Phnom Penh runs at 77 percent humidity on an average day and 84 percent through September, which puts the climate halfway to the condition that ruins a wall. Mold is not a cleaning problem. It is a sequence of design decisions, set at orientation, ventilation, and material selection, that arrives on schedule. Here is how a serious builder keeps moisture from becoming a stain.

The WELL Building Standard does something no other major green certification does. It comes to the finished building and tests air, water, light, sound, and thermal performance with instruments. Ten concepts, four certification levels, third-party verification every three years. A clear read on what WELL measures, how it differs from LEED and EDGE, and when pursuing it makes sense for tropical residential buildings in Phnom Penh.