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"Building with the Earth in Mind and Hand" by Josh Trought, as published in Permaculture Magazine No. 44, Summer 2005

As of November 2004, chickens, goats, and heat-loving plants are sharing a greenhouse structure in Dorchester, New Hampshire. We at D Acres of NH dedicated a summer of effort to an experimental combo structure. The building has various functions. The concept is a cumulative design that complements energy uses, inputs and outputs. By maximizing resources through design, we hope to save human labor hours and increase the quality of life for humans, animals, and plants.

The idea of a multi-use animal husbandry greenhouse sprang from the necessity of this climate. We need greenhouse space to extend the possibilities of food production in this region. Faced with the windy, slippery and frozen landscape that is out of doors here for 6 months of the year, we pondered improvements through design. Many traditional homes in New England are a combination of house, garage, and barn all connected under one roof. Combining greenhouse and animal husbandry structures was spatially beneficial because both these buildings require daily attention. Combining the two saves steps required to accomplish the same work. Placing these activities closer to the Community Building where winter staff are housed helps staff accomplish their work more easily.

Design Specifics
We combine energy cycles with this structure. The sun provides heat energy for both the plants and the animals through windows. The walls provide high insulation value and thermal mass. The earthen mass of the wall material moderates high and low temperature spikes. Woodstoves were placed strategically to heat internal air as well as the thermal mass of the walls. The waste of the animals ultimately becomes compost for the plants. Even air is recycled within this system as the Oxygen that the animals breathe is then exhaled as Carbon Dioxide, which feeds the plants, who in-turn produce more Oxygen for the animals. Reused glass, discarded as waste at the transfer station, extends the amount of energy originally invested in producing the glass. Plants and animals both consume water and require electricity, so sharing how they are delivered makes sense. Windows allow heat and air transfer between units.

The southern wall of the animal husbandry section is a half moon that collects the sun's energy throughout the day. The greenhouse occupies the three southern facades of this semi-circle. Considering the shadow of the building in the afternoon, the structure was sited southeast of the community building. The greenhouse is placed as closely to the community building as was deemed safe considering possible fire danger from the woodstoves.

Built to Last?
New England is a difficult place for a building. The extremes of cold and moisture combined with heavy snows and wind routinely destroy poorly constructed structures. We put a lot of mental and physical energy into this construction and we built it to be usable well into the future.

The most basic prescription for making structures last is to give them "good boots and a hat."[EAT5] We started from the bottom and gave serious consideration to the foundation. By observing heavy rains we noticed that the surface run-off was substantial at times. We addressed this by hand digging trenches using the existing slope and building swales to redirect surface water away from the building. The winter frost heaves of our area move the soil down to depths of 4-6 feet. Water saturated soil is particularly affected.
We chose to build separate but equally experimental foundations for the inner structure and the outer greenhouse perimeter. The inner foundation of the animal area combines two concepts. We used a floating Alaskan slab design, which was adapted to our landscape by embedding it into the slope below grade. Hopefully we have achieved the beneficial earthen temperature of a full basement without having to dig that deep. The perimeter foundation of the greenhouse was poured onto a rubble trench foundation. We dug a foot wide trench approximately 3 feet deep around the perimeter so that water drained away from the building. Then we put a 6" perimeter drainpipe in the hole and filled it will rubble. We then poured concrete up to a nominal height from which it carries the walls of the greenhouse. The concrete provides a dry and rot resistant base for the greenhouse construction. All the concrete was reinforced with steel so it should remain a stable fixture for the future of the structure.

Building walls was perhaps the most rewarding and definitely the longest part of the process. The walls were constructed using three earthen building techniques. Building with cob was an excellent opportunity to utilize many hands (or more accurately feet) to turn locally available materials into sturdy walls. The combination of sand, straw, and soaked clay was either made into cob balls to be thrown from the mixing site to the wall, or transferred into forms to create stackable adobe bricks. Building with cordwood proved quicker than the other two methods, though the earthen mix was still integral as a mortar between the stripped logs.

Cob is a great material to sculpt a structure. Here are some ideas to make it work well for you. Good dance music is essential for mixing. It is nice in bare feet but mud boots protect you day after day especially in colder weather. Mix as close as possible to the wall under construction and locate the raw materials close to the mixing site, this stuff is heavy. We used a ½" inch drill with a rebar whisk attachment to pre-mix clay and water into a slurry that was readily accepted by sand. Next comes hay or straw which comes in many varieties. In Argentina I learned first hand that hay can come with long thorns so beware. The idea of mixing in hay/straw is to incorporate long fibers that weave the cob together. When applying cob try to stage the site so that you can comfortably apply the material at waist height. This is important so that you can put adequate pressure to bond the cob as well as maintain the plum vertical integrity of the wall.

