News, music, movies & restaurants from the editors of the Silicon Valley's #1 weekly newspaper.
Serving San Jose, Palo Alto, Los Gatos, Campbell, Sunnyvale, Mountain View, Fremont & nearby cities.

News and Features
April 25-May 2, 2007

home | metro santa cruz index | features | santa cruz | feature story

Green paint

One technique for reducing home energy use: Phosphorescent paint's active ingredient, strontium aluminate, has been tested repeatedly for environmental safety and found virtually nontoxic. The paint stores energy from light--either natural or artificial--and releases it when darkness falls, for up to 12 hours after significant light exposure.

Paint It Green

By Paul Wagner

Humans have been painting things even since before we were human. Yes, the earliest known cave paintings--Australia's brightly-colored Gwion Gwion images of tall, slim and fashionably dressed human figures, socializing in groups--are only 50,000 years old. And Homo sapiens emerged some 100,000 years before that.

But those paintings--let alone the famed later cave art in France--aren't the earliest evidence of artistic activities. The earliest are actually pigment-grinding tools, and ground pigments themselves, found at Twin Rivers, Zambia, in caves, for painting purposes. They're between 350,000 and 400,000 years old.

Which means that Homo erectus painted, too. Which in turn means that the desire to decorate and adorn has passed, uninterrupted, through our genetic code since before modern humanity first appeared.

And that desire has proven a strong one. Determined painters first made colors out of blood, milk, egg, minerals, colored soil and animal waste--anything to produce the hue they imagined.

Dynastic Egyptians made several types of blue glass just for the purpose of crushing it, grinding it up and using it as paint color. The Aztecs pulverized up to a million female cochineal beetles in a season to produce paintable reds, while the Romans, always compulsively ambitious, crushed 4 million mollusks at a time to produce a pound of their signature purple. Indians fed their cows mangoes and then collected and concentrated the resulting urine to produce bright yellows, while others dried out the ink sacs of squid to get rich browns. Indian Red was made from "colcothar of vitriol" (we didn't dare ask). The Canaanites and Phoenicians, hot after dark royal purple-reds, got them by squeezing the mucus out of marine snails.

And for good reason: well-chosen colors mightily impress. As the Cultural Affairs Bureau of PingTung County, Taiwan, points out about its museum's Ming/Ching period pottery, "It's color made up a lot of golden powder. The effect of the sense of sight is thick-colored resplendent gorgeous and able to sufficiently appear the manner of emperor." When's the last time any of us sufficiently appeared the manner of emperor? That's what dabbing on gold can do.

Hence the early searches for pigments with which to produce colorful paints. Later searches, even more extreme, have continued--all the way up to today's convincing metallics and eye-rolling fluorescents--uninterrupted for millennia.

Unfortunately, paint-related disasters have occurred uninterruptedly, as well. Arsenic and lead appeared in hundreds of ancient pigments. Orpiment (a bright yellow) and Realgar (a reddish-orange), both based on arsenic sulphide, poisoned male and female eye-paint wearers and artists alike since the time of pyramid-era Egypt. Emerald Green, alternately known as Paris Green because Parisians also used it to poison rats, and Cobalt Violet, used as recently as the Impressionist era, were also laced with arsenic. So were many bright green pigments produced in India and Australia.

Some more recent formulations have proved no better to human or animal health. Tributylin (TBT), a marine paint ingredient that prevents barnacles and algae from growing on ships' hulls (one of a class of paints known as "anti-fouling coatings") chips off in icy conditions, and when it does, and floats downward and dissolves in seawater, it sterilizes many species of marine mammals. Its recent replacement, a copper-based formula, has turned out to be just as toxic.

Mercury, another of the leading universal toxins, crept its way into many paints for a century, only replaced in the 1990s by less toxic alternative ingredients. Radium, a component of the World War I luminescent military paint product "Undark," helped cause anemia, jaw necrosis and bone fractures among women brushing it onto glow-in-the-dark watch dials in the 1920s. And we have not yet begun to get the lead out of the atmosphere a quarter-century after banning it from paints. It's still there chipping and peeling away in older paint jobs, breaking down into dust, blowing in the breeze and entering nearly every home in the industrialized world, even if in small amounts.

