Housing costs: three levels of causes and the lever inside buildings

Three levels of causes

The causes can be sorted into three levels. They differ above all in who can influence them.

• World markets: Crises drive up the prices of gas, oil and electricity. In 2025, heating a 70 m² flat with gas cost €1,170 on average, 14% more than the year before (Heizspiegel 2026). Owners, managers and residents have little influence on this level.
• Economy and politics: High interest rates and construction costs slow down new building: in 2025, 206,000 homes were completed in Germany, 18% fewer than the year before (Destatis). Laws and funding programmes address this level; their effect takes time.
• The operation of existing buildings: People spend 80 to 90% of their time indoors (German Environment Agency). How much energy is used there and how healthy the air is depends heavily on how heating, ventilation and technical systems are run. This level is in the hands of owners and managers – and it is the least discussed.

For energy, the lever is measurable

An analysis of 643 non-residential buildings by Lawrence Berkeley National Laboratory (2011) found a median of 16% lower energy use from better operation alone – without renovation, and with a payback of around one year. The causes were often inconspicuous: wrong setpoints, misadjusted sensors, systems running at full load around the clock.

The study looks at non-residential buildings; its figures cannot be transferred one-to-one to residential buildings. The pattern, however, is the same: a large part of consumption comes not from the building fabric but from how the building is run.

For health, it is about indoor air

In homes, many sources of air pollution come together:

• People: exhaled CO₂ and moisture.
• Cooking: gases and particles.
• Furniture and building products: volatile organic compounds and formaldehyde.
• Moisture: with too little air exchange, the risk of mould rises.

Possible effects range from headaches, poor concentration and irritated eyes and airways to allergies and asthma caused by mould (German Environment Ministry, BMUV).

Using less is not the same as using right

Energy and health are directly linked. Ventilating less to save money lowers heating costs but lets CO₂, pollutants and moisture build up in the air. Conversely, constant ventilation while the heating is on can cost a lot of energy without noticeably improving the air.

What matters, then, is not the lowest consumption but the right one: as much energy as healthy rooms need, and as little as possible beyond that.

Why the lever so often goes unused

• Everyday feedback is missing: The heating bill shows consumption only afterwards, and poor air is often noticed only once a headache sets in. Most buildings lack a system that continuously shows how heating, ventilation and habits affect consumption and indoor air – and what could change.
• The solution is sought only in major renovation: Renovation matters, but it is expensive and slow. Alongside it, there are approaches that leave the building infrastructure unchanged and achieve a lot with little effort – from data collection through analysis to optimised operation.
• Existing technology is barely used: Sensors have become affordable, and software recognises patterns in energy and indoor data automatically. Both are still rarely used at scale.

What follows

Using energy right needs a system that looks at energy, health and operations together. Young companies working on IoT and AI for buildings can play an important role here. Nebatic works in this field too: with sensors, existing building data and AI that considers indoor climate and energy use together.

Which of the three levels achieves the most in practice remains open. The third, however, is the one owners and managers can act on themselves, without waiting for markets or laws.