I have found the best way to seal an unused fireplace flue is to install a piece of slate or thin stone on top of the unused flue tile using masonry caulk to adhere the stone.
How to seal an unused chimney top.
Sealing your older unused chimney should not be a complicated task as long as attention is paid to prevention of air intrusion as well as environmental and pest control.
How to temporarily block a chimney.
This way if the fireplace is ever to be used in the future the piece of stone can be removed easily without causing any damage to the flue.
This way you or the next owner have the option to have it open or closed at will.
Installing the chimney cap.
The long term savings associated with sealing the chimney has already been mentioned.
Plug and seal air tight the horizontal line at the level of the vapour barrier in the house and cap the top.
But for a masonry chimney that has a clean out in the basement tape that clean out air tight as well because it can be a source of warm moist air getting inside the closed chimney.
Gradually move to the top of the chimney.
Does an unused chimney need ventilation.
Seal unused chimney top and bottom about the author renee miller began writing professionally in 2008 contributing to websites and the community press newspaper.
If you want an easy way to temporarily block and unused fireplace flue to stop a draft you should consider installing a top sealing damper.
How to permanently block a chimney.
Capping the flue is one of the best ways to close up the top of the chimney as it will still allow air to get in and out preventing condensation from building up.
While you do want the top capped you should not seal it off completely.
Even if you are not comfortable with climbing up to the roof and doing it.
When retiring a chimney many chimney experts recommend using roxul a hydrophobic mineral wool insulation which means that it will dry out if it ever gets wet.
Wait for at least 10 to 15 minutes before applying the second coat and once again begin from the bottom.
The top 5 chimney killers.