Natural (or sustainable) building appeals to people
who are concerned about climate change, affordable housing, energy
costs and resource availability. Natural building provides solutions
in all these areas plus allows you and your family to live in a healthy
chemical-free home that you may have built yourself.
If it's not affordable ... it's not sustainable!
What's the Difference between Green Building and Natural (or Sustainable)
- Eco-Sense defines natural building as the use of plentiful
local and marginally processed natural materials to build a structure
with systems (water, energy, waste, recovery) with the most neutral
ecological footprint. Natural building also captures the footprint
of the building over its entire life span.
- Sustainable building is AFFORDABLE ... checkout our info sheet **updated** [ PDF ]
- Green building promotes using less energy AFTER construction
is complete, reducing energy use for the homeowner. Often to achieve
this energy efficiency, highly processed products and materials must
be used that require valuable resources.
Natural Building Choices
The building materials used, the building’s design and how
systems are integrated are all based on the buidling’s site,
geographic location, and climate information. Systems may include
power generation, water collection and re-use, heating, passive solar
design, resource recovery, house shape and space design. By assessing
what you have on a site-specific basis, you design an appropriate
home using the most cost effective and natural materials.
Designing a Natural Building
One of the most important aspects of natural building is designing
a structure that reflects the needs of its inhabitants. By identifying
needs and space requirements one can combine function and beauty.
Building small is the biggest step towards a sustainable and affordable
home for your family.
Structural Lightweight Insulated Cob (SLIC)
- Testing is done by crushing test cylinders in the same manner as concrete
- Our samples have come in extremely high with a value of 1.25MPa (mega Pascal)
- Test samples fractured in a perfect cone. Even after failure no visible cracks could be seen. This suggests that
even after failure from an earthquake the cob may maintain the structure and still hold up the roof.
- Addition of pumice (30%) makes the cob much less heavy
- The addition of this identical pumice (called ¾ minus) into concrete increases the insulation (R-Value) by 260%.
- It is assumed that based on the different thermal properties of cob that the insulation value for cob will increase
by 100%. Standard cob has an R-value of 0.5 per inch. For our walls we are assuming an R-Value of 1.0 per inch
for 20 inch walls. This means an estimated insulative value of R-20
- We will be installing temperature sensors into the cob walls to gather data on how our home performs.
- All cob was mixed with a rototiller using only 24 l of gas
- Increase in efficiency (speed) of 500% over traditional foot mixing of cob.
- No sifting of materials
- More straw can be added to cob
- Mix is 30% clay, 30% sand, 30% pumice and lots of straw
- Cob pit is a slight depression in the ground with two sheets of thick plywood in the bottom.
- Ours is a 1962 5HP Gilson with dull blades (very important)
- Our rotating blades are on the front of the rototiller and we took off the wheels and put the tilling bar down
in the rear. This tilling bar allows the entire beast to be pivoted up and down to allow the straw to be left behind as it builds up and to facilitate turning and rotating.
- Basic Method
- Add straw first to cob pit
- Add clay and sand on top of straw
- Mix dry
- Add pumice and mix some more
- Add water
- Add more straw
Engineering/Seismic Wall System
Seismic Walls systems developed by our Engineer Kris Dick from Building Alternatives
- Method for using diagonal tension members (cables) to tether the foundation to the concrete bond beam
- Compressive strength of cob can easily be measured (see below) but the tensile strength is more difficult to measure. Tensile strength is how strong the cob is when being pulled apart from an earthquake.
- Engineers need numbers in order to stamp the plans. We are hoping that with the very strong pumice cob (see below) that future engineering of load bearing cob structures will not require as many tension cables or perhaps something like bamboo instead.
- The diagonal tension cables force the cob into compression rather than tension during an earthquake. Cob is very strong in compression.
- Bond beam is 4 inches of reinforced concrete that sits on top of the cob walls all the way around. Purpose is to distribute the load of the weight of the upper story and the roof and to provide attachment for the cables from the foundation.
Rain Water Harvesting
- Check out the books by Art Ludwik at Oasis Design
- Our design of the "worm composter to filter grey water" is coming soon
- Check out The Natural Plaster Book by Cedar Rose Guelberth
High fly-ash concrete
for engineering data
- Reduce the amount of cement used by replacing some of the Portland cement with fly ash.
- Fly ash is a waste product from coal powered energy plants.
- Fly ash is a pozzolan. Check out Pozzolan
- Reduce the carbon footprint of your home by using high fly ash concrete
- ICL was able to supply this for almost the same cost
see fabric form
- Less waste
- Less wood for forms
- Easy to make curves
- Save money
Initial Design considerations
- Solar Hot Water, meeting the intend of the code [ PDF | 428KB ]