Is venting this chimney necessary?

Discussion in 'Builders' Talk' started by gslocblue, Feb 13, 2020.

  1. gslocblue

    gslocblue New Member

    I am closing up a disused fireplace opening with studwork and plasterboard. It is a brick chimney stack but above the roofline the chimney has been removed and there is just a metal flue. Ideally, I'd rather not fit a vent due to draughts and I think they are quite unsightly.

    I am aware it is good practise to keep the stack ventilated but my question is this: If I remove the flue and tile over the roof again leaving the chimney open in the loft space, protected from the elements, does that mean it will be acceptable to not have a vent downstairs in the room?

    If the top is protected from the elements by the roof I struggle to see how it makes plasterboarding over the fireplace any different to my single brick layer bay windows with studwork and plasterboard?

    I am considering having it swept first to remove as much hygroscopic material as possible. Thanks.
  2. Bob Rathbone

    Bob Rathbone Well-Known Member

    The reason that the flue should be vented is to prevent or reduce condensation in the void. The stupidity of all this is that we vent it from a warm wet space, a room. This introduces wet air into the flue and creates condensation. The best way to vent the flue is from outside, cold dry air.
  3. James Mulvenna

    James Mulvenna New Member

    Chimneys can cause all kinds of problems with Thermal Bridging but the main rule of thumb is you cannot have a stagnant space within a house for health reasons(as well as damp). A good solution which we do a lot of is to fill the Chimney Flue(s) with granular insulation like Perlite/Silver lite etc which is quite cheap. 12p a Litre = £12.00 for a 100 litre bag. You could make a hole in the breast in the roof space and just pour it in. You can then finish the top with ordinary Quilt. We would normally pour it in from the top of the Chimney down through a up turn traffic cone as a funnel(2 Man Job)
    Bit more awkward in the roof space. But never have a stagnant space in your house, which is why Suspended Wooden floors need to be vented below also.

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