Bright Lights, Big City (Hot Time in the Old Town Tonight?)

“Many clever men like you have trusted to civilization.  Many clever Babylonians, many clever Egyptians, many clever men at the end of Rome.  Can you tell me, in a world that is flagrant with the failures of civilization, what there is particularly immortal about yours?”

--G.K. Chesterton, The Napoleon of Notting Hill (1904)

We at Myrtle’s place do not believe in the cynical philosophies of survivalists, nor do we believe in the fatalist philosophies of nihilists.  Neither, however, do we believe in the supremacy of human beings central to the dominant moral, social, and economic philosophies of the Judeo-Christian capitalist West. 

People are great – don’t get us wrong.  It’s just that we aren’t the center of the universe, as you would be led to believe if you follow the teachings key to the ideological structures underpinning most of what we recognize as “civilization”.  There is a dichotomy in most systems of thought between “natural” and “man-made”.  We do not make that distinction.  As far as we are concerned… it’s all“natural” and is all subject to the immutable laws of physics.

In fact, in the World According to Myrtle, the inevitable truth of everything being interconnected is so obvious that we sometimes don’t think about the fact that not everyone shares this basic understanding.  Which is why we are so often astounded by things like global-warming-denialism, trust in petrochemical companies, and big grassy lawns.

One of the basic facts of life regarding how so-called “civilization” fits in to the natural world is something called the urban heat island, and though the concept has been around since the first decade of the 1800s, when an intrepid investigator named Luke Howard first described the phenomenon of cities being warmer than the surrounding countryside, there is a surprisingly large percentage of the modern population that is utterly unfamiliar with the idea.

Basically, not only do cities generate more “man-made” heat (though, again, we think this term is preposterous) than do areas outside the urban center, cities also retain more heat, owing to 1) more materials with heat retaining properties, such as asphalt, cement, insulating materials in houses and commercial properties, vertical structures with large volumes of retained non-externally-circulated air (i.e. “buildings”); 2) fewer radiating surfaces such as open fields, tall trees with upward-facing surfaces of high albedo (i.e., glossy leaves); 3) numerous heat-generating entities such as power plants, automobiles, street lamps, etc. and 4) lots of houses with central heat in winter, and air conditioners in summer (which, since most people are short-sighted, they don’t realize put out more heat than cold, only the heat goes outside, not in).

There are a number of secondary effects generated by heat islands, most of which people simply choose to ignore.  Monthly rainfall, for example, is much higher downwind from most cities, in large measure because the urban heat island effect causes a change in the windflow around cities.  In Bryan-College Station, people sometimes humorously refer to the “Aggie Dome” which causes large storm systems to “magically” break up shortly before hitting the city-proper, only to reform once they move South and East of town.  Guess what?  It’s not magic… it’s civilization.  The “Aggie Dome” is a locally obvious manifestation of a very well known scientific principle.  It is a real thing, and it is a direct response of the environment to the activities of human beings.

Conservative blogosphere types frequently decry the possibility of macroscopic versions of this same phenomenon – to wit, they refuse to accept the possibility of anthropogenic climate change – but this strikes us at Myrtle’s place as not only wrong, but downright infantile.  Of course humans have an impact on the environment.  Everything has an impact on the environment, and the last time we checked, human beings are a subset of “everything”.  We promise we will update you the first time we encounter any evidence to the contrary.

The only question is not “do we have an impact on the environment” but “how big an impact do we have?”  There is certainly plenty of room to discuss this question on the macro level (we have done so before, and will unquestionably do so again), but equally important, we think, is a discussion of the micro level, which generally goes unexamined.  Regardless of what is going on in the climate generally – and rest assured, that is certainly a massive question – what is going on in the microclimates of individual human habitations is just as important.

So, to begin with:  what causes the urban heat island?  Long story short, the principle cause is the fact that short-wave radiation absorbed during the day by asphalt, concrete and buildings of wood, glass, ceramic, and various other modern construction materials is released as long-wave radiation during the night, making cooling a much slower process in urban areas than in the pastoral surroundings.  Basically, stuff people build generally cools down more slowly than stuff Mother Nature built.  There are plenty of counterexamples, but basically the “slow-to-cool-down” stuff in nature is concentrated in the hands of homo sapiens because we feel more comfortable in houses and office buildings made out of such stuff, and such stuff is also easier to drive on/more resilient to store still-other-stuff on.