If we are, therefore, going to get and give the delights of painting without collecting or spreading disaster, it's good to know a bit about paints and the choices available before following our apparent genetic mandate to go forth and adorn. And that's what this article is about: how to avoid hurting, and actually improve, one's own, others' and the planet's health through informed painting.

We can't of course cover every aspect of the subject, so we're going to skip over the information any paint store willingly provides, such as how to use primers (types of paint that make surfaces ready for the main action) and proper surface preparation (colloquially known as "prep"). We'll also touch only minimally on the complaints involving chemistry ("FILLED with dangerous chemicals!") because there are tens of thousands of articles that already expand, very fully, on the examples of toxicity listed above.

And, regrettably, we're not going to be able to cover the hundreds of newly emerging brands and formulations that have appeared within the last few years to address environmental concerns, the number of which have multiplied remarkably within the last year alone. Not only would doing so take up the entire issue of this publication, but many are new enough that their claims are unevaluated, reformulations and refinements continually appear, and their technology--whether deliberately ancient low-tech or consciously high-tech (as in the case of vinyl and ceramic paints)--is still untested for either durability or safety.

In short, we're going to have to restrict this article, despite having used and been very impressed with some of the brand new paints, to what most people will usually find in most paint stores.

For the determined and curious, please use the principles covered here, but go beyond them in searching through the excellent group of local eco-stores, take a look at's Environmentally Preferred Purchasing Program, and check out paint safety ratings at There is a new world of possibilities beyond what we can possibly run over here.

What we are going to focus on in this article is how well-considered painting, even using common products, can not only decorate, not only protect, but actually improve the function of rooms and homes by helping to stabilize temperature, increase healthy air circulation, improve home safety, reduce the overall use of chemical compounds for cleaning, and cut energy use, thus lowering overall atmospheric pollution levels. With modern paints, thoughtfully applied, that can all be accomplished, and in minimal time.

And it all begins with knowing a bit about what paint actually is.

Perhaps the most elegant definition of paint comes from the National Parks Service: "Paint is a dispersion of small solid particles, usually crystalline, in a liquid medium."

And to most of us, that's how paint appears: bits of pigment (color) floating in goo (formerly known as the carrier or resin; in modern lingo, the binder). Anyone who's opened a long-neglected can of still-wet paint has seen the two: pigment sitting contentedly on the bottom, nearly clear binder resting comfortably on top.

There are, however, two more components of paint: the thinner and the additives. And those primarily contain the environmental risks, or benefits, Let's take the four in order.

Pigments, the color components, are for the most part as formulated today just color, and nothing to worry about. No longer made from mollusks, urine, charcoal and the like, they're instead manufactured from ground-down, relatively innocuous plastics. This is one rare case in which natural, at least on the consumer level, is not necessarily better; modern synthetic pigments offer few of the dangers that many older organic pigments did.

True, some artists' formulae still contain bits of lead, cadmium, chromium, manganese dioxide and, in some blue pigments, cobalt, but those are rarely if ever components of room or house paint.

Even some of the most suspicious-looking contemporary metallic pigments contain very little actual metal; the thin sheetlike natural mineral mica, for which there are no identified health issues unless inhaled as dust, provides the glow.

In short, if we don't snort or inhale most modern pigments, they're pretty close to entirely safe.

Binders, the goo in which the pigments swim, have historically been, and remain, nontoxic for the most part. In the tempera paints we as children glopped onto construction paper, the binder was egg. In what were once called "distemper" paints, the binder was common glue.

Historically, outside of those two, the most popular binders have been olive and other vegetable oils and seed oils. Linseed oil, for example, historically the most widely used binder, is made from flax. Even the petroleum-based binders--oils and the more recent alkyds (synthetic versions of oils), objectionable as they may be holistically, were and are fairly safe compounds.

