Eighteen to twenty degrees, fifty percent humidity, all year round: for decades, that’s been the unquestioned rule for protecting cultural heritage. But is it actually necessary,  and can it survive a decade of EU energy targets?

That was the question REHVA put to a conservator, an HVAC manufacturer and a building scientist at the first SIMIACCI webinar, Conservation vs. Efficiency: The IAQ Challenge for Cultural Institutions. Moderated by REHVA’s Pablo Carnero, the roundtable brought together perspectives that don’t often share a table, and the answer came faster than expected: sacrificing health or the planet to protect an object is “completely irrational,” said Anaïs Ortiz, Head of Preventive Conservation at the French National Archives, any conflict between the two is a legacy of poor understanding, not a real trade-off.

Manufacturer Werner Adler (Condair) agreed, with a condition: the sector needs to drop the idea of one ideal climate for every room and start treating this as risk management instead. Monitor the building, the collection and the people continuously, he argued, understand where the real risks actually sit, and apply technology precisely where it’s needed,  nowhere else. Researcher Manuel Gameiro da Silva added a telling detail that undercuts decades of conservation orthodoxy: some of the tight bands still written into specifications today trace back to one designer’s arbitrary decision decades ago. It became convention simply because nobody questioned it.

What’s actually changing

Ortiz’s own institution has already moved: her building now runs between 16–24°C and 40–58% RH, controlling not for a fixed value but for rate of change — no more than 1°C or 2% RH per day, 2°C or 5% RH per week. It’s a strategy built around stability of trend rather than stability of value, and the building’s energy model projects savings of around 60% as a result.

Adler explained why that distinction matters so much on the equipment side: chasing a fixed set point means constantly adding moisture and then stripping it back out again, cycling equipment and burning energy for no real gain. Give the same system a wider, well-managed range instead, and it simply runs less. Gameiro da Silva offered a number worth remembering too: double the ventilation rate “just to be safe,” and energy use doesn’t double — it multiplies roughly eightfold, making over-caution one of the more expensive habits in the sector.

There was even a surprising health angle to the conversation. Gameiro da Silva pointed to research on people living long-term in perfectly stable temperatures — including studies of populations sheltering in the Moscow metro — who showed signs of losing some of their body’s own thermoregulation after prolonged exposure to constant conditions. A climate that breathes gently with the seasons, without sudden shocks, may genuinely be healthier for occupants, not just cheaper to run.

Where it gets harder

The panel didn’t agree on everything, and that’s where the discussion got most useful. Ortiz pointed out that even well-designed adaptive specifications often meet equipment on site that’s still locked to rigid set points — buildings that are contractually permitted to save energy but mechanically unable to. She also raised a problem the panel hadn’t anticipated: sometimes the source of airborne pollutants isn’t the occupants or outdoor air, as HVAC design usually assumes, but the artefacts themselves — objects and storage materials that off-gas compounds ventilation and filtration simply can’t fix at the source. And on pollutants specifically, she admitted the sector is still working largely on smell: undetectable compounds go unmonitored until the damage is visible, and by the time something is noticeable to the human nose, “it’s usually too late.”

Perhaps the most striking moment, though, was a barrier no engineer on the panel could solve: loan contracts and insurance policies that still demand strict, fixed climatic conditions for borrowed art and archival objects, regardless of what the receiving building’s own systems or science can support. Even an institution that has fully embraced adaptive ranges can be forced back into rigid set points the moment a loaned object arrives. Carnero flagged insurers and loan negotiators as a stakeholder group future SIMIACCI events need to bring into the room.

Adler’s closing advice doubles as a design brief for the sector: swap the ideal set point for an acceptable risk range, stop assuming every room needs the same climate, treat ventilation as an air-quality system rather than an air-volume one, and remember that monitoring without minimum performance requirements and a defined response plan is just data collection. Ortiz’s closing point rounded things off: most conservation professionals are already ready for this shift — what’s holding them back is budgets and understaffing, not resistance.

The full recap of the discussion will be available in the latest issue of the REHVA European HVAC Journal. This was the first of a series of SIMIACCI webinars,  future sessions will follow the project’s pilot sites as the technology moves from prototype to building.

For those who couldn’t attend live, or would like to revisit the discussion, here are the materials from the webinar:

• Slides: https://simiacci.eu/wp-content/uploads/2026/09/SIMIACCI-PolicyWebinar1.pdf

• Recording: https://www.youtube.com/watch?v=XSBHMM3ILog