Most people don’t know what an attic fan is or what it does. Knowing what an attic fan does can help you decide whether it’s a good idea for your house.
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An attic fan sucks hot air from the attic of a house and expels it outside. Typically, an attic fan is installed with vents in the attic. When hot air is pushed from the attic, the vents suck in cold air from outside the house. The combined action of the attic fan and the vents cools an attic.
To know whether you should install an attic fan in your house, you should understand how it works. Additionally, there are several types of attic fans. This article will explain how an attic fan works to cool the attic, explore the different types of attic fans, and discuss the advantages and disadvantages of having an attic fan in your house.
How Does an Attic Fan Work?
Fans are simply blades rotating around. How does that rotation result in the sucking out of hot air from an attic and the intake of cold air through the vents?
An attic fan works by sucking out air. When the fan blades rotate, they create negative pressure in the attic. The resultant partial vacuum accelerates the intake of air through the vents. The action of the blades also makes the air surrounding the fan flow outward, which expels hot air.
In the summer, the air in the attic will be hot, sometimes even going up to 150°F (65°C). One of the reasons behind this is that hot rays from the sun heat the attic. Such high temperatures can affect the temperature of your house, especially if it has a second floor.
Attic fans are therefore essential in keeping the attic cool in summer.
However, most people don’t buy attic fans to keep their attics cool. They buy them to help cool their houses in summer.
While we’ve seen how attic fans cool the attic, are they really effective in cooling entire houses?
To answer that question, we’d first have to know whether a hot attic can raise the temperature of the rest of your house.
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Does a Hot Attic Heat Your House?
The attic can get really hot in the summer. If that heat raises the temperature of lower levels of the house, your air conditioning system will have to do more work, and your electricity bill will increase.
A hot attic heats your house if it is insufficiently insulated or if there is air leakage between the attic and the rest of the house. This allows the attic to heat the air in your living space. Air leakages allow hot air to seep from the attic into your living space, raising the temperature.
If your house is adequately insulated and there is no air leakage, a hot attic should not affect the temperature of your living space.
R-values are used to define the thermal resistance of insulating materials. The higher the R-value, the more effective an insulating material is in blocking heat flow.
Proper insulation is between R-22 and R-49, depending on the region you live in. If your insulation is lower than R-22, the temperature of your living space will likely be vulnerable to heat from the attic.
Consult with a local expert to determine the appropriate insulation for houses in your area.
Air Leakage Between the Attic and Your Living Space
If air can flow into and out of your attic from the lower space, the temperature of your attic will affect the temperature of your living space. The exchange of air will increase the temperature of your living space.
Often, leakages in the attic are hidden, and it can be challenging to locate and deal with them. This doesn’t make draft proofing (finding and plugging leaks) any less necessary.
Common leakages to the attic include:
- Pot lights
- Service shafts
- The attic hatch
- Attic knee walls
- Penetrations around fixtures
Consider getting a draft proofing expert if you want your living space temperature to be immune to attic temperature, even in the hottest summer months.
Attic temperature can affect the temperature of your living space. And since an attic fan can help you regulate the attic’s temperature, it can help keep your living space cool.
How Does an Attic Fan Cool the House?
It is possible to insulate your living space from the attic. If you haven’t, an attic fan might help you cool your living space. Even with insulation, it may be prudent to do what you can to keep the attic fan temperature down – it will make your insulation more effective.
An attic fan cools the house by cooling the attic. A hot attic can raise the temperature of your home. An attic fan helps regulate the attic’s temperature, reducing potential heat flow from the attic to the living space.
If you haven’t insulated your living space from the attic, having an attic fan can help you keep cool.
However, attic fans come with certain disadvantages.
Disadvantages of Attic Fans
The most significant advantage of an attic fan is that it can help you keep your living space cool during summer. Attic fans do this by keeping the attic cool and are most effective when there isn’t enough insulation between the attic and the house.
However, attic fans can come with the following disadvantages:
- Increased cooling costs
- A higher electric bill
Increased Cooling Costs
If your attic is not properly insulated, the attic fan’s negative pressure will cause air to be sucked inwards not only from outside through the vents but also from the living space in your home.
In the summer, you’ll probably be cooling the air in your living space using an air conditioner. If the cool air is sucked into the attic, the air conditioner will have to do more work to replace it. It will have to cool more air.
The extra work done by the air conditioner will increase your electricity bill.
A Higher Electric Bill
Most people consider attic fans cheap. While they are much more affordable than insulation, they are not exactly free.
A typical attic fan will be powered by electricity. It will therefore cause an increase in your electric bill.
The average power rating of an attic fan is 300 W, which is the equivalent of about five 65 W bulbs. Granted, this will not result in a particularly significant increase in the electricity bill, given that the average refrigerator uses about 1,400 W per day.
However, the operation of attic fans can be boosted with appliances like humidistats. A humidistat controls the operation of an attic fan according to the humidity in the attic, improving the overall experience of using the attic fan.
A humidistat can increase the cost of running an attic fan by up to $150 a month.
There is a way to use an attic fan with very little recurring cost – using a solar-powered attic fan. I’ll now briefly explore the types of attic fans.
Types of Attic Fans
People have different preferences regarding the price, cost of ownership, convenience, and range of functionality of the home appliances they use.
The following are the primary types of attic fans in today’s market:
- Smart attic fans
- Traditional attic fans
- Solar-powered attic fans
Smart Attic Fans
These are the most modern. They offer the best convenience and range of functionality. However, the added functionality comes with a higher price tag and a steeper cost of ownership.
You can access and control most smart attic fans via a smartphone app.
Additionally, they come with added tools such as the thermostat and humidistat, which allow the fan to self-adjust based on the humidity and temperature conditions in the attic.
Traditional Attic Fans
The traditional attic fan comes equipped with a thermostat. The speed of its blades cannot be altered.
It is powered by ordinary electricity. However, since it doesn’t have the advanced features of the smart attic fan, its cost of ownership, especially electrical consumption, is relatively low and affordable.
Solar-Powered Attic Fans
These fans are powered by the sun, allowing you to save on electricity costs. Modern solar-powered attic fans can automatically switch to mains electricity when solar power is unavailable.
If you strictly want to use solar power, you can disable the automatic switch.
An attic fan creates negative pressure in the attic, causing hot air to flow out and cold air from outside to flow in through the attic vents.
Most people use attic fans to cool their attics, and their houses, during summer when the heat can become unbearable.
Without proper insulation, a hot attic can heat the living space – this is where the attic fan becomes relevant. If you can cool the attic in an uninsulated house, you can keep the temperature of the living space low.