Monthly Archives: May 2013

Tiny update…


Posted on May 23, 2013 by

Progress seems to have stalled, or at least we are not aware of any in the past week or so.  I thought we were moving at the start of the month, but I have not heard much lately.  I emailed the architect again today to ask, but with the long weekend coming up…

In the mean time, I have started purchasing components for my temperature sensor array.  This will help me monitor temperatures under the home, as well as some of the earth tube and internal temperatures.  This project will require me wiring up the semiconductor chips to some circuit boards, writing code, etc.  I bought, and already mostly read, an ExtremeTech book on the subject.   I also purchased some circuit boards and a USB connection from

DS18S20 from Maxim Dallas Semiconductor...  I will build an array with these, wire them into a circuit board, connect that to my computer and write code to record and display the temperatures under and around my home...

DS18S20 from Maxim Dallas Semiconductor… I will build an array with these, wire them into a circuit board, connect that to my computer and write code to record and display the temperatures under and around my home…

I separately ordered some DS18S20 one wire temperature sensors directly from the manufacturer, Maxim -Dallas Semiconductor, because Hobby-Boards wouldn’t meet their price.  Maxim is actually being somewhat strange about it and require that I send in a signed statement saying that I don’t plan to use them in military applications or resell them…  I need to get this all figured out ahead of time so I can test/debug the array before it gets buried.  The soil temperature experiment used more expensive plug and play sensors, but these ones cost just a few percent of the price, allowing me to afford many more of them.

We have also got going on the bank paperwork.  Part of the construction loan process is something called the “Sworn Statement”.  It is a big long document where I will list the names and estimates from all my contractors, etc.  The second page asks for information about the type of construction, down to detail such as the type and spacing of the floor joists or if the gutters will be aluminum or vinyl.  It even asks about “sizes, features, brand, etc.” for the microwave.  This is quite a paperwork hurdle, but I can understand why the bank would want to be sure we have our ducks in a row.  Trying to put a positive spin on it, I guess this paperwork gives us a framework to organize our quotes over the next 6 weeks or so.

No time for eye candy today…

We don’t like our underground house!!!


Posted on May 11, 2013 by

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 there aren't any good ones ;^)

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.

Early May Update


Posted on May 9, 2013 by

Here is a bit of an early May update…

Architect/Engineer You may recall that the last bill (5 weeks ago) said everything was done and payment was due, but everything was not done and there were a number of errors to correct on both the architect and engineers drawings…  And on top of that, my engineer wrote to the architect to say that he thought he should get more money. I disagreed and sent in my argument to the architect who hired the engineer.  You can go here to catch up on some of the past details.

Anyway, my architect decided that we should just wait until we had everything else done and then send the engineer a “final” list of issues.  I guess that is how we should have worked from the start.  In the mean time, they drafted (but have not sent) a letter to the engineer based on my arguments.  Last weekend, I found at least one more big problem in the form of a support bracket that doesn’t fit inside the wall and would radiate heat to the outside…  So that whole engineering issue is just waiting on hold, more to come.

Meanwhile, the architects assistant and I have completed our exams (I got 95% on mine) and got back to work on the plans.  He is working his way thru my comments and most of the serious issues are sorted.  We have some disagreements to work out in a few areas, but the biggest remaining problem is the windows.  We had visited the architect after getting our final window quote but they seem to have lost or confused the notes we gave them with notes from an earlier meeting and some other things they thought they should figure out on their own, so I will need to get that sorted out…

I decided not to wait any more before talking to the neighborhood association.  I wrote to them asked what they want and how they wanted it.  Maybe things will be ready in time, but even if not, I would still like the approval process to get started.  The current state of the drawings is probably enough for that process.  The association requirements that that the plans need to be submitted along with landscaping.

I am planning to do the landscaping myself (along with help from my wife) and bought some software (Punch Lanscape Deck and Patio) to help out, but first I needed the topology.  I played with it a couple weekends ago to figure out how to create the topology for the landscape.  One way to do it was to trace the lines of the survey pdf (image) in Autodesk Revit and export that as a DXF and then set the elevation for each line in Punch… but I asked the architect for the AutoCAD files and he sent them over…  I have not done anything with the file yet, but I really appreciate that he was willing to do that because it will save me a lot of time.

I have also installed AutoCAD on my machine so I can do the shop drawings for some of the steel beams that the architect/engineer do not see as part of their scope, as well as to design the forms for the concrete ribs.  When I was in high school, I won awards for my AutoCAD skills and I worked as TA in my Engineering CAD classes, but that was all a long time ago.  Hopefully the skill is still there and the newest version is not too different ;^) 

Sourcing This week I am working on getting prices for the steel arches and the construction loan… Again, the plans are not quite done, but I am hoping that I can get these started now so everything will be ready when the plans are done.

Temperature Probes I really want to put a number of sensors into my house so I can understand the heat profile and hopefully validate my theories.  They will also help me keep the home comfortable by giving me understanding about the temperature conditions in the soil around my home under my umbrella.   The sensors that I bought for the soil temperature experiment were expensive.  I didn’t feel I had much choice because I needed it to work with a data logger…  However, for this application, I will need a lot more sensors to really understand the umbrella.   I will also be able to connect the directly to a computer, so I am looking into designing and assembling a much cheaper array of “1-wire” sensors (DS19B20).  These sensors cost about 1/10th the price, so I can afford 10 times more, but I will need to build my own circuit board, program my own code, etc…  I bought a book, Weather Toys, which is the best source for information about how to build these systems and I am reading thru it now that school is over.  I am looking forward to the engineering of it, but I am a bit short on time and will probably want the array to be ready and tested before I bury it so I will probably need to get started on buying the components soon.

Eye Candy  These are just some of the fun things that have caught my eye lately, even if they are not all related to earth sheltering.  I appreciated the engineering and creativity of the bicycle chain clocks (the simpler looking one retails for a ridiculous $2400) and I also really appreciated some of the good construction techniques shown on the RM Dev blog. (I just included a few relevant pics here)  You can tell that I have been thinking a lot about how to cover the trellis lately…  No I don’t plan to use hundreds of colorful umbrellas, but that pic still caught my eye and colorful fabric might not be a bad idea while I wait for the vines to grow in.

I also found two more interesting “earth sheltered” hotels, but I will put those in as another post.