A hotel can say that its rooms are quiet, dark and healthy; almost none publishes the figures that show it.

Why it matters

At home, the advanced guest sleeps with a CO2 sensor, a sleep app, sometimes a sound level meter. At the hotel, they have only adjectives. They only know what they are buying after they have slept.

Publishing dated readings, room by room, changes the nature of the promise: it becomes verifiable.

What science establishes

When quality is invisible, the market pays poorly for it. The economist George Akerlof showed that a buyer unable to tell good quality from bad pays an average price, which discourages the seller who invests. Akerlof, 1970. A truly quiet, well-ventilated room is a good of this kind: nothing distinguishes it at the moment of booking. Established, in economics.

Displaying the measurement raises quality. In 1998, Los Angeles County required restaurants to display a hygiene grade in their windows. Inspection scores rose, demand became sensitive to hygiene, and hospitalisations for food poisoning fell. The authors show that the effect does not come only from customers shifting elsewhere: the restaurants themselves improved. Jin and Leslie, 2003. Established, in another sector.

Building labels measure, but by sample and for the building. WELL v2, the standard of the International WELL Building Institute (IWBI), requires on-site tests by approved agents: particles, volatile organic compounds, water, light, thermal comfort, acoustics. The number of measurement points depends on the project's floor area, not on the number of rooms. CO2 is not part of these one-off tests; it falls under continuous monitoring, as an option. Certification is valid for three years. IWBI, 2025. Established, according to the official guides.

The WELL Health-Safety Rating, adopted by hotel groups since 2020, mainly verifies policies and protocols: cleaning, emergency preparedness, air and water management, communication. Aimbridge Hospitality, 2021. Established.

A label therefore says that a building passed an examination, on a given date. It does not say what room 214 measured last night.

What is emerging

Affordable sensors make publication possible. Low-cost air monitors are multiplying indoors. Researchers at the University of Toronto draw more than an average from them: from the CO2 and particle curves, they estimate how quickly a room's air is renewed. They also point out the limits of these sensors: imperfect absolute accuracy and drift over time. Du and Siegel, 2023. Emerging. Hence the need to calibrate and date every reading.

Displaying readings in hotels has not been studied. We found no published study on the effect, for a hotel, of displaying the measurements of its rooms. The analogy with restaurants is sound in theory; it remains to be verified in the hotel sector.

What we refuse to say

We do not say that a room that publishes its readings is better for health. We say that it is verifiable.

We do not say that a building label is useless. It attests to a design and an examination. We say that it does not replace a dated measurement, room by room.

We do not say that displaying readings, on its own, allows higher prices. No hotel data shows it to date.

What a hotel can do

Why no one publishes. Three reasons recur. Risk: a poor reading shows. Assumed cost: people imagine a laboratory. Habit: the sector sells an atmosphere, not figures.

The values to publish. IO8 uses six indicative target values for the longevity room: CO2 at night under 800 ppm; noise under 30 dB; evening light under 2,700 K; temperature of 18 to 19 °C; filtered water; morning light above 1,000 lux. Each room publishes its own readings, including the gap where there is one.

Minimum baseline (around 100 to 250 € per room for the CO2 sensor, see no. 04). Measure the six values in the rooms concerned, record the date, display the result on a card in the room and on the booking page.

Optimised baseline. Permanent sensors in the longevity rooms, the previous night's reading readable by the guest, periodic remeasurement by a third party. The Audited by IO8 label attests that the measurement was made and published; it promises no effect.

The target. That the guest knows before booking what they will find, and can verify it on arrival. The hotel measures its environment, never its guests.

What the Living Lab measures

Measurement planned. The Living Lab, near Lisbon, is being equipped in waves. The six values of the room (night-time CO2, noise, evening colour temperature, temperature, water, morning light) will be recorded over several nights and published here with their date, including those not yet reached.

This is the rule we propose to hotels. We apply it to ourselves first.

Sources

• Akerlof GA. The Market for « Lemons »: Quality Uncertainty and the Market Mechanism. Quarterly Journal of Economics, 1970. doi:10.2307/1879431
• Jin GZ, Leslie P. The Effect of Information on Product Quality: Evidence from Restaurant Hygiene Grade Cards. Quarterly Journal of Economics, 2003. doi:10.1162/003355303321675428 · notice IDEAS/RePEc
• IWBI. WELL Performance Verification Guidebook, 2025. storyblok.com
• IWBI. WELL Program Guidebook, 2025. storyblok.com
• Aimbridge Hospitality Achieves WELL Health-Safety Rating at Hotels Across North America. Hospitality Net, 2021. hospitalitynet.org
• Du B, Siegel JA. Estimating Indoor Pollutant Loss Using Mass Balances and Unsupervised Clustering to Recognize Decays. Environ Sci Technol, 2023. doi:10.1021/acs.est.3c00756

Also from the founder

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The longevity audit for venues  ·  The Research Journal

IO8 Living Lab, near Lisbon. Measured, never promised.

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