+25%
doubling outdoor air supply from 20 to 40 cfm per person raised cognitive scores by a quarter
Exact: 25% increase
Doubling outdoor air ventilation raised cognitive scores by 25%
In a controlled study, 24 office workers spent six full workdays in a simulated office where indoor air quality was manipulated. Comparing a Green building condition to a Green+ condition, in which outdoor air ventilation was doubled from 20 to 40 cfm per person, participants scored higher on Green+ days in eight of nine cognitive domains tested, producing a 25% average increase in cognitive function scores.
For those overseeing office design or building operations, this points to ventilation rate itself, separate from reducing volatile organic compounds, as a factor that affects occupants' higher-order thinking. Facility managers and employers concerned with worker performance have reason to treat outdoor air supply as a variable worth attending to, alongside material choices that lower VOC concentrations.
The evidence is well supported: the effect was statistically significant and the study design controlled conditions directly, isolating ventilation rate from other variables across all nine cognitive domains. It comes from a small sample of 24 participants in one simulated office environment, so how far the pattern extends to other workplaces, tasks or populations remains untested.
- Cognitive Task Performance
- Standardized cognitive task performance
Workplace
Participants scored higher on the Green+ days than on the Green day in eight of nine domains, resulting in a 25% increase in scores on average when outdoor air ventilation rates were increased.
Used in these factorsheets
Ventilation rate raises information processing.
CO₂ Concentration (ppm) probably lowers information processing.
CO₂ Concentration (ppm) probably lowers productivity.
Ventilation rate probably raises comfort.
Ventilation rate probably raises productivity.
Put to work
Architect
Outdoor air rate is the ventilation number worth specifying
The ventilation specification survives the value engineering round when a client can weigh a number for the benefit against the saving.
Asset manager
Ventilation moves the rent only through the whole certification label
A certification's rent premium prices your building on a category average, so the ventilation spend that earns the label is only as defensible as the standard you require against it.
Corporate real estate
Air quality outweighs the energy line
Cutting CO₂ from 2,100 ppm to 900 ppm predicts a 12 per cent gain in work speed, and staff cost runs 100 to 200 times a building's energy cost.
Developer and investor
A CO₂ logger shows the air a building delivers; a green rating does not
Air quality reaches your rent roll only through the people who occupy the space, and only the first link of that chain is graded solid.
HR and workplace
More outdoor air raises measured task performance
You own how the office affects your people. Facilities and finance set the ventilation budget, and the effect on your people is what you answer for. This sheet gives you the figure to raise with them.
Marketing
Only the ventilation category is an air claim you can verify
The air quality claim a compliance officer can sign off on is the one you can measure and cite, and this sheet gives you that sentence before the copy goes to the owner.
Workplace strategist
Ventilation raises cognitive performance
Ventilation raises information-processing performance by 1.7 to 7.4 per cent, an effect size specific enough for a line in a capex paper.
Related findings
2 of 16
HRV mediated the effect of PM2.5 on 2 of 16 executive function cognitive skills
Reduced HRV due to elevated PM2.5 exposure mediated the effect on 2 out of 16 assessed cognitive skills, both related to executive function
Jiaxu Zhou et al., 2024, Environmental Research
9 of 16
Office workers performed significantly better on 9 of 16 cognitive skills in the cleaner-air condition
In the intervention condition, office workers showed significantly better performance on 9 out of 16 cognitive skills, with the most notable effects in memory and attention
Jiaxu Zhou et al., 2024, Environmental Research
1.31×
higher odds of MCI in poor vs comfortable home environments
Adults in poor-quality residential environments had 1.31 times the odds of developing mild cognitive impairment compared to those in comfortable environments
Dandan Zhang et al., 2024, Journal of Neurological Sciences
Read more in
Workplace 
Workplace Four design choices that change office work
Even under conditions counted as acceptable, air quality takes 5 to 10 per cent off performance. Speech disrupts memory in the open plan, light shifts sleep and circadian timing and the view evidence stays thin.
Workplace Why open-plan offices break concentration
When a workplace moves into open plan, the work that staff lose to noise can double, and how clearly nearby speech carries predicts that cost better than sheer volume.