Finnish Log Building (some internet awesomeness)

Every so often I find something while being led down the rabbit hole that is YouTube, that just speaks to me.  In this case I can't make out what it's saying (as it's in Finnish with no subtitles) but it captured my attention none the less.

I've always enjoyed watching craftspeople at one with their tools.  Highlights for me were:

• Use of moss as chinking throughout the building. Even around windows.
• The axe work in general and how many tasks they were put to.
• Use of a two man plane (around 9:30)
• The  broad axe with the ambidextrous head (@ 13:00) Yep, he flipped it around so he could hew into an opposite corner. I'd heard that before and discounted it as Eric Sloan type imaginations
• Dinner! (@16:16)  :)
• Using Birch Bark as a moisture barrier under the floor sleepers (@16:40)
• Awesome fence (@ 24:50)

The were a couple things I didn't understand:

• Why was sand/earth used to infill around the floor sleepers? This is protection from drafts/insulation? Seems like a prescription for rot.
• What about the sawdust between joists? That seems like insulation for sure.
•  Was this video shot as demonstration of skills in the past? I saw NO power tools, but this is clearly depicting modern era men. My biggest clue being the amount of electrical tape on tool handles and as a depth mark on an auger. :)

If anyone knows the answers to these quandaries, please leave them in the comments below.

ENJOY!