A fireplace insert for a fireplace cavity that includes a venting passage comprising an enclosure dimensioned to be insertable within the fireplace cavity and fill substantially the entire cavity to define a combustion chamber. A passage and an aperture are provided for communicating the combustion chamber with the venting passage. There is a connection system for quickly and efficiently connecting the enclosure to the venting passage while the enclosure is within the fireplace cavity. The ability to connect the insert to the existing venting passage while in place permits the full fireplace cavity to be used. Previous inserts of this type were substantially smaller since there had to be room to manoeuvre and attach the vent by physically reaching into the fireplace cavity.