ID#2800 made on
EQc7 - Air filtering
LEED BD+C: Homes, LEED BD+C: Multifamily Midrise
This project is using the Trane CleanEffects filter. It includes both an electronic and media filter, and it claims to be more effective than a HEPA filter. According to the marketing, it has a "...
This project is using the Trane CleanEffects filter. It includes both an electronic and media filter, and it claims to be more effective than a HEPA filter. According to the marketing, it has a "clean air delivery rate" that is much higher than 5" media filter. However, it's hard to find a MERV rating. This is a very popular product - how do we handle this?
Further input from the Green Rater on another project:
I did some research on the Trane Clean effects and have convinced myself of the following: It is most likely closest to a MERV 15 filter. Below is my reasoning:
The test data that they utilize to determine its CADR was done by very well respected scientists. The full study is here:
http://www.trane.com/Residential/Downloads/EHE_study.pdf. If you look at page 23 of that study, they give a chart with particle removal efficiencies for different particle size ranges. You will note that the removal efficiency for all particles between 0.3 microns and 20 microns are above 90%.
This can then be overlayed on MERV charts. One can be found here: http://www.allergyclean.com/article-understandingmerv.htm. The smallest group of particles (E1 on that chart - 0.3 to 1 micron) are the hardest to filter. A MERV 15 filter is 85-95% efficient at removing them. The clean effects is 90% efficient. A MERV 13 filter (USGBC's highest category) is >75%, so we are well over that.
The only other remaining question is whether the air speed during the test matches up with allowable test speeds for the MERV test. The test allows speeds ranging from 118 to 748 fpm, and you are supposed to report your MERV based on the speed, though you never see that. From digging in the report, the flow rate through the filter was 1273 cfm. I don't know the exact cross sectional area of the filter, but it's probably about 4 sf. This would be 318 fpm, which is nicely mid-range
at least. If we bracket worst case, 118 fpm would be a 10.8 sf filter (I know it's not that big), and 748 fpm would be a 1.7 sf filter (I know it's not that small).
There is no industry consensus about how to evaluate the performance of electronic air cleaners. Therefore, until or unless ASHRAE or some other independent institution develops a verifiable, repeatable test for both short-term and long-term performance of electronic air cleaners, they cannot be used to satisfy the prerequisite in LEED for Homes, with one exception: if an electronic air cleaner includes a media filter that is MERV rated, this is acceptable. This reverses an earlier project-specific ruling related to Trane CleanEffects filters.
Updated 10/1/13 for rating system applicability.
Related Addenda (Corrections & Interpretations)