STUDY: Air Quality in Passive House Schools Supports Learning

by Zack Semke

According to the EPA, not only does IAQ impact the health and academic performance of our kids, IAQ is even more impactful on kids than adults because kids’ bodies and brains are still developing.

Yet, it’s common for indoor CO2 levels to regularly exceed ASHRAE’s classroom guideline of about 1,000 parts per million (ppm). The Texas Elementary School Indoor Air Study (TESIAS) found that of 120 randomly selected classrooms, 66% exceeded 1,000 ppm as the average CO2 level, with regular spikes over 2,000 ppm.

This bad air in classrooms is bad news for learning.

A 2015 study by the Harvard School of Public Health (Allen, J.G. et al.) found that increasing interior CO2 concentration from 550 ppm to 945 ppm reduced cognitive function of study subjects by 15%. A concentration of 1,400 ppm reduced cognitive function by a whopping 50%. So, CO2 levels that are commonplace in US classrooms dramatically interfere with our ability to think.

It should come as no surprise, then, that school districts are keen on creating better IAQ in their schools. The question is how to do so, reliably and year-round.

An IAQ monitoring study of various schools in the United Kingdom may provide an answer. Conducted by Architype (the UK architecture firm) in partnership with Oxford Brookes University, the research project provides evidence of the power of Passive House design and construction to deliver healthy indoor air conducive to learning.

In 2014, the research team monitored the indoor CO2 concentrations of three Passive House schools (mechanically ventilated with HRVs) completed between 2011 and 2014, two “naturally-ventilated” non-Passive House schools built to high environmental standards in 2009 and 2010, and one unimproved 1970s school for baseline comparison. The team found that the Passive House schools provided consistently better air, with lower CO2 levels.

Unsurprisingly, the Passive House schools vastly outperformed the 1970s school. The 1970s school routinely exceeded the CO2 thresholds that the Harvard School of Public Health (HSPH) study found to dramatically reduce cognitive function, even regularly surpassing 2,500 ppm, the threshold at which the HSPH researchers canceled testing on ethical grounds (set at one-half the Threshold Limit Value of 5,000 ppm set by the American Conference of Governmental Industrial Hygienists).

But the IAQ of the Passive House schools also easily beat that of the naturally-ventilated schools in all seasons except summer, when CO2 levels of the naturally-ventilated schools and Passive House schools were equally good.

Only the Passive House schools consistently kept CO2 levels below the 955 ppm line, the threshold for 15% less cognitive function according to the HSPH study. Alarmingly, daytime CO2 levels for the naturally-ventilated schools remained well above the 1400 ppm threshold in the winter, exposing students to levels of CO2 pollutions correlated with a 50% decrease in cognitive function.

These findings suggest that the mechanical heat recovery ventilation of Passive House schools is a better, more reliable approach to providing fresh air for students than natural ventilation.

We all want our kids to be learning in environments that don’t hinder their ability to think. It looks like Passive House school design and construction is a great way to provide the fresh air our kids need to thrive at school.

Thank you to Elrond Burrell for pointing us to the published results of Architype’s study.