Odds 'N Ends - Lesson from a Tepee (Cont'd)

The first post on tepees covered many of their unique features such as shape, orientation, materials, smoke flap function, insect control and some of the Youngs' camping experiences in a tepee, including winter camping.  This post adds other interesting tepee factoids.

Tepee Poles

The plains Indians lived nowhere near good trees for poles and had to travel several

Lodgepole pines

hundred miles west to the Rockies to harvest lodgepole pines.  Consequently, poles were
cherished and lasted a long time.  The 14 poles supporting the cover were traditionally several feet taller than the cover while the two poles that moved the smoke flaps were shorter. Two of the oldest and most dispensable poles were used for the travois which meant that dragging them on the ground behind a horse wore them shorter.  So they were relegated to smoke flap poles.  I suspect the extra length for the other poles was intended to delay pole-cutting treks to the mountains as long as possible.  As the bottoms of the poles deteriorated from being in contact with the ground, the extra length allowed the poles to be shortened many times before having to be demoted to smoke flap duty or replaced entirely.

For a 20' tall tepee like those we had, the poles needed to be at least 24' long.  The unique thing about a long lodgepole is that the diameter at the tip is only slightly smaller than the diameter at the base -- only about 2 - 3" for tepees.  The minimal taper gives them the stiffness they need to carry the weight of the canvas despite being so slender.

Pitching the Tepee

If the squaws were responsible for pitching and striking the tepees, ever wonder how agile some of them must have been to shinny up the poles to tie and untie them at the top?  Didn't happen.  The three sturdiest poles are tied together flat on the ground then spread out and tilted into place to form a tripod.  The excess rope dangling from the top is more than long enough to touch the ground.   The other 11 poles are then laid into the forks of the first three in a very precise order.  After the poles are in place, the excess rope is wrapped from the ground around all of the poles and tied off to one of the tripod poles.

The cover is raised and secured just as easily.  It is laid on the ground around the periphery of the tepee with its midpoint directly opposite where the door will be.  Then the smoke flap poles are inserted into the pockets for them at the top of the smoke flaps and used to lift the cover into place.  It is subsequently draped around the poles towards the door then overlapped over the door and laced together with 1/4" thick sticks that fit in matching pairs of "button holes".  The nearest thing to climbing the squaws might have had to do was to secure a stick across the door opening on which to stand while lacing the cover together.

Doesn't It Rain In Around the Poles?

Yes, but not much. Most of the water runs down the underneath side of the poles to the ground unimpeded as long as the poles are smooth and there are no obstructions.  Consequently, the poles have to be debarked while they are green and the knots that are left where the limbs were have to be shaved smooth.  Moreover, the ropes that attach the liner to the poles cannot lie directly against the poles.  Instead, two small twigs are wedged under the rope to hold it away from the pole on the underneath side, providing a clear waterway to the ground.

As mentioned in a prior post, our first tepee was pitched in Illinois in the mid-70's.  Rather than having 16 lodgepole pine poles shipped from one of  the Rocky Mountain states, we used native trees with terrible results.  They were bulky, heavy, crooked, tapered too much and were difficult to get smooth enough to carry the water to the ground without drips.  We ended up shortening the poles to just above the liner and covering them with a god-awful metal lid from a hog feeder.  Ugly and insulting to tepee-ism.

After a couple of years of making do, we took the tepee to Colorado for a two-week camping vacation.  We arranged a head of time to pick up new lodgepoles near Aspen (which gave us an opportunity to tour the town overnight).  We then hauled the poles on the rack atop of our DIY trailer behind our 4-W drive International Scout to Crested Butte, a ski town that was the nearest civilization to our planned campsite at 11,000 feet. Interestingly, Aspen and Crested Butte are hiking distance apart as the crow flies but multiple hours apart by road because they are separated by the continental divide. One of the ski resort motels in Crested Butte stayed open during the summer so we touristed Crested Butte by evening and de-knotted our tepee poles with butcher knives on the motel parking lot by day.

Eventually, we did have a second set of poles shipped from Montana when the original set deteriorated after about 15 years.  The truck driver was amused by a bundle of "What?" that was more than half as long as his trailer.  As mentioned in a prior post, we took the cover home during the summer but we left the poles in place and unprotected.  Otherwise, a second set would not have been necessary. 

Isn't the Tepee Smokey?

Also as explained in detail in a prior post, the smoke from the campfire is at the mercy of wind direction and barometric pressure.  The relationship between the liner and the cover in conjunction with the smoke flaps limit the amount of smoke campers have to deal with -- much less actually than around a campfire in the open -- because the fire inside is controlled and predictable.  

There is no wind inside, so the heat of the fire causes the smoke to rise naturally whereby the air coming in between the liner and the cover picks it up and carries it out through the smoke flaps.  Make-up air for the fire enters in an intentional manner either below the door or through an opening around the door that is tailored in size to the amount of air needed for the fire -- much like opening and closing a stove damper.  

Okay, What Is the Lesson That the Tepee Teaches Us?

For some it may be a stretch but for me it is easy to see a parallel between the tepee and green building to the degree that both work with nature instead of against her. In my view, that characteristic goes a long way in defining sustainability.

Odds 'N Ends - Lesson from a Tepee

The tepee is such an unique and interesting shelter that it takes two posts to do it justice.Several visitors over the years said things like "Wow, this is cool space" or "I had no idea". Where I am going with this Odds 'N Ends piece is to draw a parallel between the tepee and green building with respect to working with nature instead of against her.  Also, I am betting that most readers have never given tepees much thought and might find the following information interesting.

