Using Good hay bales as Chinese-style Greenhouse insulation. Can I maintian feed quality

I am wanting to use hay bales as greenhouse insulation, and also have them maintain quality to be used as stock feed if needed.  (I would have two greenhouses, one with hay I intend to use that year with my winter greens, and one with my 3 month emergency reserve that I hope to keep with insulation all winter with my heat-loving plants, but will sacrifice if needed.  I will alternate them each year.  Avery lows in winter at 2C and max low on record is -4C so plants pasture/lawn stays green even in winter here).

 I am looking at a  Chinese style greenhouse, with single row of straw at the front, and sides, but three or four rows high at the back.  
I see two concerns, humidity on the side of the walls, and moisture from below.  We are looking at building the frame anyway from pallets, and so I am thinking that having the hay a bit from the side and/or doubling lining the pallet frains with plastic inside and outside would help a lot with condensation.

I could put the hay on a raised bed of stones, but then this would allow the cold air through at ground level with the coldest frost, so again maybe covering the base of pallets on the ground with plastic and then filling them with wood shavings, (which we have a pile of).

I would like to avoid as much plastic as possible, but there seems little other good choice at this stage for greenhouses.  

First, protect the hay. Good hay is precious, expensive, and hard to get. Other insulation is cheap and easy to get. My 2c.