Energy Efficiency

Claiborne Electric Co-op encourages its members to make wise use of electric energy. Louisiana's Electric Cooperatives, in conjunction with the LSU AgCenter, developed "A Guide to Energy Efficient Homes in Louisiana." This guide helps Louisiana Residents build an energy-efficient home, or assists them in making their existing home more energy efficient. The co-op has limited copies of this guide available in booklet form, but most of the information has been reproduced here for your convenience.

A Guide to Energy Efficient Homes in Louisiana

1. Introduction
2. Plan Efficiency
3. Insulation
4. Roof & Ceiling
5. Wall Strategy
6. Floor Strategy
7. Sun Protection
8. Infiltration
9. Attic Ventilation
10. Kitchen, Bath & Laundry Ventilation
11. Whole House Ventilation
12. Sizing Equipment
13. Equipment Efficiency
14. What is a Heat Pump?
15. Energy Loss Through Duct Walls
16. Thermostats
17. Install Spot Heaters in Baths
18. Utility Room
19. Water Heating
20. Select Energy Efficient Appliances
21. Lighting
22. Use Efficient Outdoor Lamps

Introduction

The following information will introduce you to the most modern standards of construction specifically designed for Louisiana's hot, humid climate. Such a home will have greater comfort, quality, convenience and value than conventional homes along with drastically lower utility costs. With the passing of abundant supplies of low-cost fuels and energy, it has become clear that although an energy efficient home may initially cost more, savings in utility costs can exceed the initial investment in two to five years. In fact, your utility bills can be about half that of a conventional home.

While the majority of professional homebuilders in Louisiana are quite naturally opposed to the imposition of mandatory standards for energy efficient home construction, they are not similarly opposed to the adoption of more energy efficient construction measures. In fact, the majority of professional homebuilders recognize and support the need to adopt such measures. One of the major reasons such measures have not been more widely adopted is the lack of reliable, easy to understand information.

Homebuilders and consumers are literally flooded with information about supposedly energy efficient construction measures. Much of this information may be contradictory and/or is not appropriate to the climate of Louisiana. Information developed in relation to climates where heating is the overriding energy concern is not applicable to the cooling oriented, hot-humid climate of Louisiana. Also, some information is designed to promote a particular product or a particular pet measure (such as solar) rather than being carefully considered in terms of overall economic feasibility in Louisiana.

Thus with little reliable, easy to understand information about energy efficient measures that are economically feasible for this climate, home-owners and home builders may tend to abandon the whole idea of energy efficient home construction even though they recognize the need for it. The objective of this guide is to provide residents of Louisiana with a simple, easy to understand description of reliable energy efficient construction measures that are specifically oriented to the unique climate of Louisiana.

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Plan Efficiency

At today's construction costs, few people can afford to build the sprawling, space-wasting home of the 1960's. But you need not settle for tiny bare-boned rooms or sacrifice quality and livability to get space you need if you know how to select or design a "space-efficient" home plan. Careful floor plan design or analysis can:

• Increase the value per square foot of a home, by eliminating wasted space and materials
• Make a home "feel" larger than it is
• Make a home more convenient and comfortable
• Create a nicer visual impact
• Save you thousands of dollars and enable you to afford larger rooms
• Save the monthly cost of heating and cooling wasted space

Minimize Total Conditioned Area

• Try to select or develop a house plan which packs the maximum livability into the minimum floor area. Avoid inefficient plans containing large amounts of corridor space or space that is wasted because it is arranged awkwardly and is difficult to utilize.
• Plan your traffic paths carefully for convenience to avoid disruptions and to minimize hall space. Place the main entrance at a central location to reduce the need for a long path to the rest of the home. Locate stairs to land at the center of the upper level to reduce the length of hallway needed to reach each room.
• Avoid unnecessarily high ceiling heights.
• Provide unconditioned living spaces such as screened porches or a deck. Ceiling fans can make these areas comfortable over a longer time span of the year.

