I'm a newbie to posting here but have gotten a lot of good information over the years by reading others' posts so I'm hoping to get some good advice and ideas.

I have been doing a lot of research online as I prepare to talk hubby into building a greenhouse. My main goals are to extend my Wisconsin growing season by a few months and have a place to overwinter a few things that aren't reliably hardy in my zone (4).

I think a pit greenhouse would meet those needs the best for me with the least amount of cost in the long term - mostly heating costs in the winter. I have read a lot of good information online and plan to also order some books that have been recommended.

Here's where the marital dispute arises. Hubby is all on board with the idea and we do have plenty of room to build a typical pit greenhouse as well as loaders, etc for the hard digging so that isn't the issue. I would like to use an old block milkhouse that is already on the property as the "pit". The plan would be to bring soil (as well a possibly broken up concrete, etc) to cover the walls and berm up the north side after adding to it. This would save a lot of the cost of new blocks plus the hard work of digging and setting blocks would be mostly done. So, rather than dig down we would be creating a hill around the structure already there. (maybe even in a hugelkultur type process to grow on) In addition to the greenhouse part we could also plan a root cellar area where the door is to the barn (which is no longer there)
The milkhouse is about 14 x 14 with 6 foot block walls. it has a drain in the floor. The tin roof would probably need to be completely replaced as it is oriented facing east / west. We so have some salvaged double pane windows we could possibly use. From what I have read I think the angle of the windows would be about 60 degrees as we are about 45 degrees latitude.

Hubby's concerns are:
1) the amount of dirt that would need to be brought in to cover the whole thing. Although we live on a farm...seems like plenty of dirt around here to me :)

2) would we also need to have windows extending up some on the south side wall?..I think with a 6ft depth that that wouldn't really be needed

3) Would this even work? A lot of work for nothing if it doesn't.

I know he would be swayed a little if we could do some aquaponics, chickens, etc as well but that is not my primary concern.

Haas anyone done this? I haven't been able to find anything about repurposing a structure other than a concrete swimming pool or using the side of a structure.

What other considerations should I be thinking of? Is this even feasible?

Any advice or suggestions would be appreciated.