Monthly Archives: October 2012

Construction industry insight

Posted on October 29, 2012 by

While sourcing to build your own home, you can find out all sorts of interesting things about the industry.  Of course, a lot of money goes into the housing industry, and along with that money comes incentives for various groups and corporations to game the system…  Here are two short examples.  For a third one, consider the Low-E, High SHGC controversy on the Windows Page.

Flush-less urinals

A typical toilet uses a lot of water to flush away a liquid.  Euro toilets have a second “number 1” button that uses much less water.  A urinal uses even less water, but still a lot.  A “flushless” urinal uses no additional water and with two boys, could save me thousands of gallons a year.  I asked a plumber about it and he said “no, those are very dangerous, you shouldn’t install one, they aren’t even legal in most states”.  Well, I have seen them in many airports and public buildings, and I know that the US Core of Army Engineers has switched to flushless urinals exclusively, so that didn’t sound right.

TO THE INTERNET! for research.  I found a lot, here is one with some good numbers and details, and here is one source that had a nice video, but here is the jist of the story in my own words.

Illustration of how the Falcon Waterfree Tech flushless urinal works… This is really the money maker behind the business as it represents a continuous revenue stream (no pun intended)

These flushless urinals are more common in Europe.   An american business man (James Krug, ex-exec of Disney corp and big donor to Al Gore) thought it would be a good green business opportunity here in the USA and started a business, Falcon Waterfree Technologies.  Not being totally altruistic, his design is based on a cartridge fluid trap that need to be replaced periodically at $40 a pop, but it would still be much cheaper than all the water that a regular urinal requires. I personally prefer the H2Zero model by Caroma because of its longer lasting trap design.  Click Here for a demo video.

James and others in the industry were “blindsided” by the plumbers union.  Of course, the union claimed it was a public safety issue and had some unqualified hack write a ridiculous report (based on no research, she had never even seen a urinal before being hired) to support their position that the urinals were actually “deadly”.   You don’t need to stretch your imagination to suspect that the union was actually more concerned about the fact that people who install flush-less urinals wouldn’t be paying plumbers to install water lines or do as many repairs.  Whatever story you believe, the building code was actually adjusted to ban the flush-less urinals.  But James Krug couldn’t let that happen to his fledgling business, so he used his connections to push the green angle.  So now the Democrats (yes it gets political) were on both sides of this one. They had union lobbyists trying to keep the plumbers paid and they had environmental groups lobbying for the water savings…  They had to come to a solution that made everyone happy, and they did, sort of.  The residential building code was adjusted so you can now install one of these flush-less wonders, and save all the water you want, but only if you also have water lines run to it (preferably by a union plumber ;^).    That is what political compromise looks like.

Steel stud framing

The front wall of the main portion of my home will not be earth sheltered or significantly load bearing… As a result, I am planning to use 6 inch steel stud framing.  This was definitely my architects preference (over wood studs).

We could not use ICFs for that south wall because there are too many windows (and not enough structure) to support the weight of the concrete above.  I guess we could have used ICFs below the windows, but the startup costs would be too great.  Also, ICF can be made to handle curved walls, QuadLock does it better than others, but it is still relatively expensive.

There are many advantages to steel studs, including reduced cost, longer life, increased precision, no chemical treatment, etc.  From an environmental perspective, wood is renewable but the steel is much lighter, longer lasting and very recyclable…   The only clear downside is excessive thermal bridging with the steel studs. Even though these steel studs are thin, they still act like a heat conduction highway.  In addition to allowing the heat out via high speed conduction around the insulation, they also produce cold spots on the interior walls that can result in condensation and visible ghost lines as dust and soot in the air get stuck in the condensation.

As usual, when looking for a solution…  TO THE INTERNET!!!

