UC Davis

Compartmentalization has been proposed as a strategy to improve indoor air quality (IAQ) and energy efficiency in multifamily buildings. California’s 2022 Building Energy Efficiency Standards requires multifamily buildings to either meet a unit airtightness requirement of 0.3 cfm50/ft2 or provide balanced ventilation. While there is consensus that compartmentalization enhances building performance, not enough studies exist to accurately quantify the impacts of different compartmentalization levels on pollutant exposure and energy usage. Furthermore, builders have raised concerns over the difficulty of meeting the airtightness requirement. Such discussion has called into question whether the IAQ benefits and energy savings achieved from compartmentalization justify the current requirement or support a stricter or more lenient requirement. Regulators need this primary data to develop well-informed building codes that promote safety, affordability, and energy efficiency. The study found that new-construction multifamily buildings are meeting the compartmentalization requirement with an average unit leakage of 0.16 cfm50/ft2. Ventilation flow testing suggested that adjusting flow rates down to the minimum ventilation requirement for each unit and installing air filters on dedicated outdoor air intakes could improve IAQ and save energy. Inter-unit transfer of secondhand was modeled to reduce significantly for tighter units, resulting in concentrations below hazardous exposure limits in non-smoking units. Annual energy savings from compartmentalization were estimated to be as much as 6% and GHG savings as much as 10%, however results were highly sensitive to climate zone and ventilation strategy.