A CRITICAL LOOK AT MY MOTHER'S HOUSE

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THE SLAB

A house such as ours could be built without pouring a slab ... as long as the footings were adequate to support the weight of the structure and to resist tilting at the rear wall. By going that route, we could have saved about 35 yards of concrete (at $42 per yard) and $100 worth of wire mesh reinforcement. Our alternative flooring would have been rammed earth with quarry tile, or something similar, atop it. The total thermal mass available for heat storage would have been comparable, though the labor involved in preparing the rammed earth would have been considerably greater.

ROOF DECKING

We decided to experiment with a roofing system made by the Homasote Company. Including the sheathing material for the above-grade roof and the 3-1/2 "-thick polyurethane insulation for both roof sections, we paid $5,300 to "top off" our building. Broken d n on a cost-per-square-foot basis, that amounts to $2.50 for sheathing and insulation on the rear section and $1.75 for the sod roof insulation alone. The shingled ... a could , instead, have been sheathed with 1/2" plywood and insulated to an equivalent value with rigid board for about $1.75 per square foot, and the sod roof could have been thermally protected for $1.50 per square foot.

There are two important trade-offs to be considered, however. First, the Homasote products are very easy to apply and thus can save a considerable amount of labor. This might be important for someone who's trying to build his or her own home and hold a job at the same time. Second, the Homasote roof decking has a finished material on its inner surface. It can be laid on top of the rafters, and no Sheetrock or other drywall is needed to produce an attractive ceiling.

ACTIVE SOLAR SYSTEM

We tried as many different materials and techniques as we could while building the house (a procedure that certainly added to the cost), and the active solar system we included'is largely for demonstration purposes. We tied up $1,125 in materials for the rock storage bed and ducts, and a great deal of labor was involved, as well. The system performs nicely, but the fireplace we put in should actually provide more than enough backup heat for the passive solar elements in the building.

COOL TUBES

We experimented with various groundsource heat exchangers to cool our residence, and they were by no means inexpensive. All the 15" pipe, backhoe work, and miscellaneous ducting and registers cost $3,600 ... which would buy a pretty big air conditioner. Of course, the cool tubes cost nothing to run, but we don't know for certain—at this time—how they compare in performance with a conventional system. We're most concerned about the possibility of the home's overheating on warm days in the fall, when the angle of the sun is dropping to the point where passive gain is significant, and the earth temperature is still warm from summer. Because Eco-Village visitors were coming through the building every day during the autumn, it was difficult to get heating/cooling performance figures ... but we did see indoor temperatures warmer than those outdoors on a few September days.

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