Indoor air quality in California homes with code-required mechanical ventilation

Data were collected in 70 detached houses built in 2011-2017 in compliance with the mechanical ventilation requirements of California’s building energy efficiency standards. Each home was monitored for a one-week period with windows closed and the central mechanical ventilation system operating. Pollutant measurements included time-resolved fine particulate matter (PM2.5) indoors and outdoors and formaldehyde and carbon dioxide (CO2) indoors. Time-integrated measurements were made for formaldehyde, NO2 and nitrogen oxides (NOX) indoors and outdoors. Operation of the cooktop, range hood and other exhaust fans was continuously recorded during the monitoring period. One-time diagnostic measurements included mechanical airflows and envelope and duct system air leakage. All homes met or were very close to meeting the ventilation requirements. On average the dwelling unit ventilation fan moved 50% more airflow than the minimum requirement. Pollutant concentrations were similar or lower than those reported in a 2006-2007 study of California new homes built in 2002-2005. Mean and median indoor concentrations were lower by 44% and 38% for formaldehyde and 44% and 54% for PM2.5. Ventilation fans were operating in only 26% of homes when first visited and the control switches in many homes did not have informative labels as required by building standards.

Methods
Overview of HENGH Study

The HENGH study was conceived, designed and implemented for the purpose of evaluating impacts of residential mechanical ventilation equipment requirements that have been part of the California’s Building Energy Efficiency Standards since 2008. Starting in 2009, these standards have required bath and kitchen exhaust fans and dwelling unit mechanical ventilation with sizing and performance levels based on the residential ventilation standard (62.2) of the ASHRAE organization. The ventilation standards are intended to help maintain indoor air quality as homes are constructed with tighter shells to reduce uncontrolled outdoor air infiltration for energy efficiency.

The study was led by Lawrence Berkeley National Laboratory (LBNL). All study protocols involving interactions and collection of data from private individuals and monitoring in occupied homes were reviewed and approved by the LBNL Human Subjects Committee. Research Funding and technical contributions of collaborators are noted below in the acknowledgements. 

The field study included the following data collection elements:

Homeowner survey about household demographics, ventilation practices, activities that can impact indoor air quality, and satisfaction with environmental conditions in the home.
Compilation of basic data about the houses (location, size, number of bedrooms, etc.) and gas appliances and mechanical ventilation equipment (technology type, make, model, etc.)
Measurements of air leakiness of the building envelope and forced air system ductwork.
Measurements of the following parameters over a weeklong monitoring period:

Airflows of all mechanical ventilation equipment;
Air pollutants and environmental parameters indoors and outdoors;
Cooktop and oven surface temperatures to identify burner use.

Participants were expected to complete a daily activity log. 

What is contained in this dataset?

The dataset contains the most relevant information collected about the 70 houses and their mechanical equipment, results of the participant survey, results of air leakage and airflow measurements at the homes, pollutant concentrations measured by time-integrated passive samplers inside and outside of the home, usage of cooktop and oven, external door open state, and time-series or air pollutants and environmental indicators measured within and outside of the houses. 

Organization of Dataset 

Airflow

This folder contains time series data of monitored mechanical ventilation equipment, estimates of air infiltration rate, and overall air exchange rate.  There is one csv file for each home. See HENGH_Airflow_ReadMe for more details. 

Ambient_PM

This folder contains a summary of PM2.5 data reported by one or more ambient air monitoring stations nearest to each study home. There is one EXCEL file containing PM2.5 data reported from up to three closest regulatory monitoring sites. A composite estimate of ambient PM2.5 was calculated for each home using an inverse distance weighing method.  

Home_Equipment_Data

This folder contains data about the house, including basic characteristics, air leakage test results, and measured airflow rates of mechanical ventilation equipment. There is one EXCEL file containing the data for all homes. The EXCEL file has ReadMe information about the data provided and a note about data quality issue concerning exhaust airflow measurements of over-the-range microwaves.   

IAQ_Monitoring

This folder contains time-resolved air quality data, including estimated PM2.5 as measured by photometry (PM), carbon dioxide (CO2), nitrogen dioxide (NO2), formaldehyde (FRM), temperature (T), and relative humidity (RH). There is one csv file of 1-minute time-series data for each home. See HENGH_IAQ_Monitoring_ReadMe for data header definitions and data issues. 

IAQ_Sample

This folder contains the results of time-integrated air quality samples, including passive measurements of formaldehyde, nitrogen dioxide and nitrogen oxides, and PM2.5 gravimetric filter measurements. There is one EXCEL file containing all data. Detail information about chemical analysis of air samples are provided elsewhere in the journal paper and report. 

Occupant_Activity

This folder contains tabulated information provided by study participants from their daily activity logs. There is one EXCEL file containing data transcribed by a staff member, which was independently spot checked by another staff to confirm accuracy. The PDF file is the daily activity log used. 

Occupant_Survey

This folder contains results of a survey about the occupants, their general activities related to ventilation and IAQ satisfaction, completed by study participants. There is one EXCEL file containing data transcribed by a staff member. Two homes did not complete surveys; these homes have "No survey" in each data file. Questions for the occupant surveys are provided in MS Word and PDF formats. 

State_Monitoring

This folder contains time series data of cooking burners monitored with iButton temperature sensors and open/close status of external (mostly patio) doors monitored with state sensors. There is one csv file for each home. See HENGH_State_Monitoring_ReadMe for more details.