Thursday, July 1, 2021

Design - Annualized GeoSolar System - Second Thoughts On Its Configuration

Annualized GeoSolar (AGS) is explained in a string of posts early in my blog that can be accessed by clicking on "Timeline - Annualized GeoSolar" near the top of the column at the left under the heading "Featured Post".  This post now questions whether our interpretation of AGS was ideal, at least for our build, and, if not, what might have been better.

Our AGS system utilizes the insulation/watershed umbrella and collector system first advocated by Stephens who, in turn,

Solar collector in front of house
borrowed the umbrella concept from Hiatt.  Our system followed Stephens' prescription to the extent that the conduits run parallel from the collector to the front of the house then fan out under the floor of the house.  But, instead of converging behind the house in a "solar chimney" as Stephens recommended, our conduits continue on straight paths and emerge
Conduits widely separated behind the house

to daylight individually.  My reasoning was that, the conduits were slanted upwards sufficiently from the collector to daylight behind the house that the heat generated by the collector 
would rise through them unassisted.  I gambled that ending the conduits in a solar chimney would not significantly improve convection while anticipating that backfilling with the track loader around divergent pipes would be much easier than backfilling around convergent pipes (which largely would have been an arduous shovel and wheelbarrow job).

However, as explained in an earlier post, spontaneous convection did not occur due, I suspect, to the earth under the house being so cold as to reverse the airflow -- suck air through the upstream end of the conduits and expel it at the collector end -- to extent that the heated air generated by the collector was unable to reverse the flow.  I also suspect that, in a few years after the thermal mass under and behind the house warms to a constant year-round temperature in the '70s, a reverse flow would be much less likely to be a problem.  The basis for this assumption is thoroughly examined in the three posts at the top of the column at the left under the heading "Understanding Our Project".

Temporary Solution

Obviously, it would take a fan to change the direction of the airflow.  For it to work, the conduits would have to converge and empty into

The temporary configuration
a solar chimney just like Stephens recommended.  So we dry-fitted 4" drain pipes to connect the conduits with a temporary solar chimney made with dry-stacked concrete blocks with a stucco coating to seal any air leaks.  For a fan we repurposed a squirrel cage furnace fan and enclosed it in an airtight box setting on top of the blocks. 

It was soon obvious that the fan moved more air than necessary but we could live with that since the whole ugly-beyond-words setup would be replaced within at least a couple of years with a less complicated underground piping system and a permanent solar chimney outfitted with a proper-sized fan, either solar or hardwired.  The conduits have both  smooth and corrugated sections with the corrugated sections located under the house floor to caused turbulence in the air stream so that it would transfer more heat to the soil.  Interestingly, the air flow with the over-sized fan was strong enough to cause a gurgle/rumble sound that was detectable at the solar collector due to the air passing, probably too fast actually for greatest efficiency, through the corrugated sections.
Heat Transfer 

It took several weeks for the exhaust air to warm perceptively (holding a hand in front of the blower) because the soil surrounding the conduits was so cool that it absorbed all of the heat from the airstream before it made its way through the conduits even at the accelerated air speed.  The persistent coolness of the airstream was a positive in that it meant that heat was being lost to the soil as planned.

This scenario was playing out during July when temperatures -- day and night -- are as high as they get in the St Louis area.  So I suspect warming of the airstream was due to a combination of hot ambient air pulled through the solar collector by the fan and heat radiated by the solar collector.  I further suspect that the former contributes more heat than the latter.

Is the Solar Collector Really Necessary?

It is not a stretch to think that maybe the solar collector is overkill.  Maybe the AGS system could run on ambient heat without radiated heat -- at least here with our long and hot lower Midwest summers.  It is not hard to imagine a system without the collector that would comprise a "reverse solar chimney" or  "intake chimney" at the downhill side similar to the solar chimney at the uphill side.  The conduits would start out together at the intake chimney, spread out under the house like ours then rejoin at an uphill solar chimney that is outfitted with a fan to pull air through the conduits.

A simple store-bought thermometer inside our collector topped out at 120 degrees on sunny days so we do not know the maximum temperatures produced by the collector.  But it is safe to say that the temperature of the radiated heat is higher than the ambient heat passing through the collector from the outside.  But the solar collector is incapable of producing the volume of heat that can be realized from a constant stream of ambient air, especially on cloudy days when temperatures still reach the eighties and nineties and during hot summer nights.  However, harvesting warm air on cloudy days or at night would require a timer-controlled hardwired fan rather than a solar-powered fan.

Hiat demonstrated that just the heat gain through a few south-facing windows during Montana winters was enough to create comfortable year-round environment in a modest earth sheltered home that did not have an underground network of conduits and a solar chimney but did have a insulation/watershed umbrella.

In Passive Solar Energy Book, Edward Mazria

describes a school in Wallasey, England that runs entirely on passive solar energy.  It is a masonry building (lots of thermal mass) that is insulated on the exterior with 5" of foam board and has a glass south-facing wall comprising mostly translucent glass rather than transparent.  Its thermal performance in a climate thought to be marginal in terms solar energy harvesting was surprising.  Half of the energy required to keep the building comfortable year-round (fluctuations averaging only 7 degrees throughout the year) was provided by the sun with the other 50% supplied by heat from lights and waste body heat from the students.  The conventional HVAC system went completely unused.

What I Would Do Differently

I am beginning to feel that a full-blown Stephens-like AGS system is unnecessary, at least in our climate.  Here are the reasons why.

The thermal performance of our partially-insulated house last winter -- insulation in the walls and ceiling of the first floor and some of the walls on the second story (but not the ceiling) -- and how subsequently the fully-insulated house has remained cool well into this summer even with all operable windows open fulltime and a large industrial fan pulling warm outside air through them 24 hours a day (which we are doing in order to drive more heat into the thermal mass, making the house warmer for the first winter), leads me to believe that, if...........

-- A house is at least partially earth sheltered and has an insulation/watershed umbrella extending outward from the house 16 - 20' in order to increase the amount of dry thermal mass beyond just the floor,

-- There is an abundance of south-facing windows with as much translucent (vs.transparent) glass as possible and there is minimal glazing on the north and west sides,

-- The house envelope is super-insulated and equipped with high R-value windows and doors,

-- The colors of the exterior of the house are highly reflective,

the amount of heat gain needed to warm the thermal mass and maintain comfortable year-round temperatures becomes so minimal that it can be accomplished without a labor-intensive and rather expensive solar collector.

