Timeline - Estimating Costs

Past Year

St Charles home

Our Budget

Both Dorothy and I had already downsized considerably when we bought the house in St Charles, MO.  And we agreed that, since our house was paid for, it made no sense at our ages to rob other assets or borrow money for a new house.  Our construction budget, after selling our modest home in St Charles, MO during the great recession and paying for the land in Collinsville, IL, turned out to be $72,000 and the final design turned out to be 2,100 sq ft.  Do the math and we are talking $34 per sq ft which is about 25% of contractor prices.  But building at this price is a challenge worth confronting, not only for the satisfaction of succeeding but to set an example for what can be done.

Revised Drawings

The drawings scenario that played out before costs could be estimated accurately was as follows:  Amateur pencil drawings -Quarter-scale model of the house - First set of cad-cam drawings - Revised cad-cam drawings - Another set of amateur pencil drawings.

I had barely started estimating before it was clear that we were still way over budget even though we had down-scaled considerably from the first set of cad-cam drawings.   Earth on the roof, the timber frame to support it and the attached greenhouse were the first major deletions before doing the revised cad-cam drawings but, even then, we were still over budget.  

Back to Pencil Drawings

As I looked for ways to cut costs, I decided it would be easiest to trace onto velum paper the things on Steve's drawings that should be kept then draw in the changes required to meet budget.  By the time the estimate was complete, the drawings I gave to Steve to use for the final iteration were mostly pencil drawings.

Crane truck required for a St Charles County timber frame

An interesting observation
While seeking ways to cut costs, it became apparent that merely reducing square footage did not have the impact that one would expect.  If the price per square foot for everything from metal roof down to gravel base under the slab -- sheathing, insulation, drywall, tile floor, concrete -- is added up, the total is not impressive.  Cost cutting is better done by modifying methods and materials and eliminating rental equipment and professional labor. An example...... rental on a crane service to erect timber framing and structural insulated panels would constitute 7-10% of our budget and the frame and SIPs together would have surpassed our entire budget.

Estimating

Professionals use their experience to develop strategies and shortcuts for estimating jobs. In the absence of experience, I created an Exel spreadsheet for line-item estimating.  It ended up being 12 columns wide and over 200 lines deep on which I included every item I could think of that needed to be budgeted.  For example, I drew a wiring diagram in order to get numbers for such mundane things as electrical boxes, switches, receptacles, cover plates, Romex, etc.

Click image to enlarge

The first few columns of the spreadsheet were descriptive and the next few were per-each costs and extensions which were then tallied at the bottom in order to know total costs.  The last few columns broke costs down into phases of construction to provide a timetable as to when the money would be spent.  This was important because the track loader represented a big chunk of the building budget and would have to be sold during the latter stages of construction to free up cash with which to finish the project.

Click image to enlarge

Pricing

The prices for the spreadsheet were obtained in many ways. Some came directly from manufacturers and vendors, e,g,, geo-textile fabric for French drains and rice hulls for insulation.. Some prices were from subcontractors who will help with a few phases such as concrete work and waste plumbing (labor costs only; I shopped the materials that would be used).  Some came from distributors such as those for insulated concrete forms and fiberglass windows and doors.  And a lot of pricing was done piecemeal by shopping online at the home improvement centers or walking their aisles, by noting the price of diesel fuel for the track loader at the local gas station, by continuing to shop Craigslist, etc.

Click image to enlarge

Finagle Factor
If our estimate can be faulted, it is because the finagle factor is too small. Some wiggle room was created by using retail prices at the big boxes that will be negotiable when it comes time to buy. And some choices in the finish phase are flexible -- laminate or DIY wood or concrete counter-tops instead of stone; Habitat Store floor tile instead of tile store tile or homemade interior doors instead of prehung.


During construction, we will be reporting on how well.we are tracking against the $34 per sq ft budget.

_________________

Update:  Winter 2021

Well, reality has a way of shackling naivety.  Before the year is out we will have moved into the house and I will have the time to dig up several years worth of invoices and other documentation to understand the true cost of the build and just how futile my DIYer attempt at estimating was.   At this point, I would guess that the figure is at least twice as much as my estimates here.  The review will probably show that I grossly underestimated the cost of subcontracting for such jobs as excavating and concrete work as well as the amount spent on salaries when a second or third pair of hands was unavoidable like for setting roof trusses and sheathing the exterior shell.  And, since construction has been strung out over multiple years, the costs for materials rose beyond anything that I envisioned, particularly the past year during the COVID-19 disruption to the supply chain.  I will link back to this post in the future when the follow-up analysis is posted.