Thinners--the part of paint that evaporates as it dries--are another story. Thinners are the source of most common significant health and environmental problems associated with paint.

That's because as paint dries, it, like any drying thing, has to release something into the air to do so. When that's water, little damage arises. When it's other than water, chemicals are released.

And those chemicals released, collectively known as solvents, can be grossly damaging to both breathing life forms and to the atmosphere itself. The worst, in general, are volatile organic compounds, or VOCs--compounds of carbon which, when evaporating, hit sunlight and promptly form lingering ozone, one of smog's most significant components.

In addition, VOCs are respiratory, eye and skin irritants. And as a nasty bonus, they disrupt the nervous system, often leading to headaches, nausea and muscle weakness.

Given that VOCs are already 10 times as present in indoor air as outdoor, simply from building materials and daily human activities, the hundredfold increase in VOCs while painting is not good news for those breathing them in. And we continue to breathe them in after finishing, because the more volatile continue to evaporate, even if at a low level--a process called off-gassing.

Nor are they good for the atmosphere. In fact, solvents released into the air from painting constituted some 9 percent of VOCs released into the earth's atmosphere--a release level second only to that from internal combustion engines--until just a few years ago. The EPA cracked down in 1992, but we still have lots of cans of old paint which we open, use, and in using, release the older, higher levels of VOCs.

That's one reason to take older paint to household hazardous waste facilities at landfills, and start home projects with newer, less solvent-heavy paints. If you're going to follow current trends and recycle paints for further use, please do so thoughtfully, and avoid introducing decades-old, high-solvent paint back into the consumption cycle.

Additives--the fourth common component of paints--are both potentially the most toxic, and in other cases the most helpful, to health and environment.

We've already mentioned the disaster of adding lead, used until a few decades ago to quicken drying, resist moisture and extend durability of paints. Lead could do all that because it's a fundamentally inert compound that helped paint resist corrosive interactions. Inert compounds, however, when introduced to organic life forms, tend to make them inert, too: brains get slow; people die. So the tradeoff was paint projects that lasted longer than some of their appliers. Copper, tin, nickel and other additives are not much better.

Ironically, though, additives also can give current, safer paints some of the more compelling environmental advantages now available. So the general rule is: read labels, and look for the additives you want without carrying home the others.

Now, what kinds of formulations do these four components come in? There are essentially, to put it broadly, two types: those that release and clean up with water, and those that release and clean up with solvents.

Water-based paints contain pigments floating in binders of lime, clay, milk and most commonly, "latex." There's no actual latex, in the sense of rubber, in these popular and widely available formulations; the goo just looked like liquid rubber, so paint makers gave it that nickname, and it stuck. The actual binders are vinyl and acrylic compounds. More acrylic equals higher quality.

Water-based commercial latex and latex-acrylic paints do contain small proportions of solvents but less and less as time goes by. The others, such as clay paints, contain far less solvent content, and in some cases, none. One relatively new development among water-based paints is vegetable-oil paints, which offer the toughness of oil paint but still clean up with water. Overall, water-based paints release only around 27 percent as much VOCs as oil-based.

Solvent-based paints. The second kind of common formulation is paint that contains and cleans up with solvents--turpentine, paint thinner, etc. Most are oil or alkyd (oils modified to bind more effectively) formulations. Their solvent content makes them approximately four times as VOC-laden.

This might indicate, on first thought, that using water-based paints is environmentally superior to using oil-based versions. That's not, though, necessarily so.

Oil-based paints, while releasing solvents, often offer tougher surfaces and in many cases far outlast water-based paints, which means that over the life of a home, applying longer-lasting oil-based paints may end up cutting the eventual chemical burden on the environment more than using shorter-lived water-based ones.

In addition, there are certain conditions in which using solvent-thinner paints might do a far better job of protecting home dwellers, and the air mass, from the release of lead and other compounds. More on that later.

