Green Roofs
Published in the Sun October 21, 2012

Recently installed green roof at Indian Springs Elementary, San Antonio.  Plants provided by Joss Growers.

If you have ever worked on a Texas roof in the summertime, you know it is a hostile environment.  Even when the air temperature is a mere 104 degrees, on a sunny day the temperature on the surface of a roof can reach 170 degrees, easily hot enough to burn your tender posterior were you foolish enough to sit down.  Urban areas, with a lot of hot roofs and pavement, are “heat islands.”  The ambient temperature in the city can be 10 degrees hotter than the surrounding countryside.

 

Besides being hot, commercial roofs are unattractive, usually consisting of some black goop with gravel interspersed with overworked air conditioners.

 

A “green roof” uses vegetation to solve the problem of hot, ugly roofs.  Plants are by nature designed to absorb energy from the sun for photosynthesis, so with enough plants on the roof, the heat gain to the roof deck can be reduced by as much as 90%.  The plants accomplish this feat not only by shading the roof, but also by the cooling effect of evaporation.  A cooler roof deck transfers much less heat to the building below, decreasing energy costs for air conditioning.

 

But how does one successfully create a green roof?  If you just put some potted posies on a Texas roof they will be cooked by midafternoon.  David Scott, a horticulturist and owner of Joss Growers near Jonah, has been studying the green roof business for about 7 years.  His first efforts resulted not in the attractive roof-top meadow he desired, but in a few spindly survivors and a lot of heavy dirt in an elevated location.  Plants just didn’t grow quickly on a windy, superheated roof.  It could take three years to grow enough coverage for a cooling effect on the building, and most clients were not that patient.

David Scott (right) and Steve Roberson at Joss Growers

with modules containing ice plant and purple heart

 

Four years ago David attended a trade show in Vancouver, and discovered Live Roof, a company with a new system.  Live Roof uses special trays about the size of a cookie sheet, filled with a lightweight engineered soil made primarily of expanded shale and rice hulls.  An assortment of appropriate plants is grown in the modules under greenhouse conditions until the tray is completely covered with healthy plants.  The modules are then transferred to the roof and lined up side by side, creating one continuous shallow planter.  Because the plants are big enough to shade their own roots, the substrate stays cool, and the plants thrive.  The special soil does not decompose, and does not wash out of the modules when it rains.  In fact, the soil retains water and reduces storm runoff from the building.  Stormwater management is a serious problem for cities where naturally green areas have been replaced by impervious cover.  This is one reason green roofs are so popular in Vancouver, where it rains a lot.

 

David points out that choosing the right plants is crucial.  In Germany, 14% of all flat roofs are green roofs, but the climate is far different there.  Sedums are the most successful plants for green roofs in more temperate climates, because they, like many succulents, use a special type of carbon dioxide metabolism called Crassulacean Acid Metabolism (CAM).  That means they keep their leaf pores closed during the day to conserve water, and then open them during the cool night to take in carbon dioxide. The CO2 is stored as an acid until it can be used for photosynthesis the next day.  It seems as if the water-conserving characteristics of sedums would make them successful in Texas.  Unfortunately sedums are highly susceptible to Southern Blight Fungus, which thrives in our high summer humidity, and can rapidly convert a lovely sedum roof into a wasteland.

 

David has a whole list of plants that have proven to do better than sedums in our area, including some beautiful native grasses, lantana, purple heart, Ice plant, blackfoot daisies, and many others.  Most amazing to me was horseherb, which you would instantly recognize as the “weed” with heart-shaped green leaves and tiny yellow flowers that is growing profusely now in my yard wherever the grass has died, which is mostly everywhere.  It turns out that horseherb makes a stunning groundcover, and is also drought tolerant, evergreen, and can prosper on a roof.

 

Joss Grower’s biggest green roof so far is the Hipolito F. Garcia Federal Building in San Antonio, with more than 13,000 square feet of greenery installed this year to replace a leaky, asbestos-contaminated, gravelly roof.  The plants are now growing so vigorously that some of the sprinkler heads couldn’t pop up properly and had to be readjusted.  In Texas, green roofs do have to be irrigated, but they only require about 50 minutes of irrigation every four to five days.  Some buildings use the condensate from the air conditioner to water the green roof.