My late wife, JoAnn, grew up in the country back when there was no indoor plumbing and, early on, electricity as well.  She was only too happy to enjoy the benefits of city living and was not terribly interested in camping, at least until the youngest of our four kids was potty trained ("I am not going to wash diapers in a bucket"). When it was time to begin camping, I researched the subject thoroughly and decided that the tepee was by far the best choice for semi-permanent camping.

Subsequently, our family wore out two tepees between the time our youngest kids were grade schoolers and our grandkids started noticing girls.  We treated them as "permanent" shelters by leaving them in place from year to year rather than moving them around like folks who attend rendezvous on weekends.  The only breaks in this routine in Illinois were for a two week tepee vacation just below the treeline in the Colorado mountains and two years in the north woods of Michigan.

A good downloaded image; the only thing that is
missing are the tethers for the smokeflaps

Shape

Ever notice the shape of a tepee?  It's conical so that it funnels smoke up and out during winter and sucks heat out during summer.  It also restricts the amount of unusable space above the living area that must be heated and cooled.  And it allows the poles to be thinner and lighter because a cone (triangle) is the strongest of all configurations. Our tepees were 20' in diameter and 20' tall, fitting the definition of a cone.  There was plenty of room for five army cots around the periphery for seating and sleeping. The middle was used for cooking and clean up with the fire-pit situated between that area and the door.

Orientation

A tepee always faces east so as to turn its back against the prevailing west winds (northern hemisphere) and to orient the smoke flaps (located just above the door) so that they draw the smoke out most efficiently.

Cover and Liner

The size of the original tepee was limited by the weight of the buffalo skins covering it.  However, when canvas was as close as the next raid on a prairie schooner wagon train, canvas became the cover of choice and allowed tepees to grow.

Hugging the inside of the tepee poles is a liner that runs from about eye level to the ground then turns under against the ground on the inside (notice in the picture how the tepee is darker near the bottom due to the liner blocking the light from the fire).   While the liner is sealed against the ground, the cover is intentionally held off the ground several inches.  This relationship between the cover and the liner creates a natural updraft that carries the smoke out through the smoke flaps.  In summer when cooking is typically done outside, the liner is also raised above the ground in order to improve ventilation.

Smoke Flaps

The smoke flaps are long rectangles projecting a foot or more from the cover above the door, the outside edges of which have rope tethers at the bottom and pockets at the top to receive the ends of two poles.  When the wind is from the north, the ropes and poles are used to tilt the flaps towards the south, much like a person would manipulate his/her coat collar or hoodie against a side wind.  When the wind is from the south, the flaps are tipped in the other direction.  When it blows from the west, the flaps extend due eastward, similar to their position in the photo.   When it rains, the degree of tipping is exaggerated so that raindrops are intercepted by the flaps instead falling on the floor of the tepee or on the fire-pit that lies immediately below the flaps.

When the wind is out of the east, which, fortunately, is relatively rare except just ahead of a front bringing rain or snow, the flaps are tipped like it was raining. Even then, an east wind and falling barometer can make a tepee pretty smokey.  Not only does the smoke have trouble bucking the wind, low pressure keeps the smoke from rising.

Insect Control Without Screens
Insects are repelled by smoke.  Having a fire inside unequivocally precludes an insect problem.  We found during the two years we camped in the north woods of Michigan that even the pesky no-seeums stayed outside at night.   Supposedly, in summer when the fire moves outside, the tepee retains the scent of smoke sufficiently to discourage insects.  However, we did not test this postulate because we disliked summer camping and the hot, humid weather degraded the canvas.  We made it a practice to camp from early September (beginning of squirrel season in Illinois) until early May (end of morel mushroom season) then remove the canvas liner and cover to storage for the summer.

Cold Weather Camping
In mid-life, I went to graduate school.  A patient invited us to move our tepee to his summer compound in northern Michigan during our two-year stay in Ann Arbor.  We had regularly camped in the tepee in winter in Illinois so the second winter in Michigan, we decided to try winter camping there.  The temperature hovered at 15 degrees below zero at night and the snow cover was over two feet deep.  We finally got settled in after digging out the tepee and schlepping our groceries and gear several hundred feet on cross-country skies.  The tepee was surprising comfortable after the fire had burned for a few hours to the extent that we could remove our coats and be comfortable in sweaters.  It did however get cold enough by morning to freeze our eggs despite keeping the fire lit by tossing firewood from under my cot into the fire-pit several times during the night.  By mid-morning we were back to wearing sweaters.  

Tepees Were Better Than Log Cabins
I was not surprised to read years ago that the Native Americans were more comfortable in their tepees than the settlers were in their log cabins, mostly because the shape and size of cabins make them hard to heat.  As the weather grew colder, the Indians untied the bottom of the  liner from the poles and let it hang straight down so as to reduce the area that needed to be heated.  In some cases, a canvas ceiling called an "ozan" was hung horizontally above the living space even with the top of the liner to create a lean-to effect to trap and hold more heat from the fire.  We actually made and used an ozan for winter camping in Illinois but without hanging the liner straight down.  Even then, it made the tepee surprisingly more comfortable on cold nights.