Finally, let's talk about gloss. Flat (also known as matte) paint has a high pigment to binder ratio--about 55 percent to 45 percent. This means that the dried, hard bits of ground pigments will attempt to poke out of the binder after drying, producing a rough surface and bouncing light hitting the dried paint in so many directions that there's virtually no sheen to the surface. That's why they look flat.

Eggshell has a bit less binder; satin or semigloss even less, and gloss and high-gloss only around 20 percent.

At that point, the high proportion of binder so buries the pigment that the dried paint will be mostly shine. The color will still be solid, but the surface will be so smooth that light will bounce directly from the surface. Hence the gleam.

Because most surfaces in need of painting are imperfect, paint buyers tend to automatically go for flat paint that won't show the bumps and grinds, and also reflexively go for water-based paint with its easy cleanup. It all seems cleaner and quicker.

That, as we will see, ain't necessarily so.

With that knowledge, we're now ready to paint our rooms and homes in an environmentally conscious way, which involves two steps.

The first is to do the least damage possible. And there is quite a bit of damage done by overuse of paint. The National Association of Homebuilders, in examining the longevity of various components of U.S. households, found that even though well-chosen interior paints last an average of 15 years before they need recoating, the average American householder paints at least one or two rooms again every two years. That's a lot of paint.

Now, no matter how little painting we do, all of it involves using up environmental resources--even using no-VOC paint involves pouring hundreds of gallons of water down the drain over the course of a large job to clean brushes and spills--we cannot directly achieve the Fifth Zen Patriarch's prime ethical directive to "First, do no harm."

What we can do, though, is to balance for that by sparing the environment in the long run. Consider it a coatings-based analog of purchasing carbon credits.

The main tactic in achieving this is reduction. Using as little paint in the first place, employing as small a volume of water and solvent as possible when cleaning up, and using the most durable paints so that we use the lowest amount of water and cleaning compounds in the long run, are all environmentally responsible practices. Here are some ways to do those:

First: avoid ever using paint as filler. If there's a gap between woodwork and wall, caulk it. If there's a large ding in the wall, fill it. If there's a mini pothole in a concrete, linoleum, tile or wood floor, pour self-leveling compound into it. If there's a set of ragged holes, use auto body filler (Bondo is the most common brand). Do these all a few days before painting to make sure they're dry and in the shape you want them.

Don't those, though, release smelly solvents, and therefore, VOCs? Yes, they do. From a small tube or can. With a small opening or top. ONCE. That's a lot less chemical release than painting a gap, hole, dent or other imperfection five or six times. And the paint job will look better, and therefore the temptation to get out the paint can again eight months later will likely not arise nearly as soon.

Second: think long and hard before automatically choosing the ever-popular flat paints. As noted above, they get their dull, imperfection-hiding characteristics by producing rough surfaces.

That means, in turn, that they pick up and hold dirt, fingerprints and grease, as well as products of air pollution--cooking odors, smoke, lead dust, spores and microbes--more easily. Which means more frequent scrubbing, especially for allergy sufferers, which, over the life of the paint, significantly increases the liquid volume of water and cleansers you'll use for maintenance, especially on exterior surfaces.

Given that pumping water uses some 30 percent of the electricity generated in California, cutting water use cuts electrical generation and therefore the emission of greenhouse gases.

Additionally, since rougher flat-paint surfaces induce friction in all objects interacting with them, they'll eat away more at the sponges and brushes you'll use to scrub them, and they'll they peel off and show old colors underneath more easily. Especially around high-touch, frequently scrubbed surfaces, such as those around light switches. And when they peel, or wear, or abrade, out comes the paint can again. For those reasons, flat paints are, unless you absolutely must use them to prevent glare, the worst environmental choice one can make when painting virtually any surface. They use up more environmental resources, long term, than any other kind of paint. I, personally, haven't used them for nearly a decade, for that very reason, and haven't missed them once.