Minimize Exterior Walls Facing East and West

A square or rectangular house shape will have less wall area per square foot of living area and therefore will have less heat gain or loss than more complex house shapes. Complex house shapes also cost more to build and require more insulation and better craftsmanship to achieve the same energy performance as simpler shapes.

Try to select or develop a floor plan that can be positioned with the long dimension walls facing north and south, and the short dimensions facing east and west. North and south facing walls can be protected from the sun with overhangs. East and west facing walls are often difficult to protect. This should be an important factor when selecting a building site.

If short east/west facing walls are difficult to achieve, the next best thing is to try to develop or choose a house plan which is approximately square because a square contains more (floor) area per unit of wall area than any other rectangular figure.

Face Glass South and North

Plan as much of the desired glass area as possible on the south side of the house. Because the vertical angle of the sun is lower in winter than in summer, south facing glass with a horizontal overhang will allow sunshine into the house in winter to reduce heating requirements while blocking it out in summer to minimize cooling loads.

Plan to have most of your remaining glass face north. North facing glass can be protected from solar gain in summer by placing shrubbery on the northeast and northwest sides of the house. Minimize glass facing east and (especially) west. In fact, if possible, plan to have no glass at all on the west wall. Any east glass should ideally consist of small high windows which are shaded mid-morning by roof overhang.

Try to select or develop a house plan with the glass openings grouped on the front and back of the house for a north-south oriented site or one with the openings grouped on the sides for an east-west oriented site. When there is a choice, north-south oriented sites are preferable.

In mid-summer, one square foot of unprotected, 1/8" sheet glass facing west will admit approximately 1,169 Btu's per day of solar heat alone. That is nearly three times more heat gain than through south facing glass:

Total Solar Heat Gain (Btu/Sq. Ft./Day)

• North Glass: 552 Btu's
• South Glass 450 Btu's
• East Glass 1,169 Btu's
• West Glass 1,169 Btu's

Group, Isolate and Zone Low Use Spaces

Many homes in Louisiana have spaces such as formal living rooms, formal dining rooms and guest rooms which are used only on rare occasions. The volume of the home which must be heated, cooled and lighted every day can be significantly reduced by grouping these low frequency use spaces together. Provide doors to isolate them from the more frequently used spaces of the house. Use dampers to supply these low use spaces with a very minimal amount of heating or cooling except on occasions when they are used. This strategy has become even more feasible with the advent of the zone controlled and variable speed heating and air conditioning units.

Group the bedrooms together and supply them with a separate heating and cooling system from the rest of the house. This way you can fully heat and cool only the sleeping zone at night and only the activity zone during the daytime.

The low use areas should be supplied with at least a minimum of heating and cooling to prevent excessive humidity problems and mildew.

Sun Protection

Cooling and dehumidification (rather than heating) are the largest energy users in most homes in Louisiana. When a home is exposed to the hot sun in this climate, two things may occur:

• The temperatures of the exterior surfaces of the roof and walls exposed to the sun may be as much as 100°F greater than the temperature of the inside air. This will increase the energy required for cooling.
• Solar heat passes directly through unshaded glass areas (even double or triple pane) and adds significantly to the interior heat gain (cooling load).

Use Trees, Plants and/or Shade Structures

Probably the most cost effective energy conservation measure in our climate is the use of strategically placed plants, particularly deciduous trees and vines, to block intense solar heat in summer, thereby reducing cooling loads. (Without shading, the surface of a west wall or a south roof can reach 150°F and 50 to 60 square feet of unshaded west glass can use up to one ton of air conditioning in summer from solar heat alone.)

Deciduous trees and vines are prefer-able because they provide protection from solar heat in summer and shed their leaves and admit solar heat in winter when it is beneficial.

• Use tall shade trees, close to the house on the south, southeast, and southwest, to block the sun from the roof in the middle of the day during summer.
• Covered porches and patios can also prove beneficial. The best location for a porch or patio is on the south side of the house because the winter sun will warm the floor and keep it dry. Summer sun will be blocked by the porch roof.

