Polk County Project

Sports lighting in action in high school

New Standard

A new standard (ASHRAE 241) has recently been published at the request of the White House, which specifies that classrooms need to triple the amount of ventilation flowing into classrooms in order to effectively reduce airborne transmission.

Upper-Room GUV (UVGI) is a technology known to provide the highest rate of reduction for airborne pathogens (double or triple the rate of ASHRAE 241), and is introduced on EPA, CDC, and Harvard websites as an efficient, effective, and safe ventilation technology.

Info on UVGI

Background

It is common knowledge that when one student in the classroom is sick, it spreads to other students in the classroom. This is in part because current building codes are designed for control of temperature and humidity, not for control of infectious aerosols.

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Benefits

Current best practices for installation of Upper-Room GUV systems is to achieve 4.0 μW/cm² room-average fluence rate in order to provide airborne pathogen removal rate of 24 equivalent Air Changes per Hour.

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Since studies have also shown that human thermal plume effect alone induces 16 equivalent ACH, UVCUE installations in Polk County has been designed with 70% - 2.8 μW/cm² in 900 sq ft rooms, to be sufficient dosing for 16 equivalent ACH.

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INSTALLATION COST

Each installed classroom cost the school district $1,350, roughly at $1.50 per square foot. This compares very well with renovation of HVAC systems which cost $20~$30 per square foot.

ENERGY COST

When comparing with other measures, UVCUE uses much less energy

Taking calculations from various references cited in DOE-funded study, annual energy costs of various methods for 900 sq ft classrooms are below, assuming $0.16 cents/kWh electricity rate:

HEPA: $100.38 (for 5 equivalent ACH)
MERV 13: $39.07 (for 5 equivalent ACH)
UVCUE: $13.04 (12~16 equivalent ACH)

For 7,500 classrooms, this results in $655,050 annual savings compared to HEPA filtration and $195,225 less compared to MERV 13 in energy cost alone, all the while providing more protection against pathogens.

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