Another way to cut paint use: when choosing paint, be careful of barely tolerable color choices that you'll soon want to paint over. Four-year-old children might love that Barney purple, but will they love it when they're 7? Ten? Thirteen? One can easily quadruple or quintuple one's paint use by choosing colors that become nerve-wracking soon after. Children will often like shades a few tones less vivid if given the choice, and so will most adults. The point here is not to play it safe, but to plan long-term to minimize use.

The same principle of minimizing long term use applies when choosing between water-based and oil/alkyd-based paints.

Because the odor levels and clean up rituals involving water-based paints are so much more pleasant than dealing with the smelly solvents involved in using oils, most paint purchasers skip the oil and alkyd aisle and immediately reach for latex or other water-based products. And usually, that's a very good choice, especially if they're semigloss or gloss.

There are, however, exceptions, especially when it comes to paints with hard, virtually impervious surfaces such as enamels.

While water-based paint manufacturers have, every year for at least three decades--usually just in time for spring/summer painting season--crowed that "water-based paints, once inferior In durability and stability to oils, have now caught up!"--for some kinds of paints, it's usually simply not true.

There's little doubt that some manufacturer, somewhere, can honestly claim that "our Otherworldly Yellow Special Hard-Surface Formula outperformed every oil paint" on some use or other. But overall, most water-based enamels you'll see when wandering through paint stores simply don't last. Put them on that door frame people regularly grasp while turning a corner and it will require repainting far more frequently than it will if you use oil-based enamels.

Oil and alkyd paints also do a far better job of sealing moisture in or keeping it out of walls. They also stand up to the inevitable scraping that occurs when moving things from one room to another and stay intact through repeated scrubbing. In environments featuring heavy moisture, constant use and frequent cleaning (such as kitchens and bathrooms) oils are still superior overall.

Vegetable-oil-based paints, which clean up with water and therefore smell less than traditional oils but harden more than water-based paints, are a good, environmentally balanced choice.

The other category where oils still shine is in floor surfaces. Most water-based floor paints are, to put it mildly, Gaia-awful. One locally owned store, in fact, held a special event to unveil a highly reputed manufacturer's new water-based floor paint, and found it so thin, runny and inadequate in coverage that the employees ended up shutting down the demo and sending out apologies to its customers, via newsletter, for having taken their time to witness an embarrassing failure. Use oils. They work.

The final case in which it's wise to pick oil-based paints over water-based is when covering older oil paint in areas, especially exterior, subject to significant changes in moisture or temperature levels, including surfaces bathing in direct sunlight.

The reason to brush exterior oil, rather than exterior water-based paints, on top of older exterior oil is the two kinds of paints dry, and maintain their surface structures, very differently.

Oil-based paints' thinners evaporate, and then they continue to dry by oxidation. They interact with air to pull oxygen out of it and form hard surfaces--actually, a kind of rusting that produces a yellowish sheen over time. Their surfaces grow harder and tighter over time, and continue to, for the life of the paint. This is why you'll often see old oil surfaces still clean, shiny and capable of taking hard whacks with no damage, and with only occasional cracks. Think of century-old Turkish coffee houses with walls still emblazoned with their original coat of paint.

Latex and latex/acrylic paints as well (as some other water-based paints), on the other hand, evaporate and then continue to dry by coalescing. As moisture continues to escape, the particles pull closer together, forming a film which remains partially flexible in shape and size.

So what happens when oil paint is brushed onto the wood siding? The wood, being absorbent, expands and contracts with moisture and temperature, and the ever-hardening oil paint covering it segues in and out as best it can. So far, so good. But put another layer of flexible material--latex paint--on the outer side of the oil paint, and now it's got two surfaces flexing around it (think of an old, grayed, weathered board sticking up between two bending willows on a windy plain) and eventually it'll dramatically crack.

