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Bojan Milovanović
Episode · #502

ZGRADONAČELNIK Bojan Milovanović

Guest Bojan MilovanovićHosted by Tin BašićMay 3, 2026
About this episode
What you'll hear in this conversation

For years, the promise of energy efficiency has driven significant investment in building renovation, often backed by public funds and official projections. But what if the actual savings fall short of what was promised on paper? Bojan Milovanović, an associate professor at the Faculty of Civil Engineering at the University of Zagreb, has spent years examining this precise question, moving beyond theoretical models to measure real-world performance. His work focuses on building physics, moisture problems, and the often-unseen discrepancies between design and reality in Croatian buildings. He leads the Congregate project, an international effort to discover if the money spent on energy renovations truly delivers the expected fifty percent energy reduction. Readers will leave this conversation questioning the assumptions behind energy efficiency claims and understanding the gap between projected savings and the lived experience of building owners.

Insights from the conversation
What to take from this episode
01
The Congregate project started with a simple question: 'Do we spend money well?' It aims to verify if the measured energy savings after a building renovation actually match the fifty percent projected savings required for funding. When public funds are involved, relying solely on projected savings without real-world measurement is a systemic blind spot that risks misallocating resources.
02
Asked why it took until 2023 for the Congregate project to start measuring real energy savings, Milovanović explains it's because 'we just now found funding.' This highlights that the absence of dedicated funding for post-renovation measurement means crucial insights into actual performance are delayed for years, perpetuating reliance on theoretical models.
03
More than fifty percent of multi-residential buildings in Croatia are in energy class C or lower, a category Milovanović notes was the standard for *new* construction until approximately 2008. This shows that the majority of the existing building stock is operating at a level that was considered adequate for new builds fifteen years ago, underscoring how quickly standards evolve and leave older structures behind.
04
Milovanović distinguishes between achieving fifty percent energy savings, which he describes as 'relatively easy' with basic insulation and windows, and the eighty to ninety percent savings that require the designer to 'think a bit more.' Settling for the minimum threshold often means missing the opportunity for a significantly better, albeit slightly more expensive, long-term outcome in building performance and quality.
05
While most people only ask for the 'letter' (A, B, C) of an energy certificate, Milovanović emphasizes that the accompanying detailed report, or 'elaborat,' is the real value. This report outlines specific inefficiencies like poor lighting, old boilers, or problematic plumbing, making it a crucial diagnostic tool for targeted improvements rather than a mere grade.
06
The public discourse around energy renovation includes claims that it's a 'scam,' that savings are 'imaginary,' or that poor materials are installed. Such strong, polarized opinions point to a significant trust deficit in the renovation process itself, suggesting a need for greater transparency and verifiable results to counter widespread skepticism.
07
New multi-residential buildings in Zagreb are now constructed to achieve thirty to forty kilowatt-hours per square meter, which is 'double better' than the hundred kilowatt-hours per square meter typical for new construction just fifteen years ago. This rapid advancement in building standards creates a stark performance gap between new and even relatively recent older buildings, making the latter significantly less efficient by comparison.
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