There is a heated debate about whether using an attic fan help lower air conditioning bills. What is the truth?
Attic fans, if run properly, can reduce air conditioning costs. By reducing the attic temperature, an attic fan reduces the heat seeping into the living areas from the attic, thus reducing the load on the air conditioner.
But please note that the stress is on ‘if run properly’. If you are wondering what this means, and whether the attic fans can practically reduce air conditioning costs, continue reading.
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How does an attic fan work
An attic fan is installed in the attic of the house, either on the roof or on the gable. It works just like an exhaust fan by venting the hot air inside the attic. As you know, the attic temperatures often exceed outside temperature without proper ventilation. An attic fan helps t pull the relatively cooler air from outside into the attic, thus lowering the overall temperature there.
How does an attic fan help air conditioning?
To understand how an attic fan helps air conditioning, we have to first understand the relevance of attic temperature to in-house temperature.
The attic and the living areas of the house are separated by the ceiling. However, a ceiling will not 100% prevent heat transfer between the attic and the living areas. So if the attic is hot, this heat will slowly move into the house, raising the in-house temperature.
Take the example of a hot summer day. During the peak sun hours, it is guaranteed that your attic is like a hot box. Even with insulation on the floor, this hot attic will transfer some of its heat to the rooms below. But you may not feel this heat thanks to the air conditioning. However, since there is heat transfer, the air conditioning unit will have to work harder to maintain the room temperature.
What an attic fan does is remove the excess heat in the attic before it is transferred into the house. As a result, the air conditioning won’t have to remove the extra heat, thus working less to maintain the room temperature. Since the air conditioner does not have to work extra, its power consumption will be lower, and so will the power bill.
Is the attic fan cheaper to run?
Attic fans consume way less power compared to air conditioning.
When you compare the power bill of running AC alone 24X7 for the entire month, to that of running an attic fan and AC (not 24X7), according to your cooling needs, you’d be able to realize the cost-saving potential of using an attic fan.
Does an attic fan increase the longevity of air conditioner
Any product will last longer if they are used properly; this is true for your air conditioner as well. By not overloading the air conditioner, attic fans help to increase its longevity. This saves you money on maintenance as well.
That’s folks, how attic fans help air conditioning!
But I am pretty sure you already guessed that, and what you are eager to know is the ‘if run properly’ I mentioned earlier. Without further ado, let’s jump into why attic fans won’t always help air conditioning;
Why attic fans won’t help AC if not run properly
Removal of heat from the attic, preventing the heat from reaching inside the house, and lowering the load on the air conditioning works well on paper. But this is not without some caveats;
As you know, attic fans are mechanically powered; they forcibly suck the air out of the attic. This creates a negative pressure in the attic which should be filled by the cool air from the outside. For this process to work properly, there should be enough intake ventilation. But in some cases, the main intake vents like soffit vents could be blocked due to insulation covering them. In such cases, due to a lack of intake vents, the negative pressure in the attic can suck the conditioned air from inside the house. That, is a problem. By removing the conditioned air, the attic fans actually force the air conditioner to work more. So instead of helping with air conditioning, the attic fans here are overloading the AC system.
An attic fan can help reduce the load on your air conditioning. But only if it is done right. Also, it depends on the area where you live. If you live in hot areas, like Texas, use an attic fan. A better alternative is using a whole house fan. While the savings you make using an attic fan are debatable, a whole house fan saves on air conditioning costs hands down!
Continue reading my article, are whole house fans worth it, to know the savings you can make by combining whole house fans and air conditioning.