The Risks Associated with Wildfire Smoke

Homeowners who have experienced a nearby wildfire know the eeriness of darkened skies and red clouds shrouding the horizon. Even in the middle of the day, the heavy smoke that comes from fires will smother the atmosphere in a dangerous smog that contains a mixture of carbon dioxide, water vapor, carbon monoxide, particles, hydrocarbons, and other organic chemicals, nitrogen oxides, and trace minerals.

According to the U.S. Government service Air Now, “fine particles (from wildfire smoke) are respiratory irritants, and exposure to high concentrations can cause persistent cough, phlegm, wheezing, and difficulty breathing. Exposure to fine particles can affect healthy people, causing respiratory symptoms and reductions in lung function. Particle pollution has the potential to affect the body’s ability to remove foreign materials from the lungs, such as pollen and bacteria. Studies have found that short-term exposure (i.e., days to weeks) to fine particles, a major component of smoke, is linked with aggravation of pre-existing heart and lung disease.”

The Air Quality Index (AQI) studied and published by the EPA measures ground-level ozone and airborne particles. The index slides on a scale of 0 to 500, with levels under 50 being good air quality and any rating over 300 being potentially hazardous. The infamous Camp Fire that burned tens of thousands of acres in California in 2018 led to dangerous air quality index levels over vast areas of the state. One study even found that breathing the smoke-infested air in regions affected by the Camp Fire was equivalent to smoking 13 cigarettes a day.

The Role of Passive Homes in Protecting and Preserving Indoor Air Quality 

When the air quality index is compromised due to nearby wildfires, the EPA will recommend that people limit the time spent outdoors. Unfortunately, many homes suffer from air leakages. Besides radically reducing the structure's energy efficiency and thermal performance, leaky structures pose a risk for contamination from wildfire smoke.

Taping up your door and window frames, replacing your air filter, and using caulk on some visible cracks and fissures around your home are a few quick fixes during heavy wildfire smoke. However, investing in an energy efficiency retrofit that takes your home to passive house standards is a much more effective long-term solution. Passive homes, as we will explain below, are an essential element of a resilient home. They are a necessary element for homes located in areas at high risk for wildfires.

Airtight Building Envelope to Keep the Smoke Out 

The most fundamental aspect of passive homes is that they are designed to be completely sealed. The building envelope receives extra attention, and traditional ventilation such as attic vents are avoided. High-performance windows and doors incorporated into the design can help to prevent air leaks, which are extremely common in these parts of the home.

Triple-pane windows, which are common in passive homes, offer an added element of protection. Strong winds help to spread devastating wildfires and can fan the flames of the fire. Strong winds can pose a risk to the home through whipping up rocks and debris that can damage less-sturdy window types. Even a small crack in a window caused by a fallen branch can compromise your indoor air quality during a fire. Triple pane windows offer superior protection from the winds that often accompany wildfires. By focusing attention on a super-sealed building envelope and high-quality windows and doors, passive homes do not allow wildfire smoke an entrance into the house.

The Use of Heat Recovery Ventilators or Energy Recovery Ventilators 

Passive homes always incorporate a heat recovery ventilator (HRV) or energy-recovery ventilator (ERV) as part of a holistic indoor air quality management system. A good HRV or ERV is an energy-efficient ventilation system that is necessary for airtight homes. Besides improving the energy efficiency of your home, HRVs and ERVs offer excellent air filtration properties. Most HRV or ERV systems offer up to 14 microns of filtration. This type of filtration system will be able to keep particles that are smaller than 0.3 microns out of your home. For comparison, a Canadian government guideline states that coarse particulate matter from wildfires ranges from 2.5-10 microns in diameter, while the fine particulate from fires generally has a diameter of 2.5 microns. The filtration capabilities of an HRV or ERV will filter out even the finest particulate matter associated with smoke dust. You can read a review of the five top HRV or ERV systems for passive house design here.