Floor insulation - Why this way?

[Nygge72]

Hello, I have an old summer cottage from the 60s. It stands on high pillars. When I look at the foundation, the insulation is in black plastic bags, resting on the subfloor. Why was it done this way?

Did they used to insulate like this back in the day, or could it be because the cottage is located by a lake that had a huge flood in the 70s, and they thought to protect the insulation somehow?

I think these shouldn't provide much insulation if they are in plastic bags anyway, right?

 

[Stugmannen]

Hello, I have an old summer cabin from the 60s. It's standing on high pillars. When I look into the trossbotten of it, the insulation is in black plastic bags, then resting on the subfloor. Why was it done this way?

Did they insulate like this in the past, or could it be because the cabin is by a lake that in the 70s experienced a massive flood, and they thought they would protect the insulation somehow?

I think these probably don't provide much insulation if they're in plastic bags, right?

It probably insulates, but I think there's a risk of moisture and mold since condensation can occur in the plastic bag.