When we started our wee project, we thought a lot about energy conservation. We enlisted the help of the amazing Frank Schiavo on passive solar, and we (meaning not me) thought a lot about how to cool the house in the summer without installing air conditioning that neither of us wanted. And, rarely need. During our occasional very warm days, Bill knew that he wanted to leverage the cool air from our crawlspace to help draw down the temperature inside the house. He installed a whole house fan upstairs, and wanted it to draw cool air from downstairs via the crawlspace. Through the magic of the interwebs, we found this cast iron grate and it is now in place. You can feel the cool air coming up from below even when the fan is not running. His grate idea is helping us cool with science, and that's pretty cool.