 

So why should a commercial builder bother with a green roof?  Why not just buy some extra insulation and forget about the roof?  Protected from excessive temperatures and ultraviolet radiation, a vegetated roof can last twice as long as an exposed roof.  There are psychological benefits also, especially if the roof can be seen and accessed from other parts of the building.  Tenants will pay more to live or work in a beautiful building than they will for an ugly one.  Hospital patients have been reported to heal faster if their room has a view of nature.  Some say workers are more productive and relaxed when they can look out on a lovely green meadow.  Perhaps our subconscious brain recognizes that plants are the source of our oxygen and food.  For whatever reason, people just feel better around plants.

Renewable Energy Roundup in Fredericksburg
Published in the Sun October 7, 2012

Johnny Delirious took off his hat, pointed to his very bald head, and said, “We need to think round.”  Mr. Delirious was only one of the many speakers at the 12^th annual Renewable Energy Roundup and Green Living Fair in Fredericksburg last weekend who advocate for a radical shift in how we think about building homes.

 

Building square houses out of sticks is a technique of the past, claims Mr. Delirious.  Johnny’s company, Monolithic Constructors Inc., builds domes for homes, churches, gymnasiums.  The domes are made by spraying polyurethane foam and concrete in the inside of a giant inflatable form.  The resulting structure is so tough it can withstand a direct hit by an F-5 tornado, and Johnny had pictures to prove it.  He also claimed that the domes are fireproof, bulletproof (good for survivalists), and that one unfortunate dome had been pulled intact out of a crevasse after an earthquake.  Johnny goes by the name Delirious because twenty years ago he turned down the opportunity for a liver transplant for hepatitis C but survived anyway.  I found his arguments for domed structures more persuasive than his medical advice, but there was no denying his enthusiasm for both topics.

 

Other speakers at the fair were less colorful but no less passionate about new ways to tackle 21^st century problems.  Peter Pfeiffer, renowned Austin architect and green building scientist, used the USDA’s food pyramid to demonstrate the relative importance of various energy efficiency techniques.  Just like whole grains and vegetables should make up the bulk of our diets, sensible measures such as shading windows, radiant barriers on roofs, and living in appropriately sized homes provide far more bang for the buck than sexy additions like solar panels.  As attractive as solar panels may be, they are like dessert, and should only be considered after the rest of the home’s energy efficiency diet is healthy.

 

Janet Meek, retired US diplomat to Korea and Djibouti and former midwife, was in Fredericksburg to testify to the benefits of living in a cob home.  Cob is a mixture of mud and straw.  Because air conditioning is by far the largest consumer of electricity in a Texas home, Janet had made the principled decision to build her dream home in Hunt without air conditioning.  Her cob walls are hand formed and two feet thick.  But lest you get the wrong idea, this home is not a hut such as might be seen in National Geographic, but rather should grace the pages of Southern Living.  During the hot part of summer Janet lets the house ventilate at night, and then she closes up to keep the cool in during the day.  Janet admits that when the outside temperature rises above 100 degrees, the practical solution is to relax on the porch with a cold drink.  During the summer of 2011 the interior of the house reached the high 80s, but with ceiling fans it felt much cooler, and her electric bills are next to nothing.  Most of the time she is well acclimated and comfortable, as were our ancestors for thousands of years.  Her spare bedroom has a small air conditioner for guests who have not yet adjusted to the low carbon lifestyle.

 

Kindra Welch, the architect who designed and built Janet’s house, said the majority of homes built in the US these days are in a “Race to the Bottom Line.”  She means that today’s houses are often built fast and cheap, and designed for profit in the short term.  In her opinion we should be looking at things in the context of 1000 years.  Builders should consider the life cycle of the materials used and the cumulative effect on the environment.  There are three possible qualities for any building: Good, Fast, and Inexpensive.  You can have any two, but not all three.

 

The Roundup was not just about green building.  Alternative energy was also a topic of interest.  Gary Krysztopik, an electrical engineer, has been building electric cars in San Antonio for six years.  Gary says that a car can be run on the same amount of electricity that would be required just to refine the equivalent gasoline, eliminating the energy costs of exploring, pumping, spilling, and transporting the oil.  According to Gary, “We are better off buying foreign cars that run on US electrons than buying US cars that run on foreign oil.”

 

The Roundup featured innovators in solar energy, biodiesel, water conservation and rainwater harvesting, wind energy, and organic farming.  Attendees ranged from engineers to hippies to hippy engineers with a few survivalists in the mix.  It was a great opportunity to think outside the box, or as Johnny Delirious would say, “Think round.”