Protection from the sun on the west is the most important because, although the solar gain is approximately the same in the morning and afternoon, the afternoon gain comes on top of the heat build-up of the day. Evergreen shrubs and small shade trees may be used effectively here because they block the harsh, glaring sun as it rises and sets in the east and west. Evergreens on the north/ northeast and northwest wall also tend to block the cold winter wind.

Where the use of shade trees is impractical, consider using shading structures such as arbors and open, slat trellis structures with fast growing deciduous vines or solid, secondary roof structures. Surrounding porches, perhaps with louvered blinds, which are characteristic of the plantation houses of Louisiana, are the classic example of the use of secondary shading structures to minimize solar heat gain into the house.

Use Ground Cover, Avoid Unshaded Paving

• Avoid the use of unshaded paved areas (patios, terraces, driveways, and sidewalks) near the house because unshaded paved areas will both reflect solar heat onto the house and collect heat during the day and re-radiate it onto the house long after the sun has gone down.
• Ground surfaces near the edge of the house should be planted with ground cover to minimize reflected solar heat and air temperature.
• Try to use deciduous shade on the south, southeast and southwest sides because the reflected radiant heat and the re-radiated heat are desirable in winter.

Maximize Surface Reflectance

Consider white or light colored exterior walls and roofing because light colors tend to reflect radiant heat while dark colors tend to absorb it and transmit it by conduction into the house.

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Insulation

The amount of heat gain or loss which passes through the materials of a building shell in a given time by conduction is a function of three things:

• The area through which the heat passes
• The difference in temperature between the two sides of the material
• The thermal resistance (R-value) of the material.

Installing insulation in the shell of the house will reduce this heat gain or loss and result in large energy savings and much greater comfort.

Home insulation is available in many forms for specific applications. In making a choice for each application, consider the product's properties, advantages and disadvantages along with its installed cost per R-value for the area you need insulated. Do not compare costs based on thickness (inches) since each type of insulation has a different R-value per inch.

The most commonly available insulation products and their properties are summarized on the table below. Newer types and forms of insulation are entering the marketplace. Most noteworthy are insulations that are sprayed into open framewalls and provide an excellent barrier to air infiltration as well as increased R-value. These include sprayed cellulose, rock wool or foam products.

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Roof and Ceiling Strategy

When the outside air temperature is 95°F in summer, the air in an attic may reach temperatures of 160°F or higher, due to solar heat absorbed by the roof. Three methods to reduce this heat gain into the structure are:

• Provide adequate attic ventilation to reduce the attic temperature
• Shade the roof
• Install sufficient insulation above the ceiling.

Use R-30 in Ceiling

Many national recommendations, including those of insulation manufacturers, recommend less ceiling insulation than R-30. Such recommendations are based primarily on heating oriented considerations which decrease as one moves further south. The cooling oriented concern of heat gain in the south becomes more critical and accounts for larger percentages of a home's total annual energy consumption. Therefore, additional ceiling insulation becomes a cooling strategy. Summers in Louisiana can cause a well ventilated attic to reach 110°F-120°F. In a poorly vented attic, temperatures of 150°F-160°F are not unusual. Therefore, R-30 is recommended for ceiling insulation.

Because R-30 insulation is usually at least 9" thick (depending on the type of material used) a problem may be created at the attic wall line. Special care must be taken to avoid cutting off the air circulation from the soffit vents under the overhangs needed for adequate attic ventilation and yet avoid a hot spot caused by reducing the thickness of the attic insulation near the exterior walls. Baffles may be needed.

Thick insulation applied directly under the roof sheathing may cause sufficient heat build-up to cause deterioration of asphalt shingles. Careful roof design is needed to provide adequate air flow above the insulation to dissipate this heat.

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Wall Strategy

It is not unusual for the surface temperature of an unshaded west wall to reach 150°F in the summer in Louisiana due to absorbed solar heat. Therefore, you are actually insulating against an interior-exterior temperature difference of 75°F rather than the 20°F between interior-exterior air as normally assumed. That's why adequate levels of insulation are just as important in summer as in winter.