What are the impacts of this basic reality?  First, night time temperatures in the city are mostly higher than they are in the country.  The people to first notice this truth are gardeners… especially tomato gardeners.  Fruit set for virtually all vegetables, but for tomatoes in particular, depends upon sufficiently warm day time temperatures for energy creation (critical for growth and development) coupled with night time temperatures low enough for consolidation of sugars (a process in large measure dependent upon the differences in fluidity of various chemical components at different temperature gradients which then utilize gravity – basically, the stuff that solidifies at lower temperatures sinks faster than the stuff that solidifies at higher temperatures) in order to create a “fruit” (aka a tomato) which has the proper nutritional value to ensure the germination of its progeny (aka a seed).

As finicky as tomatoes are, it becomes apparent quite quickly to connoisseurs that Fall tomatoes taste better than Summer tomatoes in the Brazos Valley, because while the daytime temperatures stay high enough well into the Fall… during the Spring and Summer, the night time temperatures get too high far too quickly.  Sure, the plants still set fruit… but the flavor is just, well… wrong.  And it’s wrong because it’s too hot at night.

There are other, more dramatic impacts, of course.  You will occasionally hear stories of large tornadoes hitting urban areas.  However… your everyday, ordinary garden-variety tornado almost never hits an urban area.  The trailer park on the edge of town, sure.  But town square?  No way! 

Why?

Because small thunderstorms almost never happen in urban areas.  The urban heat sink causes lower-level temperature inversions that most cumulonimbus constructs simply cannot penetrate – they hit the heat island and “poof!” The system may (if it is strong enough) recreate itself once it moves past the interfering heat source (see:  “Dome, Aggie”), but otherwise it just disappears in a puff of disappointed agricultural chappiness.  Only a very large storm system is likely to be able to penetrate the urban heat island, and as a consequence only a very large tornado is likely to impact an urban environment.

So… what should people do about this phenomenon that we have created?

The answer to this question depends upon the answer to a vast number of other questions, not least of which is “What do we want?”

If what we want is to control nature, then, hey, do whatever you want.  You’re not going to succeed, so you may as well go down swinging with whatever ridiculous philosophy you were wanting to pursue in the first place.  If you’re going to be a failure, you should at least be a self-satisfied failure.

If, on the other hand, what we seek is a way to live in a more sensible, survivable equilibrium, then there are several steps we can take, some of which have plenty of empirical support, and others of which make good sense based on what we know about the laws of physics, in addition to several decades of meteorological evidence.

One of the first cities in North America to take this problem seriously was Atlanta, Georgia, which in the 1990s instituted several statutes related to building and development aimed at lowering the urban temperature.  Rooftops and roadways in Atlanta must be built of certain materials and of certain colors which increased the city’s albedo considerably.  White or grey replaced black and brown… and the citywide average temperature dropped by nearly 3° Fahrenheit over a decade.  Given that during that same decade the global average daily temperature rose… yeah, Atlanta was on to something.

In addition to cool roofs (about which we have written before – if you haven’t yet painted your roof white, hey, get on it!), cool road surfaces, permeable asphalt, increased greenways, replacing lawns with herb gardens, shrubberies, and tall trees (capable of both absorbing heat, and reflecting any unused solar energy so as to avoid heat pollution) are all effective mediators of urban heat.  Replacing combustion engines with electric vehicles is another obvious reduction urban dwellers can implement… and better still, getting rid of engines altogether (also known as “ride your bike to work, ya bum!”)

Sometimes we are accused by traditionalists of taking glee in the idea that Western civilization is going to crumble.  Note that we didn’t say in the possibility that Western civilization will crumble – that is an inevitability, as an serious student of history would know.

Well… we have to confess to being more or less guilty to this charge.  The thing is, the fall of one form of civilization has always led to the institution of another.  And we are not pessimists, focused on what we will be losing when the status quo comes to its inevitable conclusion.

No, we are optimists.  We see that the way of life to which the vast majority of our species has become accustomed is unsustainable, and cannot last.  And we look at the possibilities and realize… you know what?  We can do better.

In fact, we are quite sure that, even though we’ll be dragged there kicking and screaming, humanity will do better.

Happy farming!

Fiddler on the Rooftop? No, that's some nut with a paint brush...

Barrington Farm is a living history museum on the grounds of Washington on the Brazos State Park, just about a 30 minute drive south of College Station.  For anyone in the area who has never gone, let us highly recommend it – the museums related to Texas history are, of course, significant (Washington on the Brazos was the location where the Texas Declaration of Independence was approved and signed, and was the first capital of the Republic of Texas), but the real draw is the living farm.

There are interesting things to see and do on the farm all year round, but the most interesting, to us, happen in the summertime, when the weather is the most unbearable.  That’s because it is instructive to see how folk managed to survive at a time when there was no air conditioning, and Slurpee® was not even yet a dream.  There are inevitable comments, too, from any women in your tour about the unpalatability (to put it mildly) of wearing corsets under such conditions.

