A furnace may include a furnace cabinet, an inducer blower, and a flue vent adapter. The furnace is configured as a multi-poise furnace and configured to be installed and operated in each of the horizontal left flow orientation, the horizontal right flow orientation, the upflow orientation, and the downflow orientation. The flue vent adapter is used when the furnace is installed and operated in the downflow orientation. Alternatively, the flue vent adapter is used when the furnace is installed and operated in each of the horizontal left flow orientation and the horizontal right flow orientation. The flue vent adapter has a unitary construction to reduce manufacturing costs, reduce a pressure drop through the flue vent adapter, and reduce leakage.

A method of relining a chimney includes: coating the inside surface of a chimney flue with a first layer of a flowable refractory material to provide a wet and sticky surface on the inside of the chimney flue; providing an insulating sleeve on the refractory surface so that the insulating sleeve adheres to the refractory surface; coating the inner surface of the sleeve with a second layer of flowable refractory material effective for hardening to provide a refractory surface on the inner surface of the sleeve; and allowing both layers of flowable refractory material to harden, thus providing a hardened relining comprising a first refractory layer, an insulating layer, and a second refractory layer on the inner surface of the sleeve.

A furnace may include a furnace cabinet, an inducer blower, and a flue vent adapter. The furnace is configured as a multi-poise furnace and configured to be installed and operated in each of the horizontal left flow orientation, the horizontal right flow orientation, the upflow orientation, and the downflow orientation. The flue vent adapter is used when the furnace is installed and operated in the downflow orientation. Alternatively, the flue vent adapter is used when the furnace is installed and operated in each of the horizontal left flow orientation and the horizontal right flow orientation. The flue vent adapter has a unitary construction to reduce manufacturing costs, reduce a pressure drop through the flue vent adapter, and reduce leakage.