Whole-House Fans

Improve Cooling and Conserve Energy with Whole House Fans

According to the EPA, there are several ways to improve cooling in residential buildings. The current trend in home building is toward energy efficiency and green construction. Knowing what types of money savers and environmentally friendly options to offer can give contractors more business:

• Insulation is the most obvious investment. Look for insulation with a high R-value (insulating capacity) to keep the attic cooler during warm weather. Note that it’s easier to install insulation during home building or roofing.
• Photovoltaic (PV) solar panels use light to generate power. PV systems are becoming more affordable, but check to see if there is enough harnessable solar energy in your area before installing.
• Solar hot water heaters use sunlight to heat water for home use. They can be used with a gas or electric back-up heater.
• Light-colored roofing materials can keep a house cooler in warm weather, saving homeowners money on cooling costs.
• Whole house fans help cool a home by drawing cool air in and exhausting hot air outside. Whole house fans offer huge savings to homeowners at one-tenth of the cost of running a central air conditioning unit. Whole house fans have been around for years and they’re a great way to cool a home, either as a supplement to air conditioning or alone. Consider the energy output of residential HVAC: a five-ton A/C can use over 6000 watts of electricity in one hour. Whole house attic fans use up to 800 watts per hour. This type of fan system makes sense when it comes to energy efficiency and money.

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Whole House Fans vs. Attic Fans

Whole house fans provide cooling by exhausting hot air from the attic and living spaces. They are sometimes confused with attic fans. Attic fans can help keep a house cooler, but they only remove hot air from attics.

Whole house fans are installed in the ceiling, in a central location of a home (or sometimes in a wall, but rarely so). They are located in a place where air can blow into the attic. Whole house fan blades are large and provide significant ventilation pressure to cool a house. This type of fan can exchange the air in a 2400-square foot home within five minutes, allowing homeowners to turn off A/C at night. In areas of low humidity, whole home cooling fans can work without A/C, even on the hottest days, to make a home comfortable.

Attic roof fans are smaller than whole house fans. They are designed to move air out of an attic only. They help cool a home by venting hot air from an attic space and take a considerable load off of A/C by keeping ceilings cooler. Both attic and whole house fans need to exhaust and take in air to work.

Be sure to install enough intake vents in the roof to avoid drawing air from inside the house, rather than from outdoors. Drawing air from indoors can overload an A/C unit and send energy costs sky high. Similarly, with whole house fans, installing enough exhaust vents through the roof is essential for efficient circulation. Failure to do so will keep fan blades from moving enough air.

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Whole House Fans and Noise

Whole house fans are a great alternative to air conditioning. They can be used at night when air conditioners are turned off, or they can be used alone. Using a whole house air movement fan alone can cool effectively when temperatures reach 82 degrees F and below, and windows can stay open to let fresh air in. Rather than install expensive air conditioning units, use a more eco-friendly, cost-efficient ventilation design to keep homes cool.

Some people object to whole house fans because of the noise they create. Whole house fans can be noisy at times, but this is due primarily to faulty design, construction, or installation:

• A good fan is a quiet fan, constructed to run without motor vibration or shutter rattle.
• Fan size is important in reducing noise. A larger fan, running at a lower speed, will generate less noise than a small, fast-spinning fan. Larger fan blades move more air. The point? Bigger really is better when it comes to fans.
• Along with size, weight can be an issue. A heavier fan will stay firmly in place with the force of its own weight.
• Another factor in fan noise is insulation. Be sure your fan is installed with foam strips or rubber mounting to keep the fan from sending noise through the framework of the house.
• High-quality shutters are heavier and prevent vanes from oscillating, opening, closing, then reopening.

Using a timer rather than a thermostat with a whole house fan will keep your fan from running when you aren’t prepared. Before running a fan, be sure to:

• Open windows
• Extinguish fire from the fireplace
• Turn of heating or air conditioning units

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Attic Fans for Savings

Anytime the temperature reaches 82 degrees F and above, you can rely on your attic fan to shave 30 percent off air conditioning costs. Attic fans exhaust hot attic air that can turn a home into a sauna. Without proper attic ventilation, rooftops, attics, and ceilings get super-heated, making internal temperatures soar. By drawing hot air out and allowing fresh air to come in, the hottest part of the house will stay cool, helping the rest of the house feel comfortable.

