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How to cool your home naturally

Staying cool inside your house when it is hot outside is a problem. The sun hammering down on our house creates indoor temperatures to increase to uncomfortable levels. Air conditioning provides some comfort. But costs of installing an air conditioning system and the electricity costs to keep it going can be high. Also, standard air units use refrigerants made of chlorine compounds, which are suspected contributors to global warming and the depletion of the ozone layer.

There are low cost alternatives that can help you stay cool while reducing dependency to conventional air conditioning.

Keeping Cool

Another way to keep a cool house is passive (or natural) cooling. Natural cooling uses non-mechanical techniques to maintain a reasonable home interior temperature.

The best way to cool your house is to prevent the heat from gathering up in the first place. The main source of heat gain is the suns rays being absorbed by your house through the walls, windows, and roof. Another source is heat-generating appliances in your house and air leakage.

Methods to prevent heat gain include reflecting the suns heat away from your home, blocking the heat, removing stored heat, and getting rid of heat generating sources in your house.

Reflecting The Heat

Dark-colored home exteriors absorb 70% to 90% of radiant energy from the sun’s rays that hits the house’s visible surfaces. Part of the absorbed energy is then flows into your house by conduction, creating heat gain. In contrast, light-colored surfaces will reflect most of the sun’s rays and heat away from your house.

4 factors affect heat accumulation in a house: internal heat gain, air leakage, solar heat gain, and temperature difference.

Roofs

Approximately 1/3 of the heat that builds up in your house comes in through the rooftop. It is hard to control with the standard roofing materials that are used today. For example, unlike most light-colored surface panels, even white fiberglass and asphalt shingles absorb 70% of the solar rays.

Applying a reflective coating to your current roof material is a good solution. You may find these coatings at your local lumberyard. They have both reflective and waterproof properties and are promoted primarily for trailer homes and RVs.

One type of coating is a white latex that you can applied over many standard roofing materials, such as fiberglass and asphalt shingles, metal, and tar paper. Most manufacturers will give you a five-year warranty on their products.

Another coating is asphalt based and contains aluminum particles and glass fibers. It can be applied to most metal and asphalt roofs. Because of its sticky surface, it attracts dust, which will reduce its reflective properties somewhat.

Yet another technique to reflect heat is to put a radiant barrier on the underside of your rooftop. A radiant barrier is a sheet of aluminum foil with a paper attached to its backing. When installed properly, a radiant barrier can reduce heat build up through your ceiling by about 1/4.

Radiant barriers are very easy to install. It doesn’t matter what direction the shiny surface is facing—up or down. But it is important you install it on the underside of your roof and not horizontally over the ceiling. The barrier must be facing an airspace.

You may want to install the barrier on a cool cloudy day for your own comfort. Use wood or plywood walking board planks over the ceiling joists for extra support. Warning: Don’t step between the ceiling joists, you may fall through the ceiling.

Attach the foil to the bottom or side of the rafters by stapling it, apply it by draping it from rafter to rafter. Don’t be concerned about a tight fit or small tears in the material; radiant transfer is not affected by the air movement. Staples should be no more than 2 to 3 inches apart to prevent air circulation from detaching or loosening the radiant barrier.

To make the installation permanent you can use a caulking gun and apply a thin bead of construction adhesive to the rafters along the seams of the radiant barrier.

Walls

Wall color does affect heat gain slightly, but not as much as roof color. Lighter colored walls will absorb heat less than dark exterior walls. Light colors will reduce the amount of damage on siding and other materials over time especially on the South, East and West sides.

Windows

Approximately 40% of the heat that builds up in your home comes in through your windows. One way to reduce this heat through the windows is to use a reflective coating on your glass. These special window coatings are usually plastic sheets treated with thin layers of metal or dyes. These coatings can also reduce damage to your curtains, furniture and carpeting over the long haul.

The two primary types of coatings include combination films and suncontrol films. Suncontrol coatings are best used for warmer climates because they can reflect up to 80% of the radiated heat from the sun. Many of these coatings are tinted, thus darkening the room.

Combination coatings allow more light into a house but they also let some radiated heat in and prevent interior heat from flowing out. These coatings are best for regions that have both cold and hot seasons. Study their differences carefully so that you choose the correct coating for your application. Note: Do not apply these coatings to south facing windows that you intend to use to increase heat gain in the winter.

This type of coating is applied to the interior panels of the glass. These coatings are best installed by professionals especially if you have several large panes to affix the film. A pro will give you a more aesthetically pleasing and durable window film.

