Chimney removed, seal up?

[tedted22]

A few years ago we removed the chimney above roof level due to recurring leaks and other issues.
It was removed, the roof made good and tiled over.

The chimney now ends in the loft, below the roof timbers on the inside.

However, it was left like that, so the two chimney holes that feed the downstairs and upstairs fireplace are open.

In the living room, the original fireplace was boarded up at the base and sides, and a piece of ply was stuck in to stop any debris falling down (before the chimney was removed to below roof level).

Upstairs, the fireplace was bricked up.

There are no chimney air vents in any room.

Now the external chimney has gone, no fireplace is or ever will be used, what should I do in the loft space? Can I close the holes up with insulation in black bags? As there is no ventilation any more, is that an issue as it's not being used, nor goes above the roof?

https://files.catbox.moe/ljfye4.png

The reason I want to do something with it is that our loft is humid and I was thinking that when the heating is on, it's being lost through the chimney wall internally and going up the chimney to settle in the loft. It doesn't have great airflow in the loft (another thing I am tackling).

Thanks

 

[mrrusty]

More likely it's getting past the ply. I would seal it up top and bottom. You certainly don't want warm humid room air continually going in to a cold loft space.