Construction - AGS System for Passive Solar Heating and Air Conditioning - Cont'd

This is the second of three posts on the actual design and installation of the AGS system. The first post dealt with the conduits that distribute solar energy through the thermal mass under and surrounding the house.  This post focuses on the second important element of the system -- the solar collector.  Another element is the insulation/watershed umbrella.  I will describe it in detail once it is installed.  Its installation will fall sometime between wrapping up the concrete work and beginning wood construction -- possibly as soon as a couple of months out, weather permitting.

(Reminder: click on any photo below to enlarge it for closer inspection.)

Depth of the Solar Collector
My initial concept of the solar collector was not well thought through.  I simply failed to realize that the 15 degree slope in front of the house was too shallow for the floor of the collector to be 9' below the floor level of the house and still be even close to the height of the surrounding grade.  Fortunately, having to bury the collector does not significantly limit solar gain because the summer sun orbits so high in the sky that, even when the glass is 4 - 6' below the surrounding grade, it will shine on the collector a sufficient number of hours each day. This is in contrast to a typical winter passive solar system for which the glazing would have to be closer to the surface in order to catch the low-angle winter sun,.

Size of the Solar Collector
Several years ago, we visited near Spokane an AGS-conditioned straw bale house having 3' x 20' glazing for its collector in a climate with a third more heating degree days and considerably less available summer sun than we have here.  Therefore, I was confident that the tempered glass panes we found for free on Craigslist -- enough for a 4' x 18' collector -- would do the job.  I could easily conceptualize the 18' dimension but not the 4' dimension. Once I determined the angle that put the glass perpendicular to the summer sun, I realized how flat the glass would be and how big the shell for the collector would have to be.  Unfortunately, I didn't do the math before the excavation for the collector was done and had to have the contractor dig some more and, even then, the pit was too small in the N-S direction for easy wall construction of the south wall of the collector.  In the second photo below, notice the proximity of the excavation to the south (right) wall of the shell for the collector.

Excavation Between the House and the Collector
As detailed in the first post , the nine corrugated conduits begin at the future front wall of the house, fan out under the house to connect with smooth pipes in the backfill behind the

View showing the extent of the excavation for the smooth
pipes; a few of the corrugated pipes can be seen at the
base of the drop-off; the rest have been buried by gravel
and soil washing out of the conduit trenches; the
tripod at the right supported a rope and pulley for swinging
heavy items into the pit while working alone

house that run to daylight.  At the front wall, they are bunched together so as to be lined up for a run to the collector in parallel using smooth PVC pipes. Rather than trenching for the smooth pipes individually, the run to the collector was opened up completely with enough depth that the smooth pipes will increase slightly the 3 degree inclination that was already built into the corrugated pipes. (The inclination is critical for the heated air from the collector to pass passively through the conduits and exit some 70' later behind the house).

The excavation between the house and the collector was not inconsequential, being over 20' square and sloping from 5' deep at the corrugated pipes to 6' at the collector.  It also undermined the front wall of the house to such an extent that five piers on individual footings resting on virgin soil in the floor of the excavation were installed before backfilling the excavation. The footing for the foundation will be doubled in thickness (height) since it spans the excavation as a beam supported jointly by the piers and rock backfill.

Excavation for the Collector

The excavation for the collector was not inconsequential as well. The pit for the collector was dug 22' in the E-W direction and 10' in the N-S direction.  As already mentioned, it would have been better had it been 12' north to south and 24 feet E-W to give more room for dry-stacking the block walls. The original depth for the excavation at the collector was approximately 9' below the floor level of the house. The conduits will eventually penetrate the wall of  the collector about 3' above the floor of the excavation and the north wall of the collector will need to be at least 6' higher than the conduits as a retaining wall for restoration of the original slope of the ground in front of the house. The the other three walls will need to be more like 3' higher than the collector.  The disparity in wall heights will be handled with natural rock retaining walls extending outward from both ends of the north wall.

Unfortunately, I did not photograph the pit before installing the first three courses of blocks. So this picture, taken after the first bond beam course was partially filled with concrete, is a little premature for this post but is included to give perspective on the size of the excavation for the collector.  The rigid AGS conduits (smooth pipes) will connect with the collector on the north side (left in the photo).

Glazing
The link "Duration of Sunlight for 2015" for Collinsville, IL, shows almost identical "solar isolation" (maximum amount of available sunlight) for the weeks leading up to June 21 versus the weeks following. The website does not account for cloudy weather so I am betting there are more clouds interfering with solar collection during the rainy weeks preceding June 21 than during the dry summer weeks following it. Accordingly, I decided to use the sun angle for July 10 instead of June 21, which was easy to do by going online to Solar Position Calculator.  Our sun angle for July 10 is a steep 74 degrees off horizontal. The most efficient angle for the glass is one that is perpendicular to 74 degrees  or 16 degrees off horizontal.  

 "April showers bring May flowers" seems be an oxymoron anymore.  Our Spring rains seem to come later and later to the extent that this year our rainfall for June was three times normal and the rain during July is running above normal as well. Maybe, in the future as the weather changes in response to global warming, a July 10 target will prove to be too early for capturing the most sunshine .  Although we are not doing it, it might make sense to consider making the tilt of the glass adjustable.