Knowing what I do now, I would be inclined to replace the solar collector with an intake chimney and add a solar fan to the solar chimney to pull warm-hot air through the conduits from late spring until early fall then welcome passive solar heat through the south-facing windows from late fall until early spring.  Then, with the addition of a third heat source --heat generated by merely living in the house such as cooking, baking, dishwashing, showering and waste heat from the bodies of its occupants -- I am confident that the three heat sources would be enough to maintain a comfortable environment during the cool/cold months and the insulated and reflective house and insulated thermal mass would extend the comfort through the warm/hot months.

Cost Considerations

So, is our AGS system with its solar collector, conduits and solar chimney considerably more expensive than a system without the collector would have been?  The collector indeed was the most expensive component in the system -- cost of excavation, cost of concrete blocks and parging cement, cost of corrugated roofing, tempered glass and fencing to finish it off.  My original intent was to hold the cost of the entire AGS system to something less than conventional HVAC but, if it did cost less, it was only marginally.  Without the collector, it definitely would have cost less and would have chopped several weeks off of construction time.

Future Reporting

We will be moving into the house in a couple of months which will give us a chance to begin monitoring and reporting on its thermal performance over time.  Popping up through the floor in the middle of the house is a PVC pipe that was installed a few years before ground was broken.  It was one of four piezometers used to monitor the water table so as to be sure that it would not rise during wet years and syphon heat from the thermal mass under the house.  I plan to repurpose it as a way of dropping a thermometer into the thermal mass to measure its temperature at various depths and intervals.  Eventually we will have a better data with which to judge the efficacy of eliminating the solar collector from the design of the AGS system.

Wednesday, May 26, 2021

Design -- Sustainable Flooring Choices

The time is drawing near when decisions about flooring have to be made.  The substrate for the first story floor is concrete while that of the second is tongue and groove OSB.  When it comes to winter heating for our passive solar house, the difference in substrates dictates flooring choices, irrespective of the usual factors such as esthetics, durability, ease of installation, ease of maintenance, life expectancy and price.  Following is the reasoning behind our final choices.

First Story

Deciding on the type of flooring for the first floor is a no-brainer -- either concrete as the finished floor or concrete overlaid with porcelain tile, either of which fits with our AGS design*.  Porcelain tile is reasonably easy (but time-consuming) to lay, quite durable and there is an abundance of patterns nowadays mimicking wood grain in all price ranges.

Direct gain on an insulated concrete floor (the thick
 black border outlining the house represents insulation).

The concrete floor and the soil beneath it are part of the thermal mass that makes our AGS system work.  The nearby picture illustrates the classic passive solar design -- sunshine on an insulated concrete floor.  In our case, the floor is not insulated so that the earth below the floor (not just the concrete) is warmed by the sun shining through the windows (direct gain) during the cold months to supplement the indirect gain it gets from the solar collector during the warm months.  Concrete, and presumably porcelain tile, are good choices because they conduct heat in and out of the mass, although I was unable to find any definitive information about whether thermal conduction for tile and thin-set match that of concrete.

At first blush it might seem that concrete or tile would be cold underfoot during cold months as would be expected with tile over concrete in a conventional HVAC environment whereby the air is heated rather than solid matter and the soil under the slab is poorly insulated.  In our situation, the heat is in the mass, not the air, so that the floor temperature tracks with the temperature of the underlying mass, varying only a few degrees year-round -- maybe a little warmer in summer and a little cooler in winter but remaining within a narrow comfort range.

Final Choice for the First Story

Having said all of this, our final choice was to bypass the tile altogether and return to our original inclination -- polished and stained concrete.  We had four reasons for favoring bare concrete.  First, tiling 1,700 square feet would have been a job too difficult and time-consuming for DIYing despite owning a commercial-grade tile saw and having considerable experience with tile work.  Second, buying the relatively inexpensive woodgrain porcelain tile of our choice at $1.79/sq ft plus $8/sq ft for professional tile setting would make the total cost just under $10/sq ft.  The cost of polishing and staining the concrete ran $6/sq ft, saving us a little over $7,000.  Third, we were not willing to commit to a forever responsibility for cleaning and maintaining a houseful of grout joints when polished concrete is about as low-maintenance as floor surfaces get.  Finally, in order for our AGS system to function properly, heat must pass freely through the floor to and from the heat storage mass below and the living space above.  By dispensing with tile, except for the airlock inside the main entrance, the issue about its thermal conductivity relative to concrete becomes moot.

Second Story

Flooring choices for the second story are less stringent because the amount of thermal mass is so limited.  Having said that, there might be one instance in which it might be marginally important.  If we were to overlay the OSB subfloor with a layer of cementitious board then install thinset-bonded porcelain tile, the cementitious board, thinset, tile and subfloor together would provide a thin veneer of thermal mass capable of absorbing a limited amount of heat on sunny days and re-radiating it at night.  But, since the glass of all but two of the second story windows is translucent rather transparent, most of the winter sunlight is diffused rather than concentrated on hard surfaces like the floor.  The diffused radiation, while it will not heat the inside air, will randomly warm the contents of the room, in which case, the floor would receive some of the energy and contribute slightly to a comfortable environment.

If we wish to overlook the slight thermal advantage of the tile floor, there are three other flooring materials that we might consider and one other that, for a green build like ours, should be avoided.  First, the one to be avoided -- the popular solid laminate flooring.  With a nod to its beautiful wood patterns and its DIY-friendly installation, it is a petroleum product that does not fit our commitment to sustainability.

That leaves three other choices -- bamboo, real hardwood and a new product, composite laminate flooring.  Bamboo at first glance would seem to be a good choice from a sustainability standpoint since it comes from a rapid growing ubiquitous grass instead of mature trees.  However, its embodied energy, mainly from manufacturing then transportation from the orient, makes it less appealing and its durability and life-expectancy is less than tile and real wood.  Hardwood flooring would be a good choice if limited to native species (excluding old-growth stock) rather than exotics from distant lands.  Wood composite flooring is the new kid on the block.  It looks and installs like solid vinyl laminate but is a certified green product eligible for LEED points made mostly from post-industrial recycled wood chips.  It also has all of the qualities of the best of vinyl products such as hardwood realism, stain and scratch resistance and 100% waterproof protection.  Needless to say, composite flooring was easy choice for the second story.


Of the choices we would consider, hardwood is the most expensive at +/-$8 per sq ft DIY-installed and +/-$19 per sq ft contractor installed.  Tile, even with the added expense of cementitious board, is least expensive at a little more than $2/sq ft if DIY installed (but +/-$10 sq ft, if professionally installed)  Bamboo is intermediate.  The DIY-installed composite laminate that we selected ran $2.75/sq ft.

What About Carpeting?

