Below this intro is an interesting article that was published in Popular Science magazine a number of years ago. It is clearly American, but some of the measures can be applied anywhere. Hence looking at it here.
Natural cooling goes hand in hand with passive solar design, as we don’t want to naturally heat a property to find that it overheats to an extent requiring us to use air conditioning to keep it cool, so negating much of its carbon-replacement goal.
Dan Seitz, the author of the Popular Science article, mentions a natural cooling method that I have neglected to mention in the past – the cooling effect of plants. And well done to him for picking this up! Many plants thrive on moisture – like palms, but they don’t produce moisture vapour. Neither do they absorb moisture or ‘dry’ the air sufficient for any kind of climatic effect inside a normal dwelling or office. What they do is provide shade to surfaces that themselves will help cool the air. As I have said elsewhere materials of high thermal mass have the interesting property of storing and radiating heat if they are in the sun, but acting to cool if they are in shade. The closest example is an old thick-walled cottage or church on a hot day. Go inside and the temperature drops like a stone. Why? It is all that thermal mass in shade that cools the air. This is what plants do – they can provide shade to materials of high thermal mass – but you have to have the thermal mass there in the first place. So, having abundant plants will not act to cool much in, say, a timber framed structure.
What Dan doesn’t mention are the lessons in natural cooling handed down to us by generations of Arab and Muslim builders. The use of materials of high thermal mass, courtyarding, and the use of water – notably fountains – to provide natural cooling – has been used for thousands of years in such places as the Alhambra in Spain, and from Tripoli to Teheran and well beyond. The cooling effect of high thermal mass isn’t mentioned in the following article at all, which is most surprising. However the article gives an interesting perspective of what natural cooling means to Americans.
It is the peoples who have inhabited the hottest places on the earth – those that have done so since before the advent of oil and gas – that one should study when looking at natural cooling. What the ancients used for natural cooling, from the Navajo to the Moghuls were:
- Materials of high thermal mass for walls and floors. Using the cooling properties of thermal mass in shade.
- Deep solar shading from roofs or other structures.
- Cross ventilation via openings on the opposite sides of buildings. Some ancients also used wind-scoops to supercharge cross ventilation.
- Stack ventilation. Hot air rising through draft ‘chimneys’ or up staircases or other vertical structures with openings above them. Some ancients built whole towns of such hot air exhaust stacks.
- Shading plants. Plants shading materials of high thermal mass, and shading water.
- Water in shade. Particularly moving water. Water sprayed into the air is a form of aircon anyway.
Imagine a hot hot day outside. You walk into a courtyard with roofs all around it forming a surrounding veranda there. In the middle of the courtyard is a group of palms and maybe a wooden trellis surrounding a pool with a fountain splashing water over stones. Imagine the cooling effect of these things, and you are actually imagining one of the courtyards of the Alhambra, built AD1200. Nothing is new.
As previously mentioned natural cooling goes hand in hand with solar passive heating. They are both free of charge and available to all who use them without the need for manufactured machinery. So they are both inherently democratic. Solarity practice both simultaneously. So, part of any of our designs might well be an extended roof or trellis over a pool, or plants and pools drawn right up to a building or within it, to cool it naturally.
Here is the article:
Strategies for chilling out – by Dan Seitz
Great for cooling air indoors…not so great for the environment.
Air conditioning makes it much easier to work through the summer. In fact, it’s an important tool for public health. But running your AC also increases your utility bill, drives up pollution by forcing power plants to burn more fossil fuels, and makes hot nights even hotter.
If you’re ecologically minded, you can look into installing renewable power for your house or buying energy from renewable sources. But whether you care about the environment or just hate the giant bill at the end of the month, one easy fix is to use less air conditioning.
Outside the house, regulate your body temperature and drink lots of water. Inside, you can do a lot to drive down the temperature before you flip on the AC.
Heat and humidity
When going without air conditioning, you need to consider two factors: the overall heat and the humidity. On a hot day, sweating is a surprisingly effective method of returning your body to its core temperature. As the droplets on your skin transition from liquid to gas, their evaporation pulls warmth away from your body, cooling the blood underneath your skin, which goes back to your body’s core, reducing your overall temperature.
Moisture in the air, however, stalls this process. In meteorological terms, humidity is the amount of water vapor the atmosphere can hold. The more humid it is, the less space there is for your sweat to evaporate. And without your body’s natural chilling system, everything feels hotter. Just to rub it in, hot air can hold more water than cold air, so humidity is likely be higher in warmer months.
What this boils down to is that keeping cool is a matter of getting as much sweat as possible to evaporate off your skin. To do that, you need to keep relatively dry air moving across your body. And your home’s setup can help you do that.
Take advantage of your architecture
Chilling out your environment is largely a matter of working with convection, the tendency of hot air to rise. The best way to cool off a room is to pull heat up and out. As a bonus, proper ventilation also controls humidity, so that gross sticky feeling can fly away too.
First, take a look at the construction of your house. Hot summers aren’t a new problem for housebuilders, and older houses may have design features you can use.
For example, “shotgun” houses, which are one room wide and extend back, create cross breezes through screen doors and open windows. A cross breeze helps pull away hot air, making a home feel more comfortable. You can enhance these breezes with electric fans (more on that later).