Timeline - Early Professional Drawings

One Year Ago

Cad-Cam Drawings

By late summer 2013, Dottie's son, Keith, no longer needed my full-time help on the house that we started together a year and a half earlier, so it was now possible to rev up our project.  We had already met several months earlier with Steve Rehagen, an engineer with considerable cad-cam experience, and had shown him our scaled pencil drawings and house model.  He kept the drawings and we took the model in hopes of using it in an exhibit on sustainability in St Louis (but failed to make their cut).

Overview of first set of cad-cam drawings (click for larger view).

Now we asked Steve to start professional drawings based upon my pencil drawings.  Unfortunately, he could not find my drawings, but, since the model was done to scale, it was all he needed to proceed.  The model showed earth on the north half of the roof, but my education on earth sheltering had matured to the extent that my pencil drawings showed no earth on the roof and neither did Steve's.  But, for reasons that I can't recall, the timber framing that was originally designed to support the earth (lower right image in the picture above) did appear in Steve's drawings.

Second set of drawings (click on image for a larger view

Second Set of Drawings
The first drawings were modified almost immediately to eliminate the timber frame and the attached greenhouse. The latter would not only have added unnecessary costs but would have complicated the concrete work beyond what I felt comfortable doing. Now we had a set of drawings that we could use for preliminary budgeting.

Still Way Over Budget

Second set (click to enlarge)

It became obvious that more would have to be done to reduce cost even before starting an estimate.  So I made some design changes to reduce floor space and earth contact wall area. In the process, the garage moved into the hillside beside the workshop and faced south instead of east. The entry way with its timber frame was de-timber-framed and reoriented to face south rather than east.

The front bedroom was moved into some of the space the dining room had occupied and the walk-in closet moved such that the back bedroom gained first story windows in addition to its clerestory windows.  The second level remained essentially unchanged from the professional drawings except for tweaking the window design.

Second set (click to enlarge)

Back to Pencil Drawings
As these changes evolved, it became easier to trace onto velum paper the parts of Steve's drawings that remained as is then use a pencil to draw in the changes. We then ended up with another set of pencil drawings as a basis for the final construction drawings. They did provide details on non-traditional construction, such as truss walls and frost-protected shallow foundations, that Steve will not have to detail in his drawings.

Second set (click to enlarge)

Arrangement with Steve
In order to allay any apprehension on Steve's part with regard to working with an amateur, we asked that he do the design work and the drawings on a time and materials basis.  Even then, he seems a little frustrated at times but that's understandable.

Estimating
The combination of pencil drawings and unaltered professional drawings were sufficient for estimating purposes. The DIY method I used to reach a doable figure is covered in detail in another post, Estimating Costs.

Timeline - House Model

Three Years Ago

House Model

During the winter of 2011, we decided that a scale model of the house-to-be would be helpful for a couple of reasons: To help Dorothy and I visualize the rooms and furnishings in 3-D and to facilitate communication with potential consultants, vendors and permitting authorities.  We had just put our dog down so her bed became a convenient container for the model.  I constructed the model from wood and Plexiglas with green carpet 

representing organic surfaces.  Miniature furniture, cabinets, built-ins, appliances and bathroom fixtures were detailed.

Roof and AGS Components

The silver portion of the roof represents metal on the south, single story, half of the house.  The overhangs, which keep the summer sun from penetrating, make it 

difficult to see the south walls with the roof in place.  The "metal" roof though is removable in sections. The "green" (earth contact) roof over the north half of the house hinges out of the way. The white "pipes" sticking out of the ground behind the house represent individual solar chimneys for the Annualized GeoSolar system (first post on AGS; second post on AGS).  The "pipes" in front of the house in the second view represent the conduits for the AGS system which were left uncovered for demonstration purposes.  The concept at the time of the model was for the garage and main entry to face east as shown in the third picture but were reconfigured to face south in the final iteration.