In construction, installing whole house attic fans creates an attractive incentive for homebuyers. For contractors and homeowners, retrofitting an attic fan makes sense, as the energy savings will make up for the cost of installation. Fan installation is also a great way to go green—fans lengthen the lifetime of roofing materials, keep attics dry in the winter, and help keep A/C emissions down.

To make the most of an attic fan, roof ventilation design requires careful consideration. Choose the fan based on manufacturer specifications for square footage in the attic space. For larger houses, two smaller fans might be recommended. Mount the fan(s) two feet down from the peak of the roof. Fans can also be mounted to gable ends.

If you use an existing vent to install the fan, there must be two additional vents for intake air—too little ventilation can keep the right amount of air from circulating. Do not install vents beyond manufacturer recommendation, as too much ventilation can cause rain and snow to leak into the attic. After installation, the fan will operate with a thermostat. It will run the fan when roof temperatures exceed thermostat settings. Optimal thermostat settings for roof fans is 90 to degrees F, depending on climate.

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The Whole House Fan: A Worthwhile Investment?

Whole house fans not only make houses and buildings more comfortable, they also safeguard your health by providing ventilation, cooling, and fresh air. Most houses are designed to be heated and cooled through a central heat and air system. They’re built to be airtight, with fresh air entering only through a mechanized system or by accident. Open windows and doors, cracks, leaks, and holes are responsible for most of the fresh outdoor air building occupants breathe when HVAC systems are in use.

Stale air could very well be the culprit for a number of health complaints from homeowners, office workers, and anyone who stays indoors for a prolonged period of time. Problems can arise from heat, mold, mildew, dust, and lack of clean air. Some of the symptoms include headaches, drowsiness, and respiratory problems. Most people are healthier when supplied with a direct source of fresh air from attic vents and open windows. Using a whole house exhaust fan ventilates and cools by drawing outdoor air into a home or building and exhausting stale air out in a ratio that’s healthy for building occupants.

Not only is ventilation good for your health, it’s also good for your house. Poor ventilation can cause attic temperatures to reach 160 degrees F or higher, which can reduce the structural integrity of a building, ruin insulation, destroy shingles, cause mold and mildew, and raise energy bills. Given that most homeowners view their homes as investments, it’s fair to say that proper ventilation can add value to a home (or, that poor ventilation can reduce the value of a home).

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When to Use a Whole House Fan

A whole house fan benefits building occupants by cooling a structure and exhausting stale air. It can be used in conjunction with A/C to reduce cooling costs, or alone in less humid regions of the country to create a more natural way to beat the heat. At just a fraction of the cost of A/C ($150 to $350 vs. $2,000 to $4,000), whole house fans can run at .01 to .05 cents per hour. Compare that to the .20 to .25 cents per hour it takes to cool with A/C.

Whole house fans work best when used at night, when outdoor air is cooler than warm indoor air. In high heat and humidity, run the A/C during the day. Once the temperature starts to drop for the evening, turn off the A/C, open the windows, and run the fan. Closing windows in unused rooms will increase cooling to more populated rooms of the house. The fan can be run during the day if temperatures are below 85 degrees F. If temperatures are predictable, a timer can be used to turn the fan on and off—just be sure to open windows before turning on the fan and close windows before running A/C.

Sometimes you can find a two-speed model that will allow ventilation on high speed for immediate cooling and low speed for gentle, quieter circulation. For sizing, it’s important to strike a balance between exhaust and air intake. Look for a design that will provide one square foot of attic ventilation for every 300 square feet of total attic space. You can also select a fan based on total home square footage x ceiling height (usually eight feet). The fan should deliver 1/2 to 1 times the amount of CFM (cubic feet per minute) at .1 inch static pressure (pressure exerted by air).

Since whole house fans can pull large quantities of air from a home, take care to avoid backdrafts in combustion appliances. Be sure to keep windows open to avoid accidents. Educate occupants on the use of the fan—let them know that the fan should only be turned on when at least two windows are open and A/C units are turned off. It is not recommended to use a thermostat to control a whole house fan.

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