I found lots of very interesting papers such as this one or this one. They all seemed to be about 10 or 12 years old and they included lots of interesting ways to reduce the heat conduction…  The three main categories were;

  1. cut slits or holes into the stud to increase the distance the heat must travel thru the stud (like a maze).
  2. Stamp the faces of the stud to reduce the contact (conduction) with the wall coverings
  3. wrap the stud or the whole wall with insulation


The first two options are just a stamping process and could actually reduce the weight and cost of the studs while improving the thermal performance.   However, they did require an investment in research to figure out how best to stamp the steel for minimal conduction with maximum stiffness.  The third option is the simplest in terms of technology, but increases the cost of building considerably.  The third option could be done by wrapping each stud individually or by sheathing the wall its self, which is the most expensive because it uses the most foam and then also requires special attachment of an exterior covering to protect the rigid foam sheathing.   So, clearly improving the efficiency of steel stud construction would be in the best interests of the home owner, the steel companies and the planet.  Clearly, there would be a lot of money available for research and the winning design should easily take over the market…  But the steel companies didn’t count on the power of the petrochemical lobby.   While the steel researchers were busy figuring out a better steel stud, Dow Chemical and others were lobbying and adjusting the building code so it now requires all exterior steel stud construction to include insulation sheathing.  This undercut the innovative efforts of the steel industry and I couldn’t find any companies that sell the more advanced steel studs.  (Update, actually, now MarinoWare does sell studs like this, but you will need to special order to get them).

Here is a gallery of pics to illustrate…






Posted on October 21, 2012 by

Last week I got to go out and help out with the earth shelter being constructed near Battle Creek.  As usual, there is nothing as enlightening as seeing things first hand…  If you are planning on building an earth sheltered home, I really recommend you find one in progress and visit as often as they will let you ;^)


When I got there, I saw that Scott (the home owner, GC and whatever other role is needed) had done a lot of work since the last visit in September.  He had completed the rebar work, including a second layer on the larger dome.  He had setup the ICF (Insulated Concrete Forms) on the south side and a pumper truck with a tall boom had come out to fill the forms for that front wall.  His carpenter had also installed most of the windows.

This close up shows the wires coming thru the two 1″ overlapping layers of butt jointed polystyrene and tied around the wood baton… On the back side, the wire wraps around the rebar, but loosly so there is room for the concrete to get between…

While other jobs were being done by professionals, the home owner had started on wiring up the polystyrene on the inside of the domes.  The polystyrene is used as backing to prevent the shotcrete (sprayed concrete) from just blowing right thru.  The basic process, as specified by Formworks Inc, involves carefully cutting sheets  of 1 inch thick polystyrene (what white coffee cups are made of) to fit in the space between the IBeams.  Two overlapping layers of butt jointed polystyrene need to be placed at once.  The attachment is made, starting on the outside of the dome, by taking a “u” shaped piece of wire placed around an intersection in the rebar and pushing it thru two layers of polystyrene.   The wire is wrapped around a thin wood baton that prevents it from simply pulling thru the polystyrene.  The polystyrene is installed loosely to the rebar, with at least “one finger” of slack in the wire, to allow the shotcrete to envelope the rebar.  Cutting the sheets to fit the 6 ft spans between the IBeams is a bit of a hassle, but making the precise cuts to fit two overlapping offset layers and wiring it all up is very time consuming.  Working high off the ground, where the shapes only get trickier, adds its own special pain.    Seeing that the cold weather was coming and he needed to speed things up, the homeowner called in some hired hands so he could be ready to shotcrete before the really cold weather hit.  They got the job finished in 10 working days.

This is a wider view of the insulation inside the smaller garage vault. A lot of effort went into this part of the puzzle.  You can see the light coming thru both layers.  I suspect things would have gone more smoothly if the outer cracks had been taped to prevent shotcrete from getting between the layers, but that is probably easier said than done with all the rebar in the way.

View from garage looking toward the larger main home vault thru the corridor. Keep in mind that this is two layers wired from the outside thru to the batons on the inside… A lot of time and effort I am sure…  The rebar will later be cut from this opening, but it is left in place to help hold the shape until the shotcrete hardens.

The “Formworks” process starts with the polystyrene on the inside as a backing for the shotcrete, but it doesn’t stay there.  After shotcrete, the polystyrene is removed and then used again on the outside as insulation (out-sulation) and protection for the waterproofing.  Since the insulation is usually pretty cut down or broken up by then, it doesn’t really form a nice continuous layer and additional insulation will probably be needed…

Electrical boxes and conduit were also set in place between the polystyrene and the rebar.  These will eventually be enveloped by the shotcrete, but open to the inside.  Of course, the electrical inspection had to be done before they “closed up the walls.”