Use R-16 to R-19 in Wall Construction

There are basically two ways of obtaining R-16 or R-19 in exterior frame walls:

• Use 2x6 studs with R-19 insulation and conventional sheathing
• Use 2x4 studs with roll, sprayed cellulose or rock wool, or foam R-11 or R-13 insulation and R-5 to R-7 insulating sheathing. Proper installation of insulation is of critical importance. Time and care should be taken to make sure insulation is not compressed and all gaps are filled.

Insulate Knee Walls

Another critical area of concern are knee walls. Knee walls are interior walls located within the attic space of the home. Since the temperature difference between the attic air and the inside conditioned air can easily reach 75° in the summertime, these walls should be insulated to at least an R-25 level.

Use Insulated Exterior Doors

Technically, an exterior door is part of the wall. A 3'x6'8" door is 20 square feet of wall area. If the R-value of that door is significantly less than that of the remainder of the wall it can account for a significant amount of heat gain or loss. Conventional solid-core wood exterior doors have very little R-value, whereas, doors with an insulated core can have an R-value as high as 15.

Use Double Pane Glass

Windows, fixed glass, glass doors and other glass areas are also technically part of the wall area. Again, if the R-value of these areas is extremely low (as it is for single pane glass), it can account for a large amount of conductive heat gain or loss. Therefore, double pane glass is recommended in new construction. (It should be pointed out that retrofit storm windows are not as cost effective in the deep south as in the north because we have a far lower difference of temperature between inside and outside air in winter.)

In addition to using insulated glass, limit the total glass area to ten percent (10%) of the floor area. While double pane insulated glass doubles the R-value of single pane, it still only provides an R-value of about 2. If you want to exceed the ten percent glass area rule, it may be cost effective to invest in low-E windows designed especially for a warm climate (not the low-E windows meant for winter-dominated climates). Low-E and other glazing technologies now produce windows with R-3 to R-8 values.

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Floor Strategy

Use R-11 to R-19 Under Floors

Houses built on raised framed floors or with unheated/uncooled crawl spaces should have the floors insulated with R-11 to R-19 insulation. Not only is this measure cost effective in terms of saving in direct heat loss and gain, but people tend to turn the heat up in winter if the floor is cold, even if the air temperature in the house is acceptable.

Slab Construction

Slab construction in Louisiana normally does not require any type of insulation. This is because temperatures do not remain low enough to cause a frost line which would cause significant heat loss through the slab. However, it can be cost effective (especially in north Louisiana) to include R-8 rigid foam insulation around the perimeter of the foundation.

Vapor Barriers

Vapor barriers attached to building materials should be placed toward the warm side of the ceiling, walls and floor. Their purpose is to prevent humidity from migrating into the insulation from the area of warmer temperature (and higher humidity) and condensing in the insulation, thus reducing its effectiveness.

There has been much debate about which is the "warm" side in Louisiana's climate. Recent research indicates that in Louisiana's warm, humid climate, a vapor barrier is not absolutely necessary, but if used, is best located on the outside of the walls. Foil backed or extruded polystyrene exterior sheathings can serve as an exterior vapor barrier, particularly if the seams are taped. Interior plastic sheeting vapor barriers should not be used in this climate zone. In general, a vapor barrier is not needed at the ceiling, but good attic ventilation is important year-round for moisture control.

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Sun Protection

Solar heat passes directly through any clear material such as glass almost as if it was not there. Double or even triple pane glass offers no significant protection against solar heat gain. The rays of the sun and reflected rays must be blocked in order to provide effective protection. Interior shading devices such as venetian blinds or lined drapes can reflect a small part of the heat rays back out through the glass, but a large part of the heat stays inside and contributes to the cooling load.

Without protection, both east and west glass admits more than twice the summer solar heat gain of north or south glass. Moreover, it is much easier to protect (shade) glass on the north and south sides than on the east and west. Western solar heat gain is more critical because it comes on top of daily heat buildup.