Blocking Heat

Two very good ways to block heat are shading and insulation. A shading device blocks solar rays and absorbs or reflects the sun’s heat. Standard insulation will help save you money on mechanical cooling systems such as electric fans and air conditioners. It also helps to keep your home more comfortable.

Insulation

Weatherization measures-—such as weatherstripping, insulating, and caulking will help seal and protect your home against the sun’s rays while keeping out the cold winter air.

An attic is a great place to start insulating due to its enormous heat gain potential. Properly insulating an attic will protect the upper floors of your home. The type and installation of insulation will vary depending on your location. In most climates, you will want a minimum of R-30 insulation. In extremely cold winter climates, you may go as high as R-49. Check the DOE fact sheet in making this determination.

Wall insulation is less a concern for cooling as the attic insulation because attic temperatures get much hotter than outdoor temperatures. Floor insulation has almost no effect on cooling your home.

Although it is not a great contributor to heat gain, leakage around windows, doors, outlets, foundations and other cracks can be easily sealed with caulking and weatherstripping.

Shading

Proper shade planning for your home can reduce inside temperatures as much as 20°F. It can be done by use of trees and other vegetation.

Landscaping

Landscaping is a the best choice and most beautiful way to block the sun and shade your house. A well placed bush, tree, or vine can give you an effective shade and add to the beauty of your property. Try using native plant life while designing your landscaping. This will help with longevity and ease of care.

Deciduous trees that lose their leaves in the fall are most effective at reducing energy cost. If properly placed around a home, they provide great protection from the sun in the summer and permit winter sunlight to warm your home. Growth rate, branch spread, height and shape are all considerations in choosing a good tree for your yard. Vines are a quick way to create cooling and shading. Vines can shade windows or an entire side of a house. Local nurseries will know the best vines to use in your climate.

Planning Your Landscaping

Where you place plants is important when working out the landscaping for your house. Here are some suggestions to help gain the most in your planting.

1. Place your trees on the northwest-southwest and the northeast-southeast sides of your home. Unless of course you live in a climate where it is hot all year long, don’t plant trees directly to the south. Even bare branches of large deciduous trees can reduce the amount of the sun’s heat from reaching your home in the winter.
2. Plant shrubs and trees so that they can help direct breezes. Don’t place a thick line of evergreen trees or shrubs where they can block the flow of cooler air around or through them.
3. Try to set trellises away from your home to allow for air circulation and keep the vines from attaching to your home’s surfaces and damaging the exterior. By putting vegetation too close to your home you could trap heat and make the air around your home even hotter.
4. Be careful not to plant large bushes or trees where the roots can damage sewer lines, underground wires, septic tanks, or your home’s foundation.
5. Make sure you use plants that are native or can handle your local temperatures.

Along with shading, vines and trees create a cool micro-climate that drastically reduces the temperature in the surrounding area sometimes as much as 9° F. During the process of photosynthesis, lots of water vapor escapes through the leaves, cooling the passing air. Also the coarse and dark leaves absorb solar rays.

Try using low ground cover such as small plants, grass, and bushes. A grass covered yard can be 10° F cooler than bare lawn in the summertime. If you are in a semiarid or arid climate, use native ground coverage that require very little water.

Shading Devices

Both interior and exterior shades control heat build up. Exterior shades are generally better than interior shading because it blocks the sunlight before it gets into the windows. When making a device choice and where to use them, consider whether you would be willing to open and close them regularly or just use them for the hottest season. Ventilation is another consideration.

Exterior shading devices include louvers, shutters, awnings, rolling shutters and shades, and even solar screens. Awnings are very useful because they block the direct sun. They are generally made of metal or fabric and are attached above the windows and they extend down and out. If you properly install an awning it can reduce heat gain up to as much as 65% on south facing windows and up to 77% on east facing windows. A light colored awning will do double duty by reflecting sunlight as well.

Creating a gap between the side of your house and the top of the awning will help vent built up heat from under a solid surface awning. If you are in a cold winter climate, you probably want to remove awnings in the winter, or get retractable awnings, because you may want to take advantage of winter heat gain.

How far down the awning comes or the amount of drop you will want depends on which side of your house the window is located. An west or east facing window needs a drop of 65% to 75% of the window height. A south facing window will only need a drop of 45% to 60% for the same amount of shading. A pleasing angle to the eye for mounting an awning is usually around 45°. Make sure that the awning is out of the way of foot traffic if it is below 6′ 8″ off the ground.

You can use slatted awnings to reduce the disadvantage of loss of views that are common on east and west facing windows.

Louvers are attractive because they have adjustable slats that control the level of sun rays entering your house and can sometimes be adjusted from outside or inside your home. The slats can be horizontal or vertical. You can attach louvers to the exteriors of window frames.

