Cold chimney insulation

[perstorp..]

Have district heating and a new ventilation system
So the chimney is not used for anything
The plaster/mortar has started to fall off in the attic
What to do, insulate it?
Replaster it?
Cold attic

 

[BigR]

Fire occasionally so you get the moisture out of the chimney.

 

[perstorp..]

Have nothing to burn with, there is no boiler left, just a hole in the wall.

 

[Einh]

I have nothing to burn with, there is no boiler left, just a hole in the wall

I recommend that you install a stove there. That way, you can keep the house warm even during a power outage (and cook simple meals if the stove has a hotplate).

If you don't want to do that, then you can instead seal all the flues in the chimney (I assume your new ventilation system doesn't go through the masonry). Seal the flues at the top with something like mineral wool. Then you can always open it up if you change your mind and want to install a stove sometime.

 

[perstorp..]

Is a laundry room today so can't put anything there. Just a hole in the wall behind the washing machine. Good tip to put insulation on top so the next owner can choose sometime in the future. No ventilation goes up in the chimney anymore. The question is if you should cover the hole in the wall where the boiler has been, it's an open hole about 30x30 cm.

 

[Einh]

Is a laundry room today so can't put anything there, just a hole in the wall behind the washing machine.
Good tip to put insulation at the top so the next owner can choose sometime in the future.
No ventilation goes up the chimney anymore.
The question is whether to seal the hole in the wall where the boiler stood, it's an open hole about 30x30 cm.

Yes, it is probably good to seal the hole in the wall too. So that moist air doesn't go up in the chimney and condense on the cold surfaces there.