Timber Framing and SIPs

The fourth picture, with the north roof hinged away, shows the "timber frame" supporting the heavy earthen roof.  In the very beginning, we dreamed, not only of a timber frame, but of exterior walls and a roof done with structural insulated panels, which are both green and typical for timber frame homes. However, sadly, SIPs,  the earth contact roof and the frame all had to be jettisoned shortly after the model was completed when early quotes clearly showed that our budget could not support them.  It was hard sacrifice to make because we both like the rustic look of a timber frame and felt that we were already compromising by using the frame for only half the house.

Furnishings

Miniature furnishings were added to the model to help visualize the spaces in 3-D. The picture at the right is included to show the amount of detail given to the furnishings.  It also shows the timber frame from a different perspective.  The screened porch (lower right) made the cut for the final construction drawings but the aquaponic greenhouse (lower left) did not.

Even a small house yields lots of good lumber

Building Director Buys In

The Building Director, who is solely responsible for issuing building permits and doing the inspections, met with us at the building site with the model in front of us 

Good looking "bones" for salvage

and was okay with our design.  We had shared our general concept with him before buying the property and had met with him several times in the interim as our plans developed but the model was a positive communication step.  And it was at that meeting that the Director pointed me to a house that had defaulted to the City and needed to be torn down. Within a couple of months, the deal to tear it down was done and, two months later, the basement was ready to fill and I had added substantially to my stash of recycled lumber.

The model proved invaluable in an unexpected way as mentioned in another post -- Early Professional Drawings.

Timeline - Surveying the Building Site

Two Years Ago

Rotary Laser

An early Craigslist find was a rotary laser for $80 that sells at the big boxes for three times more.  It came with the tripod, the leveling rod and the sensor for the rod.  My experience with a rotary laser was nil but it seemed reasonable that it would be the ticket for surveying the building site, instead of paying for a professional survey, and would have myriad uses during construction. 

Tripod station facilitates the excavation

Advantages of a Rotary Laser
The rotary laser has advantages over a conventional transit for the DIYer working alone. The battery operated sensor on the leveling rod beeps loudly when it is level with the laser beam. Consequently, measurements can be made working alone as opposed to the two-person team required for a transit -- one person to sight through the transit and the other to operate the leveling rod.

Tripod Stations

In order to standardize and expedite setting up the laser, I made two tripod stations near the east property line where they would not be in the way of future excavation. Each station comprised two half sheets of salvaged plywood weighted down by stones.  I set up the laser on each platform in turn, marked where the tips of the tripod touched the plywood and drilled holes just large enough to accept the tips.  I reset the laser and marked the tripod legs with permanent marker at the telescoping point for each leg in case the legs were moved between uses. Then to store the laser at the end of the day, the laser could be left on the tripod, the tripod lifted from the plywood and the legs folded together without un-telescoping them.  Each subsequent use of the laser then required only spreading the legs and setting them into the holes in the plywood followed by minimal tweaking of the laser for level as necessary.

Data points (20" x 20" grid) recorded on site

"Surveying" the Building Site

The summer of 2012 was droughty.  Our cool weather grasses were brown and flat for weeks on end which gave me a rare opportunity to survey the building site and the level ground north of the building site.  I used a tape measure to mark off a grid of 20' x 20' squares and mark the intersections with marking paint.  The dead grass was ideal for displaying and holding the paint for the couple of days it took to complete the survey.

Survey

The day before surveying, I plotted the grid on a piece of stiff project board that would not blow around in the wind.  I set up the laser on the station highest on the slope.  I then moved about among the paint marks with the leveling rod and detector and recorded each elevation that could be measured from the first station.  Next I moved the laser to the lower station and finished recording the paint marks.

Data points (20' x 20' grid) plotted against sea level

The data points on the project board were transferred to a spreadsheet and given values for elevation above sea level.  The sea level figures were based upon a Goggle Earth value for the highest point on the area surveyed.  The square in the middle of the spreadsheet represented the proposed building footprint.

Accuracy

The data points are not close enough together to plot the contour lines that would be standard for a professional survey.  However, they gave me, as the builder, all of the information I need.  I did not pass the DIY survey on to Steve, who is doing the construction drawings, in order not frustrate him by its lack of sophistication or cause him to stew over proper siting of the building.

