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passive house wildfire air quality

Passive Houses and Indoor Air Quality During the California Fires

By Tobias RobertsRise Writer
Dec 4, 2019

Earlier this year, I visited Los Angeles where I toured the first four Passive Houses in Southern California - all very unique projects that showcased the benefits of Passive House even in warmer climates. While the Passive House requirements are much less stringent in California than they are in Eastern Canada, the same principles apply. And one major benefit of owning a Passive House became incredibly apparent while on these visits - air quality. During the wildfires, (and without me prompting them), these homeowners all commented on their experience living in a Passive House during the wildfires. At a time where the air quality in LA was observed to be the absolute worst (on the entire planet), these homeowners barely noticed a difference standing on the inside of their well mechanically-ventilated home. Thanks to an airtight envelope and impressive HRV units, these homeowners were largely directly unaffected by the fires. - Matt Daigle, CEO at Rise.

Much media attention has been given to the role climate change has played in increasing the severity of mega-storms and potentially devastating billions of communities located in low-lying coastal areas. However, a warmer global climate can drastically change established weather patterns upon which our society has come to depend. For example, small farmers in the Global South are increasingly forced off their land due to the unpredictability associated with the beginning and the end of the rainy season. Similarly, shifting precipitation patterns are leading to more frequent and severe droughts in many areas across the world. More intense hydrological cycles characterized by extended drought followed by massive precipitation events increase the risk of vulnerable communities to mega-storms. These events increase the threat of devastating wildfires.

Already in 2019, the state of California has suffered through astounding 6,402 wildfires affecting over 250,000 acres of land. That number is over one thousand fires higher than the five-year average. Wildfires in the state of California and across other arid and dry areas of the country have become a severe threat that homeowners should take into consideration. In a recent article, Rise has written about tips to protect your home from wildfires. Taking steps to “fire-proof” your home is undoubtedly wise, given the increasing frequency of fires.

Another consequence of wildfires that often goes undiscussed is the hazard of wildfire smoke and its effect on our health. Passive homes offer the absolute best standards for interior air quality. Might their focus on super-tight and sealed building envelopes and advanced ventilation systems contribute to protecting the indoor air quality of homes located in areas where wildfire smoke is a common occurrence?

forest fires

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.

air quality wildfires
Photo Credit: Peter DaSilva

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
Blower Door Test. Photo Credit: Hammer and Hand

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.

hrv erv
Photo Credit: Cold Climate Housing Research Center

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.

rainwater harvesting wildfires
Water from this 10-barrel BlueBarrel System was used to wet down the roof of this Santa Rosa home as the wildfire encroached upon the urban area.

Other Sustainable Elements of Passive Homes 

Passive homes do not necessarily have to incorporate different aspects of sustainable home construction, such as renewable energy, rainwater harvesting, and greywater recycling systems. Due to their focus on sustainability, however, many passive house homeowners will do all they can to increase their homes' sustainability and regenerative aspects. Local utility companies will often shut off power to damaged grids during active wildfires to avoid electrical sparks during active wildfires. Even the smallest spark could lead to further fire damage. Passive homes with solar panels or other renewable energy systems will thus be more resilient in the face of fires. Having an HRV or ERV without a power connection will do you no good, and passive homes with renewable energy systems will be best prepared to stay protected from wildfire smoke.

In addition, passive homes with rain harvesting and greywater recycling systems will have more vibrant landscaping to protect their homes from wildfires. Lush, well-watered vegetation can protect a home from the sparks and heat that come with fires. By recycling water back into the landscape around the home, passive house design can further increase their resiliency to wildfires.

Major wildfires will continue to be an occurrence that homeowners in California and other arid regions of the country will have to face. Protecting your family from the horrible air quality of wildfire smoke is one essential element of a holistic mitigation strategy. Upgrading to an energy-efficient home through a passive house retrofit can protect your indoor air quality and keep you and your family safe.

Disclaimer: This article does not constitute a product endorsement however Rise does reserve the right to recommend relevant products based on the articles content to provide a more comprehensive experience for the reader.Last Modified: 2021-07-21T12:27:40+0000
Tobias Roberts

Article by:

Tobias Roberts

Tobias runs an agroecology farm and a natural building collective in the mountains of El Salvador. He specializes in earthen construction methods and uses permaculture design methods to integrate structures into the sustainability of the landscape.

Vents Solar Powered Ductless Fresh Air Wall Vent PSS 102
Vents Solar Powered Ductless Fresh Air Wall Vent PSS 102
The US Vents PSS102 Solar-powered wall vent is an air handling unit designed for continuous air exchange and supply of fresh air to residential and non-residential premises. It's a cost-efficient and autonomous device for more intensive air exchange as compared to passive airing. The specially developed design of the inner grille allows you to control the amount of fresh air flowing into the room (it can also be closed) via the inboard solar-powered fan, providing for a steady inflow and uniform distribution of fresh air in the room. Keep in mind the unit relies solely on Solar to power the internals and should be installed in a sunny location. At night the unit (minus the fan) can be used for passive, nonpowered ventilation.Perfect for off-grid cabins, cottages, tiny homes, and passive houses where nongrid, autonomous fresh air intake is a priority. Benefits Suitable for air handling of small and middle-size premises (depending on the way the unit is installed). The airflow direction can be easily changed by turning the motor 180 degrees; The solar panel provides for more intensive air exchange as compared to regular passive airing; Cost efficiency: the natural solar power is used; Independence: The motor is powered by a solar panel. The supply voltage of the motor is 9…18 V. Electric parameters of the solar panel change depending on the intensity of the solar flux. In dark hours of the day, the ventilator operates as an element of passive ventilation; Possibility to manually control the cross-section of the airflow.
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