Assessing the energy and IAQ potential of dynamic minimum ventilation rate strategies in offices

Abstract

The energy and Indoor Air Quality (IAQ) implications of varying monthly minimum ventilation rates (VRs) in California offices were assessed using EnergyPlus and its integrated multi-zone contaminant modeling feature to predict HVAC energy use and average indoor concentrations of formaldehyde. Minimum mechanical ventilation rates were varied monthly: rates were lowered below Title 24 prescribed values for months when the energy penalty of providing ventilation air was highest; rates were raised during temperate months. For each of California's sixteen climate zones numerical methods identified the optimal combination of monthly ventilation rates that both lowered annual HVAC energy use and maintained average annual formaldehyde exposure below specified levels. Reference models used the fixed minimum ventilation rates prescribed in California's Title 24 Standard. In buildings without economizers, optimal monthly strategies reduced total HVAC energy consumption up to 21.7% and reduced indoor formaldehyde concentrations up to 44%. The benefits in buildings with economizers were much smaller with a maximum energy savings 0.3%. In temperate climates, in buildings without economizers, increasing ventilation rates all year round reduced annual contaminant exposures and lowered annual HVAC energy. A secondary benefit of the optimal variable ventilation strategy was a reduction of peak cooling electricity up to 17% in hotter climates. © 2015 Society for Modeling & Simulation International (SCS).