While we must admonish our ancestors for their foolish fashion choices, we also must admit there are numerous things they did to make use of what few cooling tools they had, and we would do well to emulate these strategies.  For starters, the orientation of their houses was often chosen more for the ability to capture prevailing afternoon breezes through the dog run that was a staple in early 19th century Texas farm houses.  On a 100°F afternoon, the porch would often feel 15-20 degrees cooler than the fields.

Similar effects could be found in the placement of arbors about the grounds.  At Barrington Farm, the slave quarters are surrounded by grape arbors whose purpose is less about fruit, and more about shade.  Again, taking advantage of orientation and the afternoon breeze, we once visited the farm during corn harvest, and despite the high heat and humidity, the guide was happily roasting corn over an open fire, from under the shade of a muscadine trellis.

Another thing we noticed at Barrington Farm the last time we visited was that “the big house” was painted the brightest white imagineable.  We particularly made note of this fact because we last visited about the same time that we decided to paint our tin roof white for the purpose of cutting our cooling costs.

Non-white roofs are the modern equivalent of the lunacy of wearing corsets in 100° weather.  To put it simply, the laws of physics are either your friends, or your enemies, depending on how stubbornly you adhere to social norms in the face of real needs for change.  Light colors absorb less heat energy and both reflect and emit more heat energy, while darker colors absorb more heat energy and both reflect and emit less heat energy.  In plain English, a dark-colored house with a dark-colored roof makes no sense whatsoever in a Texas summer.

Traditional roofing surfaces in the United States can reach summer peak temperatures ranging from 150-185°F (66-85°C), which not only makes it much more difficult to cool the building, but also contributing to something called the “urban heat island”.  When you consider that the average city is approximately 20% rooftop by area (per a survey done from 1998-2002), that means there is a considerable amount of heat being retained in our cities by black tar, gray slate, and other dark roofing materials which amplify heating problems, making bad situations worse.

There are several solutions to this problem, the best of course being to encourage the growth of trees tall enough to shade not just your yard and maybe a few windows, but also the roof of your home.  Sunlight which never reaches the surface cannot, obviously, contribute to excess heat.  Barring the advent of magic beans to make your trees taller, however, the next best solution is to change the surface of your roof to reflect more sunlight and emit more heat into the atmosphere and away from your home.  That’s where “cool roof” technology takes over.

Cool roofs are basically just like normal roofs, with one of two differences – either a coating which adds albedo (reflectivity), reduces absorption and increases emission; or else a basic material which accomplishes the same functions.  An example of the kind of coating we are talking about is the specialized white paint we used on our own home.  Available at all major hardware stores, and many of the minor ones, look next to the roofing materials rather than in the paint section because while this is technically “paint” it is not like other paints.

To begin with, most house paint is not designed to be applied to surfaces which regularly reach 180°F.  Further, this stuff is designed to be laid down in a fairly thick swath.  We used a regular roller to apply it to our metal roof, but it would not be amiss to suggest simply pouring out a quantity on the area you are wanting to cover and then using a push-broom to even it out at 1/8th to 1/4th of an inch thickness.

Once it is spread and dried, a roof painted white with an elastometric polymer will provide 65% or higher solar reflectance and have a thermal emittance of 80 to 90%.  We noticed almost immediately that the areas where we were standing while spreading the material were exceptionally hot (and it was still just March!) whereas the areas with the paint were almost immediately cool to the touch.  And as the satellite photos from Google Earth show, there is a tremendous amount of sunlight getting reflected straight back into space.  Our attic is kept cooler, and College Station is also a tiny fraction cooler.

There are other kinds of roofing paints, including a cementitious paint (paint with cement material), and a combination of cement and polymers.  The advantage of the polymers is that they provide a waterproof seal; the cementitious paints would only be practical on surfaces which are themselves already impermeable – we could have used one ourselves had that been our only option, but we painted our roof long before we learned all the different elements of cool roof technology.

In addition to paint, there is also the option of using a polyurethane foam barrier on a rooftop.  This is common on commercial buildings; Texas A&M started putting this type of cool roof on buildings as early as the early 1970s, and that same technology is fairly common all over the country even today on new school construction, as well as in some industrial and warehouse developments.

Finally, rather than using a coating, there are the cool roof building materials, where the roof itself is simply built from material which has high reflectivity and emissivity.  An example of this type of material would be a white vinyl sheeting, used instead of traditional shingles or metal sheeting.  By contrast to asphalt (which has a reflectivity between 6 and 26%), white vinyl rooftops reflect more than 80% of the suns rays, and emit at least 70% of the solar radiation the building absorbs.  Depending on roof tilt and latitude, a white vinyl roof is the cool roof champion.

