we neared pivotal points on the project.

With the emails and my gut instinct, I created a list of duties for each person who would be working on our crew during shotcreting. I figured that we could shotcrete the domes in six days and that would allow us to work normal length days that would not only keep our crew fresh but also avoid any overtime charges from the pump company or the concrete company. Skeptics of this system of shotcreting for an underground structure often mention the fact that ‘cold joints’ were the biggest issue in multi-day concrete pours. Cold joints are basically the point where concrete meets when poured at separate times, for instance, pouring concrete on a Monday and then finishing the pouring of more concrete the following day.

The cold joint concern came to me in an email from some random person who was watching the weekly videos. This cold joint concern got me thinking, so I contacted the founder of the earth shelter dome company and told him what I was thinking. My idea was to stop the shotcreting each day in non impacting areas, such as the center of connector tunnels and not stopping on the sides or parts of the domes. He agreed that the best way to avoid cold joint problems was to stop and start the concrete pours in the areas with the less force against them and/or in areas that didn’t create a breach in strength in any one of the domes. Can you imagine what would have happened if I didn’t get those emails? Thank you everyone who was back seat building while watching the videos, you all helped save me a lot of grief!

Now that we had a very clear path of what we needed to do to successfully shotcrete the largest underground and off the grid farm on the planet, the next issue was getting Mother Nature to cooperate. The weather was warming up and we finally were able to schedule the pump truck and the concrete and get our game faces on for a week of shotcreting.

Stay tuned for Part 10 and ride along as the small crew sprays nearly 900,000 pounds of concrete in a week to create the outer shell of the largest underground and off-the-grid farm ever built!