In 1906 after a horrific fire, San Francisco brought in urban planner Daniel Burnham and architect Willis Polk, taking tragic devastation as an opportunity for a reset. Present day Los Angeles is facing increased heat in the 21rst century, rain of higher intensity but less frequency and will face more urban fires. More resilient design can improve how L.A. functions.
Resilient design leads us to Bermuda, which has 181 islands, over 71,000 people, half a million tourists per year and no major natural water sources.
How do islanders survive and thrive?
Bermuda is committed to three resilient design choices.
- For over 400 years, Bermudans have built every home and business with stepped white roofs – which reflect sunlight, reducing heat for those inside.
- Every home is required to set up gutters that capture all the rainwater that hits that white roof and take it to an on-site cistern, providing 100% of the water used in every home on every island, except part of one city.
- Every property has solar panels on top of the white roofs, providing each property owner with energy independence.
White Rooftops
Consider those fairytale white rooftops which reflect heat. Not only do white rooftops make the houses look like wedding cakes dotting the landscape, due to the high albedo of the color white, (light reflectivity) according to scientists at Yale, white roofs reduce heat by 30%.
What if post-fire rebuilds could all have white roofs? Imagine the enormous, lasting and measurable impact on how much energy we use in L.A.
In addition, white rooftops would be a beautiful look for L.A. the 21st century.
Cisterns at Every Home and Building
Architect / artist John Gardner has been designing buildings featuring stepped roof/ cistern pairings for his whole career, as his father, who co-founded Cooper Gardner, did before him. When the North Santa Monica Bay Watershed Community, a project of Safe, Clean Water L.A., reached out to Gardner about the feasibility of creating a demonstration project replicating these beautiful and hard-working roof/cistern pairings in Southern California, Gardner was intrigued.
Image by: John Gardner
From the onset of the conversation, Gardner understood that living in a house with a cistern might sound like a tenuous answer to water supply needs for people on the mainland accustomed to the consistency of municipal water supply. However, math is on the side of the cistern: an inch of rainfall on a square foot of surface area yields .623 gallons. Thus a 2,000 foot home captures 1,246 gallons per each 1” inch rainfall event. In Bermuda, with an average rainfall of 55” inches per year, this brings the amount of available water for those living in a 2000’ home to about 68,530 gallons per year. Divide that by 365 days per year and this theoretical household is living on about 188 gallons of water a day. Can rainwater capture from roofs and cisterns work in rain-limited locations?
Currently California has a goal for each person to use 47 gallons of water a day.
The 188 gallons from the potential home in Bermuda comes to … 47 gallons per person for a family of four.
As a comparison, imagine a potential project in Topanga, an unincorporated city in Los Angeles County, where the average square foot of a home sold last month was 2,716 square feet. Given an average annual rainfall of 19.4 inches, that could come out to 52,690 gallons a year, or 144 gallons per day…enough for a theoretical family of three. While there are many houses smaller than this and multiple- family units are a totally different animal, there are many homes, businesses, schools and municipal buildings in L.A. County (and beyond) that could benefit from a Bermuda roof and cistern retrofit.
As we rebuild, finding a way to incorporate rainwater capture and cisterns into future buildings is good sense from both a water and an energy perspective as imported water uses approximately 30% of the total energy use in California.
Image by: John Gardner
Gardner explains, “In the Bermuda context, the purpose is to catch as much rainwater as you can and hold it safely for your use as there is no real alternative that is accessible on a residential level historically. The alternatives are to drill a well, which is not always potable or to use an RO (reverse osmosis) plant which is not really practical unless you’re by the sea or to be on a municipal system, which is not that good.” Bermudians understand the vulnerability of their own residential water supply so in drought conditions, “We modify our behavior accordingly: when there is a drought, we use less water. It’s the culture to use water this way.”