The width of the four panes of glass is 4' and their total length is 18'. The perpendicular angle to the sun angle is close enough to horizontal that the glazing for the collector will cover 80% of the total area inside the concrete shell.  There will be only 18" of access space along the south wall for maintenance, such as cleaning the glass and clearing out leaves, and to allow an unobstructed flow of air into the front of the collector.  The glazing for the collector is quarter inch tempered glass which may be not be strong enough, at such a flat angle, to withstand the kind of hail storms we see frequently here in the Midwest.  If not, it may have to be replaced with 3/8 inch tempered or a plastic/fiberglass material of some kind.

Clear Glass or Translucent?
When sunlight passing through glass strikes various objects and surfaces behind the glass, the short wavelength energy is converted into long wavelength energy that is incapable of passing back through the glass -- hence, the "greenhouse effect". Darker objects tend to absorb the energy and lighter objects tend to reflect the energy.  For our AGS system, we want as much energy as possible not to be absorbed and bound up in the collector but to be reflected and encouraged to leave through the conduits.  With our clear glass panes, a white gravel floor for the collector that reflects rather than absorbs will be best even though some of the energy will not be diffused and will be lost back through the glass.

However, the best of all worlds would be translucent glass instead of clear glass.  To paraphrase one authority, "translucent glass is transparent to the incoming wavelength and opaque to the outgoing wavelength".  The glass itself diffuses the incoming energy and traps it all rather than some going back through the glass.  I suppose this is why old-fashioned greenhouses with real glass roofs usually have what looks like whitewash on the glass and why untinted translucent fiberglass is recommended over clear materials for homeowner greenhouses.  We will be using this principal for the second story windows of the house as will be discussed in a future post.

Update - Summer 2016
When this post was written, I thought I had a grasp on how the solar collector should work. Since then, a scientist friend has helped me understand the design from a thermodynamic perspective which is much different than what I wrote above.  In the near future, I will be devoting an entire post to the design of the collector.  Stay turned.

Timeline - Alternative Certifications to LEED

The quest for some sort of sustainability recognition for our project started with the assumption that LEED (Leadership in Energy and Enviromental Design) certification

would be attainable and affordable.  As discussed in the first post on certification, the LEED fee of up to $2,000 turns out not fit our budget and certifiers seem to be uniformly disinterested in residential construction.  This post shares some of the information gathered while searching for an alternative to LEED. Most of it comes either from Johnston and Gibson's book, "Toward a Zero Energy Home - a Complete Guide to Energy Self-Sufficiency at Home”, or from Stan Clark (Advance Green Consulting, LLC), a local energy consultant that I trolled onto while looking for a LEED certifier.

A big positive for LEED is that it rates sustainability from conception to completion. The other green ratings/certifications, except, to some extent, NAHB, focus on energy conservation of a built house.  In addition to the requirements listed below for other certifications, LEED is unique in requiring the following:

• Site selection:  In-fill and urban instead of suburban, exurban and rural
• Proximity to infrastructure:  Schools, shopping, medical care, entertainment
• Site stewardship during construction:  Erosion control, minimal site disturbance
• Green building practices:  Off-site fabrication, FSC-certified lumber, materials with low embodied energy and salvageable end-life, recycled materials, advanced framing, minimal construction waste

HERS Index (Home Energy Rating System)

• HERS is the most economical alternative to LEED -- $700 - 800 -- but still has high kudos in the green building industry
• Rating is based upon a hypothetical code-compliant "conventional home" (a production home as opposed to a highly detailed custom home); the conventional home is given a HERS SCORE of 100 against which a subject home is compared; a score of 20 or below is excellent and rare
• Certification includes a plan evaluation and computer modeling
• Periodic inspections by a certifier are done during construction to monitor and test energy efficiency procedures, both before and after the insulation is installed
• Inspections include blower door testing and HVAC duct pressure testing
• The process culminates in a report and certificate

Energy Star Version 3

• $850 - 1000
• More stringent guidelines but higher recognition
• Plan evaluation and computer modeling
• Inspections for insulation and air infiltration control
• Blower door testing, HVAC duct pressure testing
• Report and certificate; certificate sent to a federal registry

The interesting aspect of the Energy Star approach is that a project is rated against a hypothetical "Benchmark Home".  According to Stan, our project may not be Energy Star certifiable because it is too non-standard.

NAHB Green Build Standards (National Association of Home Builders)

• $1400-1500 which includes the price of submission to NAHB national registry
• Many guidelines regarding sustainable practices during construction (similar to LEED requirements)
• More compliance inspections than for HERS and Energy Star

Stan Clark, who's certified in HERS, Energy Star and NAHB, says he will be able to obtain certification for our project but it will require some creativity on his part.  Isn't it ironic that a project can be potentially so out-of-the-box energy efficient and sustainable as to defy certification?

Timeline - Certification - Is LEED worth chasing?

Why Certification At All?

We field this question often and those asking are usually professionals such as contractors, architects, engineers and consultants who are not yet involved in green building. They contend that the energy performance of the house will speak for itself through utilities bills.  So why pay for a certification?  One green building contractor said that we should "use the money spent on LEED certification for something nice like marble counter tops" and go with a less expensive certification program.  Several others in the green building movement voiced the same opinion.  As for the question, "Why certification at all?",  we feel that certification fosters discipline and presents challenges that we might not meet otherwise.  Also we plan to make our home available as a demonstration site for which some kind of certification will lend authenticity. 

