A portion of my IPE deck will only be approx 12" above the dirt(2x8 support beams in this area). This segment follows a 25' wide garage wall with about 8' long before the ground falls off allowing more ventilation.

Thinking about following steps:

1) slightly wider board spacing in this section.

2) prestain bottom of IPE boards in this section

3) some form of floor vents.

Not sure of effectiveness of (1) and (2). Not sure of how much venting is needed for (3) or where to get vents or how to make attractive vents. I have heard that 2' high decking would be minimal that ventilates adequately without extraordinary measures. I am using thicker 5/4x6 boards to reduce cupping risk. Soil drainage in area is better than average.