Top 6 Best Roof Mounted Attic Fans (2023 Review)

What Size Attic Fan Do I Need?

Roof mounted attic fan sizes are rated in CFM which stands for cubic feet per minute. If an attic fan is rated at 1,000-cfm, it means that it can exhaust 1000 cubic feet of air per minute.

According the Home Ventilating Institute (an industry non-profit), they recommend that your attic should exhaust your entire attic at least 10 times per hour. And HVI provides an easy rule of thumb for choosing the minimum CFM for your attic size.

Simply take your attic size in square feet (the "floor" of attic) and multiply it by a 0.7 multiple. And if your roof is very steep or dark colored, increase it to a 0.805 multiple.

So if your attic is 1500 square feet, then you multiply it by 0.7 to get 1050-cfm (minimum).

Read Also:What Are The Best Gable Mounted Attic Fans?

How Much Passive Venting For An Attic Fan?

It’s important to note that attic fans (roof mounted or gable) works in unison with passive attic venting because that’s where it pulls in outside air. Passic attic venting includes the ridge vent, soffit vents, gable vents, and turtle vents.

If there isn't enough passive venting, then the attic fan performance (CFM) may drop significantly, and it may start pulling in air from your home's interior.

Interior air will get sucked into the attic from all of the cracks and crevices in the ceiling and walls adjacent to your attic such as from the attic hatch, top plates, and recessed lights.

If this happens, it definitely isn't good for your indoor comfort, but it can significantly lower the efficiency of your HVAC.

Carbon Monoxide Hazard

It may also create a carbon monoxide hazard if you have low efficiency gas appliances such as a furnace or water heater.

Backdrafting occurs when the exhaust gases of your appliances get pulled into the home rather than getting sent outside.

Read Also:How To Install An Attic Fan On Roof?

The Best Passive Vent

The best and most logical place to have adequate passive venting for an attic fan is at the soffits. This is because hot air rises from the soffit and naturally goes high up the ridge.

底和脊通风系统创建了一个自然suction. And the best soffit venting iscontinuousso there aren't any breaks.

The Home Ventilating Institute recommends havingat least one square foot of soffit venting per 300-cfm of attic fan performance. So if your attic fan is 1050-cfm, then you want to have at least 3.5 square feet of passive soffit venting (or 504 square inches).

Read Also:What Are The Pros And Cons of Attic Fans?

What Are The Benefits of Roof Mounted Attic Fans?

One of the biggest benefits of roof mounted attic fans is that it can be installed near the ridge of the roof and catch the rising hot air.

Attics have a natural suction and funnel of hot air. Hot air gets pulled into the attic from the soffits and then it rises to the ridge. Since the fan is roof mounted, it can be installed near the ridge and work more effectively. In contrast, gable mounted attic fans miss out on this naturalstack effectof rising hot air.

Read Also:What Are The Best Solar Powered Attic Fans?

Interior Comfort

And probably the biggest benefit to homeowners is interior comfort. Hot attics canreach a temperatureas high as 160-degrees on very hot days.

When attics are cooler, it will make the whole house more comfortable, especially the upper level of the home. And your HVAC system will run more efficiently, and will reach your target interior temperature more easily.

Theleastcomfortable homes have extremely hot attics that ruins interior comfort.

These are the homes where the upper level bedrooms are always 10 degrees warmer than the rest of the house.

HVAC Longevity

Even though the energy use of a roof mounted fan may offset any HVAC efficiency gains, it can still help your HVAC run better and extend its life.

If your A/C doesn't have to run as long to reach your target temperature, then it can extend its life.

When an HVAC system is constantly running because your home isn't effectively cooling down, you can just imagine how much wear and tear this puts on your system. And the average life expectancy of HVAC systems is in the range of 15-18 years, so if it isn't running efficiently, it may reduce its life to as little as 7-10 years.

Roof Protection

And one of the little known benefits of cooling down your attic is that it can protect and extend the life of your asphalt roof.

Asphalt shingles is an oil-derived product, and when these shingles get very hot, they dry out and prematurely age. So very hot attics can reduce the life of your roof from 25-years down to maybe 10 or 12 years.

Read Also:What Are The Best Master Flow Attic Fans?

What Are Roof Mounted Attic Fans?

A roof mounted attic fan rests directly on top of the roof and helpsregulate a property’s temperatureby removing hot air.

Roof mounted attic fans are generally rated for only sloped and asphalt shingled roofs. They are generally not installed on flat roofs or slate shingle roofs. As a comparison, the other main type of attic fan are gable mounted attic fans which are mounted vertically on the gable vent.

Attic fansrequire cutting a hole into the roof sheathing and the asphalt shingles. Roof mounted attic fans are generally made of galvanized steel.

Roof mounted attic fans are wired into the homes electrical system, either hardwired at a junction box or plugged into an outlet. There are also solar powered roof mounted fans which don't need any electrical wiring connections.

Read Also:How Does An Attic Fan Work?

Reviews Of The Best Roof Mounted Attic Fans

Here are my reviews of the best roof mounted attic fans with their pros and cons...