Electrical boxes and conduit are wired to the rebar and will be set within the shotcrete. When the insulation is removed the front of the electrical boxes will be open to the inside of the earth sheltered home.

Ready for Shotcrete.  The front of the home was done with ICFs (Insulated Concrete Forms).


Back of the home, ready for shotcrete. The shiny silver is just the reflective backing on the polystyrene. It made the home look very space age though.   At one point, a large flock of cranes (maybe 100 of them) kept circling the house.  I wondered if they thought it looked a bit like water…  Scott commented that he noticed a lot of human traffic slow down as they passed by.



This was the shotcrete crew’s first earth sheltered home, but they have lots experience with various other shotcrete structures, including some with shotcrete placed overhead.   I first spoke to Nate well over a year ago.  He stood out from the shotcrete guys I spoke to as someone who not only knew what earth sheltering was, but thought it was a good idea.  (one of the others said “you mean like a zoo habitat?  Why would you want to do that?”)  I meet up with him in a McDonald’s and he had almost as many pictures of earth sheltered homes on his computer as I had on mine… It turned out that he had already had meeting with another potential earth sheltered home builder who was also planning an earth sheltered house.  Not sure if Scott had to convince or educate him about earth sheltering, but I appreciated that he was already interested.  One thing lead to another, and I got Nate to introduce me to Scott so I could get some first hand experience.  Plus, how often do you get to see a contractor work on a similar project before you hire him?

Shotcrete uses a cement pump and a powerful air-compressor to blast (with air pressure) low slump cement onto the structure.  This concrete mix has much less water than a pourable mix, which results in higher strength (6500 psi in a week, 8000 psi in 28 days).  Also, the heavy sprayed cement is moving quickly (inertia) and compacts tightly as it hits the rebar and previous shotcrete without needing any vibration.  The result is a dense and very strong cement structure with no seams or cold joints.  One of the main benefits of shotcrete is that you don’t need traditional formwork, which means you are not as cost-constrained to building with straight walls.  However, it does help to have some sort of backing to control the shape and prevent some of the cement from being wasted (by just shooting right thru the wall).   The shotcrete stiffens quickly and locks on to the rebar and previous cement.  It easily spans over the many small (1 or 2 inch) gaps in the insulation.  The “gunner” starts with a thin layer and keeps the gun moving so the shotcrete has time to set before too much is added (so it doesn’t just slump off the wall).  They keep moving and gradually adding thickness to the cement until it reaches the specifications.  In this case, the engineered drawings specified 12 inches at the base tapering down to about 8 inches at the 10 ft level and then down to 4.5 inches at the top of the larger dome.  The top of the smaller dome only specified 4 inches.

With shotcrete design, some curvature is actually an asset as it helps the wall stand on its own without as much bracing (A curved piece of paper can stand on its edge) and a convex curve resists earth loads with less thickness or reinforcement…


I am sure the Shotcrete guys had lots of practice/experience with swimming pools, but this slippery, flimsy and loosely-wired polystyrene backing was new and there was a learning curve.  While the shotcrete thickness can be applied over several days without a “cold joint“,  they generally want to apply each pass as thickly as they can while moving around…  However, while that shotcrete is still setting, its weight, along with the impact force, is all against the polystyrene.  Also, since the polystyrene is only loosely wired to the rebar, it moved around alot as the shotcrete hit it and made a lot of noise (until some shotcrete thickeness built up).  During this shifting, gaps opened up, etc.   It is actually amazing that the easily broken stuff didn’t just tear off…  There were a few bulges where the rebar sagged and actually pushed in (from convex to concave, oil canning)….

This section of rebar bulged in, but we caught it on the inside and prevented the polystyrene from blowing out… They were able to chain it to the lift and pop it out again without any major damage.

