You can use a drainage mat or a draining insulation with no additional air cavity. (buildingscience.com)
Then go with a minimum 3 / 8 - inch air cavity with vent openings top and bottom. (buildingscience.com)
Hydrostor's proprietary technology is based on a simple idea: Anchor a low - cost air cavity to the bottom of a lake or ocean floor, and store energy for use when it is most needed. (marsdd.com)