Gardner comments that Bermuda roofs are “said to slow [rainwater] with the steps on the roof. The construction includes 1” inch thick roofs that connect in vertical edges, unlike the eaves under roofs in other countries, that then funnel the water directly into pipes that feed into the cistern.” Cisterns are covered, preventing propagation of mosquito larvae and dark, barring algae growth, while air ventilation prevents stagnation. Gardner adds wryly, “One accepts that dirt gets on the roof, blown dirt, bird poop. The tank is still, so sediment falls to the bottom.” Nowadays, most people filter the water prior to drinking. Cisterns have to be cleaned on a regular basis, ideally every 2 years, often closer to every 5 years.
Image by: John Gardner
When asked about construction Gardner clarified that the traditional limestone roofs are historical now, as Bermuda has chosen to limit removal of limestone from quarries for conservation purposes. “Nowadays slate is in common use, as are non-stone product like SKB and others, including glass fiber reinforced concrete board, foam profile on top, finished with polymer, painted white with latex paint.” Historically, builders “made lime in kilns, slaking that on roofs and it came white. That’s where the white roof started. A white roof does not have the same heat build-up.” Conversely, he adds, “Tar or paper roofs which are dark grey or black, cause the need to fight heat gain”. Using the color white to create cooler interiors is a powerful tool to help reduce climate change impacts.
Construction requires expertise in building stepped roofs, Gardner adds, “The eave detail is critical as is spacing of rafters to provide support for the roof and the weight of rainwater. Builders need to be sure that the board is strong enough and set nails properly. I would be careful of the substrate, and paint it white.” Gardner emphasized that there is a maintenance issue, roofs which can become mildewy if unattended. “Property owners have to clean the roofs every two years. The taste of the water becomes a natural litmus test whether roof is clean or not.” In Bermuda many homeowners paint their own roofs and Gardner talks fondly about how the new paint goes on “soft, like a cake.”
Image by: John Gardner
Using cisterns to store drinking quality water could be a bit of a mind-binder for public health officials in California and elsewhere. Gardner explains that Bermuda is using “a modified universal building code, … dealing with water codes. Everything goes back to two laws in 1949 and 1951 which are the regulations about how you collect and store water.” When asked about the certification process, Gardner explained that construction workers know how to make these roofs, “It is a culturally standard practice, we don’t really need to draw it out. Everyone knows how to build it. Finished roofs are inspected by the health department.”
To be clear, in Los Angeles, the conversation about cisterns to capture rainwater centers on providing water for irrigation for landscaping. Potentially, cisterns could support fire suppression via connection to pumps for use by professional firefighters or to in-house sprinklers or misters to help reduce ignition
.
Solar
Bermuda is way ahead on climate change action, creating sustainable energy and managing climate change inputs by going solar. Architects have created a process to lay in photovoltaics, made of glass and metal, a few inches above the top of a Bermuda roof. The gaps allow the rain to funnel down on to the classic roof underneath.
Considering the frequency with which massive fires in California have been tied to energy transport systems – on site solar begins to look like a safety choice for the whole community.
Moving forward
Imagine a rebuild in the areas devastated by the Eaton and Palisades Fires that included,
- White rooftops (reducing the amount of air conditioning required)
- Rainwater capture and cisterns for safe water storage
- Solar on every roof to reduce the need for transporting energy (which often causes fires.)
Would this be expensive?
Not as expensive as ongoing energy costs for air conditioning, the cost of using imported water for landscaping and current ongoing monthly energy bills. Not as expensive as climate change.
What do you think?
Please share your insights with the Safe, Clean Water Program survey.
By Melina Sempill Watts
Sierra Club member since age 16
Watershed Coordinator for Safe, Clean Water L.A.
Watershed Coordinators are contracted to educate and build capacity in communities and to facilitate community and stakeholder engagement with the Safe, Clean Water Program. The opinions expressed in this article are the viewpoint of the author only and do not represent the SCWP, County of Los Angeles, or Public Works.
Original interview with John Gardner published by http://www.happyeconews.com/,