LEED 
In the beginning, I (more than Dorothy) was determined to go after the highest LEED certification possible and I was not willing to abandon this goal even after receiving input from the professionals.  Since LEED is a function of the Green Building Council, I downloaded from their website a document titled "LEED for Homes -- Frequently Asked Questions".  From it I got the impression that their pilot program for homes ended in 2006 and home certification would soon become commonplace despite the anticipated fee of $500 to 2,000 per dwelling.

However, my enthusiasm soon waned.  In the first place, it seems like LEED certifiers are still interested in commercial projects, not residences.  Among the list of certified buildings on the local Green Building Council website in 2012, there were only a few certified residences and most of those were Habitat for Humanity Homes. I left messages on the local GBC website and tried to contact certifiers listed for our area on the national GBC website as well as on the website given in the document that I downloaded -- all to no avail.  I tried networking through the building trades to find a certifier.  I did a presentation before the local chapter of the GBC during which I specifically asked for help finding a certifier.  Afterwards, two architects said they would see what they could do to find someone but I heard nothing from them.  It has been one frustrating blind alley after another.  But maybe it is just as well.

Cost of Certification

Realistically, LEED certification is too expensive for our budget and the fee probably would not pay for itself through any bump in resale value anytime soon, as much as anything because the public will not be sufficiently educated on sustainability for who knows how long.  If this is the case, the only justification for chasing LEED would be for non-financial reasons such as ego gratification and recognition.  Personal kudos are not our goal.

Early Adopters

Recognition in itself might not be all bad, though.  I have heard that early adopters of new technology must reach 20% of the population before mainstream even notices.  The number is probably bogus but the concept is not.  I believe that we early adopters should do whatever we can to popularize sustainability and, in that context, any recognition that comes with certification is probably a good thing. 

Alternatives to LEED

In my next post, I will discuss three other certifications, any one of which probably makes more sense for individual residences with a reasonable budget than does LEED.

Construction - AGS System for Passive Solar Heating and Air Conditioning

This post is the first of three on the design and installation of the AGS system.  It focuses on the conduits that carry the heat from the summer sun to the thermal mass under and around the house.  The other posts will be forthcoming as soon as the associated installations have been done.  One will cover the design for the solar collector and the excavations necessary to get it installed.  The last will discuss the construction of the shell for the collector, joining the conduits to the collector, insulating and backfilling the excavations.

AGS Design Review
The design of the Annualized GeoSolar system has been detailed in earlier posts (first post, second post, third post).  In a nutshell, the heat distribution system itself has two components -- a solar collector for harvesting the heat from the summer sun and a series of conduits for conveying the heat from the collector to the soil under and adjacent to the house for storage.  Another important element is the insulation/watershed umbrella extending +/-20' outward from the house about two feet below grade so as to insulate and keep dry a thermal mass larger than the footprint of the house.  The necessity for dry soil is covered in the three posts cited above and more recently in one of the posts on French drains.  The construction of the umbrella will be detailed later after it is installed, which will take place after all of the concrete work is done and before wall construction begins.

Conduit Configuration
The conduits comprise two types of 4" pipe -- rigid smooth-walled Schedule 40 PVC and flexible un-perforated corrugated drain pipe.  The smooth pipes extend from the collector to just under the front foundation where they are joined to the corrugated pipes then again in back of the house between the corrugated pipes and daylight above the north grade which will be nearly two-stories high. The corrugated pipes are limited to the area under the slab floor.  

The heavy-duty smooth pipes serve two functions -- to withstand the weight of 8 - 14' of backfill and their smooth walls should expedite the flow of heated air from the collector. The corrugated pipes maximize heat transfer from the conduits to the soil by creating air turbulence. They can be utilized for this purpose because the weight of backfill is rendered moot by filling the trenches with gravel and pouring a concrete floor over them.

Designing the diameter, number, depth and inclination of the pipes was an educated guess on my part after reading the article describing AGS (Don Stephens paper) and visiting one of the houses he designed near Spokane (the Mica Peak residence mentioned in the paper) and research on earth homes.  In our iteration, nine conduits were installed which means they are about 10' apart after flaring out under the floor. As for depth, they leave the collector 6' below floor level, pass under the front foundation at 5' below floor level, pass under the back wall of the house 3' below floor level and run to daylight behind the house at a 45 degree angle.  Except for the latter, the inclination is about 3 degrees above horizontal which should be enough slope for passive convection of the heated air but not so much that the flow rate is too fast for efficient heat transfer to the soil.

The decision on the diameter of the pipes was based primarily on a good book on earth sheltering that I have since lost track of and on Hiat's book, "Passive Annual Heat Storage".  Before reading them, it seemed reasonable to me that the larger the pipe the more heat transferred to the soil, so my early thinking was to use at least 6" pipes. However, it turns out that a large pipe with a given internal volume has less external surface and therefore, as a conduit, less contact with the earth than several small pipes whose combined internal volume equals that of the large pipe. The situation is analogous to human body types.  Compared to heavier people (endomorphs), skinny people (ectomorphs) typically tolerate summer heat better and tend to chill more in cold weather because they have a high ratio of skin to body mass and therefore more surface area for heat transfer.  I also reasoned that going smaller than 4" might not suck the heated air out of the collector fast enough to keep the collector from overheating unless the number of pipes was increased beyond reason.

Installing the Conduits
Installing the conduits was a cakewalk compared to installing the French drains.  Our

Installation of the corrugated pipes

contractor, Brian Hayes, brought in an industrial-strength trencher.  As soon as he dug a trench we dropped in the corrugated pipe, connected a smooth pipe to it at the north end, backfilled to within a foot or so of floor level with man-made pea gravel then backfilled to grade with soil.  Most of the soil will be removed during the final grading for 4" of rock sub-base and 4" of concrete.

