Case study: County buildings upgrade HVAC
Indoor air quality was a large factor in Boulder County’s HVAC systems upgrades
Boulder County, Colo., retained PCD Engineering’s expertise when seeking indoor air quality solutions for three prominent county facilities during the pandemic. Facilities included the old courthouse building, east office wing of the courthouse and offices of Boulder County Building Services.
The facilities initially closed following the onset of the COVID-19 pandemic in March 2020 and the county was looking to improve IAQ before reopening. The office facility contains a health clinic on the first floor that was seeing patients, potentially with COVID-19. There was also some concern with the air intake locations around the buildings, which exist at grade level of the historic facades and where people may congregate.
The building heating, ventilation and air conditioning systems range from 10 to 50 tons and include two indoor variable air volume units, two roof-mounted VAV units and one indoor multizone air handling unit. The county worked to increase HVAC system filtration levels to the highest level possible within the fan power limitations. Only the rooftop systems on the office/health clinic building were able to be increased to MERV 13 without affecting HVAC system airflow and performance.
Germicidal ultraviolet light (UVC) and needlepoint bipolar ionization systems we next considered for installation into each air handling system. NBPI was ultimately selected for its abilities relative to cost. NBPI also provide a suitable application in all AHUs including older units which have limited space for installation of UVC systems, which disinfect surfaces visible to the light source.
Ionization units are design using 6-foot modular bars run lengthwise along the upstream side of the cooling coil. Power to the unit is interlocked to operate with the unit supply fan. Power supplies for each bar were extended to local existing 120-volt circuit. Each bar draws only 15 amps. Sensors exist in the design connected to the building automation system to monitor the level of ions produced in the system and confirm they are operational.
The construction phase of the project was completed in January 2021. County offices remain closed during the pandemic.