Construction - Back to Dirt Work - The Insulation/Watershed Umbrella

As much as I would have liked to have continued with the carpentry phase of construction, the reality was that it was mid-September and we had only a few weeks to finalize the grade in front of the house and get it planted with a cover crop to control erosion during the rainy season next Spring.  Consequently, with the internal bearing walls in place, it was time to shift our attention to more dirt work.

The main job was to get the insulation/waterhed umbrella installed.  (Click on the "Featured Post" feature in the left column for linkage to Annualized GeoSolar and the role of the umbrella.)  However, loose ends had to be taken care of first.  The porch foundation had to be insulated and clad in the manner described for the east garage wall.  The exterior of the insulated concrete forms for the house foundation wall had already been covered with cement board but still had to be parged with stucco.  The grade needed tweeking before the umbrella was installed.  The umbrella needed to be laid down and covered with topsoil and the topsoil needed to be blended with the grade further down the hill in front of the house.  Finally, the cover crop needed to be planted no latter than mid-October.  Oh, boy! The race was on.

Insulation for the porch foundation; the footing extends
below the insulation and will be insulated eventually with
more foam board laid horizontally

Insulating the Porch Foundation

Cement board over the insulation

The foundation for the screened porch needed to be insulated in order for it to meet code as a frost-protected shallow foundation.  The porch floor was intentionally poured 3 1/2" wider than the foundation wall on all sides in order to accomodate 2 1/2" of foam insulation and +/- 1" of cement board parged with stucco. For details on the DIY insulation for concrete walls, check out a prior post.  In addition to vertical insulation for the wall, horizontal insulation laying on the footing and extending out 2' on the three sides that are not part of the umbrella is necessary to complete the frost-proofing.  It will be installed in conjunction with final backfilling against the porch foundation before winter sets in.

Stuccoing the Foundation
The house foundation was insulated automatically by using insulated concrete forms but

Stepson, Keith parging the cement board with stucco

Friend, Roger, parging the cement board that covers the insulated
 concrete form

needed to be veneered for appearance-sake and to protect the foam from damage.  Again, I used 1/2" cement board. The next task was to stucco the cement board on the porch and house foundations in exactly the same manner as described in the prior post. The stucco serves two purposes.  It improves the appearance of the top part of the foundation visible above grade and it seals the cracks between the cement board panels against freeze-thaw damage.

Insulation/Watershed Umbrella
The grade for the umbrella was largely done months earlier with the track loader but had been overtaken with grass and weeds that I did not attempt to combat because they controlled erosion.  Now it was a matter of using the trackloader blade, tipped up as a scraper, to remove the vegetation then spending a couple of days tweeking the exposed dirt with hand tools to be sure the insulation met the foundation footing correctly, the soil surface on which the umbrella would lay was as smooth as possible and that the entire area would drain properly.

The grade after removal of vegetation with the track loader
and tweeking with hand tools; notice that the dirt is still not
smooth enough to protect the plastic sheeting from puncture

Parenthetically, parts of the umbrella were already in place.  The insulated and impervious garage and screened porch floors comprise most of the umbrella on the east side of the house. I will install the rest of the umbrella on the east next year before the concrete walkway to the main entrance and the driveway are placed over it.

Building the Umbrella
The umbrella consists of ten layers as follows, starting from the grade and moving up through the umbrella:

Sand / 6 mil plastic sheeting / foam insulation board / sand / 6 mil plastic sheeting / sand / 6 mil plastic sheeting / sand / two layers of recycled carpet laid upside down / topsoil.

This configuration for the umbrella deviates only slightly from the one John Hiat describes in his book, Passive Annual Heat Storage, primarily by virtue of our liberal use of sand.  I will discussing the first three layers of the umbrella in this post and the last seven layers in the next post.

SAND

Two-inch thick sand layer over the raw soil to protect the
overlying plastic sheeting

Fortunately, I was able to enlist the help of step-son, Keith, and our friend, Roger, for the installation, which would have been extremely arduous for me working alone after having just done the dirt phase alone.

The dirt surface, despite all of the hand work, was too rough on which to lay the first layer of plastic sheeting without worrying it being compromised when loaded.  So we covered it with +/- 2" of clean sand.  I could bring the sand only to the periphery of the umbrella with the loader so we had to use wheel barrows to distribute it.  We found that a push broom, used mostly upside down, to be the most useful tool for spreading and leveling the sand.  

PLASTIC SHEETING

First layer of plastic sheeting with foam board on it
to help hold the top edge in place as it is stretched out

The best buy on 6 mil sheet plastic that I could find was at a farm and home center in the form of a 24' x 100' roll which was only a little more than what we needed for each layer of plastic going into the umbrella.  We cut and laid the first layer of sheeting over the sand base.  I previously had left two layers of plastic sheeting hanging out under the cement board/stucco covering for the house foundation and from under the rock retaining wall to the west of the house that needed to be woven into the sheeting of the umbrella. The first overlapped in shingle fashion the edge of the first umbrella sheet.

FOAM INSULATION
Most of the umbrella extends 16' feet from the house (20' would have been better but the

Most of the foam board in place and anchored for the night

placement of the solar collector and the under-dug embankment west of the house changed the rules). So the pattern for the foam insulation, based on Hiatt's prescription, was as follows:  4" thick for the first 8', 3" thick for the next 4', 2' thick out to the 16' periphery.  And in the few places the full 20' was possible, 2" thick for the last 4' (Hiatt recommended 1" but a sheet that thin at the periphery could be crushed too easily).

Balance of the foam in place; notice that the weaker white EPS
board in the first tier has been covered with the stronger XPS
 board in the second tier

In all, it took 70 sheets of 2" board, 20 sheets of 1" board -- all laid as much as possible so that the cracks between sheets in the first layer did not line up with the cracks in the second layer. Expanded polyethylene (white board in the pictures) is half the cost of extruded polyethylene (blue board) so about 40% of the 2" boards were EPS installed under the more rigid and relatively crush-proof  XPS.

Part of the hand work for the grade preparation was to make sure the first 2" layer of foam board butted up against the footing and was flush with the top of the footing.  In this way, the second layer rested on the footing and against the foundation wall so as to fulfill the requirements of a frost-protected shallow foundation. As mentioned above, the cement board/stucco cladding for the foundation wall was backed by two layers of plastic sheeting that stuck out quite a ways at the bottom.  The innermost layer overlapped in shingle fashion the plastic sheeting that laid directly on the sand bed.  As we will see in the next post, the outermost layer overlaps the top layer of the umbrella plastic.  The loose ends of plastic sticking out from under the stone retaining wall were handled in the same way.