Closing off a flue

shane0007

From an engineer/architect's point of view, what is the correct method of closing off a disused flue?

The only practice I know are either fitting a rain cowl, blocking the builder's opening & installing a vent in the bricked up opening to prevent condensation within the flue (obvious downside is efficiency of the home)

Or

Fitting a rain cowl, blocking the builder's opening without a vent & filling the flue from the top with sand.

Are these practices incorrect and/or are there better methods?

dathi

shane0007 wrote: »

Fitting a rain cowl, blocking the builder's opening without a vent & filling the flue from the top with sand.

?

our English cousins recommend permanently sealing the top of the chimney pot and filling the flue with vermiculite.

esox28

If you adequately seal builders opening and termanation flue pot interstitial condenstion shouldn't cause an issue, with it then being air tight moisture laden air from dwelling can't enter the flue to cause condensation.

one option spring to mind for sealing the termanation flue, cut a 8 1/16" diameter wood disc fit about 12" into the flue then fill to the top with sloppy cement and cap with a lead cap and secure with a suitable clamp.

using vermiculite to fill the cavity would be a good addition due to the insulation properties therein.
Hope this helps shane.

shane0007

The consideration I am looking at would be the issue of interstitial condensation. Sealed voids if opened aired could potentially cause this.

I think the idea of using vermiculite is good.