What Homeowners Need to Know About Roof Ventilation

Inadequate ventilation leads to excess moisture, which can cause degradation of your roof. Learn the proper approaches and benefits to roof ventilation so you can make an informed decision.

On this page, we'll discuss...


How Roof Ventilation Works

roof ventilation diagram

Ventilation involves combining various types of vents and fans throughout a house in order to keep air moving steadily.

The goal is to draw warm, humid air out of the attic while replacing it with cooler, drier air. Doing so reduces the humidity levels in the attic, therefore reducing the amount of moisture damage to the underside of the roof.

This is typically accomplished with exhaust and intake vents. Exhaust vents are located in or on top of the attic and help warm air flow out from the roof. They include ridge vents, roof turbines, and gable vents. Intake vents assist in drawing cooler air through the soffit, eaves, or even the foundation.


Attic Ventilation

Proper attic ventilation provides year-round benefits to homeowners, helping to prolong the life of roofing materials while keeping utility bills down and improving the quality of life inside the home.

An attic with regular air flow helps fight excessive summer heat, moisture buildup in the winter, as well as reducing ice dams.

The best forms of attic ventilation occur when an equal amount of air is coming in through the intake vents and going out through the exhaust vents. This allows cool, dry air to enter the attic at its lowest point and pushes warm, moist air through the attic and out the exhaust vents.

Attic Ventilation Systems

Ridge and Soffit Vents

Vents installed under the eaves of the soffit and along the roofline allow for proper passive ventilation. This simple system allows fresh air to flow in, up, and out of the attic.

Fan Powered Roof Vents

These electric fans are very similar to ridge vents, only they can be operated manually or programmed to run when a predetermined internal temperature has been reached.

Attic Exhaust Fan

Attic exhaust fans are installed in the gable of the attic rather than along the ridge of the roof. This system usually requires extra ventilation due to the amount of hot air they blow out, and in turn fresh air they draw in. This system can greatly reduce energy costs for homeowners.

Roof Turbine

Turbines are installed on top of the roof and use wind power to draw hot and humid air out of the attic. Roof turbines have a series of vanes that spin when the wind passes through them, and this movement creates ventilation. In an area with a lot of air movement, turbines offer a great solution. 

 

Learn more about ventilation systems: Roof Ventilation: Roof Turbines and Ridge Vents


Calculating Attic Ventilation

Before deciding which ventilation products are right for your home, you’ll have to calculate how much ventilation is needed.

Almost all building codes call for a ratio of 1/300 — For every 300 feet of attic floor space, there should be 1 square foot of ventilation space.

As an example, let's determine the necessary ventilation space for an attic measuring 25 ft. x 50 ft.

25 ft. x 50 ft. = 1,250 sq. ft. of attic floor space

1,250 ÷ 300 = 4.16 sq. ft. of ventilation space

A balanced ventilation system should always be the goal. The amount of exhaust ventilation should never exceed the amount of intake ventilation.

The ratio of 1/300 is a general rule and does not apply to all building solutions. If you’re at all concerned about the proper ratio for your home, contact a qualified roofing contractor.
 

Learn more about inspecting your roof: What You Should Know Before Attempting a DIY Roof Inspection 


man applying sealant to ridge vents

Benefits of Proper Roof Ventilation

Proper roof ventilation allows cool, fresh air to enter the attic, and expels hotter, moist air through exhaust vents.

This cycle plays a key role in prolonging a roof system and prevents many expensive problems both inside and out.

In colder climates, proper ventilation mixes cool outside air with the warmer air from the attic, allowing for less snow melt. This prevents problematic ice dams.

In warmer regions, regular air flow helps expel moist air, which can lead to rot, mold, and other forms of deterioration.

In general, proper ventilation should:

  • Reduce damaging moisture
  • Allow for increased savings on utilities
  • Prevent early roof deterioration
  • Decrease ice dams
  • Moderate internal home temperatures 
It’s important to remember that a proper ventilation system removes and intakes air in an equal proportion. A balanced flow of air will create the most benefits for homeowners. Before installing a roof turbine or an attic fan, it’s a good idea to consult with an experienced contractor to get a professional opinion about the best ventilation system for your property.
 

Learn more about how to hire the right contractor for your home:


attic beams with window

Costs of Roof Ventilation Systems

Ventilation System Cost
Static vents $35 - $50 per vent installation
Roof turbines $70 - $200 per turbine installation
Gable vents $45 DIY installation / $185 professional installation
Soffit vents $375 professional installation
Ridge vents $245 professional installation
Whole-house fan $1,000 professional installation

The cost of roofing ventilation systems varies depending on a number of factors, including:

  • whether you DIY or hire a professional
  • whether you choose an active or passive system
  • the size of your home
  • etc. 

Roof Ventilation Maintenance

Once you determine what roof ventilation system works best for your home, it should be checked annually to ensure it runs at full capacity.

Follow a regular maintenance program to ensure your ventilation system is in good condition.

  • Clear the vent screens of dirt and debris.
  • Check for rips or tears.
  • Inspect for rust around the framing.
  • Clear insulation away from vent openings.

Learn more about the costs of roof repairs and replacements: