The Video:
I thought this video was more interesting than some of the recent ones. Hopefully you enjoy it also.
The Story:
I got there a bit early and got to sweeping off my newly poured concrete, but I was really doing some last minute thinking about where the well should go. Factors to consider range from ease of hookup now, to constructing around it and eventually living with it.
The well drilling crew from Cribley Well Drilling arrived and we settled on a location they could access. They actually wanted to put it about 10 or 15 feet out from the house, but it would have made it difficult later as I tried to get equipment and trucks around my house… I had originally wanted it further around the side of the house (which is why the camera angle had been set up that way), but they didn’t think they could drive the truck over there because of the soft sand, and if they did, the well would have been too far from the building and in the way later. Eventually, they agreed to get it as close as they could to the front of the house. The main constraint was needing room for the large drill fluid recycling tank behind the well head. The final location will end up behind a retaining wall, out of the way.
I dug to level the ground for this tank and they filled it with water from the second truck.
The drill bit was a 9 inch tricone bit. As an engineer, I have worked on computer simulations for these for my companies “oil and gas” clients, so I know that these are designed for crushing rock and stone. As the bit turns, the three roller “cones” rotate to break-up and scrape away rock. Water is pumped in thru the shaft, both to cool the bit and to push the debris out the hole. You can find an animation here… It was definitely overkill for drilling in my soft sand, but it got the job done.
They started things off without water, just to locate the hole… But then they pulled the bit up again and added a spout collar to direct the drill fluid (water with a bit of bentonite clay mixed in) into the recycle tank. Sand and gravel settles out in the first section of the tank and the cleaner water/clay mixture flows over to the other end of the tank where a hose sucks it back into the truck and thru the drill shaft and down into the well again. If they didn’t recycle the water, it would take a large swimming pool worth and would make a huge mess. Every now and then they would need to dig (or dump) the sediment out of the tank.
After they drill the first piece (with the bit on the end) in to the ground, it is time to add an extension to the shaft. The $600,000 Versa-Drill rig is designed and built for streamlining this task.
It comes equipped with two hydraulically activated wrenches. First, the one at the bottom comes out of the back of the truck to hold the lower portion of the shaft still. The operator runs the drill backwards for a moment to loosen the end piece and then pulls back the “wrench”.
Then they raise the drill up to the top of the mast. The rig also has a carousel with 15 extensions (capable of drilling 300 ft with what they brought, but they can bring additional shafts if necessary). The carousel rotates the next 20ft shaft section into position and the rig screws its self in loosely. The second hydraulically operated “wrench” moves into place to hold the new shaft section still while the drill tightens into it. Then the new shaft is moved into place above the previous piece.
The lower end is threaded in with the shaft below it held in place by the lower hydraulic wrench… and the rig can drill the next 20 ft down. This process was repeated 20ft at a time, over and over. See the video.
On my site, it was nothing but sand for the first 116 ft. Then they hit gravel and it made a lot of noise… Enough to bring me out of my mobile office to see what was going on. That layer only lasted about 4 ft and they were back to sand. My neighbor, who lives higher on the hill, came to check it out and told us that he hit water after only 117 ft. Actually, the same guy who drilled my well had also done the neighbors, but with an older version of the drill rig. He said that the water table is definitely not flat.
My well didn’t reach “water bearing fines” until about 185 ft… At nearly 16$ per ft, just for drilling, that difference adds up. The guys from Cribley joked that they wanted to drill further to help pay off their new six hundred thousand dollar rig (yes, he mentioned that price several times and that Obama was letting him write it all off in one year)… But they stopped at 186ft.
The Versa-Drill V-100NG drilling rig comes equipped with 500/200 air, 3×4 centrifugal mud pump, 15 rod carousel (3½” x 20″, 9GPM water injection, built in 2″ Bowie grouter, 12K winches with job booms, hose reel, and mounted on a 2014 Peterbilt 340 6×6.
With the water table reached, they began the process of pulling out the drill, piece by piece, back on to the carousel. It was pretty much the inverse of the previous process, but went much more quickly.
The next step was inserting PVC casing into the well to keep it from collapsing. The first piece, the well intake, was special with perforations to let the water in… The rest were just 6” PVC tubes. They glued one into the next and lowered it down, repeat.