If you've seen huge curving peels of flat paint peeling away in stiff sheets on the sides of houses painted just a few years ago, that's most likely what happened: someone walked into a paint store, bought exterior latex/acrylic, and slapped it on top of old oil paint. Lesson: use oil, not latex, on top of oil.

Using these techniques together--preparing surfaces well, using glossier-surface paints, choosing colors for long-term enjoyment, and employing oils when appropriate--can cut paint use, painting frequency, and overall resources used immensely. In one case, the EPA found that a town using these approaches during a renovation cut its paint use over the course of the project by 78 percent and it looked far better years later. And every one of us can do the same.

And now, we get to the fun part; namely, how to use paints to not only minimize damage to but actually positively improve our own environment and that of the planet.

Let's start with how the thoughtful use of color can cut home energy use.

It's well known that light shades reflect light, and dark shades absorb light, and therefore, in each case, reflect or absorb heat. How much they absorb is, outside of pure black and white, far less known. Few would guess, for example, that medium-shade yellows and medium-shade blues share virtually identical reflectance and absorption values.

But they do., an environmental coalition, offers an online chart of the reflection/absorption ratio of virtually all common types of paint colors, and it's an eye-opener.

Let's cover it briefly. All paints (in fact, all solid colors) have a measurable Light Reflectance Value, or LRV; it's the vague equivalent of light temperature ratings of light bulbs. The LRV rating of most paint colors are usually noted on paint-color samples, and virtually always, on paint cans.

A high LRV, near 100, means that a color reflects lots of light. A low one, near zero, means it absorbs most of it. For all practical purposes, the real range is not zero to 100, but more like 5 to 85. Regardless, it's a dramatic range. And it is unrelated to intensity. A nauseatingly vivid orange might have the same reflectance value as a pea-green. LRV measures only light bounce, not perceived presence.

Now, how much difference does that single factor--reflectance--make in how much energy, such as lighting--we building occupants use?

An immense difference. Here's just one example, which is so telling that we're going to quote it fully, from an EPA-funded project:

"In several recent school and office projects in Pennsylvania a 25 percent reduction in the number of light fixtures was achieved simply by selecting a slightly different shade of paint for interior walls.

"A minor increase in the paint light reflectance value (LRV) from .68 (68 percent) to .74 (74 percent) eliminated 25 percent of the lights in classrooms and open office spaces. This reduced not only the first cost of the lighting and electrical system, but also reduced lighting energy use for the life of the building.

"But that is not all. The 25 percent reduction in the number of light fixtures resulted in a further 25 percent reduction in the amount of heat given off by lights--which reduced the overall building cooling load. This reduced the HVAC system size and first cost, and subsequently reduced the energy used by the HVAC system for the life of the building."

In other words, lightening up the interior paint color by just 6 percent lowered lighting use by 25 percent, and heating, ventilation and cooling (HVAC) use remarkably. For decades.

This is why one rule of green painting, as cited by the magazine Architectural Record, is:

"Opt for light-colored surfaces wherever possible. Inside, they will reduce lighting needs. Outside, they will lower the need for cooling energy by reducing solar gain."

Now, as in all cases in thoughtful environmental practice, there are exceptions. If you live in an older, uninsulated house, you may want to paint some interior walls which get direct sunlight during the day a dark, low-LRV color so that they absorb light during the day, store it as heat, and radiate it back at night. The difference won't be earth-shaking, but may well be noticeable.

In fact, a good technique for conserving heat, where one needs to, is to paint ceilings, exterior walls (which in uninsulated homes won't store heat for long anyway) and any painted floors the lightest, most reflective color possible, and interior sun-catching walls the darkest color possible. This way, light bounces around from surface to surface and eventually lands on the dark wall, which absorbs the energy and releases it during colder hours. This is also helpful to visually impaired, people, who depend in great part on highly contrasting reflectance values to help find their way around.

