Winter house banking (cost, store, plumbing)

[Bonneval]

My question is about best materials to bank a house for the Midcoast Maine winter, in particular around an old bathroom addition which has a very low space underneath it (not enough to crawl under, maybe several inches). I'm unsure of the wall insulation.

The past 2 winters, as previous owners had done, we used lathe to secure 4 mil plastic all around and put rectangular hay bales up against that, just one hay bale tall. However, this year I was thinking of putting up the plastic as before, and then butting up blue board insulation against that, instead of the hay bales (which are a bit cumbersome).

The hardware store recommended another option of an insulating tarp - which apparently has some layers of bubble wrap? wrapped in black tarp good for exterior use (I think it was a 6'x25'x1/2" piece for $53, so not really high end). This seems like the easiest option, but can a tarp like this by itself really protect in the same way as plastic and hay bales?

Is banking more about stopping the wind than actually insulating the wall? Would either the plastic+blue board, or just the tarp be sufficient protection, especially for a wall with plumbing?

Any advice is appreciated! I would like to try something other than hay bales, but really want to avoid frozen pipes and am concerned with trying a new method over the tried and true one!
Thanks!

[phoebesmom]

Can only speak to haybales; we've always done that, two bales higher, lowered the cost for propane.

[Northern Maine Land Man]

"Is banking more about stopping the wind than actually insulating the wall?"

Yes. The plastic should prevent water from flowing into your house and also prevent cold air from blowing into your house. Think of it as a sealing membrane. The insulation is the snow and the air entrained in it. Many people use snowblowers to blow snow onto the plastic.