Since the 6 inch tubes were dropped into a 9 inch hole, there was still some space around the outside. Leaving this open would let sand fall down the gap and clog the well tip. To prevent this, they inserted a flexible 1” white tube into that space. Like before, they put down 20′ at a time and just pushed (without glue) one section into the next. They pushed it down to just above the water bearing layer. Actually, they did it so fast, the time-lapse camera didn’t really catch it. Once it was ready to go, they started mixing bentonite clay into a slurry and pumping it down into the well (at 35$ per bag, you can count them in the video, I didn’t want to). As they did so, they pulled up the white tube. This effectively filled the gap around the pipe with clay that would hold the pipe in place without letting water flow around it or sand get down into the water bearing fines…
Done drilling, it was time to clean up the equipment and pack up…
Overall, they ended up digging nearly 40% deeper than the 135ft that I had estimated. That increased my cost a couple thousand dollars over the initial estimate (but they have not set the bill yet and it has been over a month). On the plus side, they estimated my well was producing about 50 gallons per minute, which is quite a bit more than the 18 g/m pump that I planned to install. That means I will have more water than I need, which is a good thing. Pumping well water is also much cheaper than city water. At current electric rates, I will pay about 25¢ per 1000 gallons. My current rate for city water/sewer is about ~8$/thousand gallons. If we used the 400 gallons per day that the standard American family uses, the well drilling should pay itself off in a little over 5 years. That swells to 16 years if I include paying off the septic field (which also went about 30% over budget).
They will send a different crew to dig a trench and run water pipes to my mechanical room. A third crew will eventually install the pump and pressure tank after my mechanical room floor is poured. That will need to wait for spring.
The Mistakes:
I don’t know if I made any here yet. It probably helped that I had experts do the actual work. But if I find out about any later, I will come back and add it here. ;^)
The only think I can think of was that after the job was over, there was a lot of bentonite laying on the ground in the area… It holds the water well and stayed annoyingly squishy for days after the rain passed. I knew it would be a drainage barrier, so I didn’t want to bury it in place… Instead I decided to spread it out (with the skid-steer), thinking that might even improve the properties of my surrounding sand… However, a little of that stuff goes a long way and even spread out, it just made the sand squishy and more difficult to deal with. I should have just scooped it all up and saved it for later.
(rough thoughts for now, will polish later)
There are many articles on the subject of on demand hot water heaters vs. the more common (in the USA) hot water tank, but this one is tailored to new construction of an earth sheltered home. I personally plan to install some on demand electric hot water heaters because they suit my situation. Your situation may require a different choice.
Check your sources. Most of the sites that talk about how great on demand hot water heaters are are selling them. Most of the sites that talk about how bad on-demand hot water heaters are, especially electric ones, are “electric cooperatives” who would rather sell you more electricity over a longer period of time. If you focus on articles written by consumers groups, they tend to be more neutral and articles written by end users tend to be very pro tank-less.
Also check the logic behind the complaints. Often they may say something general like, “On demand hot water heating costs so much that it will fall apart due to old age before it pays its self off.” If you check the actual numbers you may find that they spent thousands on a very expensive gas unit which had to be professionally installed in existing construction. In your situation, you may pay off your investment much more rapidly.
Retrofit vs New Construction?
If you are in an existing home with fixed wiring and you are happy with the performance of your perfectly good hot water tank (gas or electric), just keep it. Energy is energy and the heat capacity of water is the same in both cases. While there are probably some inefficiencies with the way the energy is imparted to the water, the biggest efficiency difference between a tank or tankless water heater is how much of that energy is lost thru the walls of the tank into the home. Modern methods of insulation make the tanks pretty good at holding on to their heat.
If your hot water heater simply lacks capacity, think about how old it is. Hot water heaters only last 10 or 15 years so you probably don’t need to feel too guilty about replacing it with a larger capacity hot water heater.
However, if you are building a new home and can design your electrical service and plumbing with tank-less in mind, I really think it is the way to go.
Gas vs Electric
For well-sealed underground homes (or well sealed above ground homes), you should probably try to avoid combustion. Electric is much cleaner inside your home even if it is generated with natural gas some where else, and you won’t need a chimney. Of course, electricity can also be generated with clean technologies and you can even create it yourself. It is a lot harder to make your own natural gas.
