Insulate floor structure with crawl space?

[Dodger]

I have an old house with a crawl space foundation where part of the subfloor has come loose, causing the sawdust to fall under the house. Since I would prefer not to open up the floor, my plan is to crawl under the house and insulate from the underside in the sections that are now empty.

The question is how to do it best and what to use. Should I use regular insulation like mineral wool and stuff it in, then make a subfloor of asfaboard or something? Should one use paper or plastic or something?

The rest of the floors contain only sawdust and, at best, some newspaper at the bottom.

The house is an old log house with a crawl space foundation, I use wood burning and have a decent chimney that goes down under the foundation.

 

[orparn]

You should probably thoroughly check the reason why your trossbotenbrädor have fallen down (likely rot) and address any such issues before repairing. Otherwise, it is possible to place new insulation from underneath, even though it is usually tricky and cramped.

I myself have Asfabord (also trossbottenskivor in the guest cabin) underneath, resting on a 22x95 board that has been screwed along the floor joists. A problem that arises then is that the boards (both types) tend to sag in the middle over time, so I have long considered improving this by placing additional 22x95 boards crosswise under all the board joints and between them to reduce sagging.