Uunisepät’s heat-retaining wall takes advantage of the thermal energy that is released from the combustion gases and which would otherwise be expelled from the flue. A heat-retaining wall combined, for example, with a wood-burning stove that does not retain heat is an efficient way to utilise the heat that is generated.
The heat-retaining wall stores heat and releases it evenly for many hours. The surface does not reach scorching temperatures. Olivine rock is used for the body of the heat-retaining wall.
To keep the wall from heating, the ignition vent can be kept open.