Increasingly builders and homebuyers are becoming aware of the importance of indoor air quality to the health of a home and its occupants. Properly built zero energy homes are air-sealed against outdoor pollution, have fresh air systems, and are free of natural gas fumes, making them healthier than standard homes. The health benefits go beyond air quality. Added insulation and air sealing, make them more comfortable during extreme heat or cold weather, and they hold comfortable temperatures longer during short-term power outages.
Climate Disruption Calls for a New Concept of Healthy Zero Energy Homes
Now, however, as we are experiencing the early stages of climate disruption, our concept of a healthy home must expand to include resilience and safety in face of a variety of weather and climate-related threats — from wildfire, smoke, flood, and wind events. The odds of these various threats may vary depending on location – and some locations may be vulnerable to more than one of them. Home designers, builders, and buyers should identify the most likely threats to the safety of the homes in their locality and then design, build, or buy accordingly. Here are some design considerations for each threat.
WildFire Resistance
Designing landscapes with a defensible fire-free zone is the first step in protecting homes from wildfires, as it creates a buffer area near the home that is free of combustible materials, including woodchip or other flammable mulches. Check with your local fire department for recommendations specific to your location.
Insulated double or triple pane windows and insulated doors common in zero energy homes offer significant protection against wildfires. Other measures to make buildings more fire resistant include using fire-resistant roofing and siding, screening all outside vents with 1/8th inch mesh screens, using fireproof decking or flagstone patios instead of wood decks, installing self-cleaning metal gutters that do not collect debris, and considering a rooftop sprinkler system. Because the radiant heat from many wildfires is so great, attention must be paid to the combustibility of interior wall and ceiling supports and finishes, as well as to the exterior siding and roofing. For example, using metal studs instead of wood may offer more protection. Check out the FEMA fact sheets on fire proof residential construction.
There may be trade-offs between fire-resistant materials and keeping a low carbon footprint. For instance metal studs, in the example above, have a larger carbon footprint than wood. To build homes that are both fire-resistant and low carbon, consider using hempcrete, which sequesters carbon and may be fire-resistant.. Other fire-resistant, low carbon footprint building materials to consider include timbercrete and rammed earth. Building scientists should develop best practices and materials for fire resistance that have the lowest carbon footprint at the lowest cost.
Smoke Event Resistance
Because they are airtight, zero energy homes provide natural protection from smoke infiltration. In areas at risk of intense smoke events, further reducing a home’s air changes per hour will be an asset. Energy recovery or heat recovery ventilation systems (ERV or HRV) can easily be overwhelmed by intense smoke events and should be equipped with built-in HEPA filters or turned off. Additional stand-alone HEPA filters may be suggested as a backup, and an indoor/outdoor air quality monitor could be standard equipment in wildfire-prone areas.
Flood Resistance
Builders and buyers should determine the level of flood risk before building or buying. If the home is in an area of high flood risk, consider raising the home by elevating the basement or crawl space so it is above the highest projected flood level. Use building materials and finishes that are water and mold-resistant below the high-water line. Heat pumps, water heaters, solar inverters, and any battery backup should be installed well above the worst projected flood line. Also, consider some of these five flood protection techniques.
Wind Resistance
Building wind-resistant homes in areas with high risks of hurricane winds and tornadoes requires careful consideration. The advanced framing and double walls used in most zero energy homes will help, but much more may be needed, starting with strapping the foundation to the walls and the walls to the roof. Check out the techniques used to build this highly wind-resistant conventional home and this home specifically designed for wind resistance. In tornado-prone areas, including an easily accessed reinforced safe room provides additional safety. Even Habitat for Humanity is building affordable hurricane and tornado-resistant homes.
Extreme Heat or Cold Events
Zero energy homes are well designed for extreme heat and cold events because they are highly insulated and airtight and usually have heat pumps that both heat and cool. Nonetheless, the insulation should be designed for extreme heat and cold events. The heat pumps should be sized to handle projected extremes of heat or cold.
Power Outages
In cases of wind events, floods, or fire events, power outages will occur. So homes built in those vulnerable areas should include a battery back-up system connected to the solar array. Owning an electric vehicle and keeping it fully charged with a home charger, will allow owners to get around when gas stations cannot pump gas due to power outages. Some newer electric vehicles can also serve as back-up storage for the home.
Healthy Homes are Resilient Homes in an Age of Disruption
While predicting the future is always a challenge, it is safe to say that we will face more extreme climate disruption, including wildfires, smoke events, wind events, and floods. For zero energy and zero carbon homes to truly be healthy homes, they must also be designed for resilience to reduce the risks of these events — towards zero. That will take building scientists, designers, builders, building code developers, and the insurance industry to develop a new model for homes that reduces all health and safety risks of the home — putting them on the path to zero health and zero risk to safety.
Happy Hiller says:
Thank you for sharing such valuable information!
ESCO says:
These days the environmental condition requires a more conscious approach and I’m glad that people are thinking more about whether their housing is eco-friendly.
Polestar says:
It’s good news that properly built zero homes are air-sealed against outdoor pollution and have better indoor air quality because of this. However, pollution isn’t just an outdoor problem. In fact, some pollutants can be up to 5x more concentrated in your home than they are outside. Dirty air conditioner filters are often the cause of it. Remember to clean them regularly for good air purification.
Integrity says:
Thanks for sharing!