| Value | Category |
|---|---|
| 1 | Collective central heating |
| 2 | Individual central heating based on gas |
| 3 | Individual central heating based on another fuel (coal, wood, petrol, etc.) |
| 4 | Stoves (tiled stove using wood, coal, sawdust, etc.) |
| 5 | Electric heating (accumulative) |
| 8 | Unknown |
| 9 | NIU (not in universe) |