An enjoyably even heat is heat that is right for your needs and the space to be heated. So that you won't need woollen socks – unless you want to wear them – and yet your flat won’t get so warm that you need to open the window. A fireplace of the right size lets you enjoy the unique qualities of your NunnaUuni product at their best.

In addition to the size and shape of a building, its heating demands – and thus also the warm atmosphere created by fireplace heating – are affected by the heat insulation (U values), airtightness, ventilation, internal heat production, and outdoor temperature. And, of course, by the purpose of the fireplace: whether you want to use it as the main heat source or a complementary heat source, or mainly to create atmosphere. 

To make choosing a fireplace easy for you, we have divided our fireplace selection into three heat categories:

The fireplaces in heat category 1 have a useful daily heat output of max. 40 kWh. Their dimensions and heating properties make them suitable for smaller room spaces or for use as a complementary heat source.	The fireplaces in heat category 2 have a useful daily heat output of 40 to 60 kWh. Their dimensions and heating properties are designed for fairly large room spaces as a complementary, or even the main, heat source.	The fireplaces in heat category 3 have a useful daily heat output of more than 60 kWh. These fireplaces produce enough thermal energy for the needs of even a larger space.

The figures given here assume that the fireplace is the only heat source in the room. If what you want is mainly the atmosphere created by living fire, or some extra heat, a fireplace in a lower heat category might be the best solution. We don't recommend choosing a fireplace with too much thermal power for a small or closed space, as the room temperature might rise too high. In practice, a fireplace heats the areas from which it can be seen. 

Residential building in Sweden, built in the 1980s *

Heat insulation meeting the SBN 1980 standard

Select the outdoor temperature and the size of the room (in m²) from the table. By looking up the amount of heating required, you can determine the efficiency level (in kWh) of the NunnaUuni fireplace you need if you are planning to use the fireplace as the sole heat source. For instance, if the area to be heated is 90 m² and the outdoor temperature is 0 ºC, the ideal heat category for the fireplace is category 2.

A well-insulated residential building in Sweden, built in the 21st century*

Heat insulation meeting the BFS 2002:19 standard

Select the outdoor temperature and the size of the room in the diagram. By looking up the amount of heating required, you can determine the efficiency level of the NunnaUuni fireplace you need if you are planning to use the fireplace as the sole source of heat. For instance, if the area to be heated is 90 m² and the outdoor temperature is 0 ºC, the ideal heat category for the fireplace is category 1.

*The room height of the example houses is 2.5 m, the window area is 150f the exterior wall area, and the inside temperature is 21 ºC. Ventilation is calculated to be 0.5 times the room volume per hour, and the heat recovery efficiency is 50%. It is presumed that the heat from the fireplace can move without obstruction to the whole area to be heated. Insulation requirements vary from country to country. The Swedish heat insulation requirements as set forth in BFS 2002:19 are among the strictest in Europe.

Every building is different, so the need for heating energy is always flat-specific. The diagrams are for guidance only and are based on calculations from the values given, but they do add security when you are choosing your fireplace.