Ann and Gord Baird are building their home from cob and other materials drawn directly from the earth.

By Pattie Whitehouse
News correspondent
May 30 2007

Just over a year ago, the News Gazette began a series of articles about the Eco-Sense project, an east Highlands couple’s plans to build a sustainable home.

At the time, Ann and Gordon Baird intended to construct a one-and-a-half storey strawbale and cob house. A metal roof would be used for rainwater catchment to supply most of their domestic water.

They planned to be off the power grid, with electricity needs met by solar panels and wind generation.

Heat was to be supplied by solar-heated water circulating in pipes embedded in the earthen floor. Wood stoves with water jackets were to supplement the hot water heat on dull days.

Sustainable systems planned included re-use of grey water, treated in a living biofilter, to irrigate an orchard and installation of composting toilets that are odourless and pleasant to use, but require no water or electricity.

The Bairds have made considerable progress since embarking on their ambitious project early in 2006. Some of their plans remain the same, but there have been big changes, too.

One of the biggest is the decision to make the ground floor of the 1,800 square-foot house entirely of cob, instead of the straw bale — cob combination originally planned.

Research has convinced the Bairds that cob, a mixture of clay, sand and straw, is better than straw bale in Vancouver Island’s damp climate. Besides, they fell in love with cob construction when putting up their workshop last summer.

The ancient building material is versatile, lending itself to walls with graceful curves and the easy incorporation of decorative elements such as glass blocks and an arbutus branch.

Cob benches, shelving and a cubbyhole for Boo, the dog, have already been built into the living room.

Construction is done by hand, which not only is satisfying work but builds relationships among the builders, the Bairds said. Even Gord’s elementary school age children are helping to put up their new home.

The primary ingredients of cob are “dirt cheap.”
Clay, considered at construction sites a waste material that would otherwise end up in the landfill, is available at very little cost.
Sand and straw in the amounts required are also inexpensive.

The Bairds are incorporating pumice, mined in B.C., into their cob, which has increased the cost but added benefits.

Cob itself does not have high insulation value, although it is a very good thermal mass, storing heat and releasing it slowly.

With the addition of pumice, however, the Bairds estimate the insulation value of their walls will exceed R20.

The lightweight, porous volcanic rock will allow the walls to breathe, eliminating the need for a vapour barrier. It also increases the compression tolerance of the cob, making the structure stronger; and because the mixture does not slump as regular cob does, the walls rise faster.

Used steel cables will tether a bond beam around the top of the walls to the foundation, inside and out, to provide seismic stability. In an earthquake, the whole building will shift as a unit with the movement of the earth.

Another innovation is the use of a rototiller to mix the cob, which has sped up the process considerably. The machine can do in half an hour what traditionally takes two people eight hours to accomplish as they mix the materials with their feet.

The Bairds estimate they will use 20 to 24 litres of gas in the rototiller to mix cob for the entire house. The fossil fuel consumption is minimal compared with that used in the building of a conventional wood frame home, taking into account the fuel consumed in logging, transporting timber, milling, and transporting lumber.

Thanks to the new techniques, the Bairds expect construction to be completed this summer.

As they said in a recent newsletter, “There is no doubt in our minds that a small group could build a 1,500 square foot family home in three months or less at a fraction of the cost, financially and environmentally,” of a conventional wood frame house.

Moreover, the expected life span of a cob house is many times that of a conventional home. Some cob structures are still standing 500 years after they were built.

Hand-in-hand with the choice to go with all-cob construction was the decision to replace the planned metal roof with a living roof, again a change inspired and informed by the workshop experience.

When rainfall begins, a conventional rainwater catchment system diverts the first volume of water so that any debris washed off the roof do not enter the domestic water system.

That won’t be necessary with the living roof. Native vegetation growing in a mixture of compost and pumice on coconut husk matting will act as a watershed, filtering out debris before the water enters the downspouts.

From the roof, rainwater will go to a primary holding tank, then through a self-cleaning biofilter into a storage tank. During drought periods, the storage tank will be topped up with water pumped from the well by a solar-powered pump.

Both rain and well water will go through another filter and an ultraviolet sterilizer before entering the house.

A living roof has many advantages over a metal roof in addition to cleaning rainwater up front, the Bairds said. It replaces habitat destroyed by development, is prettier and lasts longer, is more cost effective, has higher insulation value and is quieter when the rain is pouring down.

The Bairds were determined from the beginning that their new home will meet the requirements of the building code.

With the assistance of engineer Kris Dick, a specialist in alternative construction, and Highlands building inspector Chris Leek, who they said is very interested in their project, the Bairds are achieving their goal and, they feel, blazing new trails in the process.

In their newsletter, the Bairds said their innovations in materials and construction techniques invalidate conventional arguments against building with cob.

“Perhaps the only reason for not choosing to build with cob now is our cultural programming about living in a dirt home,” they said.

More information about the Eco-Sense project is available at www.eco-sense.ca. Learn to build with natural materials

Ann and Gord Baird are not only passionate about sustainable living, but about demonstrating how it’s possible to live sustainably without sacrificing comfort and convenience.

To this end, the Bairds are offering a series of tours and natural building workshops at their east Highlands home.

Tours featuring the innovative systems they are incorporating in their new house are being offered June 30, July 20 and Aug. 25.

Angela Evans, a community planner with expertise in environmentally appropriate design, will lead the tours.

Evans will discuss benefits of composting toilets, solar hot water and radiant hydronic floor heating, and solar and wind-generated electricity, as well as associated building code issues.

On July 28, Evans will lead a session on the domestic water cycle. Discussion will include water conservation, grey water re-use, rainwater management and accessible technology-based sewage treatment systems.

Week-long natural building workshops are scheduled for June 17-23 and Aug. 15-19.
Led by cob construction expert Elke Cole, the workshops will provide theoretical and practical instruction in natural construction options, particularly cob.

In addition to hands-on experience, participants will be introduced to topics ranging from design considerations in alternative construction to off-grid living.

“They’re the most important (workshops) people will ever take in their life,” Gord Baird said.

Information about tours and workshops is available at www.eco-sense.ca.

editor@goldstreamgazette.com