Until I read Mazria's book, I assumed that carpeting of any sort would have no place in a passive solar build where the floor is part of the thermal mass.  However, Mazria makes sense when he says "Do not cover a masonry floor with wall-to-wall carpet.  Carpet insulates the heat storage mass from the room.  Scatter or area rugs, covering a small area of the floor, make little difference".  We plan to use an area rug in the master bedroom and a few scatter rugs around the rest of the house especially after a year or two when the year-round temperature of the thermal mass has reached equilibrium.


*For those who have not followed the blog enough to know about the Annualized GeoSolar system that will provide year-round comfort in the absence of conventional HVAC, click on the title under "Featured Post" near the top of the left column.

Monday, March 22, 2021

Construction - Drywalling

Drywalling has been ongoing since the summer of 2020.  While this post contains some new information, it also overlaps the previous post on rice hull insulation.

Atypical Sequencing For The Drywall
The sequence I am following for drywalling is dictated by the use of rice hulls for insulation and having to work largely alone during the early months of COVID-19.

The interior partitions were drywalled first followed by the exterior walls and ceilings starting 
with the lower drywall course on the walls followed by the higher courses then on to the
ceiling one course at a time (as shown in the picture).  By positioning the insulation blower (blue object in the center of the picture) at the foot of the temporary steps, all areas of house could be reached with its hose without moving the blower.

The industry standard is to drywall the ceilings first then the walls where the panels are hung horizontally starting at the top and working towards the floor with the top panel supporting the edge of the ceiling panel.  I am doing the opposite -- hanging the walls first starting at the floor followed by the ceiling. Since cutting the second or, in some cases, third course of wall panels at just the right height to support the ceiling panels is impractical if not almost impossible, I had already added nailers to the tops of the partitions to which the edges of the ceiling panels could be screwed for added support between trusses.  Instead of drywalling the entire house in a random fashion, we concentrated first on the interior walls and ceilings that will not be insulated -- bathrooms, closets, bedrooms, kitchen, dining room and living room.  The reason for delaying drywalling and insulating the shell of the house until colder weather was to allow time for the thermal mass to store summer heat one last time.

Fortunately, I could hang most of the wall panels working alone with the help of custom jigs in lieu of a second pair of hands.  For the longest panels on the second tier, I could call my wife, Dorothy, to come over from our residence next door to help.  By mid-fall, with periodic COVID testing and masking, we felt comfortable accepting help from two family members with handy skills.

Drywalling the Insulated Exterior Walls and Ceilings
The 15" thick exterior walls were drywalled one course high then filled with rice hull insulation.  We then hung the second course of drywall and filled behind it by working through the duel top plates.  The top of the wall was filled to overflowing before the first course of drywall was hung on the ceiling next to the wall and filled with hulls in order to be sure that the junction between the wall and ceiling was tightly packed.  After the first ceiling course was filled as much as possible without spilling over the edge, the second course was hung and similarly filled with hulls.  This pattern of hanging one course of ceiling drywall at a time then following with the rice hulls continued up the cathedral ceilings until the opposite wall was reached for both the first and second floors.  Segmenting the ceiling work to one drywall course afforded the opportunity to use a "T" shaped plunger made from 2 x 4s to pack the hulls as they went in, thereby eliminating any voids.

The cut-outs for pipes and electric boxes in the exterior walls and ceilings had to be handled differently with rice hulls.  Extra effort was needed to minimize the size of gaps between the drywall and a pipe or box and the holes for the wires in the back of boxes have to be occluded as well.  Otherwise, the hulls are forced through them when the insulation is blown and would probably leak out ever afterwards.  A few larger cracks were filled with minimal-expanding foam, particularly around ceiling boxes whereby the foam will be hidden under the shroud for light fixtures or ceiling fans.  A couple of larger cracks around wall boxes were filled with non-shrinking plaster-of-Paris.  As explained in a previous post, smaller gaps around some wall boxes were sealed with Zip tape including using an undersized switch plate as a guide for trimming so that the edge of the tape would be hidden under a full sized plate.   

Helpful Techniques
I had done a modicum of drywalling in the past and thought that I was reasonably good at it, that is, until I  researched the subject in earnest. 

In the end, though, all I really needed in the way of enough information to upgrade my skills sufficiently was Myron Ferguson's book, Drywall.  Following are a couple of his hints that were especially helpful when hanging the walls.

When hanging large sheets on walls working alone, he suggests starting a nail where you knew it would hit a stud then lifting the panel to place and driving the nail to hold the panel until it could be properly fastened with screws.  

A second hint was a nugget -- an easy and accurate way to cut around electrical boxes and plumbing pipes, at least for the lower course of drywall -- without time-consuming measuring and cutting before hanging the panel.   First use a carpenter's square or a spirit level to mark the coordinates of each box or pipe on the floor then hang the panel with a few screws at the top.  Using the coordinates, it is then easy to zero in on the hidden box and cut around it with the tool of my choice, an oscillating tool.  When done right, the space between the box and the drywall was essentially only the thickness of the oscillating blade which, I would like to think is enough to satisfy most drywall tapers' wildest dreams, as opposed to the cruder cuts made by the thicker blade of a punch saw or the rotating blade of a drywall router, to say nothing regarding inaccurate holes precut from measurements.  When the panel is free to slip to place around the box without forcing, it can be screwed to place.

Taping the Joints
Morrison also had four recommendations for locating the joints between panels.  First, whenever possible, run the panels horizontally and, if running them vertically, only do so when the panels reach uninterruptedly from floor to ceiling -- say, 8' panels for 8' ceilings.  In either case, the most conspicuous joints are formed by the sides of the panels that are tapered and designed for taping.  The advantage of running the panels horizontally is that it increases the strength of the wall.  A second Morrison suggestion:  when butt joints (those at the ends of panels which are not tapered) cannot be avoided, they should be located near the corners of a room where the additional bulk of joint compound is less likely to be noticed.  His third suggestion is to avoid butt joints near doors and windows where the extra thickness of compound invariably compromises or complicates the fit of casement molding.  Instead, cover doors and windows with long pieces of drywall and expose the opening after fastening.  The latter is best done by sawing the sides of the opening and using a knife at the top of the opening to cut the paper on the backside then breaking the piece before cutting the paper on the front side to free it.  With window openings in conventional walls, the top cut must be made before the panel is installed but, in our case, the walls were so thick that the window openings could be handled like doorways, i.e., reaching in to cut the back side at the top after the sides had been cut with a saw.

