Strategies to Reduce Fireplace Air Leaks in Residential Buildings

Building Decarbonization Gas System Decarbonization Climate Adaptation Tools

DNV Energy Insights USA Inc

Recipient

Oakland, CA

Recipient Location

7th

Senate District

18th

Assembly District

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$85,851

Amount Spent

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Active

Project Status

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Project Update

In 2025 the project team completed survey efforts, field testing on fireplace air leakage, and fireplace market characterization. Key results include:

~66–70% of CA single-family homes have ≥1 fireplace. Many are older open-hearth designs in pre-1990 homes.

Field tests saw up to 13% leakage reduction by sealing a fireplace.

89% of homes have central HVAC; imbalances can pressurize or depressurize the house. In our tests, 12 of 21 homes had negative pressure inducing extra chimney draft.

Leakage through fireplaces contributes to higher indoor PM 2.5 during wildfires. In leaky-home tests, indoor/outdoor PM 2.5 ratio approached 0.8–1.0; in tighter homes it was <0.5.

The Issue

Fireplace air leakage and the consequent energy loss and diminished indoor air quality has not been extensively studied despite estimated large proportions of air leakage from fireplaces without inserts. Interest in understanding and controlling infiltration of exterior air pollution has increased due to wildfire events. Testing of whole house leakage and recommendation of measures like fireplace dampers are regularly included in home energy assessments, however fireplace leakage is often addressed through dampers that can be installed loosely and allow air infiltration when the chimney in not in use.

Project Innovation

The research study will collect primary data, including building characterization, fireplace leakage, and air quality measurements, to refine estimations of fireplace leakage with and without leakage reduction measures. The project will contribute to the state’s energy efficiency goals by providing recommendations to inform state energy code and energy efficiency retrofit program updates. Further, the project will contribute to California’s current greenhouse gas (GHG) emissions reduction targets by identifying the extent to which fireplace leakage contributes to heating and cooling energy losses, and creating a pathway for mitigation.

Project Goals

Provide an inventory of California residential buildings with gas or wood burning fireplaces

Identify data on the air date on air leakage rates related to energy and health (e.g., indoor air quality)

Identify solutions and their effectiveness to minimize air leakage from fireplaces

Recommend possible updates to building energy efficiency codes and standards, and future energy efficiency programs

Project Benefits

This Agreement will result in the ratepayer benefits of lower costs and increased safety by better defining the energy loss resulting from fireplace air leakage and the relationship to infiltration of indoor air pollutants that can be detrimental to health. The research project will identify actions that residents can take to mitigate the problems, reduce energy cost and reduce infiltration of air pollutants.