Solar Chimney Discarded
The original design called for bringing all nine conduits to daylight at the north end via a solar chimney.  However, during installation, I decided to dispense with the solar chimney and run the conduits to daylight separately.  The change was driven by several things but mostly by my fear that the system might prove so efficient that the house would overheat. Stephens mentioned this concern in his paper and suggested incorporating thermometers

AGS conduits headed towards daylight; trenches filled
and the site graded for the sub-base and slab

in the soil below and behind the house in order to monitor the heat uptake and make corrections (presumably by closing some of the conduits at the collector). He suggested it might take several years in any case for the thermal mass to reach a stable year-round floating temperature so overheating would not be a problem for at least a couple of years for our project.  I decided that it made more sense to leave the conduits separated so that some could be capped for all or part of a summer following a winter with an overheating problem rather than trying to manage the problem at the collector end.  And it would be possible to reverse engineer a chimney later if proven necessary.

The other reason for keeping the conduits isolated was to eliminate the cost  and complexity of tying the conduits together and leading them into the solar chimney.

Timeline - Design Evolution - Wall Cladding

Past Three Years

Preconceived Ideas

Dorothy and I are not fond of vinyl siding.  It is unappealing because it is ubiquitous, looks cheap, is petroleum-based, has a lot of embodied energy, is subject to wind and hail damage, has a short life span and mostly ends up in land-fills. The commonplace 4 x 8 sheets of cedar-veneered plywood would not be a bad choice except for requiring perpetual maintenance.  Real cedar clapboards are beautiful but have the disadvantages of requiring ongoing care, coming from old growth trees and being expensive.  Our search for alternative cladding that was inexpensive, low-maintenance and green took some unexpected turns.

Fibercement -- the New Green
My green building research kept pointing me towards fibercement siding as the greenest

Fibercement lap siding

choice for cladding.  I even went so far as to buy a used electric nibbler to use for cutting it someday.  It is made from cement and renewable FSC-certified (Forest Stewardship Council) wood, holds paint two or three times longer than wood, is virtually wind and hail proof, has a long lifespan and comes with a reasonably low level of embodied energy.

SmartSide
At one point, a building supply salesperson tried to sway me away from fibercement with a product called SmartSide that appears to be an OSB-like board that can stand the weather. He gave me a sample and told me to take it home and soak it in water for a while to demonstrate its durability. I did and it swelled.  I emailed the company and was told that it was not designed for underwater, just wetting as would be expected with any cladding.  Fair enough.  It is indeed a green product since it comes from renewable wood chips from plantation trees and the finish comes with a long-term warranty.  For green-ness, its other attributes pretty much match those of fibercement.

Metal Siding?
Until two years ago, metal siding had not entered my mind. When my stepson , Keith, said that he was going to use it on their energy efficient house, my first reaction was, "Are you kidding?"  Bu

Siding underway for Dawn and Keith's house;
 note that, for energy conservation, the amount
 of glazing on north and west sides is minimal

t after I helped install it, I came to realize that he had made a wise choice -- it's definitely an unique finish for homes, it's DIY-friendly, it's virtually maintenance-free, it lasts for plus or minus a century and it has a recyclable end-life. If there is a knock against metal siding, it is that it has fairly high embodied energy which, to some degree, is off-set by its recycled content.

Comparative Pricing

When the various options for cladding were compared, the SmartSide was the most expensive, the steel siding was the least expensive and fibercement was intermediate. After being so impressed with the steel siding that we installed on Keith and Dawn's house, the price sealed the deal for steel.

Installation
The panels that we installed on Keith's two-and-a-half story house were long -- some were over twenty feet -- which were a struggle using ladders instead of scaffolding. All of our walls are single story height which will make installation easier. The color we have in mind is white because of its timeliness and its high reflectance against solar gain in summer.

Well glazed southern exposure

The one thing that I would change from the typical installation is the trim at the corners and around the openings.  If the appearance of the metal trim sold with the panels could be modified to look more like the trim used with old-fashioned clapboard or fibercement siding, the house would for us appear more "residential" and less "commercial". Accordingly, I plan to rabbet well-dried pressure treated 2x's to receive and conceal the edges of the metal panels just like the metal trim does. Then, in order to minimize maintenance, I will paint the wood on all four sides with the best paint I can find and hide the metal J-mold (that would ordinarily be exposed around the openings in typical installations) under the rabbets.

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Update - November 2019
We did indeed follow through with white steel siding with pressure-treated trim boards painted white.  For details, go to "Construction - Steel Siding".

Timeline - Design Evolution -- Earth Contact North Wall

Last Four Years

As a DIYer, it was hard for me to imagine ahead of time the structural complexity of a high concrete wall that is essentially a retaining wall, -- backfilled on one side and not supported on the other. It took Steve Rehagen, who drew our house plans and Mark Bachetti, our structural engineer, to educate me.  Prior to Steve and Mark, I went through a couple of budget-driven iterations that would never be stamped by a structural engineer as required by the Building Director.  

