Construction - Passive Solar Heating System Completed

The solar heating system, after ten years of trial and error, has finally been completed.  It was originally designed to be entirely passive but it did not work as planned and a fan had to be added.  (Click on any photo for better viewing.)

The original design comprised an elaborate solar collector in a pit in front of the house that would harvest sun energy during the warm months and send it as heated air through nine conduits that are slanted slightly upwards and spread out under the house.  Heated air passing through the conduits would warm the thermal mass under and behind the house so that it would in turn warm the house during the cold months.  However, we soon learned that the legacy cold in the soil in which the conduits were buried pushed cold air downward through the conduits.  And the air in the collector was not hot enough or voluminous enough to reverse the flow.  The warm air would have to be pulled through the conduits from above.

Standing on end at the right, visually aligned with the bottom of the
PV panels in the background, is the short section of culvert before
 being partially buried in about the same location.

If air had to be pulled through the conduits, they could no longer emerge behind the house individually; they needed to be extended and converged at a "solar chimney" containing a fan.  Accordingly, a temporary chimney was cobbled together and pipes were run above ground to it.  A small furnace blower on a timer was installed in the chimney.  By the time the ugly temporary arrangement was replaced with the final iteration, it had worked well for two summers.

Since the 4" PVC conduits were to be entirely buried, they were shorten back to where they were horizontal and below grade then, with couplings, transitioned to 6" PVC pipes that ran underground to the new solar chimney.  On the way to the chimney, the 6" pipes were consecutively wyed together so that only one pipe entered the chimney from each side. The vertical pipe inside the chimney that received them was a piece of 12" corrugated culvert buried deep enough to receive the pipes through holes in its sides then protrude about 2 ft above grade.

The stick-built housing enclosing the culvert and holding the blower rested on top of the culvert as well as on legs supported by

concrete pads.  The opening through which the fan blew the air, sucked from the conduits, faced north and was fitted with a door that could installed during cool months to keep cold air from falling into the conduits and diluting the hard-won heat stored in the thermal mass.  Another opening, that was large enough to allow replacement of the fan was caulked shut but could be accessed in the future. 

Our PV array is the smallest the vendor would sell us but, as we estimated years ago, turns out to be about right for our needs.  So the demand placed on it by the "non-passive" solar chimney fan has not been consequential, considering that our gride sourced electricity during the entire year of 2024 amounted to only $105.

As long as the conduits were individual and accessible above grade, there remained the possibility of capping some of them during the warm months which might be advantageous if the thermal mass gets warmer year-over-year as seems tentatively to be the case.  If so, perhaps the simplest answer will be to reduce the inflow of air by capping some of the conduits leading out of the collector.

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OVERDUE SHOUTOUT

It doesn't take much scrolling through our blog to appreciate the number of men and women who have contributed to our house building project.  Shown at the right is the plaque hanging in our entry foyer that acknowledges the many volunteers and contractors who have been involved in this ten-year project.  (It can be enlarged for better viewing by clicking on it.)

And our plumber friend Bob Morgan, who came into our lives too late to be included on the plaque, took the lead for the project described here.

Construction -- Interior Casework

It was the fall of 2023 when this post was posted -- a little over 9 years since we broke ground.  That it has taken this long to be within a few months of finishing shouldn't be a surprise considering our unwavering insistence on time as the variable and quality the constant, that we would spend whatever time necessary to do things as well as we were capable.  And, of course, much of what has gone into the project is entirely without precedent and therefore much more inefficient and time consuming than standardized construction.  Then add DIYing.  I lacked experience in the "real" construction world and, when assisted, it was mostly by other DIYers.  

The interior casework has followed the same pattern but even more so.  Doing it with raw sawmill lumber has been extraordinarily time-consuming, not even counting the time it took to sticker and dry the green lumber.  The advantage of using sawmill material, though, is that it lowers costs sufficiently that a committed worker with the proper shop equipment can produce high grade casework at reasonable cost. 

(Reminder: click on any picture for an enlarged view.)

Acclimating the Sawmill Lumber

Sawmill oak for interior trim

Using the saw table as a "paint station" when the
dedicated area for staining and painting was not enough.

The rough red oak for the interior trim was purchased from a local sawmill.  Since its lengths, widths and thicknesses had to vary to meet our needs, its sawing was done while I watched/helped.  It was "stickered", meaning carefully stacked in level layers separated by thin strips of wood (the stickers) and covered with corrugated metal roofing.  Thus it was protected from direct rain, snow and sunlight but was open on all sides to circulating air so that the sap in the wood gradually dried over time without warping.  The recommended drying time is at least a year but longer is better with the knowledge, however, that stacking too long risks "sticker burn" which occurs when the stickers cause discoloration in the milled lumber.  Fortunately, we saw sticker burn on only a few pieces despite our extended timetable,   And our extra effort in stacking and stickering paid off when even the longer pieces were straight and easy to mill.  When crookedness did occur, the boards were usually okay flatwise but somewhat bent, mostly around knots close to the edges of the boards.