Our structure combines the use of different materials. Our intention as an educational site was not only to create a functional building, but to practice and evaluate the use of different materials and methods. The different costs in labor, cash outflow and natural resource use were recorded and now we are evaluating the performance of the materials. Evaluation requires time to observe how materials insulate and serve as thermal mass and also how they last. A major question is how the time and expense saved by not digging a full foundation will compare to the longevity of a monolithic foundation. How long will clear plastic roofing last compared to metal? Will there be shrinkage and air gaps around the cordwood installed in the cob? Will the cob be affected by the severe changes in temperature and moisture levels? Thus far the animals love the warmth of the building but there have been high moisture levels in the second floor chicken area possibly a result of this warm, wet winter weather.

The roof overhangs the building strategically to keep the water away from the walls and foundation. The roof is designed to shed the snow and water to the perimeter, especially on the north side. The base of the walls was built with masonry. The stone is more durable and moisture resistant. As the walls grew above the height of danger from rain splash and ground moisture, we switched to cob and cordwood. The southern walls that are protected by the greenhouse include adobe blocks, because they are particularly susceptible to rain-splash water damage.

There are distinct advantages and considerations when working with different earthen materials. The first consideration is locating and acquiring the materials necessary. All are heavy. It is important to pay careful attention to how to transport and utilize the materials up until their final placement on the structure. Cordwood and adobe require advance preparation but the process proceeds quickly during wall construction. The cordwood logs must be stripped of bark and seasoned appropriately for best results. Adobe blocks need to dry and be protected from rain until they are used. Stonework is durable but the process requires patience and skill. Cob can be sculpted into beautiful natural forms. Applied correctly it forms a union that is structurally cohesive compared to block type construction. There is a lot of labor to mixing cob and there is a limit to the amount that can be built daily. The material will sag on the wall unless it dries sufficiently. All these techniques become difficult in freezing temperatures as the material itself freezes. It is important to decide what materials to use based on the function, availability of labor and materials, budget, and time frame for completion.

We built this structure with the intention of it being usable without major renovation for at least 50 years. We expect minor maintenance will be required annually. Some predict the concrete in the foundation will remain intact for at least 400 years. We hope that the building can be maintained for the lifetime of the foundation.

This experience affirmed some common sense expectations. Commercial materials such as concrete delivered, rough sawn lumber, and metal roofing are conventional because they save time. These materials utilize capital ($$) and unaccounted natural resources but save physical labor onsite. Earthen construction requires significantly higher resources of time and sweat equity, while conventional construction is quicker but requires more capital and is natural resource intensive. In terms of psychological sustainability, the cob walls grew slowly and the repetition drained the building crew's energy. Wood framing and roofing went much quicker to the excitement of the participants.

The cost of this building without volunteer labor would have been immense. A total of 1602.25 hours were spent on the project. We spent 291 human hours digging the foundations and building the concrete forms. Next there were 214 hours spent on the masonry stone work that is the base of the walls. The time spent dancing in the cob, building adobe blocks and raising the earthen walls amounted to 652 hours of moving mud. The wood framing, finishing the details of the woodstoves, and framing of doors and windows ended up taking 392 hours. The actual roof took less than 50 hours of labor. And there are always more details. Experienced construction workers might have built the structure more quickly than students and volunteers, but the cost of wages would have been higher.

There was also a capital outlay for this structure. We spent almost $4000 on materials. Nearly $1000 was spent on concrete, $350 on masonry cement, and almost $600 on reinforcing bar. Cob materials were less than $150. The cob mixing drill, though certainly an enormous time saver, was almost $200. The foundation materials were slightly less than $500. The dimensional lumber for the framing cost over $600 for the milling as we had cut the timber onsite. The roofing materials cost nearly $400. About 75% the materials cost was in the foundation. Although foundation cost is typically high in NH, we spend up to 1/3 of our time and money on the foundation. In this case, the material cost was high because we could not agree on an alternative to concrete.

The high investment of this project was deemed worthwhile because it served as a hands-on construction learning tool for over 50 workshop participants, 19 interns, and 4 staff persons at the farm this summer. As an educational center, D Acres of New Hampshire is committed to involving learners in the process of creating an environmentally appropriate farm system. Our organic gardening, sustainable forestry, animal husbandry, and alternative building projects are all designed as expressions of our desire for respectful interaction with the environment. The construction process was a learning experience that is a demonstration for future earthen construction projects in the North Country.

Alas, the project has not satisfied our insatiable desire for more greenhouse space. We also intend to build a greenhouse on the southern façade of the community building. Could be another long summer building project….

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