Timeline - Amount of Earth Sheltering and Configuration of Earth Contact Walls

Fits and Starts over Past Eight Years

Decision on Amount of Earth Sheltering

Our original intention was to heed the advice of Hiat, Stephens and Carmondy/Sterling and earth shelter as much of the house as was practical for our site.  Accordingly, the north wall, the north half of the roof and most of the west wall would be sheltered. The 
east wall would remain mostly unsheltered because it was an attached garage and entryway.  According to the prevalent philosophy on earth sheltering, maximizing the amount of earth contact would benefit the thermal performance of the house in two ways --  by increasing the size of the thermal mass and decreasing the amount of the envelope exposed to the environment.  Less exposure means fewer opportunities for air infiltration and fewer walls needing conventional insulation.

Green roof and earth contact west wall (all concrete)

As recently as last year, after our engineer had produced the first set of drawings, based on my amateur drawings and a model of the house, it became apparent that earth on the roof was not doable because the timber frame to support it would be too expensive.  And, in the absence of a concrete roof, there was always the issue of termites.  However, the amount of earth sheltering for the west wall remained in flux until the final construction drawings when it was reduced by one-half in order to reduce cost and simplify construction.

Earth Contact Walls in Conjunction with AGS

The only practical option for earth contact walls is concrete of some sort.  If an earth contact wall is continuous with earth on the roof, as advocated for AGS (see second post on AGS) the entire wall is protected by the insulation-watershed umbrella and could remain uninsulated.  However, in our case, at least 8" of the top of the wall will be exposed below the roof (for termite protection).  So part of the wall has to be insulated and part not, creating two zones.  The bottom zone is uninsulated so heat can move freely back and forth through the wall as part of the AGS system.  The top zone is insulated and starts a foot or so under the level of the insulation that lies horizontally as part of the insulation-watershed umbrella and it ends at the roof line.

Upper area of back wall is insulated (black); lower wall is not (brown)

Advantage of a Two-Story House
Fortunately, our two-story house will have a tall back wall.  This allows for an uninsulated zone almost as large as the back wall of a typical single story with earth on its roof which should make the AGS system just a functional as the pure design Stephens advocated. The biggest challenge will be to create stick built exterior walls and a conventional roof that will not waste the precious heat after the system produces it. However, as I will detail in a separate posts, the 15" thick truss walls and 16" deep cathedral ceilings filled with rice hull insulation will more than compensate for the lack of earth contact on the east and west walls.

Complete Block System

In order to reduce costs, the design of the concrete walls went through several iterations ranging from DIY poured concrete to DIY dry-stacked cinder blocks to a new system called "Complete Blocks" (Complete Block Company) to professionally poured concrete. The most ideal solution would have been the Complete Block System in that its precision concrete blocks come both insulated and uninsulated so they could be mixed and matched as necessary to satisfy the two zones.  However, the cost was budget-busting and the test data the start-up company was able to provide for our structural engineer was insufficient. So we went to plan B -- professionally poured uninsulated concrete.

Odds 'N Ends - Carbon, Global Warming and Native Plants

Succinct Description

Wild Ones is a national organization that promotes landscaping with native plants.   A succinct description of the carbon cycle, which under-girds any environmental discussion, appears in the March/April, 2014 issue of the Wild Ones Journal.  The author, Daniel Kjar, PhD, Myrmecology, Ecology & Evolution, had this to say:

"Carbon is an element that makes up both plant and animal life on Earth.  Carbon is the backbone for most if not all organic molecules.  Through a process called "photosynthesis" that only plants can do, they use the sun's energy to combine carbon, oxygen and hydrogen to make glucose, a simple sugar.  Every other living thing utilizes the sugar molecules manufactured by plants to obtain the carbon for whatever is needed.  We humans convert the sugar into fats, proteins, nucleic acids and numerous substances that make up our bodies.  This cycle of carbon can be represented as:

Energy from sunlight + carbon dioxide + water  ->  sugar  ->   carbon dioxide + water + energy of life."

(I guess it is safe to say that some animals exist on plants (herbivores), some exist on animals that exist on plants (carnivores) and the rest exist on both (omnivores).)

