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by David Johnston & Scott Gibson illustrations by Martha Garstang Hill

Turning an unfinished basement into living space usually involves adding new interior walls. Builders sometimes use 2 by 4s to build a conventional wall and insulate it with fiberglass batts. A vapor barrier applied to the warm side of the wall, or directly against the foundation, is supposed to keep moisture away from the concrete. But moisture that accumulates inside the wall is trapped, which can lead to mold and decay. A better approach is to attach semipermeable expanded or extruded polystyrene foam panels directly to the foundation wall and tape the joints. This keeps most air and moisture from reaching the concrete and allows the wall to dry to the inside. Gypsum drywall can be applied over furring strips for a finished wall surface, but no impermeable wall finishes should be used.

Slabs are rarely insulated, which means they constantly wick heat or cold to the inside of the house. In areas where the number of cooling degree-days (a quantitative index that reflects the amount of energy needed to cool a building) is very high, heat gain at the edges of a slab foundation can account for as much as 15% of the cooling load. In heating-dominated climates, a lack of insulation often means cold floors in rooms at the perimeter of the house. Edge insulation is an easy answer. It should be installed inside the forms before the concrete is poured. For houses in which radiant floor heating is incorporated in the slab, not only should the edges of the slab be insulated with rigid foam, but also the entire underside of the slab.

The thickness of slab insulation should be determined by climate, but use a minimum of 1 inch of closed-cell rigid foam. When the forms are removed, the insulation sticks to the

Insulating the entire slab with rigid foam is a better approach than insulating only the perimeter when using radiant-floor heating.

concrete. When siding is installed over the framing, z-channel flashing can be installed over the foam to protect it. Any foam that's exposed after the foundation has been backfilled can be covered with cement board or a coat of stucco.

reducing wood waste

Wood form material is one of the largest sources of wood waste from building a house. Dedicated plywood or metal forms for full-basement concrete walls and stem walls can be used many times. But slab-on-grade foundations are often formed with 2 by 12s, which may come from old-growth trees. They may hold up through three or four foundations, depending on how carefully they are removed from the

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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