Why is a building cold and too warm at the same time?
Where the differences come from
- Location. An end flat has two external walls, a middle flat one. The top floor loses heat through the roof, the bottom floor through the ground.
- Orientation. To the south the sun warms during the day, to the north it does not.
- Balance of the radiator network. If the network has not been balanced, the nearest radiators receive more water than the furthest ones.
- Ventilation. A flat with a larger exhaust air volume cools down faster.
- The resident. One keeps a window ajar, another covers the radiator with a curtain.
A single heating curve takes none of this into account. It responds only to the outdoor temperature.
What happens when saving is done by lowering the curve
The board decides to save, and the heating curve is lowered by one degree. The middle-floor flat at 24 degrees drops to 23 and nobody notices. The end flat at 19 degrees drops to 18, and the resident calls the property manager. The curve is raised back, and the saving is cancelled. This repeats every autumn.
How measurement changes this
Continuous temperature measurement is typically brought to 10–20 % of the flats, in different stairwells and on different floors. The control can then be based on what is really happening in the flats. Heating is lowered where there is excess heat and raised where it is cold. The cold end flat receives more heat through balancing of the radiator network or line adjustment. The curve for the whole building can be lowered, because it is no longer set according to the coldest flat.
Total consumption falls, because the excess heat is removed. The coldest flat gets warmer, because it receives the heat it needs. Nobody calls the property manager.
What one degree costs
The rule of thumb from Motiva and the Energy Authority is that one degree of excess heat throughout a building increases the consumption of heating energy by about 5 %. If half of the flats in the building are two degrees too warm, that is about 5 % of the whole building's heating bill in pure waste.
Frequently asked questions
Doesn't balancing solve this?
Partly. Balancing evens out the distribution of water to the radiators and is good to do first. It does not, however, react to the sun, the wind or a resident airing a room. Automation based on measurement adjusts continuously; balancing is a one-off. Together they work best.
Does a sensor have to be installed in every flat?
No. A sufficient sample across different stairwells, floors and orientations describes how the building behaves. The more sensors, the more precise the control, but 10–20 % of the flats is enough for reliable balancing.
Can a resident adjust the temperature of their own flat?
Downwards with a radiator thermostat, yes. Upwards only as far as the supply water in the network allows. That is why the problem of a cold flat is solved on the network side, not with the thermostat.