One final strategy worth mentioning is the ‘green roof’ system.  Particularly common with rammed earth and strawbale houses, a ‘green roof’ is literally a roof with a garden on it.  While it takes some sound engineering to guarantee the necessary load-bearing qualities of the structure below, a ‘green roof’ provides some of the soundest thermal principles for environmental control of a building you could wish for – in summer, the solar energy is absorbed by the plants growing on the roof, and converted into leaves and (possibly) fruit and produce.  While the soil will undoubtedly absorb more energy than it can possibly emit back into space, it provides far better insulation than is found in most attic spaces.

And in winter, this natural insulation makes a green roof practical in northern climates in ways a typical cool roof might not – although heat loss in winter from the roof is greatly exaggerated; the greater danger is from excessive draftiness, not from albedo and emission.

The principal advantages of cool roofing technology apply to the individual buildings where these technologies are applied – whether a domestic building where a family lives, or a warehouse where goods are stored, or a factory, where people and machinery require constant environmental controls – but there are additional benefits to the greater community, as well.  Municipalities with the forethought to subsidize cool roof technology see almost immediate impacts in the mitigation of the phenomenon known as an “urban heat island”.

As long ago as 1818, amateur meteorologist Luke Howard described the effect in his seminal work The Climate of London, wherein his careful observations of wind direction, barometric pressure, temperature and precipitation led him to conclude that there was an ineffable something about the urban environment which made it warmer and drier than the surrounding countryside.

Thanks to the far greater scope of data available in the 21st century, modern meteorologists are able to model urban heat islands far more effectively.  Basically, the darker synthetic materials used in urban construction (asphalt roadways, dark colored bricks, dark tile roofs, the darker shades of cement) absorb far more heat and emit far less back out into space than would be true of the more natural materials found in greater quantities in suburbia and the countryside.

For an experimental confirmation of this idea, try standing barefoot at noon in a garden bed, say in the shade of a nice rosemary or basil plant, and then stand on the sidewalk – most sensible people would just take our word for it, we think.

Several factors combine to make this phenomenon worse in some cities than in others – “tunnels” created by skyscrapers focus heat energy in some downtown neighborhoods and prevent its easy escape; other cities get lucky in the orientation of prevailing winds, or maybe juxtaposition to the ocean gives the heat sink an easy drain for some, while being situated in a desert basin causes others to simply sit and bake.

And sometimes seemingly unrelated weather events are the direct result of this island effect.  There is an unofficial term related to College Station weather, the so-called “Aggie Dome” which prevents rainfall on relatively small scale.  We cannot count the number of times we have sat in front of the radar, watched massive storm systems move into the area, headed directly towards us, only to see those same systems break apart just outside the College Station city limits, only to reform once the system reaches the other side of town.  This happens whether we are talking about Pacific moisture streaming up from across Mexico and the Rio Grande region, or Gulf moisture streaming up from Houston and Galveston, or with a Pacific cold front sliding in from the Northwest.

Likewise, the folk wisdom that if there is a trailer park in a town hit by a tornado, you can be sure the tornado will find it, has more truth to it than one might imagine.  Trailer parks, you see, are more likely to be on the outskirts of a town… and thanks to the urban heat island, that is also where storm systems are most likely to be.  The air over the heat island is hot and dry relative to the air in the neighboring environs; as a consequence, there is updraft and an outward force pushing against any incoming downdraft and incoming force.

Cool roofs help counter these effects by muting the initial warming quality of the urban surfaces.  Over twenty years ago now, the City of Atlanta started working with cooler technologies, and they are just one of dozens of communities where engineers have discovered that replacing blacktop roads with lighter colored materials can reduce urban temperatures by several degrees.  The difference between 100° and 97° may not sound like much to a Yankee, but to us at Myrtle’s it sounds like a pretty huge difference.

It’s the sort of thing 19th century farmers in Texas would have paid attention to, as well.  Barrington Farm doesn’t have a special roof, but I guarantee you in 1830s Texas, if they had the opportunity to use a roofing material that would have dropped the summertime temperature of their houses by any amount at all, they would have jumped on it – assuming we are only talking about 1830s Texas farmers not wearing corsets, that is; we can’t vouch for how they could possibly have jumped in those ridiculous clothes.

Anybody who doesn’t currently have a cool roof, you’ve been placed on notice – next Spring, we expect to see you climbing a ladder, carrying a big white bucket with a paint roller.

Keep cool, and

Happy farming!