If you think grassy, earthen roofs are just for Hobbits, you’ve got another think coming…
The following is an excerpt from Mortgage Free! Innovative Strategies for Debt-Free Home Ownership by Rob Roy . It has been edited for the Web.
Houses do not absolutely have to have earth roofs, even earth-sheltered houses, but the advantages are compelling and worth illuminating:
- Energy efficiency. While earth is not a particularly good insulator, the vegetation does provide extra R-value and holds the snow better than any other kind of roof. Light fluffy snow is worth R-1 per inch, so a fresh two-foot snowstorm can add a free R-24 to your roof insulation, like manna from heaven.
- Aesthetics. Of all shelter designs, an earth-sheltered house has the greatest potential to minimize the visual impact of housing on nature. It would be a shame to fall just a few inches short of the goal line with a conventional roof.
- Cooling. An earth roof stores moisture. The evaporation of this moisture on a hot day keeps the house cool, thanks to a phenomenon called, appropriately, “evaporative cooling.” Try this experiment: put a cool six-pack of beer in an empty bucket. Drape the open top of the bucket with a wet towel. The evaporation of the water will keep the beer cool . . . until the towel dries out.
- Ecological harmony. Here’s the choice: One, a black lifeless moonscape of asphalt shingles; or, two, green oxygenating habitat for billions and billions of tiny little life-forms.
- Longevity. Build it properly and forget it. In a properly built earth roof, both the soil and the insulation are on the top side of the waterproofing membrane, protecting it from the two things that break down almost every other roof: the sun’s ultraviolet rays and constant freeze-thaw cycling in the winter.
- Drainage. On an earth roof, drainage is slow and natural. During an Arkansas frog strangler, other roofs need systems to deal with thousands of gallons of water in very short order.
- Protection. What kind? All kinds: sounds, tornados, fire, radiation, U-2 spy planes . . .
If Malcolm Wells had his way, all new construction would have to go underground: houses, industry, parking lots, even bridges. I’m not kidding. To give you an idea of how this guy thinks, he’s the same one who drew all the funny little cartoons  in the book.