In Louisiana, solar heat gain through unprotected glass is a major cause of energy usage. Adequate protection from solar gain will accomplish about twice the annual energy savings achieved by double pane glass. Methods to reduce solar heat gain are as follows:

• Avoid east and especially west glass
• Use plants and/or shading structures to block summer solar heat
• Use horizontal overhangs or shade structures over glass
• Use solar screens, treated glass or solar film.

Use South Glass With Horizontal Overhang

Adequately protected south-facing glass has year-round benefits.Glass openings oriented toward the south can be effectively protected from direct solar gain from about March through September while admitting sun from September to March. The overhang should also extend about the same distance on either side of the glass opening. The sun is at a much lower angle in winter than it is in summer. Therefore, south facing glass, with an overhang about half as wide as the vertical distance from the overhang to the glass sill, will admit sun in winter and block it in summer.

Use Solar Screens

Solar screens are a very inexpensive and easy do-it-yourself way to control solar gain through windows and can be used in place of conventional insect screens. Solar screens can provide about 70% blockage of solar heat gain and are highly cost effective. These can be removed in winter for the greatest year-round energy savings.

Use Treated Glass

Several manufacturers market special glass designed to provide varying degrees of protection against solar heat. Tinted glass reflects and absorbs more of the sun's rays than clear glass. This means that while heat gain is reduced so is light. Glass with a lower shading coefficient and higher daylight trans-mittance is the most desirable.

Low-E windows have a thin, transparent coating sprayed on one surface of the glass. The low-E (low emissivity) surface slows the flow of heat through the glass. Most low-E windows are double paned, with the coating on one of the inner surfaces so it is not exposed. For our climate, this coating should be on the inside of the exterior glass to reflect outside heat better. Low-E windows with the coating on the inside glass (the most prevalent) are not cost-effective in our warm climate. They block winter heat loss better than summer heat gain. Although warm-climate low-E windows are more expensive than ordinary double pane glass, they will generally prove cost effective.

Window Film

Several types of solar film are on the market which are designed to be applied to ordinary glass and provide some degree of protection. Although they are usually used as an afterthought remedy, they can prove cost effective on otherwise unprotected glass.

Solar control films are designed to keep out solar gain and glare. Silver, mirror-like reflective films are much more effective than the tinted, non-reflective films. They block nearly as much solar gain as do solar screens.

A newer type of solar control film appears non-reflective but provides almost as much benefit as mirror film and lets more visible light through. These advantages, however, come with a much higher price tag than do the mirror or tinted films.

Another category of films is designed to provide some solar control and also reduce heat loss through the glass in winter. These "low-E", "heat-saving" or "combination" films are available with various levels of reflectivity, tint, cost, etc. To choose the appropriate window film, look for three primary factors:

• The shading coefficient, which is the percentage of solar gain it admits as compared to clear glass (the lower the number, the less solar gain it admits)
• The visible light transmittance, which is the percentage of light (not heat) that passes through it (clear glass is about 85%)
• The U-value, which is the ability of a material to conduct heat (the lower, the better to reduce winter heat loss).

Use Awnings or Exterior Shutters

Where roof overhang is inadequate, awnings or exterior louvered shutters can reduce summer heat gain and provide shading flexibility. They also add architectural richness to a home.

Use Reflective Interior Window Treatments

Interior sun control methods include venetian blinds, shades, draperies, etc. They can increase your comfort by blocking direct sunlight, but they do not prevent solar heat from entering the room. Consequently, they do not offer the same opportunity for savings as exterior shading devices.

Still, interior window treatments with special reflective backings do reflect some solar energy back out the window. So, when you need new blinds, shades or drapery liners, choose those with reflective or at least white backings.

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Infiltration

According to research data, between 25% and 40% of the heat gain and heat loss in a typical house results from leakage of air through the shell of the house. In other words, the typical house leaks air like a sieve. In Louisiana, outside air also carries a large amount of unwanted humidity which must be removed by the air conditioning system. This infiltration can also be a source of drafts in winter.

Place Sealant Under Sole Plate

Studies indicate that the largest single source of infiltration (about 25%) is the gap between the bottom of the wall and the floor slab. During construction, this can be taken care of very easily, simply by placing a sealant along the edges of the slab before the sole plate is put down. This gap is very difficult to seal effectively after construction.