Many argue that natural gas heat is cheaper than electric. This is only because the cost of natural gas is cheaper per btu than the cost of electricity, at the moment. Electricity is actually much more efficient at putting its energy into heating the water. Natural gas is a non-renewable resource and the cost is expected to rise (in the United States) while the technology for generating electricity is getting cleaner and cheaper every year so the cost for electricity is expected to fall.
The cost of a natural gas on demand hot water heater is many times higher than for an electrical hot water heater, both in terms of installation and the equipment its self. This initial cost leads to long or infinite pay back times. Electrical equipment is much cheaper, and if your electrical service has watts to spare, the install is also relatively cheap and easy and within the realm of “do-it-yourself.”
Some people claim that natural gas has the capacity advantage, in that it can heat more gallons per minute. But in reality, it is just that they have a larger natural gas capacity. If you have a lower gas pressure or if you have the capacity (120 amps) for a larger electric on-demand hot water heater, things could be reversed.
Electric on demand hot water heaters win hands down in terms of temperature control and low flow rates. People who are complaining about a lack of control or needing flow rates of 1/2 to 1 gpm are probably using natural gas on demand hot water heaters.
The Big Catch
I checked many electric on demand hot water heater sites and none of them mentioned the big catch… Powering the thing.
An electrical water heater tank uses electricity much slower, so you only need about 30 or 40 amps. It just runs for much longer. This means you can get by with a pretty typical electrical service and certainly save money in the short term.
Most on-demand hot water heater companies have a high end model that can produce hot water for 2 or 3 showers (in the northern states), but it takes about 120 amps. Adding this to your your home will usually require stepping up to a larger electric service, unless you like your lights flickering when you run your hot water.
Of course, upgrading an electrical service is very expensive. But building with a larger electrical service in mind can be done more affordably… The equipment for a 400 amp service is a few hundred dollars more than for a 200 amp service, but the hook up (where most of the money is) is only 15% more. You will also pay more for wire, etc. It is expensive, about $1500 more in my case, but considering the heater its self costs less than $500, the total is not bad. Certainly, it is cheaper than running a new construction or retrofit natural gas line.
If you have a home with 3 showers plus a kitchen and laundry and maybe even radiant floor heat, you may actually want to install two of these. You could possibly locate them close to the points of use, which is great, but you would need 240 amps to run them all. If your house has an electric stove (50 amps) and an electric dryer (20 amps) and a single lighting circuit (15 or 20 amps), you are already past the 320 amp capacity (80%) of a 400 amp service. Now you are talking 600 AMP service. The jump from 400 amps to 600 amps is significant costs thousands of additional dollars.
The solution is pretty simple… You just need to talk to your electricity provider about adding a separate 200 amp service for your hotwater/hvac needs. This will cost far less than going with a larger service and you will be able to separately track your hot water costs. In some areas, you can actually get special low rates for a dedicated meter.
Solar Hot water?
I discuss solar hot water more over here. Here I will just say that you need a tank to store the solar hot water, but you definitely don’t want to use the heating element in the tank. Get a tank without the heating element and save some money if you can. If you heat the water in the tank, it will be less able to collect heat from the sun. Ideally all the heat in the tank should all come from the solar. The output from the tank should then pass thru an on-demand electric hot water heater to add just the right amount of extra energy needed to bring the temperature up to what is desired.
See, we can all get along. Tanks and tankless, electric and solar, together in perfect harmony… Now if only I could afford it.
Heat pump hot water heaters?
You can get heat pump hot water heaters. Basically, these are a small heat pump mounted to the top of a hot water tank. They are the most expensive of the hot water tanks by a factor of 3 or 4.
They are considered very efficient if you just look at how much electricity you put in and how much hot water you get. But if you zoom out and look at the bigger picture, you see that they have to get that extra heat from somewhere.
These devices work by “pumping” the heat out of the room and dumping it into your hot water tank. In summer, this is great because they actually help cool your home (like a small air conditioner). As a bonus, the surface of the exchanger gets very cold and dehumidifies the air around it, which is usually helpful in an earth sheltered home. However, in winter, these hot water heaters are stealing heat from the home which simply needs to be replaced by the homes heating system. The energy use just moves upstream from the hot water heater to the main house heater.