Fossil Fuels  

He goes on to say that, "Organic matter.....can slowly turn into long chain carbons......that we use as fossil fuels.  The burning of fossil products that we mine from the ground.......releases far too much carbon into our atmosphere, creating the Greenhouse Effect that is heating our atmosphere."

Global Warming Controversy

When Darwin introduced natural selection, the reaction to it took several contentious decades to work through three stages that all profound truths seem to have to go through -- ridicule, opposition and acceptance -- while financial interests confuse, delay and deceive.  Do you see a parallel for global warming?

Native Plants

Native plants not only produce food for wildlife, but, by mitigating global warming, make the planet a healthier place to live.  They are easy on finite resources in that they do not need watering (water is becoming the world's most valuable finite resource) or fertilizing or mowing (both of which require the finite resource -- petroleum).  Native plants had been doing a good job of sequestering carbon for 20 million years until the Europeans came to plow them under, cut them down and burn them off.

If you have any interest in natural landscapes,  we heartily recommend becoming a "Wild Ones" member as an opportunity for networking, sharing information and exchanging seeds.  We have already started using natives for the landscaping we can do before construction is finished and plan to maximize native landscaping post-construction. Fortunately, we will be able to tap into the broad expertise of the more knowledgeable fellow members of Wild Ones.

Construction - At last!

Straw bales for silt fence

Today is August 3, 2014 and we are finally beginning construction. The straw bale silt fence is in place and excavation has begun.

Dry Season
In Collinsville, it has not rained in over a month although some of our neighboring communities have been more fortunate.   

Silt fence on the east (close-by) and the south (downhill)

We have been hauling water from home 
to fill the 2 gal containers (discussion about water containers) that keep new trees and bushes watered as well as critical plants in the garden such as tomatoes, okra and squash.  And the dry season has limited the amount of mowing necessary, thank goodness.

However, as discussed in the posts about the excavation plan, Excavation and Excavation (Cont'd),  the dryness has allowed us to begin construction sooner.  Based upon the soil cores taken when the piezometers were installed, the concern was that too much moisture in the deeper silt soils or a torrential downpour on the excavation after the organic material was removed would be too difficult for a DIYer to manage for reasons explained in the posts on excavation.

The first bucketful!

Excavation -- First Day
I developed a few track loader skills while doing dirt work at my step-son, Keith's, owner-building project. Today, I find them to be a little rusty after the layoff of a year.  However, they not only came back after the first couple of hours but I gradually added efficiency. 

The goal is to create first a north-south profile of the excavation about 15' wide just east of the footprint of the house that will accomplish two purposes.  The first will be to provide a ramp in and out of the excavation for carrying the soil for storage on the flat area north of the building site.  The second goal is to validate the elevation for the eventual floor before actually carrying the excavation westward into the footprint of the house.  

First half days worth of hard digging

Hardpan
The ground is so dry that I have spent an inordinate amount of time with the toothed bucket on the loader trying to penetrate and separate the topsoil from the soils below for separate storage.  As I continued deeper, the soil below the topsoil was also bone dry and hard to pry loose down to a depth of four feet or so.  (Makes one wonder how shallow-rooted trees survive in droughty periods.)   Below that, digging was what I would consider normal for compacted soil.

Unexpected Debris
The area of the first dig was once the site of a very large barn, according to the sons of the original owner.  Supposedly, the foundation was removed and the cavity closed with fill dirt.  Sure enough, below the topsoil I encountered a layer of clayey soil with numerous bricks and stones to a depth corresponding to the frost line.   And an iron pipe, presumably a water pipe leading from the house, added to the fun.  As is apparent in the accompanying photo, the silt topsoil in the near pile has a different color than  the underlying soil in the far pile (click on the image for a clearer view).  

Second Day -- Not so good
After 10-12 bucketfuls, the loader stopped dead -- seemingly with no power from the battery.  Most of the day was spent solving the problem because my mechanical skills are almost non-existent and it wasn't until Keith, with his  trouble-shooting abilities, came to the rescue that the problem was fixed.  Although it was not the cause of the problem, we found a fuse-link that should be replaced before the jury-rigged, "penny-behind-the-fuse", situation had a chance to cause a fire.  An opportunity to upgrade the track loader at this early juncture is a good trade-off for the loss of a few hours of digging time.

