The case below describes a retrofit project in a typical Budapest city-centre office building — a building constructed in 1910, previously partially renovated, running plant that was operational but undocumented at the start of the project.
The starting point
The owner was visibly paying a high heating bill but couldn’t say where the loss was occurring. The building’s energy certificate placed it in a mid-tier class, which would normally point to a full plant replacement as the “obvious” answer — a significant capital outlay and downtime.
Before any renovation decision was made, we installed a BIS measurement setup: zone-level temperature and heating-load metering, plus logging of the ventilation system’s run schedule, all within four weeks, with no demolition or shutdown.
What we found
The four-week measurement period surfaced three previously undocumented problems:
- Overnight and weekend heating. The heating system ran on an old, never-updated schedule — actively heating from 10pm to 6am, while the building sat empty.
- Uneven zone temperatures. Street-facing zones were consistently overheated (occupants compensated by opening windows), while interior, courtyard-facing zones stayed underheated.
- Ventilation independent of occupancy. The ventilation system ran a fixed 12-hour daily schedule regardless of whether anyone was in the building on weekends or public holidays.
Nothing was mechanically broken — nobody had ever checked what the plant was actually doing at night.
The intervention
Every issue found was a control problem, not a mechanical one — which fundamentally changed the renovation plan. The intervention that was proposed and carried out:
- Rescheduling to match actual occupancy, with occupancy-based setback.
- Fine-tuning zone-level control for temperature consistency.
- Tying ventilation scheduling to the building’s actual usage calendar.
All of this was a software and control-level intervention, with no capital-intensive plant replacement.
Why the answer wasn’t a plant replacement
- Measurement proved the equipment’s efficiency was adequate — the loss was in scheduling and control.
- The control-level intervention paid back within weeks, not months.
- Plant replacement stayed available as a future, well-informed decision rather than an immediate, rushed necessity.
The result
Four months of measurement after the intervention confirmed a 24% reduction in heating energy use, compared to a prior period with similar weather conditions. Measurement continues so the following heating season is documented too — this is exactly what an energy certificate on its own could never have shown.
We wrote about the mechanics of this measurement-and-intervention cycle, step by step, in this post.
If your building is in a similar spot — high cost, little data — get in touch. Measurement alone usually answers where to spend first.