APPENDIX A

Easy to Do and Harder to Do

Some sustainable design options are simply harder to implement well than others, or carry more risk going forward. They may still be the best solution for the problem, but must be approached with care. The difficulty of doing things well declines with experience and in some cases with improved technology; but often the limitations are related to microclimate, biological, or environmental stresses or complications.

With an excellent craftsman and the best materials, almost anything can be done in a way that works and will function well for many years. But if the workmanship or materials are not as good, things can go wrong sooner than expected.

Easy to Do Well

• Pitched roofs, greater than 4:12 (will often work long after shingles are worn out). Steeper pitch also appears less vulnerable to hurricane damage.
• Wood-framed buildings (but regional problems with termites).
• Vertical windows.
• Overhangs.
• Interior shutters.
• Interior blinds.
• Adobe, rammed earth, water tank thermal mass.
• Passive solar water heaters.
• Clotheslines.
• Microhydro (although intake grates can be problematic).
• Grid-tied photovoltaic systems.
• Basic rainwater harvesting (for garden).
• Simple gray-water recycling (washing-machine water, shower).
• Hot-air collectors and simple air circulation.
• Pit toilets.
• Septic tanks and leach fields.

Harder to Do Well

• Sloped windows and shallow-angled greenhouse roofs.
• Arbors and trellises (seemingly simple, but usually too massive and not designed to last).
• Sunspaces and solar greenhouses (overheating issues in summer, distribution of heat to house in winter).
• Roof ponds.
• Flat and low-angled roofs (shorter lifetime, leaks almost inevitable with poor maintenance or extending use past expected life).
• Subterranean houses (potential for leaks and mold; leaks very hard to find and repair).
• Living roofs (potential for leaks, leaks very hard to find and repair).
• Sawtooth roofs (potential for leaks).
• Exterior shutters and blinds (although more costly systems have a better track record).
• Exterior foam wall insulation and covering (but materials getting better).
• Earth and clay plasters on exterior straw bale walls (challenging to get it right).
• Skylights (overheating in summer, leaks, seal or glazing failures).
• Active solar water heating systems (controls, materials overheat when system is dry).
• Partially shaded photovoltaic systems (critical to get design right if some modules are shaded at times).
• Flush toilets (low cost, often faulty flush valves).
• Compost toilets (design and operation must be done well).
• More complete gray-water recycling (design and operation must be done with care).
• Biofilters and living sewage treatment systems (challenging design issues and operation).
• Off-grid electric systems (design, equipment choices, and battery maintenance and care are critical).
• Wind machines (getting better all the time, but they still work in a very hostile environment).
• Rainwater harvesting systems for drinking water.
• Hot-air collectors and gravel bed thermal storage.
• Cool tubes (design challenges with moisture and mold, maintenance).