Houses with large wraparound porches also maintain lower temperatures. That’s because the external structure absorbs the direct sunlight, allowing the inner rooms to avoid overheating.
In some cases, cooling features might be blocked off. Cupolas, for example, were originally designed to give hot air a place to escape a home. But when builders installed central air in older homes, they might have turned those chimneys into attics. If you clear any blocked vents or spaces in your attic, you may notice (and enjoy) better air circulation.
Keep out sunlight
A lot of warmth comes into your home via sunlight. In individual rooms, you should control these rays with blackout curtains or shades. If you still want sunlight, open the curtains on windows that don’t face the sun directly; this allows indirect sunlight to filter in.
The color of the curtains’ outward-facing side also matters. We see color because that particular wavelength of light bounces off an object. Because heat radiates as infrared light, “hot” colors like red, orange, and yellow will deflect the most warmth.
Of course, not everyone enjoys living like a vampire. If you need more direct light, consider solar screens and window tints instead of curtains. These treatments can remove certain wavelengths of radiation while letting others in.
Another useful technique, if you have a green thumb, is houseplants. Certain types of houseplants—including xerophytes like cacti, aloe, and succulents; “air plants” like bromeliads; and any greenery that doesn’t require frequent watering—get their water from the air around them. If you grow them in windows or window boxes, they’ll sponge up a bit of humidity while blocking some of the sunlight. However, not all greenery thrives in muggy conditions, so ask at your local garden center to find the ideal plants.
Place your fans
Fans don’t cool the air, per se. Instead, they set air in motion, which helps clear away your body’s evaporated perspiration. So you should place them to maximize air flow.
To start, place electric fans in your windows (if they open). Try to set the blowers as high up as possible, ideally in the top sash. They should face outward to suck out hot air out of the room. If you have a two story house, concentrate your fans in the upper story’s windows (or at least lower those windows’ top sashes), where they can help convection pull hot air up and away.
Ceiling fans can also help. If you have them, make sure they rotate counterclockwise, to best take advantage of convection and pull colder air upward.
In addition to enhancing convection, fans can set up a cross breeze. If you’re between these flows of air, you’ll feel more comfortable. To establish cross breezes, don’t think in just two dimensions. A fan in the door will move air, and another in the window will do the same—but if you set them up strategically, the door fan can blow cool air onto you while the window fan pulls hot air away.
Spend a little time designing a “fan network” in your house. This should keep air moving through the rooms so you have constant flow.
When things feel miserably humid, a few dehumidifiers can make a room much more comfortable. A dehumidifier really is the only machine for the job—although wall unit ACs can remove humidity, science works against them.
To draw water out of the air, you must reduce it to the dew point, the temperature at which water transitions from gas to liquid. The condensers on the back of your air conditioner can indeed go below the dew point; if you see water dripping out of an air conditioner, that’s exactly what’s happening. The issue is that the dew point isn’t a fixed number, but instead depends heavily on both humidity and outdoor temperature.
As a rule of thumb, the higher the humidity, the closer the dew point is to the outdoor temperature. At 80°F and 75 percent humidity, for example, the dew point is 71°F. But at 52 percent humidity, it’s 59°F. Even if your window unit can cool the room to that point, you will be shiveringly uncomfortable.
So unless it’s extremely hot, extremely humid, or you’re really unlucky and it’s both, don’t rely on the wall unit to pull mugginess from the air. For the truly miserable days, get a dehumidifier.
Shut down appliances
On a blazing day, you’ll want to limit the sources of heat in your home. In the kitchen, instead of using your hot oven, try cooking food in separate appliances, such as crock pots or microwaves, that don’t generate such high temps. Or just stick to uncooked meals like salads.
Beyond cooking, other appliances can also produce unnecessary heat. For example, you should wash dishes by hand instead of running the dishwasher. In the bathroom, leave blow drying and other hot grooming practices off your personal regimen—at least for the summer.
Time your AC use
These techniques won’t cool down the house quite as much as a central air system or a few well-placed wall units, but they will make your house more comfortable. And you can still use these systems in concert with air conditioning: They can lower the temperature of your home so that when you do crank on the AC, you require less of it—and you waste less power.
When you finally turn on the air conditioning, remember to use it efficiently. You don’t want to waste that cold rush, so check your windows for leaks, which you can seal up with weather stripping. If your home has a garage or breezeway, try to enter and leave your house through those locations instead of letting chill air escape when you open a door directly outside.
Just like hot air rises, cold air sinks—and you need to control this tendency. For example, in any room where you have AC, cover the heating vents to prevent cold air from sinking to the basement. You should also avoid wasting energy on rooms where the climate doesn’t matter. So close the doors of the empty spare bedroom and the storage closet while the air is running.
With the units themselves, you should install devices that have energy saver modes. Some of these will automatically shut off when the air reaches a goal temperature; others have timers you can configure so the units will leave the house at a warmer level or shut off entirely when no one’s home.
If you have a central air system, help it along with a smart thermostat such as a Nest. These smart devices will learn your AC habits over time. Then they can modulate the air flow to save energy.
Whether you want to save the planet, save the power grid, or just save a few bucks, you can avoid overheating—with minimal AC.
Well, his heart is clearly in the right place, or nearly!