Milled lumber in vertical basement

When it was finally time to begin work on the interior trim, the sawmill lumber was de-stacked and stored for awhile in the vertical basement of the house so as to acclimate to the interior temperature and humidity levels.  Thus, its moisture content was matched to that of the house so that the fit of the installed woodwork would stay tighter over time.

Milling and Sizing

In the garage workshop, a piece of sawmill lumber went through at least four processes to become a useable board.  A jointer was used to plane one side perfectly flat -- no concavities, no convexities, no twisting.  With one side flat,

The window sill is extra wide to hold potted plants.  Notice
in the background the raised metal vegetable gardens
and the fenced solar collector for the AGS system.

the thickness planner shaved the other (rough) side flat, smooth and to the desired thickness of the finished board, say 3/4" for most applications.  Next the jointer was used to true up and smooth one of the rough edges of the board.   And finally, the table saw with a long and stable rip fence was used to cut the board to the desired width, running it through the saw with the true edge against the fence.  The sharp blades in the jointer and thickness planer and a fine-tooth blade in the saw minimized the amount of sanding needed to produce a smooth surface ready for staining and "varnishing".

I milled most of the raw sawmill pieces before starting the trim work so as to know what was available to work with.  Then I segregated the pieces; first the widest for baseboards then the narrower pieces for door and window trim -- head casings, side casings, sills, aprons, plinths, jam extenders, etc. --  in order to be sure there was an adequate supply in each category to finish the job.  To my pleasant surprise, the sawmill operator and I had communicated pretty accurately on the width and thickness of lumber needed -- with one hitch -- I forgot to include jam extenders in the order but was able to use oak veneer plywood for them that blended in well enough.

Fitting, Staining, Poly-coating and Installation

We used pre-hung unpainted solid core oak veneer doors rather than making doors from scratch.  After hanging, the doors were moved one-by-one to the shop for staining and clear finishing.  And the casework was dry fitted then stained and poly-coated before installing.  Only the door frames had to be stained and poly-ed in place.

The doors and windows had been set into the 15" thick exterior walls such that there was a 5" space between the window frame and the back surface of the side and head casings that had to be filled with "vertical jam extenders" on the sides and "head jam extenders" on the tops.  Since I was short sawmill lumber for them, I used oak veneer plywood for an acceptable result.  The windows are set back from the plane of the exterior wall at least 8".  Not having them flush on the outside ruled out windows with nailing flanges, making it necessary to eliminate air leakage by traditional means.  Minimally expanding foam filled the gap between the windows and the rough openings supplemented by generous caulking when the exterior casework was installed then more caulking as the jam extenders and sills went in.

Unique Staircase

When I approached the sawmill operator about "showy" wood species for an open riser staircase, he recommended an option new to me -- hackberry.  We stickered and dried it in the roughed-in walk-in closet lined by plastic sheeting.  Aided by a dehumidifier, it was dry by the time we needed it.

The rough hackberry was drab and uninteresting but, once milled, "showy" did not do it justice.  Pieces wide enough for 12" steps were not available but, just as well, my jointer was only 8" wide.  So the steps had to be assembled from narrower hackberry boards with a filler of black walnut interposed.  The stringers were conventional 2-bye lumber veneered with hackberry.  Clear poly-coating made the unique character of the hackberry pop and the dark walnut added a nice touch.  The store-bought balusters and handrails, stained to match the other woodwork in the house, provide a pleasing contrast to the light colored stair treads and stringers.

Door and Window Trim

In order to mimic the country style of a bygone era, the head casings and the splinth blocks (below the side casings next to the floor) are wider and thicker than the 3/4 inch thick door side casings and the baseboards.  The thickness of the head and side casings of the windows are dissimilar in the same way.  And the baseboards are 6" tall, definitely a throw-back. 

Filling the nail holes in the woodwork was no small task.  It was done with stainable wood filler and a long learning curve to be able to know how soon to remove the excess stain in order to reach an optimal result. The hole filling and wood filler staining nevertheless caused enough blemishing of the poly-ed surfaces that a final (third) coat of poly was required throughout.                                                                                             

Early Spring, 2024

The interior casework is finally finished leaving only three major projects before the house is complete.  The build-ins for the second floor office still have to be done, the porch needs screening and the temporary solar chimney needs to be replaced with a proper chimney with the conduits running to it buried rather than exposed as they are now, mainly for esthetic reasons but also to make mowing easier.

