Project Summary

The focus of HENGH is to collect and analyze IAQ-related field data and occupant perceptions from new natural gas homes, built to California's 2008 Title 24 Standard, reflecting different construction types, locations and seasons to answer two key questions.

  1. How are homes built to the 2008 standards performing with respect to ventilation-related criteria?
  2. How can adequate ventilation (for reducing exposure) be provided while reducing infiltration and its related energy use?

The field data is of key importance to provide the baseline for comparison to infiltration reductions, a reference point for setting future air tightness and will be combined with modeling work to answer the questions. The vision of this project is to understand how homes built to the 2008 standards perform with respect to energy-related indoor air quality (IAQ). This information will be used to evaluate options for the future versions of the standards and zero-net-energy requirements.


Most California homes, even many recently built ones, waste a lot of energy from infiltration. Many have leaky ducts pumping large volumes of conditioned air resulting in ⅓ to ½ of that conditioned air escaping through those leaks. Although not efficient this situation supplies lots of air to dilute indoor-generated contaminants. Reducing that infiltration and duct leakage would save energy but risk negative health impacts due to decreased ventilation. Since 2008 California has had minimum ventilation for acceptable IAQ as a requirement in new homes, based on ASHRAE Standard 62.2 in order to protect occupant health, but there has been no validation of its impacts, nor is it clear that the current requirements will be sufficient as the State transitions to net-zero energy homes.

Previous work in California has highlighted contaminants of concern and documented their levels, but this was done before the standards required mechanical ventilation. It is not known how much that ventilation changed the contaminants, nor it is clear which is the best path toward achieving the net-zero energy goals the State has. More and better data on field performance as well as innovative approaches are needed to address these concerns.


The technical approach has three key activities.

Occupant Survey

Online survey of new California homes (built in 2002 or later) to gather information on mechanical systems and appliances, indoor air quality and household activities.

Field Monitoring of New Homes

In-home monitoring of indoor air quality and ventilation in approximately 70 California homes that are built to Title 24 2008 standards.

Simulation and Analysis

Simulation of the energy and health impacts to California based on information gathered from the occupant survey and field measurements.