One can imagine a humorous situation where a heat pump hot water heater would be used to heat hot water for a radiant floor home heating system… It would steal heat from its self.
A slight twist on electrical resistance heating
Most electrical resistance water heating runs electricity through a resistance element which heats to over 1000 degrees. The heat energy is then conducted to the water. In the process, minerals from the water may be transferred to the heating elements (scale), reducing its efficiency and ultimately causing the heating element to fail. The thermal expansion cycles of the heating element also contribute to its failure.
There is new technology on the market that uses graphite electrodes to conduct the electricity through the water. The water is the resistor and the electrodes never need to heat up more than the water. This saves energy and wear and tear and should be cheaper to produce (even if it isn’t quite yet). It also operates at lower flow rates than other on demand hot water heaters.
Note: For more information, check out http://myheatworks.com/
Well, hopefully Sherri and I will love our underground house. “We don’t like our underground house” was the title of a blog by MizBejabbers who wrote about the pitfalls of her underground house.
MizBejabbers’ earth shelter in Arkansas. Check out her site for more pics, but this was the best one ;^(
Miz tells about how they moved into an earth sheltered home 18 years ago (built by TerraDome for a previous owner, who may have covered up the problems to sell it) and how it has not lived up to the earth sheltered promise. She writes about how it had all the fears (leaks, mold, etc.), but without the benefits of energy efficiency. She also talks about increased construction cost, severe depreciation, pests (bugs, rats and nosy people), etc. She does have a section on “happy things” such as feeling safe during storms, enjoying the peaceful quiet, etc. but concludes that these were not worth the pain.
She even blogs about mini tremors, which she thinks are earthquakes cracking the house, but I suspect it is the house cracking and settling as the soil underneath is slowly eroded. No earthquakes required.
For someone like me who is considering a similar investment, this could be a blog from my future, so I read it very carefully…
My conclusion was that this house was just designed and built really badly and in the wrong time and place. By time, I mean that it was built in the early 1980’s when few people had worked out how to do these properly. Lets go thru the issues, as far as I can tell from the blog.
The site: This house is set below the road on the side of a large hill overlooking the Arkansas river. The U-shaped design that Miz mentions sounds perfectly designed to catch all the surface runoff from the hill above and funnel it toward the front door. What is probably happening under the ground is even more threatening… Hills do interesting things to water tables and an earth sheltered home may be sitting in an underground aquifer, like a wet pebble in a stream. Try a quick Google image search for “artesian well diagram” if you are not familiar with the concept. Miz acknowledges that the french drains are not sufficient in capacity or well placed to drain water away before it enters the house.
Our site doesn’t have such a majestic view, but it is on the top of a hill, and our hill is very permeable sandy loam that will dry out nicely. Before I bought my land, I walked around during a thunderstorm and made sure the water didn’t collect or run. After buying the land, and looked “deeper” and buried moisture sensors more than 10ft down for my Soil Temperature Experiment.
The construction:In the comments after the article, she mentions that the house was built on fill (to make a terrace on the side of the hill). If there was water flowing down, around and under her home, fill soil would wash away more easily and would lead to further settling and cracking and leaking. My home will be built on undisturbed soil with a high compression rating and no erosion threat.
She also blames a “bad batch of concrete” for the living room roof crumbling. I am not sure if that was really the problem (or if the bad conditions just wore down otherwise adequate concrete), but The TerraDome homes are monolithic structures which are poured into proprietary modular forms. If the concrete is not carefully mixed and poured, there is no good way to fix it later.
My home will use shotcrete, which (when done right) is considerably stronger than any poured concrete because of its lower water content and the way it is compressed as it is shot onto the wall.
Miz mentions metal ducts rusting and falling apart, I will be using only HDPE ducts that will never rot or leak. We also plan to heat our home with radiant floor heating, a method better suited to the heavy concrete construction. We will still have ducts, but only for ventilation and de-humidification.
She mentions drywall rotting and molding, internal wooden walls being eaten by termites, etc. we won’t have any of that in our all concrete house with a specfinish gunnite surfaces.