Shutters are movable wooden or metal and when closed can keep sunlight out. Shutters are either solid or slatted with adjustable or fixed slats. Besides reducing heat, they can give security and privacy. Some shutters can even insulate windows when it is cold.

Rolling shutters will have a series of horizontal slats that will run down along a track. Rolling shades use a fabric material. These are generally the most costly shading options, but they work well and can provide more security. Many models of exterior rolling shutters or shades can be controlled from the inside. One disadvantage is that they can block all the light.

Solar screens look like standard window screens but they keep direct sunlight from getting into the window, cut glare, and block the light without blocking most views or reducing air flow. They can also provide privacy by restricting the views of the inside of your house from outside your home. Solar screens come in a bunch of colors and materials to compliment any house. Although there are do-it-yourself kits, these screens usually will not last as long as professionally installed setup.

Even though interior shading is not as effective as exterior, it is worth it if none of the the other methods or techniques are possible. There are many ways to block the sun from getting inside your home.

Curtains and draperies made of light colored, tightly woven, opaque fabrics reflect more sunlight than they let in. The tighter and closer to the wall the more it will prevent heat gain. Two layers of drapes are more effective insulation when it is either cold or hot outside.

Venetian blinds, although they are not as effective as drapes, they can be adjusted to let in light and air while reflecting the sun’s rays. Some venetian blinds come with a reflective coating and to be effective, the reflective surfaces must be facing the outdoors.

Most interior cellular (honeycombed) shades come with reflective mylar surfaces. But they block the natural light and restrict air flows.

Opaque roller shades are good when fully drawn but will block light and restrict air flows.

By opening windows at the highest and lowest points in your home it can create breezes.

Venting can help keep your attic cool. Place exhaust (static) vents high and intake (soffit) vents low .

Removing Built-Up Heat

Nothing feels nicer than a cool breeze on a hot day. Enticing cool air to enter your home forces the warm air to go out, keeping your home comfortably cool. However, this technique only works when the interior temperature is higher than the exterior temperature.

Natural ventilation can maintain indoor temperatures close to outside temperatures and help remove heat from your house. But you should only ventilate your home during the coolest parts of the night or day, and then seal off your home from the sunlight and hot air during the hottest times of the day.

Ventilation strategies should consider the climate you live in. Areas with very hot days and cool nights, you should let the night air into your home to help cool.

If you live in a climate with daytime breezes, open your windows on the side that the breeze is coming from and on the other side of the house. To encourage wholehouse ventilation, keep interior doors open. If you do not live in a location with consistent breezes, create them yourself by opening windows at the highest and lowest points in your home. This is a natural effect called “thermosiphoning,” or “chimney,” effect and can be taken even further by adding a vented skylight or clerestory.

If you live in a hot, humid climate where temperature changes between day and night are small, try to ventilate when the humidity is not very high.

Ventilating your attic will reduce the amount of heat gain, which will eventually work down into the main section of your home. Ventilated attics are usually 30°F cooler than unventilated. Properly placed and sized roof vents and louvers help prevent overheating and moisture buildup in your attic.

Minimizing Heat Generating Sources

Lights and household appliances, such as dishwashers, ovens, and dryers are ofter overlooked sources of heat gain in a home.

Use incandescent lamps only when necessary because the energy they use is put off as heat. Use daylight whenever possible to illuminate your home. Use compact fluorescent lamps if possible. They use around 75% less energy than incandescent lamps, and put out 90% less heat and you get the same amount of light.

A large number of household appliances can generate a lot of heat. You can try to use them in early morning or late evening when you can more easily tolerate the heat. Cook on a barbecue grill or even use a microwave, both choices use less energy than a gas or electric range and they don’t put out as much heat.

Water heaters, dryers, dishwashers and washers can generate large amounts of humidity and heat. Try sealing off your water heater and laundry room from the rest of the house.

Try to use the new more energy efficient appliances. They generate less heat and use less energy to operate. Use the EnergyGuide labels to make wise buying choices.

Saving Energy

By implementing any or all of these strategies you are going to help yourself and your environment. In conjunction with an air conditioning unit these strategies should help you save on your energy bills and reduce the wear on your a/c unit.

If using all of these strategies is not enough you may want to consider using some mechanical devices to aid in the cooling process. You can use fans and evaporative coolers they are usually cheaper to install and operate cheaper than air conditioning units.

Ceiling fans can make you feel like it is cooler. You can feel 4° F cooler with a fan on you. Evaporative coolers will use about 25% of the energy that a standard air conditioner will use.

Some utility companies offer rebates to people who use energy efficient appliances. You may want to check into that as another strategy.

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