Formulas For A Warmer Floor

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Last year, the Census Bureau made the landmark announcement that 100 million housing units had been built in the United States. It happens that about two-thirds of these are single-family homes, and all have one of three types of foundation: full or partial basement, crawlspace or slab-on-grade floors (see illustrations).

The design chosen is influenced by cost factors, climate, topography, soil type, the water table and plain old tradition. But it's safe to say that, for the most part, the majority of houses in the northern and plains states (roughly above the 37th parallel) tend to be built with basements, while those in the South are constructed on slabs. The exceptions, those homes built over crawlspaces, show heavily in Oregon and the Carolinas, and moderately in the rest of the Southeast and far West-regions with a typically lower heating, and a somewhat greater cooling, load.

Constructing any of the three kinds of foundations to correspond with the latest findings presents little problem. Adapting existing foundations, however, can become a complex process with basements and may be impracticable when a slab is involved. Crawlspaces are the least difficult to retrofit, and often benefit the most since they're prone to moisture and insect damage.

The insulation methods that follow are well-suited to foundations and resolve many problems characteristic of below-grade situations. All are general recommendations, since specifics depend so much upon individual siting. Naturally, real-world cost restrictions usually determine just how far an insulation project can go-but we can at least take comfort in the fact that no matter the amount, it's money well spent.

Most crawlspace problems disappear with proper maintenance.

Crawlspaces

The customary crawlspace is the generally 3'-high (mercifully more but often less) area beneath the floor that's established when a structure is supported on its footings by a perimeter wall. Homes built on piers are included; the only difference being that the crawlspace is exposed.

Anyone who's spent more than five minutes in a crawlspace knows how it came by its name and why it kindles unpleasant thoughts. But cramped quarters aside, the tendency of that area toward excessive moisture is more often caused by poor siting than an inherent flaw. Sloping grades or slow-draining sites seem to be an invitation for the easy fix of bridging the water hazard with a crawlspace rather than confronting it; hence the to-be-expected long-term results.

Jeff Christian, technical advisor and manager for the DOE-sponsored Oak Ridge National Laboratory foundations research project, summarizes current rationale when he states that "most crawlspace problems wouldn't exist if they got the same attention as basements: proper drainage, damp-proofing and insulation in the right places."

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