The office project will be the most time-consuming in that the cabinetry will be custom-built from the sawmill walnut that I stickered many years ago then stored under cover until there was a good use for it.  A walnut dining room table is also planned.

A Note of Appreciation

Despite being 90, I continue to work on the house at least six hours daily and often seven days a week but getting up from the floor is harder now.  I completed the more accessible door and window trim but was only too happy to delegate the baseboards to son-in-law, David, a retired machinist who made hundreds of ups and downs from his knees to the saws in the workshop in order to stick to the machinist-like tolerances that made him happy.  He also took on the fastidious job of installing the balusters for the stairs and the second floor catwalk -- about 140 total -- which also required dozens, if not hundreds, of trips to the workshop in order to meet his workmanship standards.  If I had attempted the baseboards or the balusters, there's no doubt the quality would have suffered.

Construction - Drywalling, Tiling and Painting

By the summer of 2021, our construction schedule began to take on new priorities.  My arthritic hip was seriously interfering with my effectiveness and we were reluctant to ask for more help from family and friend volunteers.  And I wanted to recuperate from hip-replacement surgery in our new handicap accessible ADA-compliant house rather than in our  one hundred year old residence, a house that gives new meaning to steep and narrow stairways.  So, for the sake of time and wear and tear on me and the volunteers, we decided to pay for more hourly help and subcontract such jobs as drywall taping, painting and tile work.

Friend Myron spraying the ceiling; note the
ceiling grid created by 1 x 6 MDF boards

The creative, design-on-the-fly, one-off thought and effort that has gone into the house over the past 7 years is now behind us.  Finding experienced tradespeople was easy because the interior finishing is essentially the same as for conventional construction.

As discussed in a previous post, the concrete floor was polished and stained as the first step in finishing the interior.  To protect it from drywall mud and paint splatters, we immediately covered it with resin paper and large tarps.  

(Reminder:  Click on any photo to enlarge it for better viewing.)

Drywall Taping and Ceiling Painting

The drywall finishers

Well before the time of this writing (March, 2022), professional drywall finishers had "mudded" the walls and professional painters had done an exceptional job with three coats. The ceilings had previously been finished with a grid pattern of 1 x 6 MDF boards fastened to the ceiling trusses with 3" construction screws.  They were added to secure the drywall under the load of the rice hull insulation which has roughly three time the weight of cellulose.  And they add interesting esthetics while eliminating the need for taping.  In advance of the tapers and painters, the ceilings for both floors were spray-painted by our neighbor, Myron, with a semi-gloss white as the topcoat (instead of the more common flat or eggshell) in order to reflect more of the sun's energy coming through the windows

Scaffold removed -- a major watershed!

in cold months.  

Drywall Taping and More Painting

After the ceiling was done, the second floor temporary floors that served as scaffolding could finally be removed and the drywall hung on the wall next to where they had been.  Finally, we could enjoy for the first time the openness over the living room and master bedroom and the unobstructed view from below of the second story windows and the catwalk in front of them.  It was then time to call in the drywall finishers for taping most of the house in one full swoop -- the exception being the airlock (entryway), vertical basement (storage and utility area) and the garage, which was done a few weeks later.  

Dorothy and Sue laying resin paper to protect
 the stained concrete which is visible in the middle
(viewed from the second story catwalk)

Through the Better Business Bureau we were able to find a local painting contractor staffed mostly by his extended family with high standards for integrity and workmanship. That they were able to start work immediately meant that we suddenly had to chose wall colors that we had only casually been thinking about.  

As soon as the painters were finished with the first phase, the contractor who polished and stained the concrete floor returned for the final buffing.  The painters returned for phase two after the drywall in the airlock, vertical basement and garage was mudded.

Tile Work

Retrieving one set of repurposed
cabinets found on Facebook

The polished and stained concrete floors and the composite flooring for the second floor (discussed in a recent post) eliminated the need for ceramic or porcelain floor tile except in the walk-in shower stall, the tub surround in the guest bathroom and the front entry floor.  Despite having an industrial strength tile saw, we decided in the interest of time to buy the materials and hire professionals to do the work. 

Odds and Ends Finishes

The painters departure set the stage for a myriad of odd jobs that had to be done before move-in (which finally happened the first week of March). During the week, I would peck away on them as much as my hip problem allowed then family and friends descended on Sundays to make a huge difference.  Interior doors were hung.  Closets and the pantry were outfitted with shelves, clothes rods, etc.  Serious storage shelves for the vertical basement were made from long recycled pallets. A convenient garment station for the airlock was designed, built and installed by Myron.  The energy-recover-ventilator (ERV), installed a year ago, was balanced by the HVAC contractor.  Openings high on the first floor that allowed warm air at the ceiling to escape to the second floor on its way eventually to be cooled by the concrete north wall of the vertical basement were gentrified with registers. Kitchen and bathroom cabinets (Facebook, Craigslist and Habistore finds) were installed followed by all new Energy Star appliances.  Ceiling fans and light fixtures (all Energy Star) were hung.  And a ridiculous number of wall plates were screwed to place over switches and receptacles.

