Thread by @CorsIAQ

1/ Schools (in Texas) and ventilation.
I've done extensive work w/ schools in Central Texas and the Rio Grande Valley. All schools have centralized mechanical ventilation w/ AC (it's Texas) in permanent buildings w/ unit systems on portables.
Here's the upshot ...

2/ A large fraction of classrooms are woefully under-ventilated (well below minimum standards established by ASHRAE).

Why? The reason given is singular. It is NOT that "we did not know." It is always to conserve energy, always for budget, and never to save the planet.

3/ Just getting these schools to ASHRAE 62.1-2019 would be a win for students, teachers, and staff. Here is a plot (on right) of occupied day outdoor air exchange rates for permanent & portable classrooms in high schools.

4/ The red line is the approximate central tendency for what ASHRAE 62.1-2019 would yield based on floor area and occupancy for these classrooms and the dashed lines show spread around the central tendency.

5/ The x is arithmetic mean, internal horiz line = median, & other lines on box = 25th, 75th, & extremes. Left plot at night and is based entirely on infiltration. In both plots portables have more highly varied but generally > ventilation.

6/ This plot shows the cumulative distribution of re-breathed fraction (RF) in high school classrooms over an occupied day. By my previous calculations (webinar) we ought to be aiming for a RF < 0.008 (< 0.8%) in classrooms w/o very good filtration and required masks (both).

7/ One classroom meets that criterion and the median RF was 2.5 and 2.7% by season. The plot below is older and for K-8 classrooms, but the median rebreathed fraction (2.3%) is very similar to what we found in our more recent high school study.

8/ Note that the data in the last plot includes schools in districts in Central Texas and the Rio Grande Valley. If these are separated the classrooms in the RGV have statistically higher CO2 and rebreathed fraction.

9/ In schools in the RGV many outdoor dampers were closed and literally duct taped over or "sealed" by other means.

10/ A PhD student (now Dr. Tess Stafford) in Economics at UT Austin did a study of the impacts of a large bond package to improve school environments in one school district, including analyses of student math and reading scores before and after different types of renovations.

11/ Tess found that a number of repairs had no impacts on test scores. The only 2 that did were mold remediation and ventilation repairs, & the extent of renovations (in $) was (+) correlated to test scores (likely due to extent of original problem). In J Environmental Economics

12/ Texas likes to think of itself as a separate nation (and sometimes a different planet), but I suspect that what we have observed in public schools of Texas are similar to those of many others with mechanical ventilation. I did not say "all", so please refrain from attack.

13/ The upshot to all of this is that we should pay much more attention to providing healthy ventilation in schools coupled w/ proper filtration and source reduction, whether in times of pandemic or not. Just Do It!