Tuesday, July 28, 2015

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.

Monday, July 20, 2015

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.

Sunday, July 19, 2015

Timeline - Alternative Certifications to LEED

Past Two Years

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?

Friday, July 10, 2015

Timeline - Certification - Is LEED worth chasing?

Past  Three Years

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.