And in moisture-prone homes, which most local homes are, there's a subtle health benefit to this reflectance variation, too. By deliberately inducing a several-degree higher temperature in just one wall, one also induces a convective cycle: air hitting the wall heats up, floats upward to the ceiling, pushes ceiling air down the other wall and across the floor, and the cycle continues. This constant subtle air motion inhibits the growth of mildew, and thus helps keep even fully contained air fresher and of more breathable quality.

In general, though, with that singles exception, the lighter the interior colors we use the better. Dark interiors, filled with muted beiges and browns, may feel earthy and therefore philosophically natural, but they're not--as your eyes will tell you when you go outdoors and the natural sunlight blinds them.

Let's extend this principle to outdoor painted surfaces. If there's heat buildup indoors during warmer seasons, that can also often be handled with lighter colored exterior paint; that of a higher LRV, which reflects energy away so that the building doesn't absorb it. This also benefits the longevity of many kinds of siding, especially metal sidings, and vinyl window frames. Darker, less reflective paints will, on hot days, cause enough absorption of energy that metal sidings and vinyl frames may begin to buckle within just a few years. So lighter is better there, too.

And buildings aren't the only objects that respond to this lightening effect. If you've got a dark beige or gray concrete driveway on the northern side of a home, applying light concrete paint can significantly brighten, and slightly warm, the nearby rooms inside. "What I wanted to do was to paint sunlight on the side of a house," once commented 20th century artist Edward Hopper. Well, you can.

Another place that can often use lightening up: porches and stairs. A light color on the surfaces of exits and entrances will not only increase nighttime safety, but reflect enough ambient light and moonlight to make artificial light unnecessary many nights of the year, helping restore naturally dark skies and the beauty of visible stars.

Paying attention to reflectance is most important, though, on roofs. It's shocking how many homes across the nation, and even across the warmer parts of our own county, feature black, dark brown, dark red, dark green or dark blue roofs on their tops, and air conditioners sticking out of their eye-level windows. There is a direct relationship between the two: dark roofs absorb heat, and A/C units dispel it. Paint the first a light color, and the latter will no longer be needed most days of the year.

Again, let's cite just how dramatic the difference is. Lawrence Labs at Berkeley measured several nearby roof temperatures on a sunlit 55-degree day a few years ago, and here, as reported in their "Heat Islands" summary, is what they found: "Roof covered with black acrylic paint, 142 degrees Fahrenheit. Clay terra cotta tile : 112 degrees Fahrenheit. White acrylic paint: 74 degrees Fahrenheit." A black roof, in short, doubled the temperature.

So if heat is a problem in your home, take a look at the roof, and if necessary, get up there and paint it white, and cut cooling system use--again from the "Heat Islands" study--by up to 23 percent.

Unless you're reading this in Sedona, Ariz., in which case you're forbidden, under its planning rules, to do that. "A white or very light color, while logical to reflect the summer heat, is quite distracting and unpleasant. The amount of money saved on energy conserved is not worth causing pain to those viewing from higher vantage points."

No comment on that could possibly be adequate, so let's not dwell. Let's instead look at how to intensify the energy savings covered above--savings produced by the intelligent use of color reflectance and absorption--even further, using it to cut heating and cooling bills not just subtly, but dramatically. And here, we enter the world of helpful paint additives.

The specific additives we're talking about are ceramics; yes, the same materials that make up most bathroom tiles; durable, hard-surfaced and virtually impervious to moisture, mold and wear and tear, at least on their surfaces.

Some 20 years or so ago, a group of NASA workers wondered whether the exterior ceramic tiles that offer freakishly effective insulation to hurtling spacecraft might be adapted for more common use. They went to work and what they came up with were ceramic microspheres, which constitute--let's quote NASA's technical library itself--"in effect, a 'mini thermos bottle,' " which, it notes, acts "as a barrier to heat by reflecting it away from the protected surface."

Such as roofs. And outer doors of southern-facing uninsulated garages, which can rise to 140 degrees in summertime. And small, sunny-side rooms in general.