Since I did not intend to do the taping myself, I was motivated to take as much care as possible to make the drywall look like it was hung professionally, especially when cutting around electrical boxes and plumbing stub outs and butting at the corners.  I also took responsibility for installing the metal corner bead on outside corners.  The final step was to drag a wide taping knife over the surfaces of the drywall in conjunction with inspecting it visually to find and fix any screws that were not properly countersunk.  The last thing I wanted to do was to cause a taper to raise his or her price to cover sloppy hanging or to be unwilling to work with a DIYer at all.

Saturday, January 9, 2021

Construction - Insulating with Rice Hulls - Filling the Wall and Ceiling Cavities

 This is the fourth post on rice hulls for insulation.  The first was back in 2016, a couple of years after I learned about insulating with hulls.  That post was an attempt to confirm their efficacy and understand the uncommon logistics involved with buying, transporting and getting them into a structure.  Two recent posts set the stage for this post that describes the actual use of the hulls for the wall and ceiling cavities.

Reminder:  click on any picture to enlarge it for better viewing.

Buying the Rice Hulls and the Diatomaceous Earth

It appeared that Riceland Foods, Inc was willing to sell direct (instead of referring to a dealer) only because of the size of our order.  Their hulls come in two configurations -- large bales or 50 lb bags -- with the latter seldom sold to end-users, especially consumers, in truckload quantities.  Consequently, our order triggered a special run that needed to be picked up almost immediately after ordering.  I had been proactively in contact with a freight broker who promptly caught a ride for the shipment and was able to schedule it to arrive on Friday so that we could offload it over the weekend. 

Buying food grade diatomaceous earth (DE) was made easy by a local farm and home store that handled it in 40 lb bags for mixing with livestock feeds.  The DE as an insecticide will not only kill rice weevils but any other insects with exoskeletons (hard shells), apparently for as long as the building exists.

Receiving the Rice Hulls

With a crew of 11 and three pickups, 768
 bags of hulls were moved from the semi-trailer
 to our building site in less than 7 hours.
As mentioned in the previous post, our construction site on a narrow one-way street makes it is nearly impossible to receive shipments from semi-trailers unless the driver is willing to exit by backing for several blocks.  And, if s/he were to wait while the trailer was offloaded, we would need a forklift. Therefore, we received the order in a drop-off trailer on a merchant-friend's parking lot and off-loaded it by breaking down the pallets and handling all 768 bags one at a time. Thankfully, we were blessed with enough volunteers and pickups as well as ideal weather for December in the Midwest to have the trailer unloaded in less than seven hours.

It was a bit of a problem storing the hulls and still having access to the exterior walls for insulating and additional drywalling.  They occupied over half of the space in the garage and most of the non-bedroom, non-bathroom floor space on the first floor.  However, intentional sequencing for blowing the hulls quickly eliminated the bags that were most in the way. 

Blowing the Hulls

We positioned the blower in a central
When the blower was positioned at a central location (arrow),
the hose reached all recesses of the building.  Each bag of hulls
was opened, dumped into the mortar box in front of the blower
 and sprinkled with a cupful of diatomaceous earth.  At the time of
this picture, the bags stored in this area were used first in order to
create working space.
location on the first story from which we could reach all exterior walls, upstairs and down, with the 50 foot 3" diameter blower hose. I handled the business end of the hose, not because it required much skill, but because it was extremely dusty and not something I wanted anyone else to have to deal with. At the blower, a bag was laid in a mortar box and cut open to release the hulls that were compressed and under pressure.  The hulls were then sprinkled with a cupful of diatomaceous earth and scoop-shoveled into the hopper of the blower.  The flow rate was
Friend, Bob, loading the blower hopper with hulls at the
rate of about one bag every five minutes. 


less than 5 min per bag which we thought originally would be too fast for one person working alone to manage. However, after a little practice with two at the blower, we found that one person could in fact keep up.  The guy(s) working at the blower were already wearing N95 or equivalent masks due to COVID-19 although the amount of dust was minimal.  At the business end of the hose, the dust was so problematic that, in addition to an N95 tight-fitting mask, I wore swimming goggles, long sleeves, tight collar and gloves.

With rice hulls, as opposed to fiberglass or cellulose, the hose clogged more readily, presumably due to their greater density.   We found two maneuvers that eliminated clogging.  One was to fine-tune the flow rate by trial-and-error and the other was to make sure that the hose was kept as straight as possible and, when bent, with curves as sweeping as possible.  And, in addition to these efforts, I needed to be careful that the end of the hose did not bottom out and become blocked by the hulls already in the wall or ceiling.  The good news was that the flow rate was not diminished when the hose was elevated to reach the ceiling of the second story.

Second Thoughts About Diatomaceous Earth (DE)

After a day and a half of blowing rice hulls, we began to wonder whether the dust created by blowing was due to the DE rather than the hulls themselves.  By that time we had finished insulating behind the first course of drywall on the first floor and the interior of the building was already pretty dusty.  It was hard to say whether it was hull dust or DE dust or a combination.

During the interval for installing the second course of drywall, I did more research on the health risks associated with DE (I was definitely motivated to do so after experiencing mucus-like drainage from my red, itchy eyes for a couple of
days after the first session).  The search yielded enough information to warrant a bit of caution.  The major concerns are pulmonary effects and eye irritation.  The former was a non-issue for us in that the warnings apply to workers who experience long-term exposure such as those mining and processing DE and 
we were already wearing N95 masks which, according to the online sources, was adequate for DE dust.  The latter concern, eye irritation, was real for me after being at the business end of the hose but not a concern for those working at the hopper.  It motivated me to search for goggles that sealed against the face better than the ones I was using and to consider alternatives to mixing the DE with the hulls before blowing.

In order to decide whether to continue mixing DE with the hulls, we blew a few bags of hulls without the DE to see how dusty they would be compared to rice hulls with DE.  As I had hoped, the amount of dust with or without DE seemed to be a wash.  Since I would be the one at the dusty end of the blower hose and would rather not miss the opportunity to have walls and ceiling laced with a deadly but environmentally-friendly insecticide, I decided to continue with the DE.  By the time the second stage of drywalling was over and we were ready to resume insulating, I had bought tight-fitting swim googles that eliminated most of the eye irritation that I experienced after the first session.  However, the amount of dust at the business end of the hose, even with masking and goggles, made the job extremely unpleasant to say the least.  