There were also a few blowouts, where the polystyrene did actually fall apart.   It appeared that most of the blowouts happened when the weight of the wet shotcrete pushed the rebar so far inward that the polystyrene was stretched to the breaking point.   The other failure mode was when shotcrete got in between the layers of polystyrene and was able to flex and break of a piece of the inner layer…  I think that taping the cracks on the outside could have prevented this, but with all the rebar in the way, that is probably easier said than done.   When there was a blowout, the polystyrene and hundreds of pounds of cement came down with an awful crashing sound (I was inside about 25 ft away at the time of the largest one).

Before each blowout, we saw shotcrete pea stone pouring in between the overlapping layers and then the wall started to bulge inward.  If you can stop it then, you can prevent the blowout!  Then the shotcrete between the layers started to push into the vault and cracked off corners of the inner layer.  These cracks freed the batons and then it all came down.  All in just seconds…   Since shotcrete between the layers started the chain of events, closing those outer gaps (with tape) is probably the most important preventative measure.  Taping the inner cracks is not nearly as important.


After the big blowout, Scott decided to “phone a friend”.  The other supports seen in this picture were improvised in a hurry to combat “bulging”.  It probably prevented a few other blowouts before the shotcrete crew slowed down.

Scott handled the roof caving in pretty calmly.  While the shotcrete gunners proceeded (with more caution) on to other areas, Scott called in a friend and we quickly assembled some scaffolding and replaced the insulation.  We also added more batons to stiffen similar areas, but I am not sure how much difference that made since it wasn’t the batons or polystyrene that failed.

I was really worried about further blowouts, particularly since we hadn’t got to the even larger home dome yet.  But it turned out that “practicing” on the garage was a good idea.  I was only there for day 1, but I was told that they didn’t have any blowouts or issues on the main vault over the next few days.

The lift is used to apply shotcrete to the tops of the domes


I had posted a time-lapse video of the process right here, but after 5 years, the shotcrete contractor asked us to take it down and remove his name from these posts because he was getting criticism in the comment section. I am pretty sure he had no legal grounds, but I decided to oblige him anyway.


Lessons Learned

Between scrambling to shore up bulges or fix blowouts, there was time to chat with the homeowners, shotcrete crew and cement mixer drivers on the site.   We talked about a range of things from the cost of job site insurance to the hidden costs of heating systems to the suggestion to install cheap steel doors to close up the house (security) during construction (while the nice doors are safely away from contractors dents and scrapes.)   Some shovel based civil engineering had been done to clear water from the site, but it was clear that the shotcrete crew was struggling a little with the steep banks close to the site (although sometimes it seemed helpful to shoot from the banks.)  I reinforced my mental note to grade around my site more carefully.

During my previous visit, I was impressed with how well the Formworks steel and rebar system was designed, but this time, I was very glad I was not following their process for the polystyrene shotcrete backing.   The polystyrene worked, but it seemed like my pegboard/particleboard plan would be better in almost every respect.  The polystyrene backing required a lot of time-consuming cutting to get the two overlapping layers.  This is easier when you have the IBeam flange to hide the edge or when your arches are parallel, but I would have neither.  Also, with the Formworks plan, the polystyrene is inside the IBeams and tied, somewhat loosely, to the rebar to provide room for the concrete.   This loose polystyrene shifts a lot when the rebar hits it, and in some cases, allowed shotcrete between the layers.  In all the “post shotcrete” pics I have seen on the Formworks website, this process leaves a somewhat rough final finish on the inside of the dome because the edges never quite line up and the gaps between butt joints are at least an inch deep.  Conversely, the polystyrene itself is actually too smooth, which makes it difficult for the shotcrete to grip.  It is also brittle (easily broken).  The polystyrene is also relatively expensive and I don’t buy the argument that the cost is offset because it can be “re-used” as insulation.  By the time you take that polystyrene down, it is so chopped up that it will be impossible to form any sort of continuous layer, even overlapping it like shingles.

