What type of insulation is this (piccys)?!?

[reoreborn85]

Just removed some boards from the wooden conservatory and discovered this insulation..
I'm not an expert but i've never seen it before. To my very untrained eye it looks like roof insulation in a plastic bag lol.
The bottom half has rotted away so it does need replacing.

The windows on the conservatory are single pain so i don't think i need anything too expensive as the heat is just escaping from them.

Does this insulation have a name (is it rockwool)?
Is it worth replacing with the same/similar or getting something else?

 

[endecotp]

Looks like fibreglass to me.

What exactly has "rotted away"?

 

[foxhole]

Insulation does not usually rot so reuse it.

 

[reoreborn85]

Insulation does not usually rot so reuse it.

Looks like fibreglass to me.

What exactly has "rotted away"?

Sorry, i should have maybe been a bit clearer. The wood was rotten due to it being next to an overflowing wateerbut for GOD knows how many years.
The part where it had rotted away allowed a family of rats (and toads) to 'move in' and start living under the floor of the conservatory. This issue has been addressed.
The bottom part of the fibreglass/insulation has either washed away or been chewed away. Maybe about 50cm x 1m.

In that case then, should I just grab some fiberglass from the loft (They over stuffed it so i wouldn't miss it), ram it in, stick some plastic over it and board it up?

 

[foxhole]

The toads will have been living on a steady supply of wood lice feeding on the rotten timber .