earth berm household greenhouse.

Here is what I am looking at for a greenhouse location and a rough idea of the thinking.  The first picture is the berm at the west end of the house and is looking due north.  The second picture is looking roughly east at the end of the house over that same berm taken from far enough away that I am roughly standing at first floor level  The bank height is about 6 feet over by the house tapering down from there.  

Current thinking is first 3 feet out from the house is a rock stairs up.  Next is a window area 6 feet wide by 8 feet high to act as a retaining wall with dirt piled to the top behind it.  It will act as both added solar heat for the green house and the completely passive fan to pull the air up out of the cold sump to recharge the rock bed.   Convection and implementing Mike O's cold sump is planned to heat it at night.  Simply let the cold flow down into the bottom of the rock pile and the heat chimney back.  A single shaft with 3 butterfly doors on it rotated will change it from collector mode to night time mode.

Then next is the green house itself.  The front is planed as 14 feet high by roughly 9 to 10 feet high.  Dimension being chosen by the glass I have collected so far.   Post and beam construction to hold the weight of the roof on the front wall and simply framed inside that to allow for the assembly of a full patch work of window glass.  The roof will utilize a bunch of old beams I already have roughly 4"x8"  Over that roughly 1 foot of cob dirt packed tight with a stair step form.  Then a layer of plastic.  On the dirt steps down the roof goes a layer straw bales and over that another layer of plastic and over that another foot or 18 inches of dirt.  The back and side walls to be rammed earth reinforced with baler net wrap residue built in an arc shape so all the walls will be compressively loaded by the dirt behind them.  The back wall should be approximately 8 to 9 feet long.  The total volume if the roof is kept low in back will allow for just over 10 air changes an hour when checked against flow achieved with the current collector on the house with no fans.

In summer mode the collector will simply suck air out and vent it to the outside world.  Also intending to put a down draft solar dehydrator sucking out of the peak of the roof in.  The hope for summer months is that those 2 combined with thermal mass and night time cooling will keep the things cool enough.  Because of the outlet out of the peak the dehydrator should likely run all night long sucking a little as heat rises out of the mass.

In winter mode the plan is to add a giant plastic bag with a drain pipe at the bottom to try active foam insulation.  Will require some power but should given an R8 to the glass.  If that doesn't work a simple roll down insulated curtain is the back up plan.

The corner of the house near this is the ideal place to take wiring etc out.  So current plan is probably 2 power circuits and a couple of temp circuits and a couple of control lines from the aurdino running the collector etc.

Now as a back up in case none of this is enough will bury 2 8 foot pieces of 6" or bigger PVC.  One out of the rock sump and one higher.  If the existing stuff isn't enough add pipes going straight north along the ridge of the hill burying earth/air tubes headed back to the wind break row of trees.  Build them as 2 loops but with a T coming up from each at the far end of the look.  In winter mode simply loop the tube.  In summer mode remove the insulating plug from the T and then all 4 tubes can draw outside air in heating the earth farthest from the greenhouse most and dumping cooler air into it.

So what am I missing??

PS missed a piece, the rock heat sump I have traded for 6 cubic yards of 2 to 6 inch washed rock.  The intent is to combine 2 bulk transport bags.  One tie bottom and one flat bottom to seperate the rocks from my dirt to keep them from mixing.  This will give me a tower of rocks with a woven plastic surround 4 ft x ft ft x 10 ft.  It would be both easier and better to bury it straight under the greenhouse.  But roughly directly under the pink insulation line at the front is my sewer line about 6 to 8 feet down.  So to protect it from cold(especially if the greenhouse failed catastrophically) the rock pile needs to be barely overlapping with the back of the greenhouse just in case.  The purple circle at the top of the rocks is where I intend to pull the air back to the collector from.  The vertical tube down will be capped at the top and is there simply to provide a way to lower a sump pump down in case things ever end up flooded.(which is almost certain to happen eventually)

PS #2 what should the roof angle be.  I have been aiming at 40 degrees since that gives me the smallest volume while still meeting having sun at the back for most of the time I most need it..  But a flatter angle would certainly be easier and it would give the plants at the back more height to work with.  Problem is that drives me to less than 10 air changes an hour.