Seal Around Plumbing Openings and All Electrical Outlets

The second largest source of infiltration is electrical wall outlets and switches (about 20%). Because electrical and plumbing lines are usually installed with little consideration about the thermal integrity of the building shell and because these lines are often run through large holes in the framing, the attic, the sheathing, etc., they offer ideal paths for air infiltration. This infiltration can be significantly reduced by:

• Caulking, taping and/or applying an expanding foam sealant around all electrical and plumbing holes in the exterior sheathing, the framing, the attic, etc. Even holes in the interior walls should be sealed
• Installing foam rubber gaskets presently on the market behind all electrical outlet plates and switchplates.

Choose Tight-Sealing Doors and Windows

Seven percent (7%) of the infiltration is around exterior doors and six percent (6%) is at the windows. A significant part of this infiltration can be stopped by selecting doors and windows with good quality weatherstripping and thresholds on all exterior hinged doors.

Sliding patio doors should be avoided in an energy efficient home, but if they must be used, select models having an infiltration rating of less than 10 cfm per linear foot of crack between door and frame. Swing patio doors, which look like French doors, are a much better alternative to sliding glass doors.

Seal Gaps in Framing

An expanding foam sealant is recommended to seal all gaps in the framing including corners, interior T-joints, around the rough framing of windows and doors and any other uninsulated gaps.

Additional ways to reduce air infiltration through walls are taping the seams of foam sheathing or using a house wrap material under the siding.

Plug Other Leaks

Other infiltration sources are a collection of smaller ones:

• Vent Fans: 6%
• Fireplace: 6%
• Recessed Lights: 4%
• Dryer Vents: 3%
• Others: 2%
• Total: 21%

Together, these sources account for 21% of air leaks. Be aware that even though each one represents a small energy leak, together they are significant. Vent fans should always be fitted with a tight sealing damper. Recessed lights waste energy because of both infiltration and the insulation gap they create in the ceiling. (Fire codes require that insulation not be placed over them and sometimes not within three inches of their location.)

Fireplaces

In a home incorporating the other features recommended here, a conventional fireplace will almost certainly represent a net energy waste rather than a gain. Furthermore, if you successfully plug all the sources of infiltration, a conventional fireplace may be dangerous because it could backdraft combustion pollutants or starve the air inside of oxygen as a result of the absence of a source of fresh air for combustion.

Assuming that you will not be successful in plugging all the infiltration holes, a conventional fireplace will create a negative pressure in the home and thus pull in a significant amount of additional infiltration to make up for the air going up the chimney. In winter, that additional infiltration is cold air and more energy will be required to heat it than will be gained from the fireplace.

Then how did grandma get by with no heating source other than a fireplace? Because, given no other heat source, the radiant heat from a fireplace was better than nothing to heat people. But a conventional fireplace is not and never was an efficient way to heat a home. However, a fireplace does add to the market value of the home, so if you want a fireplace for this reason,

1. Recognize that a typical fireplace is for purposes of romantic nostalgia, rather than efficient heating, and
2. Install one of the newer types of fireplaces on the market which incorporate:
• A fresh air duct directly to the fireplace to provide combustion air from the attic or outdoors
• Glass doors
• A secondary recirculating system.

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Attic Ventilation

The amount of heat gain through the ceiling can be lessened by reducing the temperature difference above and below it. If the outside air temperature is 95°F, a well vented attic will be around 110°F compared to 160°F in a poorly vented one. That means a temperature difference of 35°F (for an interior temperature of 75°F) for a well vented attic rather than a temperature difference of 85°F or more for a poorly vented one. Methods to properly ventilate an attic are as follows:

Continuous Ridge and Soffit Vents-the Best Method

Adequate attic ventilation in the Louisiana climate means an air flow of at least 1.5 cubic feet of air per minute per square foot of attic floor area. This should preferably be accomplished by a gravity venting system (convection) rather than by a mechanical system (exhaust fan) because the electricity to run the fan will offset much of the energy savings gained by the venting.

