Design with climate improvements are traditional and modern solar design features which keep your home comfortable with a minimum of mechanical heating and cooling. These were more common in homes built before the days of central heating and air conditioning. These include: shade tree, high reflective roof, east/west home orientation, good solar access, south windows with overhang, cooling with slab, low-to- high natural ventilation, and ceiling fan.
A ceiling fan creates a “wind chill” factor that allows people (and your pets) to remain cool at temperatures above 75F. The fan breeze strips away hot air from the surface of your skin, and enhances evaporative cooling of your sweat.
A ceiling fan uses energy a lot less energy than an air conditioner.
It enables the homeowner to set the thermostat at a higher setting, and reduce the number of hours your energy hog of an air conditioner has to run.
Shading with trees, shrubs and vines is a relatively inexpensive was to keep you home cool, Shading is most crucial on east- and west-facing windows, which get the most sunshine. South windows may also benefit from shade.
Shade trees not only protect your home from sun, but they also act as air conditioners. Water taken up from the soil evaporates in the leaves to create a cooling effect. Trees also help maintain watershed balance by assisting in rain absorption.
An overhang over a south-facing window blocks the overhead summer sun. This keeps the interior of the home cool and reduces the air conditioning load.
In winter, the low-angle sun rays penetrate the window to deliver light and warmth to the interior. In climate zones which require winter heating, south windows lower heating bills.
Homes can use pre-existing concrete slabs for cooling. By day, the slab absorbs heat from the air, reducing the number of hours the air conditioner has to run.
By night the slab is cooled by the cool soil below and by cool night air from windows and screen doors. The cooling effect is enhanced if the slab is not insulated by rugs.
The most efficient way to cool a house is to exhaust hot air at a high location while letting cool air in from a lower location. This is because less dense hot air rises like a hot air balloon, and cool air rushes in to take its place.
Low-high double hung windows allow this option. An attic window or vent is even more effective.
Your siding and roof do hard duty protecting your home 365/24 against sun and rain. When it comes time to replace or paint roofs and siding, you have a golden opportunity to upgrade their performance for appearance, energy conservation, and moisture protection. Part of this equation is protect the protectors: to choose exterior coatings with own version of sunscreens and water repellents which protect them and make them long-lasting.
It is common for a conventional roof to heat up to 150o F., in the sun , while a high reflective roof remains a relatively cool 100o F. This cooling effect keeps heat from entering the attic, and gives your air conditioner a well-deserved rest. A high reflective roof plus a sealed attic can reduce your air conditioning bill more than 30 percent.
Reflecting Solar Heat Gain: Damaging UV rays and high temperatures from sunlight greatly stress exterior materials. The roofing industry has expended much effort has been to develop paints and coatings which keep themselves, and your home cool by reflecting sunlight. A good example is the rubber-like bright white elastomeric coatings used on roofs. These reflect up to three-quarters of the sun’s energy. They reflect so much solar glare that they are banned from neighborhoods near some airports as a navigation hazard.
Roof and siding with white coatings can reduce cooling loads in the range of 15 to 30%. The Florida Solar Energy Center found white metal roofs, white EPDM, white concrete tile and white cement shingle to provide excellent cool-roof performance. The maximum impact of white roofs is on homes with little attic insulation.
Besides putting on a white color, paints can also keep themselves cool by the use of metal oxide pigments. These pigments reflect solar energy in the non-visible infra-red part of the solar spectrum. They offer two advantages: 1) You can formulate attractive, colored paints still have high solar reflectivity, compared to a conventional paint with the same color. 2) They have double the lifespans of ordinary paints (12 to 15 years) in part because they are as thick and more adhesive than regular paints. The cooling effect of the paint is probably also a factor in their durability.
Protecting Masonry Walls: Another example of a high performance exterior coating is a silicate-based paint used instead of limewash on masonry walls. Silicates give concrete its strength and are found in many naturally occurring rock minerals. Tough silicate-based paints are also used for waterproofing of basement walls.
Like limewash, silicate paint it has low toxicity and a traditional appearance. However, its lifespan is 15 years, several times that of limewash. The silicate protects the masonry surface. It repels liquid water, but “breathes” to let water vapor escape. Trapped water can damage walls and grow mold.
Conclusion: The simple choice of a white material, paint, or covering for roofs and siding can substantially reduce cooling load. Another cool choice is colored paints or coverings pigmented with metal oxides. Choose a high quality material which has a long-life under difficult exterior conditions. The extra amount you might pay for a cool, high quality material can yield a high return on investment.
An east/west home orientation is very advantageous for energy efficiency and human comfort. It minimizes window and façade areas facing east and west. These exposures suffer blazing sun in the summer which can overheat rooms.
On the other hand, and east/west orientation maximizes the south facade which gathers welcome sunlight in the winter. South windows with overhangs block high-angle summer sun, but admit low-angle winter sun.
Ideal solar access may be found on sunny, south-facing roof and facades which are not shaded by trees or neighboring buildings. Strong sunshine is necessary for solar collectors to do their work of heating water or air or generating electricity. Solar collectors may also be sited on top of sunny carports or ground-level locations.
Access to sunshine is also necessary for south windows with overhangs, which heat your home in the winter. In some cases, deciduous shade trees are planted to the south of a home to filter summer sun. When autumn leaves fall, the sun penetrates through the south windows.
In the Southern Hemisphere, good solar access is to be found on north-facing roofs and facades.
A whole house fan is a cost-effective substitute for air conditioning. Whole house fans, combined with ceiling fans and other circulating fans, can provide acceptable summer comfort for many families, even in hot weather.
The conventional whole house fan, installed on the attic floor, sucks hot air from the house interior and exhausts it out the attic vents or roof. Cooler air is brought in via windows and screen doors. ( A whole house fan is sometimes confused with an “attic” fan which draws hot air from the attic alone.)
An existing home HVAC system, with heating/cooling air ducts, can be retrofitted to serve the same function. Cool outside air it comes into the home via a fresh-air duct. It then is distributed via existing ducts throughout the home; simultaneously, hot air is exhausted outside. One big advantage of a home HVAC system, over a conventional whole house fan, is its capacity to filter the air.
Another economical HVAC configuration is to feed cool outside air into the air conditioning cycle for further cooling. This technique is useful when the outside air is cooler than the inside air, but not cool and dry enough for indoor comfort. Under these conditions, conditioning the outside air will be more energy efficient than conditioning internally recirculated air.
Whole house cooling will not work on the many hot humid days in Florida and the Gulf Coast when air conditioning is needed. Nevertheless, according to U.S. Department of Energy, a whole house fan can substitute for an air conditioner most of the year in most climates.
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