Wall Insulation

Yours truly at the business end of the hose
Insulating behind the lower 4' high course of drywall was relatively easy and gave us a chance to practice our technique.  Insulating behind the second course of drywall up to the 8' level was more challenging.  Not only did I have to hassle with a ladder or a mobile scaffold and, despite using a headlight, visibility into the wall cavity was limited by the 4" space between the 2 x 6 tandem top plates.  However, insulating behind the lower course of drywall gave me confidence that gravity would pull the hulls into all of the nooks and grannies up to the bottom of the top plates.  At that point it was necessary to overfill the wall slightly then reach through the opening between the top plates and manually pack the hulls into the corners under the plates. The amount of dust raised due to the proximity of the ceiling was much worse than it had been with the first course.  I was definitely thankful for the mask and swim goggles and amused later to find hulls between all of the multiple layers clothing that I wore against 40 degree temperatures.

We filled the wall cavities brimming full so that there would be no doubt that the junction between walls and ceilings would be filled uninterruptedly when later the insulation would be blown into the space above the first 4' course of ceiling panels.  By the time the walls were filled, not quite half of the original 768 bags of hulls had been consumed.

Getting the Ceiling Ready for Insulation

First floor ceiling showing the temporary strips
supporting the weight of the rice hulls until
 they can be replaced by definitive trim boards.
In the chart comparing rice hulls with cellulose insulation in the previous post, I pointed out that the rice hulls, at nearly three times the weight of cellulose and at a depth of 18", might cause the ceiling drywall to pull loose from its screws if installed directly to the roof trusses unassisted.  So I decided to kill two birds with one stone -- add support while creating an architectural feature that we had been considering in any case.

For all of the ceilings in the main rooms, upstairs and down, the esthetic effect that we had been contemplating was a 4' x 4' grid pattern comprising 1 x 6 trim boards wide enough to cover the beveled edges of adjacent drywall panels.  To that end, we installed the drywall in the usual manner with screw spacing a little closer than normal.   As a temporary support measure, we added 3/4" x 2" strips screwed through the drywall and into the trusses.  They were less than 4' long so as not to interfere with the east-west final trim pieces that will run perpendicular to the trusses, be screwed or nailed to the trusses and cover the seams between drywall panels in lieu of taping.  The plan is to remove the temporary strips when the final longitudinal trim is in place then replace them with the trim pieces that complete the grid pattern.  

Installing the Ceiling Drywall

First floor ceiling bays being filled with rice hulls
as seen through the second floor wall.
For the ceilings on both floors, we hung only one course of drywall next to the wall then insulated it in order to be sure that the junction between walls and ceilings was thoroughly filled and compacted with hulls.  We found that the blower did not shoot the hulls with enough force and sufficient distance for us to insulate with confidence more than one course at once so we stuck with doing each course separately.  The highest part of the first floor cathedral ceiling was filled by reaching through the second story wall, as seen in the nearby photo.  The highest part of the second story ceiling -- the last space to be insulated -- was our biggest challenge due to limited access.  We switched to installing the last course of drywall one 4' x 4' panel at a time starting at the southwest corner and proceeding to the southeast corner.  That way, we were in better position to blend the insulation with that already in the wall despite having to work crossways of the trusses instead with them as was possible with the rest of the ceilings.

Sunday, January 3, 2021

Construction - Insulating with Rice Hulls - Cellulose vs. Rice Hull Insulation

Part of the shipment of rice hulls.
Part of the shipment of bagged rice hulls.

Insulating with rice hulls has been for us a drawn-out process whereby the drywalling has to be staged then filled with hulls incrementally.  Consequently, I will not be blogging on the drywall-insulating process until it is done, probably a couple of months from now.  Meanwhile, this is a good time to pause and compare rice hulls with cellulose, the only other low-cost insulating material that is even close to being as sustainable a rice hulls.

We committed to the use of hulls early on based upon the ridiculously low cost estimates put forth by Olivier in his 
quintessential article and validated later during a phone conversation with him, at least for those of us living close to the rice belt where freight costs were manageable.  My calculation at the time said that rice hulls would cost about a fourth of the cost of cellulose and about a third of the cost of fiberglass.  That said, their use did give me pause from the very beginning, despite their lure as an  innovative, intriguing  and enticingly sustainable choice for insulating.  If the millers were parboiling rice before separating the grain from

Close-up of rice hulls.

the hulls in those days, I did not pick up on it.  I expected to have to buy raw hulls delivered in bulk via a walking floor trailer (see the 2016 post on rice hulls), which would mean that managing any rice weevils would depend solely on the effectiveness of diatomaceous earth (DE) as an insecticide (DE was a topic in the previous post).  Added to that concern was the complicated logistics of receiving and storing a trailer-load of loose hulls.  As it turns out four years later, rather than being cheaper, the cost of the hulls is slightly higher than cellulose probably would have been and freight costs are much higher than four years ago due to a nation-wide shortage of trucks and truckers.  On the other hand, though, parboiling the rice before milling ostensibly solves the weevil problem and receiving the hulls in bags solves the handling problem.  So I consider the sticker shock as a reasonable trade off for the convenience of having bagged hulls without rice weevils and for the personal experience that allows me to blog on a subject for which there seems to be considerable interest but little precedent (e.g., the 2016 post on rice hulls is the second most visited among the +/-140 posts to this blog so far.)

Following is a comparison of rice hulls and cellulose.

Advantages of Rice Hulls

The advantage of hulls that appeals most to me is the lack of settling once they are blown and, where appropriate (ceilings), also packed to place.  It is comforting to know that the walls, a few of which were nearly 12' high, and ceilings will remain packed tight and maintain the original R-factor for the life of the building.  The second most important advantage would have to be the natural fire resistance of the hulls in thicknesses of 15" in the walls and 18" in the ceilings.  By enveloping the wood structural elements and the electrical system in a flame-retarding and self-extinguishing medium, the shell of the house is virtually fireproof, particularly since the exterior is covered with metal roofing and metal siding.  And the natural resistance to moisture of the hulls does two things, (a) stabilizes the R-factor that would be compromised with moisture-absorbing cellulose and (b) inhibits fungal growth without the use of noxious chemicals.  Another consideration that compliments our green project is the low embodied energy of the hulls, most of which resides in their transportation rather than in the hulls themselves, and the fact that they can be recycled indefinitely.  Still another, rather serendipitous advantage, is the excuse to introduce diatomaceous earth into the wall and ceiling cavities that will linger as an environmentally-friendly insecticide for as long as the building exists.

