Net Zero site preparation starting with soil analysis.

We chose a building lot that we considered to be most suitable for a Net Zero site preparation.  The soil turned out to be a combination of VERY fine grained sand and a clay binder.  It was decided to have a concrete slab over grade to diminish any potential for cracking and damage to the radiant floor’s hydronic tubing.  A Geo-technical engineer strongly advised us to bring in several feet of engineered fill.  The engineered fill required compacting under the frost wall and the entire 5200 square foot concrete pad.  The primary reason for such good foundation support is to avoid having the concrete crack, to do so would likely damage the radiant floor hydronic tubes which is a very expensive repair proposition.

Geo Technical Engineer Analyzing Soil

Geo technical engineer analyzing soil to determine suitability for a good foundation.

We purchased a property anticipating that the Net Zero site preparation costs would be acceptable.

The wife and I oriented the house to take the maximum advantage of the southern exposure for solar production.  We almost jump for joy every time we see the energy bill (or lack thereof).  Most of all we really enjoy the views of the valley, lake, mountains and city lights.

The photo below shows the wide excavation for the north shop wall which runs about 100 feet from east to west.   This is one of the two long trenches that determined the direction our windows and solar panels face.


Net Zero site preparation involving excavation before applying compacted engineering fill

Net Zero site preparation making way for compacted engineering fill

Frost walls are shown installed over compacted Engineering Fill, a major Net Zero site preparation.

The concrete people placed the frost wall footings over several feet of well-compacted engineering fill (a mix of rock and binder dirt material).  Also note the white Geo Foam boards on the outside of the frost walls.  The walls attracted the R10 insulation, thus helping keep the interior floors at a higher temperature than the winter outside temperatures.


Four foot R10 geofoam frost wall was a big part of the net zero site preparation.

 A Four foot R10 insulated frost wall is a part of Net Zero site preparation.

Net Zero site preparation included compacting and leveling gravel throughout the entire interior space between the frost walls.

The photo below shows Net Zero site preparation of the gravel which subsequently supports several additional layers of different materials.  Those adders include a vapor barrier, R10 foam board over the gravel, six inch steel reinforcement grid over the foam board, radiant floor tubing tied to the steel mesh and finally a concrete slab.

The sub floor Net Zero site preparation involved spreading, leveling and compacting gravel around the entire building.  A good contractor is always fighting the risky potential for concrete cracks, but this case was exceptional.  They therefore had to take extra special precautions  to avoid damaging the radiant floor tubes.  Someone would incur significant expenses if the radiant floor tubing experienced cracking problems.  Thankfully, we have found only a couple minor floor cracks in the entire building floor so far.

Net zero site preparation makes ready for a concrete slab pour.

Net Zero site preparation of the shop sub-floor compacted and leveled gravel.


In closing….

This web site provides much more information on basic building considerations for the Net Zero Energy home and garage.  Please look over the other Home Design articles which provide building details common to many energy star homes.

Thanks for taking the time to read!