The wall is 92' long, 54' of which is 12' tall with the remainder 8' tall.  In order to maximize earth contact for the AGS system, the inside of the wall must remain open to air circulation. Consequently, a long, narrow storage area will abut the wall with all of the storage taking place on its south wall so as to leave the north wall unencumbered.   The disadvantage of this arrangement from a structural standpoint is that there will be no right-angle interior stem walls to brace the north wall.  Hence, its similarity to a retaining wall.

Dry-stacked Concrete Blocks

Originally, we envisioned more earth sheltering than we ended up with and the

First three courses of dry-stacked blocks
for our solar collector for the AGS system 

quintessential text on the subject is Rob Roy's "Earth-Sheltered Houses" which was an early acquisition and influencer.  He advocates using dry-stacked cinder blocks for earth contact walls -- primarily 12" thick rather than the usual 8" thick. Apparently, dry stacked (mortar-less) concrete blocks originated with the Corps of Engineers.and produces a wall that is not only stronger than a mortared wall but a wall that rivals a poured concrete. So our first vision was a 12" dry-stacked concrete wall.  Dry-stacking would be by far the cheapest approach and the most DIY-friendly but the amount of labor involved with stacking 60 lb blocks 12' high would be formidable. Also such a wall would be hard to insulate. Insulation appended to the outside tends to be disturbed by backfilling and insulation on the inside is not as effective because it is on the wrong side of the thermal mass.

At the time of this writing, we were constructing the walls for the solar collector for the AGS

Parging dry-stacked blocks with
 fiber-bonded cement

system using dry-stacked blocks. The photo above was taken while the first horizontal bond beam course was being filled with concrete and horizontal rebar.  A second bond beam coarse was similarly used higher up in the wall and many of the cores in the blocks were filled with concrete and vertical rebar.  As is typical, both sides of the walls will be coated with fiber bonded cement which makes the joints between blocks stronger than 3/8" mortar joints. Dry-stacking is perfect for this small project but I am glad that we cannot use it for the north wall because it is not as straightforward and easy as it might seem -- minor variations in the size of the blocks complicate stacking them level and plumb, particularly when half-blocks are mixed in with full-sized blocks.  

Complete Blocks 

Last year, I came upon a St Louis start-up making insulated blocks for house walls (Complete Block Company).  After several visits with Herb Walters, the inventor, I become convinced that Complete Blocks were exactly what we needed for our project. With proper equipment, the 200 pound blocks could be dry-stacked to form our long wall in

Dry-stacking the blocks with lifting equipment; notice the
 stamped concrete exterior; the mating surfaces are sealed
with an elastomeric material as the blocks are seated

one or two days.  They would be poured off-site with or without insulation in them. As can be seen in the lower photo, they fit together in tongue and groove fashion then vertical rebar is added after stacking.  It is threaded and epoxied into holes in the slab or footing then tensioned from above.to pull the blocks into tight contact with with each other and with the slab or footing.  Our project would require insulated blocks only at the periphery then solid blocks for most of the wall in order to give thermal mass for the AGS system.  As mentioned above, the intrinsic insulation would be more effective if it were on the exterior side like with insulated concrete forms (post on insulated concrete forms).

Despite the perfect match between Complete Blocks and our needs and a generous offer

Notice the tongue and groove mating and the horizontal
rebar; note also the intrinsic insulation and furring strips
 (for attaching interior finish materials such as drywall);
the vertical rebar on 16" centers is not apparent here

from Herb to help with installation for essentially the cost of the blocks alone, we decided to go a different route.  The system was so new that there were no structural data available that a structural engineer could use to stamp our plans. We are still a couple of months away from constructing the north wall so I recently contacted the company to see if data now existed and any engineers stood ready to stamp our plans.  The answer is still essentially "no".

Poured Concrete Wall
Meanwhile, the default position was to pour concrete in order to keep the project moving. The wall that Mark designed is 1' thick and rests on a monolithic footing (poured at the same time as the slab) that is 1' thick and 8' wide.  The amount of rebar extending from the footing into the wall and interlaced within the wall is mind-boggling -- literally tons of number 4, 5 and 6 rebar.   Presently, I am vetting potential vendors and do not know yet the cost of pouring such a tall wall.

As for insulating, a poured wall would be as problematic as a dry-stacked cinder block wall.

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Update
A month or so after this posting was published, I made the decision definitely to go with a poured wall and worry later about some creative way(s) to insulate it to at least R-20.

Timeline - Design Evolution - Roof Cladding

Since Two Years Ago

Steel Panels

While we waffled considerably on wall cladding, roof cladding turned out to be a no-brainer.  In retrospect, it is hard to understand why there are so few steel roofs except in the southern

Asphalt shingles

states.  I am not sure how the cost stacks up against asphalt or wood shake shingles when professionally installed but, for the DIYer, a standing seam metal roof is cheaper than buying and installing his or her own shingles. We did consider "barn tin" type corrugated galvanized metal roofing that that we have admired in books and magazines but local code prohibits it. 

Cost

The cost of metal roofing fluctuates with the thickness of the metal and the way it is fastened.  Obviously, the thicker the metal, the higher the cost.  As far as fastening is concerned, there are two ways to fasten standing seam roofing -- exposed fasteners and concealed fasteners. The first utilizes hex screws with heads matching the color of the steel.  The screws have neoprene washers under the heads to seal out water. The other system typically utilizes clips that are installed first then the panels are snapped to place over them. 

Pros and Cons of Fastener Styles

(The rest of my comments are based partly on my research and partly on my having helped my step-son, Keith. install a metal roof recently.)  

