Insulation Problems in Straw-Bale Home

Two years ago, I purchsed a straw bale home in Minnesota. When I closed the house was in poor shape and the exterior had to be rebuilt. Our first winter in the house was cool and drafty and we were spending a fair amount on heat. We did as much research as we could, but we have struggled to figure out exactly how we should fix and maintain our home.
Fortunately when we removed the old rainscreen the bale was in good shape. It had not been plastered and the bale had settled in some places leaving air gaps. We repacked the gaps before residing the house with Hardiboard. There is a Tyvek moisture barrier between the bale and the siding, but the bale remains unplastered.
I thought that this would make a big difference in our heating costs, but last winter we continued to spend much more than we anticpated to heat the home. I suspect that the bale in the roof has settled as well, but I am loath to remove the tin roof to fix the bale.
I was wondering about blowing some kind insulation into the gaps. I also had an energy audit done on the house and they found that the house exchanges air 11.6 times per hour. The second floor ceiling is rough beam and there are gaps between the beams. On top of the beams there is a layer of felt beneath the bale. The inspector recommended caulking between the beams to help reduce the air exchange. I am worried that this could cause moisture to build up under the bales in the roof.
I would really like to shore things up before the snow flies again in order to reduce our natural gas usage this winter. Any advice would be appreciated.


I would think an inspection using infrared imagery would help you pinpoint areas that need improvement.

Do you have a post-and-beam or load-bearing construction?

Why no plaster on the bales and using Hardiboard?