Disadvantages of Rice Hulls

Aside from sticker shock, the biggest obstacle for the universal use of hulls for insulation is the high freight costs beyond the Midwest.  And there are four other disadvantages.  (1) The need for more robust ceiling construction.   The hulls have roughly three times the weight of cellulose and could cause the drywall to pull free of its screws or perhaps sag between roof trusses, especially where two beveled edges come together at a right angle to the trusses. The way we modified typical ceiling construction for additional support will be explained in a subsequent post on drywalling.  (2) The hassle for a DIYer of buying and selling a blower for a one-off project.  (3) Dealing with the excessive dust raised by the hulls.  Having limited experience with cellulose, I have no idea how dusty it would be compared to the hulls if it were to be blown into the confined spaces of our 15" wall 

Concrete first floor showing the amount of dust accumulation
despite having already been swept twice.
cavities and 18" cathedral ceiling cavities whereby the dust blows directly back into the face of the operator.  I can say with authority that the dust was so thick that it is impossible to see the progress of the filling without stopping the blower or diverting the hose to the next bay temporarily to clear the dust and check progress.  (And, as the nearby picture shows, the amount of dust accumulating on all surfaces was formidable.)  After a while, though, the blowing became so routine, especially for the ceilings, that I worked as much by feel as by sight.  It helped also to limit the amount of space to be filled for both the walls and ceilings to the width of a sheet of drywall, i.e., no more than 4' at a time. (4)  Relatively slow flow rate.  The industrial strength insulation blower that we purchased, was able to push the hulls through 50' of hose without difficulty, requiring +/- 4 min to move one bag of hulls (+/- 6 cu ft), which was about as fast as the second worker could open the bags, add the diatomaceous earth and scoop the hulls into the hopper.  

In the chart above, the rest of the factors that compare cellulose with hulls are essentially a wash.

The next posts will document our practical experiences with the rice hulls.

Friday, November 13, 2020

Construction - Insulating with Rice Hulls - The Planning Stage

So far, there are just under 140 individual posts to this blog.   Two posts have attracted far more visitors over the past several years than the others.  Most visited has been the post about the plumbing rough-in under the concrete floor, including the homeruns for the PEX water supply system.  The second-most popular, with about

half as many hits, is the one about rice hull insulation posted back in the spring of 2016 that introduced the unfamiliar concept of insulating with rice hulls.  This post and, perhaps as many as three additional posts, describe how we planned for and bought a semi-trailer-load of rice hulls, the equipment needed to blow them into the wall and ceiling cavities, the atypical sequencing of the drywalling necessary for their use and several other hints and observations that we learned about the hulls.  To be sure, the whole process has been an adventure. 

Insulation Blower

Early on, I learned that the insulation blowers available at the big box stores were incapable of handling rice hulls due to their finer texture and their slightly heavier per-unit weight.  My good friend, Keith, being a master innovator, accepted the blower dilemma as a challenge and began experimenting with non-insulation blowers, such as hand-held and tractor-mounted leaf blowers, before giving up and searching the web for alternatives.  Eventually, he learned about a commercial machine that at least one person had reported using successfully with rice hulls.  The ideal model for our situation, FORCE ONE , was one of several models made by the Intec Corporation located in Frederick, CO.  When we called the company we found that that model had been discontinued but newer models would be equally effective but at a much higher price.  Ultimately, through Keith's effort, we were able to find a used Force One in good condition on Ebay.  

Special Effort to Prevent Leakage of the Hulls

Unlike conventional insulation, rice hulls are small enough

ZIP tape sealing junction
between the electrical box
and the drywall

to escape the wall and ceiling cavities through small openings such as those in and around electrical boxes and around plumbing stub-outs.  So we spent extra time eliminating such openings with spray foam and Zip tape.  Doing so also helped to air-seal the drywall but, as discussed in previous posts a seal at the drywall side of the wall is not especially critical since, on the exterior side of the truss walls, we sealed the joints between plywood sheathing panels with ZIP tape and, on the interior, sprayed foam insulation along the mudsill, in transitions between concrete and stick-built walls and around penetrations for electrical wires and water lines.  The extra sealing on the drywall side however will help to minimize moisture penetration into the wall and ceiling cavities that, in excess, could compromise the R-value of the insulation, encourage mold and, as explained below, compromise the insecticidal effectiveness of the diatomaceous earth that we will be blending into the insulation.

Reduced size cover plate
used as a guide for cutting
the tape back enough to be 
hidden under a normal size
cover plate, shown here before
As will be described in a subsequent post on the drywalling phase, using rice hulls for insulation required an atypical sequencing of the drywall on the exterior walls.  We will start with the first course at the floor for the walls and next to the wall on the low side of the cathedral ceilings.  After the hulls are blown behind one tier of drywall, the next tier will be added and filled as well, working up the wall and across the ceiling.

Calibrating the Blower

A sample bag of rice hulls came in handy for validating the efficacy of the blower and preliminary calibration of it  by blowing the hulls back and forth between two appliance boxes that were separated by ~30 feet. It took only a few back-and-forths to determine the best size of the opening in the bottom of the blower hopper for a steady stream of hulls. The exercise also familiarized us with the remote controls on the blower.  We even took one of the boxes to the far corner of the second story to see if elevation slowed the flow of hulls through the 50' hose.  It did not. 

Friends Myron (at the hopper)
and Keith (with remote control
and hose in hand) testing
the blower.  
The sample hulls raised enough dust to warn us that mask-wearing while insulating would probably be necessary irrespective of COVID, particularly, as discussed below, when we include diatomaceous earth with the hulls.

Estimating the Quantity of Hulls

After vigorous stirring of the 50 lb sample bag in an effort to fluff up the hulls, we became skeptical that each bag would yield 7 cu ft when blown into the wall or ceiling as contended by the supplier.  Blowing the hulls back and forth between the boxes did not seem to increase the volume very much, if any, over just stirring.  So  I used 6 cu ft to calculate our needs.

The volume of rice hulls that we will need for the exterior walls (15" thick) and the ceilings (18" thick) turns out to be just under 5,000 cu ft.  A 53' tractor-trailer load comprises 768 bags (50 lb each).  The hulls are compressed for bagging such that a bag contains 5 cu ft.  If 768 bags expand to 6 cu ft when blown into the wall and ceiling cavities, the total volume for a truckload would be 4,600 cu ft, slightly less than our needs.  If they expand to 7 cu ft, a truckload might be even slightly more than enough.  The plan is to proceed with a truckload and see how far it goes then, if necessary, decide what to use to finish insulating.  If very little additional insulation is needed, perhaps locally-available cellulose would be the best choice for finishing.  If the amount needed is excessive and the price differential between hulls and cellulose is substantial, it might make sense to pay freight on a few more pallets of hulls.

Receiving and Handling the Shipment of Rice Hulls

In the March 2016 post on rice hulls for insulation, I was unaware that they could be purchased bagged and on pallets (if in fact they were actually available then).  I assumed that they would be delivered in bulk on a walking floor trailer.  Having them bagged, though more expensive, will greatly simplify their handling at every stage -- from truck to blower.