The waterproofing: TerraDome, like other earth sheltered builders (including Formworks) with “proprietary systems” does not use a waterproofing umbrella. Instead they insist on more traditional methods used for waterproofing regular basements, glued or sprayed directly to the walls. These include bentonite clay or a “tar modified polyurethane elastomer applied as a liquid”. These directly applied methods are pretty useless if the concrete cracks more than 1/16th of an inch. Even applying something like a pond liner right over the concrete before backfill is not as good as an umbrella (away from the concrete) because it can be torn by the movement of the concrete and does not help with thermal mass.
Applying the waterproofing and insulation directly to the structure also excludes the surrounding thermal mass and allows water percolating thru the ground to strip it of its heat, both of which reduce thermal performance when compared with an insulating umbrella.
It also sounds like the soil around this home was not properly drained. The French drains mentioned are not well placed or of sufficient capacity to handle the location on the side of the hill. This moisture increases the weight and lateral (hydro-static) force on the walls. Cycling moisture levels are even more damaging.
An interesting side effect of applying the waterproofing directly to the structure, and then draining around it, is that you need to make a choice about the moisture level of the soil above the water proofing… Do you want it to be dry for the structure beneath or do you want to keep plants living on the surface? It is difficult to have both. Miz ended up shutting down her sprinkler and letting her plants die. Eventually, they had to remove the covering soil completely. The umbrella solves the problem by requiring that you drain only the soil under the umbrella and allowing you to maintain the moisture in the soil above.
My home will use an umbrella with three layers and I plan to go overboard on the french drains under the umbrella. It also helps that my soil is very permeable.
Conclusion: I think I can avoid the problems shown in this blog, but I need to keep my eyes open and be as careful as I can. I am sure the builder of this home didn’t expect these problems… And neither did poor MizBejabbers when she and her husband bought it.
Caveat Emptor! Buyer beware! When buying an earth sheltered home, you must be doubly careful to check it out before buying.
What is the latin phrase for “this may be harder to sell?” There is always some mistrust between the seller and the buyer, but this gets worse when the item, your earth sheltered home, is difficult to inspect, because it is buried, or difficult to compare, because it is unique or custom built. Economic Game Theory would suggest that because the seller knows much more about the house than the buyer (informational asymetry), he would only be willing to sell the home at a deflated price if the actually thought it was worse than the buyer thought. Sellers who’s homes have no issues would be less likely to sell for less than they thought the home was worth. This would reduce the percentage of good earth sheltered homes on the market even further. Buyers could deduce this and realize that a large portion of earth sheltered homes on the 2nd hand market are likely being dumped by their owners. Therefore, sellers would be willing to offer even less. This is why earth sheltered homes tend to suffer heavier depreciation than other homes even thought they should last longer. Blog articles and anecdotes and even random experiences with cold damp basements only make it worse.
If you want to prevent or at least reduce the depreciation of your earth sheltered home, just in case you ever need to sell, you can do things to reduce the buyer’s doubt. I will start by taking detailed photos of the construction. I also plan to bury sensors (temperature and moisture) and keep good long term records. Other maintenance and utility records also help to establish the efficiency of the home. Not painting, or other wise covering, the inner surface of the home will also help to preserve trust during the sale process. The effect of these efforts would be similar to the effect of selling a used car and including a full set of records; including gas mileage for every fill-up, maintenance records, a car-fax report, etc. Increased buyer cconfidence will translate into higher offers. Of course, it only works if you actually build a good earth sheltered home ;^)
The blog mentions their attempts to enforce a warranty or get money from TerraDome or the builder, or the previous owner, but all failed. I don’t expect to get a warranty and I will have no one to sue but myself, so I will need to select the builders carefully and make as sure as I can that the concrete mix is a strong one.
The drill bit was a 9 inch tricone bit. As an engineer, I have worked on computer simulations for these for my companies “oil and gas” clients, so I know that these are designed for crushing rock and stone. As the bit turns, the three roller “cones” rotate to break-up and scrape away rock. Water is pumped in thru the shaft, both to cool the bit and to push the debris out the hole. You can find an animation here… It was definitely overkill for drilling in my soft sand, but it got the job done.