The best gravity vent system is a combination of continuous soffit vents and a continuous ridge vent. Ridge vents are marketed by several manufacturers or they may be made by a sheet metal fabricator. It is important that the roof design have enough length of ridge to allow an adequate air flow.

Gravity/Wind Driven Turbine Vents

Another alternative is a gravity/wind driven turbine outlet vent with continuous soffit vents. However, these tend not to work as well as ridge vents because there is frequently insufficient wind to drive them in much of Louisiana, and also because the number and size of turbines needed may present appearance problems which are objectionable to some home owners.

Power Ventilators

A power ventilator is a motor-driven fan that is controlled by a thermostat located either in the gable area or near the peak of the roof. These ventilators use electricity and the mechanical parts wear out and often break, so the cost of using them offsets much of the reduction in electricity costs for the cooling system.

Gable Vents

Gable vents can be beneficial if they are facing prevailing wind directions to insure cross ventilation. They are available in a wide range of sizes.

Reminders:

• Remember sufficient soffit vents are necessary regardless of whether you use the continuous ridge vent, turbine vent or power ventilator.
• Do not combine different types of roof (exhaust) vents.

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Kitchen, Bath and Laundry Ventilation

Food preparation, laundry, and bathing often add as much as 30 pounds of water (in the form of vapor) a day to the humidity of a home. At 1,070 Btu's per pound, that means that this internally generated humidity alone requires about 32,000 Btu's/day of air conditioning to remove it by condensation, without any corresponding cooling. Furthermore, the presence of humidity slows down the cooling of the body, thus causing people to compensate by turning down the thermostat, using even more air conditioning.

Use Exhaust Fans

Exhaust fans in the kitchen and bath reduce the problem with less energy than the air conditioning unit, even though some cool air is lost in the process.

• Use a 300-500 cfm fan over the range, which exhausts to the outside
• Use a 50-70 cfm fan in bath areas and in the laundry area
• Be sure fans are equipped with tight sealing dampers and properly sized ducts
• Use these fans only when excess heat and/or humidity is being produced

Make sure the clothes dryer is vented to the outside.

If the house is very tightly sealed against infiltration, it may be necessary to provide fresh-air intake ducts for these exhaust fans to work properly. If so, such ducts should also be equipped with tight sealing dampers. However, we suspect that such precautions are usually not necessary in typical construction.

Whole House Ventilation

It is unlikely that there is a way that homes in Louisiana can be made comfortable in mid-summer without some kind of air conditioning. However, periods in spring and fall when air conditioning is not needed can be extended at least a month to six weeks by providing sufficient air movement and good cross-ventilation.

Opening windows alone may not adequately ventilate the home when there is no consistent breeze. Mechanical movement of the air through and in the home is usually needed.

Use Ceiling Fans

While the old ceiling fans (which were traditional in Louisiana before air conditioning) actually add a little heat, they do help cool people by increasing air movement and thus aiding the body's evaporative cooling system. As such, they can also be used to extend the period in spring and fall when air conditioning is not essential. In the summer, the use of ceiling fans may allow the homeowner to raise the thermostat setting a few degrees, reducing cooling costs.

Do Not Use Continuous Fan on Air Conditioning System

One might reason that if increased air movement in the home aids the body's evaporative cooling and reduces the need for air conditioning, the fan on the air conditioning system should be run continuously.

That may be valid in hot, dry climates, but not in Louisiana. The reason is that water vapor condenses on the indoor air conditioning coil while the compressor is running and is drained off slowly as condensate. If the compressor cycles off and the fan continues to run, the condensed water vapor on the coil (and in the collection pan located under the coil) is picked up by the air passing over the coil and recirculated back into the home, this significantly raising the humidity level in the home.

This problem is especially critical when the compressor is cycled off for a high percentage of the time due to equipment oversizing. Unfortunately, that is exactly when the temptation is greatest to use continuous fan. The real answer to the problem is proper sizing of equipment, not continuous fan usage.

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