In order to avoid commercial warehousing fees and the inconvenience of off-site storage, it took a bit of head-scratching to figure out the best way to receive a truckload of 48 pallets on a narrow almost-one-way dead-end street in the heart of the hilly Mississippi River bluffs.  Finally, we settled on the following plan:  using a retailer friend's parking lot for a drop-off trailer, pickup trucks to move the pallets from the trailer to the storage sites in the garage and living space of the house under construction and a rental pallet jack.  The pallets will be double-stacked in the trailer.  Two double-stacked pallets weighs 1,600 lbs but we envisioned little difficulty moving them to the back of the trailer with a pallet jack then breaking them down so that bags could be handled individually. 

Rice Weevil Problem?

Also in the 2016 post, I was not yet aware of the potential problem of weevil infestation.  The ensuing years have provided time to research rice weevils.  The available information online is spotty and inconsistent but seems to indicate that, as a minimum, we should add diatomaceous earth (DE) to the hulls as they go into the wall and ceiling cavities.  (DE, also known as silicone dioxide, is the best green insecticide for weevils and most other insects with exoskeletons and works indefinitely as long as it stays dry.)  DE is the fossilized remains of microscopic diatoms that, to paraphrase Wikipedia, were protists, a cellular organism with a nucleus that is not an animal, plant or fungus.  The sharp edges on the fossils kill insects by scratching or piercing their exoskeletons, causing them to dehydrate.  (Check out the Wikipedia link for an electron microscopic image of DE particles.)

The hulls we will use come from parboiled rice.  The Riceland Foods, Inc. representative with whom I had been working, contended that parboiling kills all three forms of the weevil -- eggs, larva and adults. Again paraphrasing Wikipedia, parboiling rice makes it easier to process by hand, boosts its nutritional profile, changes its texture and makes it more resistant to weevils.  However, "resistant" is not total prevention and so far I have not found any studies that say unequivocally that parboiling eliminates weevils.

Diatomaceous Earth

In the absence of definitive information on parboiling and weevils, I decided to add DE to the hulls as we insulated but maybe not as much as would be the case if they were not parboiled.  As of this writing, our best source for the kind of DE that we need is a local farm and home store which stocks it as a livestock supplement.

A quick search online reveals that there are two kinds of DE.  One kind goes by various names -- industrial grade, filter grade, pool grade -- while the other is food grade.  The former is inappropriate for our use because it is heat treated or chemically treated that leaves it ineffective as an insecticide and tends to make it a health hazard, particularly with regard to silicosis, although several sources recommend dust masks when using food grade DE as well, not for fear of silicosis but to prevent airway irritation from its microscopic particle size. The amount of food grade DE recommended as an insecticide in grains for human consumption seems to be one cup per 50 lbs of grain, which is probably overkill for our purposes considering that parboiling probably leaves minimal or no weevils to worry about and the hulls will contain hardly any rice grains that weevils would need for long-term survival.  Nevertheless, we decided to go with 1 cup of DE added to each 50 lb bag of hulls.  It will then be in the wall and ceiling cavities indefinitely to control all types of insects with exoskeletons, not just weevils.  

The next post will chronicle our experience with the hulls from receipt to incrementally insulating with them. 

Sunday, September 27, 2020

Design - Solar Collector - Problem-Solving

This is fifth post on the solar collector but, undoubtedly, not the last since I will reporting on its performance over time. The purpose of this post is to report that it has not lived up to expectations and to suggest changes that will make it work.  

Lack of Performance
The glass for the collector was installed by the middle of July just in time for lots of clear skies and 90+ degree temperatures that should have maximized airflow from the collector into the conduits.  I gave the system a few days to rev up, thinking that it may take a while for the hot air pushing up the conduits to overcome the cold air dropping down.  During the early afternoon on a bright and hot day, I checked the air flow from the north ends of the conduits and found that, if there was any movement at all, it was so minimal that I could not detect it.  I waited for another sunny day but one without any wind in order to dangle thin strips of paper from the conduit outlets that would detect any air movement.  Still no detectable convection.

At our latitude, the temperature of the soil where the house sits would be in the mid-60s by mid-summer at the depth of the conduits.  However, since the house temperatures during the past couple of winters have stayed above 40 degrees (despite no insulation), it is reasonable to think that the temperature of the earth under the house surrounding the conduits is higher than it would be if not shielded by the house.  If so, the temperature of the air falling out of the conduits might be as high as the 70s but apparently still too cold for the heated air from the collector to overcome. 

The performance was disappointing but not totally unexpected given the dearth of practical information available in print and on the web, which means that our design had to be largely original.  I look at the situation as just another problem that needs to be solved and reported on just like many other surprises and challenges that we have encountered with such a unique build.

Are the Conduits the Problem?
In a previous post, I listed some of the unknowns that come into play.  "Assuming the design of the collector is adequate, its function is still at the mercy of many unknowns about passive air flow through the conduits.  Will 4" diameter conduits be the optimal size for sufficient airflow?  Are conduits that are nearly 90' long from collector to daylight behind the house too long to expect passive flow?  Do they angle upward enough from 10' below floor level when they leave the collector to a depth of 3 or 4' below floor level at the back wall of the house and then make 45 degree turns to daylight?  Will using the corrugated (rather than smooth) piping under the house (the intent for which is to cause turbulence in the air flow and thereby improve heat transfer to the soil) slow the flow too much?  Will the cooler soil during the first winter and, to a lessor extent, after each succeeding winter, cause cool air to flow backwards towards the collector to the extent that the warm air from the collector cannot passively reverse the flow?"   Of all of the items on the list, only the one in italics can be addressed at this point -- the rest are what they are.  At this juncture, I would add one other possibility.  The conduits terminate with two 90 degree fittings in order to keep rain out.  Perhaps if the conduits pointed straight up, there would be less resistance to passive flow.

Is the Solar Collector the Problem?
The problem could also be in the design of the collector rather than in the conduits.  Maybe one layer of galvanized roofing is not enough; maybe multi-layers are necessary.  Maybe there is so much space between the metal and the glass that the volume of heated air is insufficient for spontaneous escape up the conduits.  Perhaps the collector is not large enough to supply nine conduits passively.  Maybe it will be necessary to add to the system one or two what might loosely be called "solar chimneys" whereby the conduits would be brought together and exit to daylight through a common chimney, with or without the assistance of a fan.