The advantage of exposed

Exposed fasteners (click to enlarge)

fasteners is that the system is a third cheaper than

Concealed fasteners (click to enlarge)

systems with hidden fasteners, which is what makes the cost of metal competitive with asphalt. And they are faster and easier to install, particularly for a DIYer. 

The disadvantage of exposed fasteners is that, unless care is used in setting the hex screws so that they are not over-tighten or fail to seat fully, water will eventually follow the screws through the panels. This is one of the reasons that 30# felt is used under steel roofing.  Another disadvantage of screwed down panels is that they cannot react to the thermal expansion of the metal as it heats and cools.  This is more important as the panels get longer.

The advantage of hidden fasteners is that there are no breaks in the surface of the panels that can leak. If the panels are installed correctly, they shorten and lengthen in response to temperature changes by sliding on the clips.  The disadvantages of hidden fasteners for the DIYer is that there is a steeper learning curve and the added cost.

Slippery Slope

Installing metal roofing on a steep roof is dangerous because, unlike rough asphalt, it makes a perfect sliding board.  In my view, a DIYer might want to think twice about installing it on a steep roof.  And, if s/he does decide to do it, a safety harness is an absolute must.

Sustainability

Steel roofing is the most sustainable among roof claddings.  While it has fairly high embodied energy, it is less so than asphalt or aluminum.   It contains a high recycled content,, has a recyclable end-life and lasts longer.  It also is available in highly reflective colors which help to limit the amount of radiant heat penetrating the roof in summer. Asphalt shingles are petroleum-based, rarely have recycled content, almost always have a landfill end-life, have a shorter lifespan and lower reflectance. Shake shingles too often come from old growth trees, have a limited lifespan and end up in the landfill or, worse yet, are burned.

Our Choice

We will be using a light colored reflective steel roof.  The good-news-bad- news story is that the roof pitch is so low as to make slipping off the roof unlikely. but our budget dictates the use of exposed fasteners.

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Addendum, June, 2017
By the time I placed the order for the metal roofing, I had given up on the use of exposed fasteners due to a lower pitches to all of the roofs than originally envisioned.  

Odds 'N Ends - Managing Salvaged Lumber (Cont'd)

This is the second of two posts on managing salvaged lumber.  The first post discusses de-nailing; this one is about preserving the lumber until ready for use.

Storing De-nailed Lumber

At first, I stored salvaged lumber stacked tightly together, like on the racks at home centers, and under a heavy-duty Craigslist freebie pool cover.  Moreover, the hard-won boards were stacked on top of salvaged 4 x 4s to keep them off of the ground. Needless to say, termites found this arrangement convenient.  By the time I discovered my stupidity, their munching was still confined to some of the shortest and most expendable 2 x 4s -- but they sure got my attention.  And let me add that my experience with protecting things for extended periods of time with anything resembling a "tarp"  or plastic sheeting has made me aware that ultraviolet radiation always wins and coverings leak.  When they do, mold can be a problem, both from the standpoint of deterioration of the lumber as well as health concerns.

After my experience with the pool cover,  I followed a different  protocol.  I covered the ground under a prospective stack with something to control weeds and grass -- old tarps, old carpet, old carpet pads or black ground cloth. (as can be seen in both photos).  I then arranged salvaged concrete blocks in grid fashion.  Supported by the blocks were 2 x 4s or 4 x 4s cross-ways of the stack that were shimmed with the help of a long straight edge as necessary to compensate for the unevenness of the ground to ensure that the boards would lie perfectly flat lengthwise.  I am hoping that the 8" tall blocks, will dissuade at least the lazy termites. 

Stickering

When green sawmill lumber is stacked for air-drying, each layer is separated by narrow

Air-drying green lumber -- stickers between every layer

boards called "stickers" laid cross-ways.  It is important for drying green lumber to have all four sides exposed to air. However, for seasoned lumber, I reasoned that exposure to air on three sides should be enough to keep lumber that is stored outside dry, so I used stickers between every other layer for all the salvaged lumber.

At the time of this writing, one sizable stack of 2 x 4s and a stack of 1 x 8s have been dismantled for making wall trusses and concrete forms, respectively, and no deterioration is evident -- no termites, no rot, no mold, everything is cool except for lots of stink bugs (we are having a horrendous infestation stink bugs in the Midwest because there are few natural enemies to keep them in check (see food chain). As an example of stacking recycled lumber, the bottom photo shows 2 x 4s that were pre-cut for wall tursses then restacked with three sides of each board exposed to the air.

Covering

Using the pool cover is a bad idea because stacked lumber needs to breath.  I covered the new stacks with loose sheets of barn "tin" weighted down with heavy stones. And, since, our area is in the tornado alley of

Storing salvaged lumber -- stickers every other layer

the Midwest, I lashed each stack together by looping wire over the tin and under the stack then twisting it tight.  The loops are spaced about 5' apart along the length of the stack.  So far, we have had numerous tornado warnings and one close call but no direct hits to test the efficacy of the arrangement.

Of course, the tin does not fully cover the ends and sides of the piles but this is not important because the surfaces that are most prone to wetting are also the ones most exposed to air and sun.  The exposed areas turn gray but remain in good condition.

Spacing the Stacks
If I had it to do over again, I would have spaced the stacks so as to be able to mow completely around each stack with the riding mower.  As it it now, the mowing has to be augmented with a string trimmer, not one of my favorite things to do.