Venting a lined chimney

[ChrisField]

Hi,

I've recently had a new boiler installed to replace an old floor standing gas boiler. The old boiler had a flue which vented into a chimney. The chimney was lined with a flexible metal lining. The new boiler no longer uses this and I want to close off the hole into which the old boiler vented. The chimney is not vented at the bottom except the hole in the wall that the lining leads to. I have no idea if the cavity around the lining was filled when the old boiler was put in.

My question is this: If I block off the bottom end of the flexible metal lining by covering the hole in the wall into which the old boiler vented, how should I vent the chimney to prevent damp? Should I put in a vent at the bottom of the chimney stack or is this cavity likely to have been filled when the lining was put in? If so should I remove / make a hole in the metal flue lining so that air can travel out of the chimney from this vent?

Thanks for your advice,

Chris.

 

[blacknesh]

i would suggest removing the liner and having a cap put on the chimney these have vent holes and prevent rain from entering, gas safe enginner should advised and help,