Design - Excavation (Cont'd)

This post was written at an early planning stage whereby I intended to minimize cost by doing most of the work myself.  When it came time actually to do the trenches for the French drains and the AGS conduits, we were in the midst of the rainiest Spring in history. It became necessary to get as much work done as possible between rains so we enlisted professional help for the trenching as well as for grading for the slab floor.   It took several posts to cover the installation of the French drains and AGS conduits. Here are links to those posts:  First post on French drains, Second post on French drains, Last post on French drains,  First post on AGS system, 

French Drains
The typical French drain is a trench about a foot square in cross-section with a perforated drain pipe it it.  The pipe is laid on a 2" bed of coarse gravel then the trench is filled to the top with more gravel.  Usually, a "sock" made of geotextile fabric surrounds the pipe.  The same fabric completely lines the trench before any gravel goes in, then is folded across the top of the gravel before back-filling with soil.  (Information on French drains.)  A French drain is depicted by the lower black line in the nearby sketch of an early concept of hour house.  The drains will lie several feet below the conduits for the AGS system (red) so as to keep the soil above them dry year around for proper functioning of AGS.

Our French drains will be slightly different in that we will need a geotextile fabric that is designed for the type of fine silt laid down on our bluffs by the wind after the glaciers receded.   The type of fabric that is available in retail outlets would quickly clog and make the French drains useless. (Comparative study on geotextiles.)  



Back-filling to the Level of the AGS Conduits
The conduits for the Annualized GeoSolar system will comprise ten 4" diameter mostly flexible pipes ( red in the sketch) running between the solar collector (blue) and the solar chimney (green).   (See discussion of AGS conduits.)

After the fabric is lapped over the French drains, we will back-fill with soil until we get to the level necessary to support the AGS conduits.  The backfilling will have to be done in "lifts" (layers) of 8" or less then compacted with a rented vibratory drum roller, either the kind the operator sits on or walks behind and controls wirelessly from a lanyard around his or her neck.  

Compactibility of the Soil
The silt that we have is not as compactible as gravel or soils containing gravel and sand, or even clay. Therefore, it is necessary to amend the soil with something like agriculture lime in order to reach the level of compaction necessary to support the footings and the slab floor (input from retired civil engineer).   If so, we may have to rent a tiller for the track loader to stir the limestone into the soil before compaction.

Completing the Back-fill
After the conduits are laid -- two to a 6' wide trench positioned as far apart as possible -- filling will proceed in compacted lifts until it reaches the level necessary to support the gravel base under the concrete.

Finishing the Floor Excavation
The slab and its gravel base need to rest on undisturbed soil.  Since the loess silt is so easily disturbed, we will deliberately not excavate initially to the final depth for the floor. Then, after the track loader and other heavy equipment has stirred up the top layer of soil during excavation and back-filling for the French drains and conduits, we will carefully remove additional soil until the exposed soil is either undisturbed (between trenches) or thoroughly compacted (over trenches).  We can probably remove most of the loose soil with the track loader if done in a controlled way.  However, we will be removing some the hard way -- by hand. 

Ground-breaking Schedule
Because of the peculiar nature of our soil, the long time it will take us to excavate and our limited budget, the soil engineer recommended not starting excavation until the late summer dry season.  Then, if it rains, it will not likely be torrential and, with tarps, we might be able to keep the critical parts of the excavation from eroding or becoming saturated. 

Wind Blown Loess
Based upon the four core samples, our soil seems to be mostly wind blown loess, a type of fine silt with an interesting history.  It began as out-wash from the glaciers as they receded, then it was picked up from the Mississippi River flood plain and deposited on top of the bluffs by the wind.  Our deepest piezometer hole was 20' deep and the soil core from the bottom of the hole looked very much like the soil beginning just below the topsoil -- no clay, sand, rocks, etc., just silt.  The soil engineer says that it is 50' deep in some nearby locations.  

The particles are extremely small and elliptical-shape such that the wind action aligned them parallel to one another before rainwater locked them tightly together. Today, cuts have been made through these bluffs for interstate highways and the resulting vertical surfaces have remained uneroded as long as the organic cover has not been disturbed.  If the cover is disturbed, like we will be doing, heavy rain not erodes the soil very quickly, but, where water pools, it becomes totally unmanageable even for seasoned contractors, much less a DIYer.

