*Local Learning Series written by Amanda Fischer of Healthy Home Artisans Inc in Nevada County, CA
Fires & Healthy Homes – Choosing Better Building Materials
Building fire resistant structures in Northern California is now becoming inevitable. Fire season is growing longer and longer each year with our changing climate. We need to make some changes in the way that we live and how we choose to build our homes. If we continue to build in wildfire areas, why not choose better building materials? Materials that are not only non toxic to our health but in the event that the structure does burn, it wouldn’t be polluting our soils and water as badly. And in choosing more fire resistant materials, you may be able to heighten the chances that your belongings could be saved.
Building systems like Strawbale, Earthen Walls and Natural Plasters can be locally sourced, natural, non toxic, provide savings on energy bills, have a lower carbon footprint and to our current topic, extremely fire resistant.
These systems are also totally legal within the International Residential Code. The Strawbale Code has been adopted in California since 2015. And there are many licensed contractors and consultants that are specialized in these sustainable building practices. Strawbales are bales comprised of the byproduct of harvesting wheat, rice, rye and barley. In bale form they are used as an alternative to conventional insulation. Earthen Walls systems are cob, rammed earth or adobe and I will be addressing Cob in this short article. Cob is a monolithic wall system that uses clay rich soil, sand and straw to build. Cob has been used around the world for 1000s of years. You may recognize cob in its common use in pizza ovens and fireplaces because of it’s ability to withstand heat.
How are these systems more fire resistant than other conventional building materials?
A plastered strawbale wall system holds a two-hour fire resistance. Unplastered strawbales actually still have a 30 minute resistance, which may be hard to believe. Bales are compressed tightly, therefore do not have much oxygen present to fuel the fire. They are dense and difficult to burn, and smolder for a long time before any flames actually take hold. Plaster skins tend to be thicker than the standard conventional stucco systems because you are typically filling the uneven bale surface to get your desired wall plane. Therefore, you end up with a solid wall system that lacks oxygen to fuel fires, that is, if the fire can get pass the very high fire resistant plaster or stucco.
These wall systems also tend to use less wood framing members, unlike stud construction, in which stud cavities act like chimneys in the event of a fire. Often these stud cavities are also filled with toxic, high embodied energy insulation making for a less environmentally friendly option. Strawbale wall systems also have a high seismic resistance, making them even better for earthquake prone areas of California.
As mentioned above, Cob is extremely fire resistant and it is commonly used for pizza ovens and fireplaces giving it an excellent fire rating. In Northern California you can almost always find clay rich soil on your own property, making this a very low embodied energy material. In other fire prone areas like Australia, earthen walls have been classified along with masonry and poured concrete as the most fire-resistant building techniques known. Current code efforts are working to demonstrate that cob walls could be used at property lines as a fire line and as a common wall between residential units. The challenge with cob is that alone it does not meet California’s energy requirements. Paired with a healthy, non toxic insulative material it could be a great option for high fire resistance while still providing energy bill savings for the homeowner.
Now lets take a healthy home wall system like Strawbale and combine it with intelligent site planning and wildfire preparation on the property and you now have a very defensible home. Strawbale wall systems provide impressive fire resistance but they aren’t enough to fully protect your home. Roofing finish and assembly, ventilation systems and proximity to fuel sources on the property all play a huge role in fire safety and management. If you are considering building new construction, incorporating these materials will only benefit you. If you are looking for ways to update your existing structure consider upgrades that use these natural, healthy, and fire resistant materials. Replacing old siding materials with stucco or exterior plasters like lime or clay can make a big difference in the fire resistance of your entire wall assembly. We can do better. Let’s build better for our health, the planet and future generations.
Amanda Fischer of Healthy Home Artisans Inc
Nevada County, California
About Healthy Home Artisans Inc:
Healthy Home Artisans is a Design Build licensed contracting firm specializing in utilization of natural and sustainable materials for our built environments. We focus on better building for our health, the planet and future generations. The industries of construction and built environment are one of the top contributors to our current climate and planet crisis. Our goal is to contribute to the construction industry with building practices that promote safety, health, durability, comfort and beauty.
Our firm focuses on design that is site and climate specific, construction that utilizes locally sourced and carbon sequestering natural materials that create fire resistant, high performance built environments to last a lifetime.