Filling an Old House with Cob

As far as my limited understanding goes, cob and packed earth houses functions due to thermal mass slowly heating and slowly releasing heat over days and nights.

Owning an 1860's farmhouse in Michigan I wonder, could I attach a greenhouse to the South side of the house and fill the North side wall with cob?

The house is a 2 story house and im really wondering if you can remove the drywall and insulation and fill the wood walls, the frame of the house, with cob, up to 2 stories?

Both are structural so I imagine it will not fall over.

Do you all think I will get the thermal effect this way?

Any other thoughts on retrofitting old "standard" houses for passive heating and cooling?

This is a subject I have run through my mind many many times. I'm looking to move just now, and retrofitting an existing house is a real possibility.

The house is a 2 story house and im really wondering if you can remove the drywall and insulation and fill the wood walls, the frame of the house, with cob, up to 2 stories?

If concerned due to weather, earthquakes, etc., you can reinforce cob in many ways. Wedging sticks crossways between studs or chicken wire stapled across the approximate center of the studs. Just little things that tie the cob to the house frame. The cob itself will not stick to the wood once dry.

Do you all think I will get the thermal effect this way?

Some, but not as well as having the cob in or near the greenhouse side (south). The issue as I see is that the cob might be indirectly exposed to the northern eliminates without proper insulation. Cob can also absorb heat from your house and distribute it to the great outdoors this stuff works both ways. In the northern hemisphere as we are: the north side should be about serous insulation, while the south side is about capturing natural heat and storing for a release later when the temps drop. So you might want to consider a much thicker north wall, maybe using hay bales in between the inside and outside walls or plasters. You don't so much need a collection 'mass' on that side of the house if that's the side that most storms approach from. You need protection.

Here is how I've envisioned this (but I may modify it once I'm actually doing it) - cob is on the inside, with a few inches of protected insulation between it and a cob plaster on the outside. A sandwich of sorts, protecting what you have on the inside from the weather outside.
Note: I live in a very moderate valley and my storms come from the west mostly. But if I move to the mountains I'd be adding extra insulation on the storm facing wall (west in my case).
I call protected insulation: insulation protected from moisture, vermin and bugs. There are various ways of achieving this.

a greenhouse to the South side of the house

This is a great idea, but you'll want to research it for your area, because there are always design tweaks specific to area that need done in order to have success. For example the amount of overhang for your greenhouse roof based on orientation and latitude. And is an insulated stem-wall needed to protect from snow.... details like that.

Do you have any ideas on insulation yet? The roof and floors are of consideration too.

in Michigan thermal mass is only gonna take you so far you still need to add a lot of heat and getting the most insulation in the ceiling and outer walls as you can is vital
your thermal mass is only gonna help inside of a good insulation envelope.

so assuming you have well built floors and a sound foundation I would suggest pouring two inches of concrete on top of the sub floors for thermal mass, then doing a rather standard sort of insulation retrofit to the outer walls. if you pull the insulation and stuff the walls with cob or slip straw you are gonna need more insulation on the outside of the studs, but pulling the siding then adding a sandwich of sheathing and the hard foam insulation can vastly improve the old houses by sealing up drafts and eliminating thermal bridging.

depending on what part of the state you are in firewood can be got for very cheap so wood stoves of any sort can be your friend. hint here is call local lumber mills for slabwood