Design - Excavation

This post was written at an early planning stage whereby I intended to minimize cost by doing most of the work myself.  When it came time actually to do the trenches for the French drains and the AGS conduits, we were in the midst of the rainiest Spring in history. It became necessary to get as much work done as possible between rains so we enlisted professional help for the trenching as well as for grading for the slab floor.   It took several posts to cover the installation of the French drains and AGS conduits. Here are links to those posts:  First post on French drains, Second post on French drains, Last post on French drains,  First post on AGS system, 

Excavating to Floor Level

Since the building site slopes about 15 degrees, the excavation for the house will be 

Building site -- 15 degree south-facing slope

about 6' below grade at the back wall and at grade at the front wall, which means it will involve cutting but no filling.  I estimate that the excavation for the house and garage will take four or five days with the track loader having a 6' long bucket and carrying the soil for storage 50' to the north.  The back wall will be two stories high which will eventually require an additional 6' of backfill on top of the original grade.

Excavating Below Floor Level
The excavation would be rather simple if it weren't for the need to bury the conduits for the Annualized GeoSolar (AGS) system (previous description of conduits for AGS). The conduits will be ten in number and range from 5' below the floor level at the front wall to 3' below floor level at the back wall.  To make things even more complicated, the piezometers that we placed and monitored for three years, told us that a French drain system* would be necessary to keep the AGS system isolated from the rainy-season water table.  It will comprise seven separate drains 15' - 20' apart east to west, about 10' below floor level, canted southward by 1/4" per foot and reaching daylight downhill where they will drain into a rain garden.

Excavation Equipment
Remember the adage, "When your only tool is a hammer, everything looks like a nail"? Well, our track loader is our hammer so I need to devise unorthodox excavation methods to stretch its functionality.   Even then I anticipate having to rent a mini-excavator (small backhoe) for a few days for final shaping of the French drains.

French Drain Trenches
After the basic  house excavation is complete, it will be necessary to trench down another 10' for the French drains.  It is too dangerous to work in a narrow trench even half that depth so, if it needs to be wider, why not use the hammer I have and make it 6' wide (which is probably not a whole lot wider than is necessary for safety?).  I will be moving a lot more dirt than a professional would but I have the loader for putting it back in the hole and all it will cost is a few extra tanks of diesel fuel and a few days time.

At the bottom of the 6' wide track loader "trenches", I plan to dig proper trenches for the French drains approximately a foot wide and a foot or so deep using a rented mini-excavator then finishing with selective hand-digging.

For the rest of the story, go to more details on our excavation.
__________________
*  Information on French drains.

Timeline - Annualized GeoSolar (Cont'd some more)

This is the third in a series of three posts on Annualized GeoSolar, the passive system for heating and air conditioning that we will use for our energy neutral house. To view the previous posts, go to Annualized GeoSolar AND Annualized GeoSolar (Cont'd)

I became acquainted with the system 7 years ago when stumbling upon an online paper by Don Stephens*.

Insulation-Watershed Umbrella
Carmondy/Sterling and Hiat seemed to have been the first to advocate extending the insulation and waterproofing horizontally below grade, as opposed to attaching it directly to the outside of the roof and walls of the house as was prevalent at the time of their writings.  Hiat called the arrangement the "Insulation-Watershed Umbrella", which is the terminology that I have adopted (as opposed to Stephens' "Moisture-diversion membrane/insulation cape").

Copied from p. 41, Hiat's "Passive Annual Heat Storage" (click on the image for a larger view)

Our iteration of the umbrella will comprise (from top down) the following layers:  (a) plus or minus two feet of backfill; (b) two layers of carpet with the top layer shingled upside down (per Stephens) to protect the umbrella from physical damage from burrowing varmints, garden tools, roots, etc. as well as keeping the carpet out of the waste stream; (c) two layers of 6 mil plastic sheeting; (d) foam board insulation; (e) 6 mil plastic sheeting; (f) with a thin bed of sand between each layer.