I have seen burlap used on other earth shelters (such as the Project Michigan Earth Shelter videos available on Vimeo).  It is cheaper and doesn’t need to be removed, but it sags and gives a very ugly appearance on the inside that is not something you can just plaster over…

I had preferred the pegboard plan.  It is cheaper than the polystyrene, and strong enough that one layer is sufficient.  It is harder to cut, but if you overlap the pieces a little and not need to cut as often.  Also, with the 1/2 inch tube arches, you can tie it tightly to the inside of the arches and properly control the cement thickness around the rebar.  Also, the pegboard provides better grip for the shotcrete and would prevent some sagging.   It also provides better control of the final shape and the little quarter inch thick posts left over after the pegboard is removed provide a nice final surface for plastering the inside of the vaults.  We actually plan to use “SpecFinish”, which is a fine sand-based shotcrete, on the inside of the vaults.

However, one of the shotcrete guys pointed out that the downside of the pegboard was its susceptibility to moisture.  While the polymerized linseed oil on the surface of the hardboard gives it some water resistance, the drilled holes provide easy access for water to soak the wood fibers inside.  I would need to worry about rainy weather and the moisture of the shotcrete its self.   Also, once shotcrete mushroomed thru the holes, it may have been much harder than the polystyrene to remove later.

Apparently, the shotcrete crew had recently shot a movie set where expanded metal lath was used as the backing  (some storm-related movie, “Black Clouds” or something like that where they needed to do a flood scene).  They said the metal lath was the easiest thing they ever worked with.  The Metal lath has all the advantages of the peg board, except it is a little more expensive (20%) at roughly 35 cents per square ft.  It also has some additional advantages such as; being relatively impervious to weather, adding reinforcement and not needing to be removed after the shotcrete is applied.  Metal lath can be cut-to-fit on site with a hand-held grinder, or the sheets can just be overlapped and wired together.  The metal lath is stronger than the other options and can actually be walked on during the shoot (but mine will be below the rebar anyway).  It also holds its shape under the weight and impact of the shotcrete better than most other backings.   The shotcrete comes thru the metal lath just enough to mushroom out the other side and hide most of the metal.  This provides a nice evenly-rough surface on the inside, ideal for finishing.  I already talked to my architect and engineer about switching to metal lath.

I also noticed how much pea stone was “rebounding” off the wall and being raked away…  In my design, vaults meet at the bottom and I was concerned about where all that pea stone getting stuck between the vaults.  I discussed this with the shotcrete contractor and he said it would be a bit of a problem.  We will need to remove it, even if it means scooping it out with buckets…  On the other hand, my vaults are not nearly as tall as the earth shelter near battle creek, so it won’t be as much pea stone anyway.



Next, I hope to head out to help with the waterproofing on the shelter.  More on that later.

Quick Update

Posted on October 11, 2012 by

In the spirit of shorter posts, here is a quick update for this week.


We finally got an address, which is an important precursor for lots of things like permits and quotes.  It wasn’t easy in the small town environment where the person who does it works 6 scattered hours per week.  It took many calls, but we finally got it.  I am leaving off the full address for privacy reasons, but for those who know the town and road, the number is 10415.  Sherri liked how the guy said it, ten-four-fifteen.


This week, we got some quotes on well drilling (roughly $7k) and we visited a Pella showroom.  The Pella show room sales person was very much more responsive and engaging than anyone else we have spoken to.  I had been ignoring Pella based on early impressions, but I gave them another chance due to comments by the owner of the Battle Creek earth shelter and poor service I was getting from Marvin distributors.   Lets see how the quote works out.

I am considering ways to reduce the cost, including flattening the curved walls…  But I have not decided on that change yet.


Engineers rough reinforcement sketch on my concrete rib design…

I finally got a few hand sketched pages from my engineer.  This one has the rebar sketched out on the concrete ribs.  It was pretty much what I was expecting (maybe a bit more more and thicker rebar).  He also did some work on the arches that span between the ribs, but he must have misunderstood the examples I provided and went about 10 times over weight/cost, so we will need to get that reviewed.


Battle Creek

Next Tuesday  I am taking a day off work to head out to Battle Creek (about a 2 hour drive) and watch the shotcrete get applied.   The house is all ready with the poured slab, steel arches and rebar, and an ICF front.  This is the next big step.  It will be interesting to see how cement is sprayed on a 50ft dome (25 ft high).  I will try to bring back some pics.

Eye Candy

Here are some fun pics I have seen lately (collected across the internet) that I found inspiring in one way or another.  Enjoy.