Attic fans how do they work

The client had decided a new fan was needed to replace a solar unit they had installed several years ago. On inspection, I found the villain in the attic exactly as the customer described. A single, roof mounted, solar powered attic exhaust fan.

It was working. There was no other ducting or HVAC equipment in the attic. The temperature of the roof sheathing inside the attic was degrees.

I explained to our client that the idea of attic fans to remove hot air from the attic area might seem logical. But they actually might need a bigger and better solution. Imagine yourself laying in the sun on a beach in Cancun. All is good for about 5 minutes then you start to feel hot. You go and get a big fan and set it up to blow air over you. Ah, feels better for about another 5 minutes. Soon even the blowing air feels hot, so you exchange the fan for an air conditioner and let that blow cold air on you.

Feels great now so you stay out in the sun till you notice that your skin is red and blistered and burned to a crisp. What happened? You got zapped by UV rays, a form of invisible radiant heat! Radiant heat zips right through cold air without any affect and cooks your skin.

So, what does that have to do with your house? The roof structure of your Home An assembly of materials that enclose a weatherproof space for human living. Radiation from the sun heats the surface of the roof. From there, the entire mass of the roof roofing, roof paper, nails, sheathing, rafters warms up through conduction.

This radiant heat passes down through the attic space and hits the material on the surface of the ceiling structure insulation , wood joists, drywall , ducting etc. Very quickly the entire mass of the ceiling structure also becomes a giant heat radiator.

This heat moves back up towards the roof again and will continue to radiate heat well after the sun goes down. If your ceiling is not sealed airtight and extremely well-insulated, much of this heat is going to radiate downward into your home too.

Air in the attic that comes in contact with the surfaces of the hot framing, will become heated through conduction. This creates a kind of hot air sandwich formed between the roof and ceiling structures.

The warming of all these surfaces is why the attic interior gets so much hotter than the exterior temperature. Help diagnose hard-to-find heat-loss areas, and pinpoint water leaks behind walls with new Thermal imaging cameras. Read More…. Many homeowners use these devices during the spring and summer months in place of their central air conditioning. There are several different types of attic ventilation systems, but most of them feature small vents soffit and gable which draw in cool air, along with a primary fan that pushes air outside.

One of the most common mistakes homeowners make when using an attic fan is covering the vents with insulation.

The more insulation you can pack into your attic, the more energy-efficient your home will become. If you want your home air conditioner to cool you better, then you might want one or two attic fans. The number of fans you might need will depend on how large your attic is, your climate, and other factors discussed below. Of course not! The area between your attic, roof, and the rest of your living space is typically sealed, but if not, then the fan will become a hindrance quickly.

Leaving an attic fan on with improper seals between the attic and living space will waste electricity and money. Larger attic fans mean that they will be able to affect more air than smaller versions.

Just keep in mind that you can absolutely have too much of a good thing. If your fan is more powerful than it needs to be, it could affect airflow in the rest of your home, too.

You should treat your attic fans like you would any other fan in the house. Its job is to cool down the attic, particularly in the hotter months of the year. Now, what about the cost? Because attic fans take away some of the work that your air conditioning would be doing, you will spend less on running your air conditioning. However, running an electric fan in attics could mean the cost just goes towards the attics rather than the air conditioner.

So are attic fans good or bad? Well, there is thankfully an alternative to choosing between no attic fan or paying for an electric attic fan. Solar attic fans work just like electric fans and have all the same benefits. The difference is that after you pay to install them, you never pay for them again. They run on solar energy.

So the only thing powering your attic fan is the sun rather than your electric bill. This means that with a solar fan in your attic, you can take the pressure of your air conditioning without paying for it in your attic.

Unlike electric attic fans, this can actually end up saving you money every month, especially in the hottest weeks of summer. But a solar attic fan will do everything that you would want your electric unit to do. It will push out hot air in the summer. In extremely warm climates it has been scientifically proved to cool the attic by an average of 20 degrees. And it will keep your attic dry in the winter, preventing future costly roofing and maintenance issues.

Your fan will run 12 months of the year without costing you a dime after installation. Read our review on the best solar attic fans.

Now you know everything there is to know about how attic fans work, and you may be getting a good idea of whether it may be right for your home.

But are attic fans good or bad? Knowing the benefits as well as the disadvantages will help you decide if fans in your attic would work in your home. Based on our industry experience, the answer is, yes. Attic fans do really work. They will help to circulate air in your attic and ventilate the space so that it stays closer to the outside temperature.