Why a 20 Foot Umbrella?
According to Hiat, it takes six months for a unit of heat to travel 20 feet through dry soil. During the summer, the solar collector heats the soil under the house as well as under the umbrella.  Then it takes six months of cold weather for any heat next to and under the house to travel the 20 foot distance to the periphery of the umbrella.  By that time, the solar collector is already recharging the system.  The distance can be shortened by slanting the umbrella downward from the house.

Critical Design Consideration for AGS
For the system to work, however, the soil under and around the house must remain dry for two reasons. Water passing through the soil carries heat away to the water table faster than the collector can manufacture it.  Damp soil, much less wet soil, is more thermal conductive than dry soil and, not only robs heat from the thermal mass, but pulls heat out of the house as well.

Four white pipes are piezometers for monitoring the water table

The umbrella protects against surface water but not from the water table. In wet climates such as ours, several test holes equipped with piezometers** should be used to monitor the water table through several seasons, if possible, to be sure the table remains several feet below the level of the AGS conduits.  If it does not, a French drain system*** must be installed well below the conduits, otherwise heat will be lost to the water table.  Our piezometers (four) told us that we needed a French drain system that, unfortunately, would complicate the excavation and drive up costs for the AGS system.

By having an earth bermed back (north) wall two stories high and half of the west wall, our project will take advantage of AGS without earth sheltering on the roof nor against most of the east wall. The reason is that the floor and tall north wall provide enough earth contact for heat transfer and the house will be super-insulated to retain the heat.   Otherwise, our adaptation of AGS will be pretty much like Hiat and Stephens describe it. The exact design of the all-important north wall and the solar collector is grist for a future posts.
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* Although Stephens' paper, www.greenershelter.org/TokyoPaper.pdf, is no longer available, it can be accessed indirectly via Stephens' definitive paper.

**Information on piezometers
***Information on French drains

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Update:  Autumn of 2016
By the autumn of 2016, the AGS system was nearly complete, lacking only the umbrella for the north side of the house and the functioning parts inside the solar collector. Consequently, additional discussion on AGS and the details of construction can be accessed through the following links:

Amount of earth sheltering and configuration of the earth contact north wall
Final decision on the amount of earth sheltering

Design of the insulation/watershed umbrella - first post
Design of the insulation/watershed umbrella - second post

Installation of the French drains - first post
Installation of the French drains - second post
Installation of the French drains - third post

Construction of the solar collector - first post
Construction of the solar collector - second post
Construction of the solar collector - third post

Installation of the insulation/watershed umbrella - first post
Installation of the insulation/watershed umbrella - second post

Installation of the insulation/watershed umbrella - fourth post

Wikipedia's description of AGS  is also a good reference.

Final Cost
With sporadic help from volunteers, I did most of the installation of the AGS system except for digging the hole for the solar collector and trenching for the conduits, so our cost was mostly for materials -- foam insulation (biggest item), concrete blocks (second biggest), sheet plastic, fibercement parging, gravel/sand and piping for the conduits. Without the French drains, the cost for installing the AGS system probably would have been less or about the same as for a conventional HVAC system. However, the professional help with the collector and conduits raised the cost to at least to that of a minimalist HVAC system that would suffice for a home that is south-facing, super-insulated, partially earth sheltered and protected by an insulation/watershed umbrella.  It could be argued that the French drains were necessary anyhow for a partially earth sheltered structure in a site with potential water table problems. If they are factored in, the cost clearly exceeded that of a conventional HVAC system.

However, the story is not complete.  It remains to be seen whether our grand experiment performs as expected.  We will be monitoring and reporting here on the thermal performance for several years after occupancy.  If it performs as expected, the pay-back for the extra cost will accrue over time as we avoid the cost of energy and maintenance on heating and air conditioning equipment.  Also we will be insulated from future spikes in rates, be free of furnace and compressor noises and can take winter vacations without worrying about frozen pipes from furnace failure.  And best of all, the environment will benefit once we begin breaking even with the utility company.

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Update:  Summer of 2021

The summer of 2021 was the first opportunity to check out the efficacy of the AGS system.  We found that spontaneous flow of warm air from the collector through the conduits and exiting from the individual conduits behind the house did not occur.  It was necessary to bring the conduits together into a solar chimney and add a fan to pull the air through them.  Here is a  link to the post that describes in detail the modifications that we made and a thorough critic of our design including suggestions for a similar system without a solar collector.