At first I assumed the problem lies with the
Termini of the nine conduits.  The one in the middle was
modified to accept a vacuum hose for testing.

conduit portion of the system instead of the collector which means there is only 
one factor I can test -- the one in italics above. I manipulated the airflow in one conduit to see if it could be jump-started to overcome the effect of the cool soil by cutting away the double 90s in order to fit the end of the conduit with an end-cap having a hole the same size as a vacuum hose.  I pulled air through the conduit with a vacuum for a couple hours hoping that, when the cap was removed, I would feel warm air, or any air for that matter, coming out of the conduit.  Such was not the case. 

The next probable cause for under-performance that could easily be investigated was to measure the amount of heat the collector was producing.  Having assumed that the temperatures would be too high for plant growth, 
Thermometer resting on the metal is maxed out.

I began to suspect that heat generation was insufficient when a couple of plants sprouted along one edge of the collector.  I pulled the plants and placed a thermometer of the common type with a scale to 120 degrees inside the collector.  It recorded temperatures approaching 100 in the early morning when only the west half of the collector was sunlit and the thermometer was shaded by the east wall of the collector.  As the sun reached the glass fully, the temperature readings quickly rose and stopped at the maximum capability of the thermometer somewhat above 120.  And further plant growth has been non-existent.  So, pending the purchase of a thermometer with a higher range, the initial readings are encouraging enough to look elsewhere for ways to make hot air flow through the conduits. 

Reconfiguring the Terminal Ends of the Conduits
It is becoming obvious that the conduits will require redesigning at their terminal ends.  Instead of nine conduits exiting to daylight independently, I am now convinced that they need to converge into one or two solar chimneys fitted with a solar fan(s).  Since each conduit is nearly 90 ft long, I think two chimneys with four or five conduits each would be more efficient than one chimney located 40-50 feet from the termini of the most outlying conduits.  At the time of this writing, it is mid-September and completion of exterior trim for the house is the highest priority.  Reconfiguring the conduits will have to wait until spring.

Tuesday, September 22, 2020

Construction - Solar Collector - Safety Fence

The previous post covered the functioning part of the collector.  This, the fourth post on the collector, describes the safety fence surrounding it, the design for which needed to meet
The framework for the safety fence around the collector shell.
several criteria.  It needed to be tall enough to meet code for handrails, it needed to be as attractive as possible considering its prominence in front of the house and it should not block the view from the house any more than necessary.

(Reminder: click on any picture to enlarge it for better viewing.)

Upgrading the Top of the Wall
When the collector shell was built five years ago, the top of the walls were covered with 2 x 12 pressure treated planks that were anchored with bolts embedded in concrete.  While they protected the top of the walls, they left much to be desired aesthetically and begged to be replaced.  It took only a few minutes at the landscape supply store to decide in favor of concrete pavers instead of pricey capstones.  I dry-fitted them to determine where the posts for the fence should be located in order to minimize laborious notching of the pavers.  I then installed the posts and notched the pavers using a diamond blade in the radial arm saw.  I also custom crosscut a few pavers as necessary to filled the gaps that would not accommodate full sized units. 

Post Placement
Like the solar collector framework, the pressure treated lumber for the fencing was stickered and air-dried for several months so that it remained straight and would accept and hold paint.  Then, before assembly, it was undercoated on all six surfaces and final coated on at least three surfaces.  The 4 x 4 posts extend below the ground to the depth of 12 - 16" so they needed to be ground-contact rated; the pressure treated lumber for the rest of the railing system needed only to be rated for above-ground use.  The corner posts were "V"-shaped at the bottom so as to rest on the top of the wall and straddle both surfaces of the wall below.  Two long and robust Tapcon concrete screws through each surface was more than adequate to anchor them firmly and, with the sometimes help of composite shims, hold them plumb.  Instead of "V-ing" the bottoms of the intervening posts (south and north sides), they were reduced in thickness by a half so as to rest on top of the wall and extend downward where they were anchored by four screws each.  Backfilling and tamping the soil around all of the posts will help to support them as well.

With the posts in place I could lay the pavers in mortar.  The weather was hot and I got in a hurry to get done so I laid them without the benefit of a mason's line.  The result, I am sorry to say, looked pretty amateurish.    

East and West Sides 
The wood framework for the enclosure supports a wire grid fashioned from cattle fencing that I cut from panels that come 4' high and 12' long.

The fencing for the east and west sides of the enclosure presented a challenge in that it had to be stepped to follow the contour of the stepped walls and its top had to slant to follow
Temporary layout board.  A few of the cap stones
 are yet to be mortared in.
the slope of the stepping.  Since the cattle panels were 4' high, I installed a temporary board 4' above the lowest step and leveled it.  Off of that I could measure the amount that the fence panel would have to be reduced over each step uphill from the lowest step. These measurements, along with the length of each step and the slope at the top, were laid out on a cardboard pattern.  After dry-fitting and tweaking the pattern, I laid it on a section of fencing that had been cut to length and marked the wires to follow its edges.  An angle grinder with a metal-cutting diamond blade easily handled the 4 gauge wire.  
The cardboard was accurate enough to be used as a guide for cutting and fitting the support board at the top of the fence.  I used 2-by blocks under the wire panel to hold it off the wall slightly as I attached the board at the appropriate height to catch enough of the top of the fence board for secure fastening.

Dry-fitting the cardboard pattern to the east end of the 
The cardboard pattern in place over the cattle fencing
for the east end of the collector.

collector showed that, with one minor adjustment, it could be used for cutting the east fencing panel. I added the top board on the east at a height that matched the board on the west.  Confident that metal panels were installation-ready, I set them aside so that they would not interfere with laying the pavers with mortar.  

North and South Sides
Compared to the east and west sides, the north and south sides were easy.  For the north side, I installed the top boards at a height that matched the northern ends of the side boards and the bottom boards at 1 1/2" above the pavers.  I added 2x2 nailers to the sides of the corner posts to receive the vertical edges of the
Fencing completed except for caprails.  The ladder
used during construction is still in the collector.

fencing panels. 
 As an cosmetic touch after the panels were fastened to the top and bottom boards and to the posts, I added  1-bys on the collector side of the entire framework.

I decided to delay the fence for the south side until the glass was installed on the collector in order to leave plenty of access with the heavy glass panes.  I entertained the idea of building an access gate into the south fence but decided against it based on looks, which means that we will have to drop an extension ladder into the shell when access is necessary for maintenance.  The design of the south fence was then identical to the north fence.

Post Caps and Cap Rail
Finally, I added store-bought pressure treated post caps to the tops of the posts -- for aesthetics and to protect the end-grain of the
In lieu of a gate in the fence, a ladder will have to
be used for servicing the collector

posts from deterioration.  The caps for the top rails will be 2 x 6s that I customize with bi-sloped tops to shed moisture eventually.  Their addition is being postponed while more urgent projects on the house are handled.