Passive Solar Greenhouse - Updated Diagram

I've started prepping the pieces for the above ground portion of the greenhouse and have made a few on the spot changes. Instead of building a box unit to channel the air down the outside of the under ground insulated box, I plan on running a 1"–1.5" pvc pipe from the warm air collection fan, down through the middle of the back wall of the green house just behind the black absorption surface, and down into the perforated pipe below the rock thermal bank. This method uses up only a little space within the grow bed/wicking bed so its a much simpler compromise. In this diagram I've drawn in some simple pvc vent pipes that when opened will allow outside air into the greenhouse during both winter and summer months.