Pour a jar of tiny microspheres into that light-colored paint, stir it up, brush it on the outer surface of the roof or garage door or room, and guess what? The surfaces reject heat far more efficiently. Uninsulated garages fall from 140 degrees Fahrenheit to 80 degrees F.ahrenheit, Roof temperatures decrease even more dramatically than with white paint alone.

And here's the other part: since paints containing ceramic microsphere additive "push heat from any surface, we can also use them indoors to keep heat in. Add them to ceiling paints and far less heat will escape into the ceiling. And so on.

Nor are walls, roofs and floors the only recipients of the temperature stability that insulating paints can offer. To quote NASA again, they also help prolong the life of "steam pipes and fittings, metal buildings ... cold storage facilities (walk-in coolers and freezers), delivery trucks, buses, mobile and modular homes, and RVs and campers ... they also provide waterproof surfaces that cut down on moisture in the trailers, keeping the electronic components better protected from the environment." Pretty darn good.

So how do ceramic microspheres, of which there are around a dozen brands available as pour-in additives, accomplish this? Well, being hollow, they bob toward the outsides of painted surfaces, horizontal or vertical, and come to rest between the pigment (adding a milky tone; take this into account when using them) and the drying binder. Heat approaches, and they push it back, causing it to re-enter the atmosphere when the surface is outdoors; if indoors, they reflect it back into the room. Brush insulating paint on a cold interior wall, and after it dries, more heat will stay in the house.

A word, though, about expectations: as with all passive energy conservation techniques, the benefits of heat reflectivity (like those of using light reflectance) vary tremendously with the intensity of difference involved. Manufacturers have been caught claiming that a thin coat of insulated paint will produce "the equivalent of R-19 insulation." In doing so, they are grossly misrepresenting.

Using insulating paint to reflect heat away from a fully sunlit roof--a fairly extreme condition--can reduce its temperature by 50 degrees Fahrenheit. But using the same paint indoors in a partially lit, already significantly temperature-controlled room will produce only a 10 percent or so difference. Still, a 10 percent difference in cold weather is enough to cut heat use significantly, and with it, the contribution of one's home to petroleum production, electric production and greenhouse gas emissions.

Finally, let's cover one more technique for reducing home energy use, and that's with a kind of fun novelty paint one can use to reduce night lighting: phosphorescent paint. Not fluorescent paint, which is the kind that radiates auras under black lights, but phosphorescent. Different subcategory.

These relatively new phosphorescent paints are an entirely different formulation than the radium paints of nearly a century ago, and much superior to the zinc sulfide, glow-for-12-minutes substitutes that replaced them. Having an active ingredient of strontium aluminate, which has been tested repeatedly for environmental safety and found virtually nontoxic (unless massively breathed in as powder) to species from rabbits to river bass, this paint does one simple thing: it stores energy from light--either natural or artificial--and releases it when darkness falls. It does so for up to 12 hours after significant light exposure. In other words, it glows all night.

The Federal Aviation Administration has tested glow paints for use in airplane cabin power failures, and found that as long as the paint had sufficient prior exposure to light through cabin windows, passengers were able to find their way out of darkened cabins quickly and safely just by following the glow-painted guideways. So they work.

And how can they help at home?

They can reflect the edges of steps--either the tops of risers, or the outer edges, or both. Light up exterior porch railings and interior grab bars. Help one find mechanical, unlighted light switches. Signal a landing at the top or bottom of stairs. Give a warning, when painted onto the thin edges of that dark dining room table one is always running into, as to where it is. Indicate door frames. Knobs. Keyholes. Key hangers. In darkness, in power outages or when one does not wish to disturb others by turning on lights, phosphorescent paint can help one make one's say silently through the darker hours, with only the use of stored solar energy.

These, then, are a few of the ways in which we can use the warm-weather ritual of painting, carried on for the last 400 millennia, to make daily life more pleasant and our contribution toward it more sustainable. "Painting is the grandchild of nature; it is related to God," said Rembrandt. How related is up to us.

Send a letter to the editor about this story.