Finally, we moved my woodworking shop from the free-standing unheated garage next door to the more spacious and conditioned garage attached to the new house. 

Work To Be Done After Move-in

Some of the casework could be done with MDF boards before move-in -- the airlock, garage and master bathroom mostly.  The local Building Inspector approved a conditional occupancy permit without the complete build-out of the interior. This will allow us to live in the house while we do such things as use our stash of sawmill hackberry for the final stairway, use our stash of sawmill red oak for the casework throughout as well as finishing the guest bathroom. His leniency is probably typical of most small town officials; he appreciates the extra time it will take to use the rough lumber and respects my need to take time off from non-essential construction for hip replacement surgery (which occurred the last week of April, meaning no more serious construction work for at least three months).

Stay tuned.

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.

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

SPOILER ALERT -- Summer, 2025

Do not use rice hulls for insulation.  We did and have had to spend much time controlling the situation.  For a thorough discussion, see a recent post.

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                                                   ORIGINAL POST

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. 

t

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.

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

SPOILER ALERT -- Summer, 2025

Do not use rice hulls for insulation.  We did and have had to spend much time controlling the situation.  For a thorough discussion, see a recent post.

                                                      ORIGINAL POST

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.

Construction - Insulating with Rice Hulls - The Planning Stage

SPOILER ALERT -- Summer, 2026

Do not use rice hulls for insulation.  We did and have had to spend much time and expense controlling the situation.  Here's our story as it has evolved. 

As a methodical and cautious early adopter, I thoroughly researched rice hulls and thought I understood the risk of rice weevil infestation.  My contact person at the mill assured me that weevils cannot survive the parboiling of the whole grain that is done before separating it from the hulls.  In the absence of any information to the contrary, despite considerable research, I decided to take a chance on them.  

My research told me that weevil reproduction required a grain of rice into which an egg is laid and the larva develops until emerging as an adult weevil.  In the process. the rice grain is consumed.  If there were rice grains in the sample bag of hulls sent by the mill, they were so inconspicuous we did not see them.  Consequently, we assumed that, even if a few grains of rice existed in the insulation, they would soon be consumed by baby weevils until no grains existed.  Besides we did not see any weevils in the sample, although, in retrospect, they were much tinier than we expected and were simply overlooked. 

My research also revealed that diatomaceous earth is an insecticide for bugs with exoskeletons by finding its way under their skeletons and dehydrating them.  So a cup of diatomaceous earth was mixed with each bag of rice hulls as they were blown into he wall and ceiling cavities, all the while thinking that this extra effort was probably overkill but advisable since the stakes were high and our knowledge so limited. 

Five years later, we are beginning to think that we know more about rice weevils than those speaking and writing about them at the time we did our research.  Clearly they reproduce in the absence of rice grains.  Each bag of "hulls" would have had to include a lot of grain to have supported the exponential infestation we are now seeing.  Moreover, we not only see a large number of adult weevils outside the confines of the wall, we see quite a few what we thought were larva but now think are yellowish elongated globs of eggs. 

A major oversight on my part is that diatomaceous earth as a backup would prevent an infestation.  However, I did not account for the fact that enough adults live long enough to reproduce before dehydrating and the eggs each female is capable of laying numbers in the hundreds.  Therefore, new bugs may be developing faster than the old bugs are dehydrating.  Initially, the vast majority of adults that we saw were dead, many with their feet in the air.  So it is safe to assume that, no sooner did they emerge into the open, they died from dehydration.  Most adults are able to fly but we see very few actually doing so, partly because they are so small and fly fast.  As it turns out, the diatomaceous earth was effective only for a short while -- here is what I think happened.  Eventually enough weevils escaped from the rice hulls, primarily by following electrical wiring and plumbing pipes, and laid eggs before being dehydrated.  Then subsequent generations lived free of the earth and began reproducing exponentially so that we are now seeing weevils by the thousands instead of a few dead ones on window sills.  And it wasn't until we took close-up pictures of weevils stuck to the double-sided sticky tape laid along the baseboards in the most invaded areas that we could see the plethora of tiny immature weevils. 

Our plan now is to use whatever measures that may be necessary to confine the weevils to the non-living spaces for the remaining years of our lives.  Then, before subsequent occupation, the house will have to be gut-rehabbed to expose every nook and cranny that the weevils could possibly occupy then fumigate, possibly multiple times, before rebuilding.

*          *          *          *          *          *          *  

Original Blogpost

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.  

Atypical Sequencing

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.