Attic Ventilation: The Basics that Homeowners Need to Know

Attic ventilation is something most homeowners don’t think about, but knowing the basics can save you money on your energy bills (especially during the hot Texas summers), keep your roofing shingle warranty intact and/or prevent premature deterioration of rafters, insulation, shingles and other materials and equipment in your attic space.

Our communications/public relations director (and homeowner), Kelly Haffner, recently sat down with NTRCA associate member Robert Charanza with Attic Breeze to ask him several questions from a homeowner’s perspective.

Q: What is Attic Ventilation?

A: Attic ventilation is the replenishment of fresh air through the attic space using a passive or mechanical venting system consisting of a balance of intake and exhaust vents.”

Q: Why is Attic Ventilation Important?

A: Proper attic ventilation allows heat and moisture to escape. 

Without proper venting, the increased heat and moisture will lead to premature deterioration of anything in the attic space. This could include building materials (such as asphalt roof shingles, insulation, rafters and sheathing), mechanical equipment (like air handlers, duct systems and hot water heaters in the area) and anything placed or stored in the attic.

The attic space is also susceptible to mold and mildew growth, spongy, warped and saggy decking and possible dry rot if it is not properly ventilated. During winter months, frost may form on the underside of decking and, in some climates, ice damming can form along eave edges of the roofline.

Another concern with improper attic ventilation is that the heat build-up can increase the temperature in the living spaces below, decreasing your home’s comfort level and increasing your air conditioning bills. Your living space can also suffer from poor air quality.

And finally, all roofing product manufactures require proper ventilation of attic spaces within their respective warranties. If material failure occurs, this is one of the first items inspected, and can lead to warranty claim denial.

Q: But … Shouldn’t an Attic Be Air-Tight?

A: The only time an attic can be “air-tight” is when it is part of the air-conditioned space of the home. Some homes built today have the envelope of the home foam insulated. This means all exterior walls and roof rafters have spray foam insulation installed to create a total sealed insulated system. Some call this an “Igloo” system because it performs similarly to a Styrofoam cooler. With a system of this kind, you still must ventilate the inside air of the home, so an air exchange system is implemented within the HVAC equipment.

Q: What are the Basics of GOOD Attic Ventilation?

A: Good attic ventilation consists of a balanced system of intake and exhaust vents. Most intake vents are installed on the underside of soffits, such as rectangular screened vents or continuous perforated soffits. Some older homes were built with gable vents that have been turned into intake vents or others retrofitted with vents along the eave edge of rooflines or vents installed a few feet above the eave edge to allow air into the attic. These intake vents are balanced with exhaust vents that may be placed along the roof ridges or vents placed approximately 3 feet below the roof ridge lines. Some exhaust vents may be mechanical, using solar or electrical power to run a fan, or turbine vents that use wind to increase the airflow and exchange rate.

Q: What are Some Basic Signs a Homeowner Can Observe from the Ground and/or Inside the Attic to Spot Good or Bad Attic Ventilation?

A: A homeowner can visually inspect their home for proper ventilation. They should have intake vents surrounding the lower eave edge of the rooflines and a similar amount of exhaust near peak ridge lines of their roof. The homeowner can look inside the attic to see if daylight is visible along the eave edge. If not, it may be a sign that the eave intake vents have been covered by insulation and this will need to be removed to prevent blockage of airflow.

They can also look for the most common attic ventilation mistakes, including: 1) the mixing of different types of ventilation on the same roof which, in most cases, can lead to an unbalanced ventilation system where airflow is disrupted and heat build-up can occur and 2) improper placement of the solar panel on solar powered exhaust vents. These panels need to face in a southerly direction to work at maximum efficiency. The performance is greatly diminished when the panel is facing any other direction.

If you’re looking for a “rule of thumb” for proper ventilation, it’s the “1/300 ratio” -- for every 1 square foot of attic space, you should have 300 Net Free Airflow (NFA) divided evenly between intake and exhaust

Q: Can You Tell Me More About How Attic Ventilation Affects a Homeowner’s Heating and Cooling Bills?

A: Proper ventilation reduces the heating and cooling cost of a home. Improper ventilation can allow heat build-up to pass into homes increasing the cycling and stress upon the AC systems. Mechanical ventilation systems are better than passive venting systems because they increase the air exchange rate within attic spaces, greatly reducing the “heat load.” They can reduce attic temperatures more than 50 degrees versus a passive venting system. The lower the attic temperature, the slower the heat can penetrate the living space taking the stress off the AC System and leading it to cycle less. This saves money on cooling cost.

Q: What Products are Available to Help a Home’s Attic Ventilation?

A: Products that are available to help home’s attic ventilation are static vents, ridge vents, wind turbines, electric powered vents and solar powered vents. It’s best to work with a knowledgeable contractor to determine the best system for your home and its surrounding environmental factors.

Q: What Do Most Codes Require in the North Texas Area When It Comes to Attic Venting?

A: Most municipalities and code entities use the International Residence Code (IRC) as their guideline. The IRC uses the “1/300 Ratio” rule for ventilation as the minimum standard. Some municipalities and code entities may create an even more stringent code, so homeowners should be advised to work with contractors who stay abreast of any changes or special requirements in their service areas.

Q: Is There Any Kind of Tax Credit Available for Attic Ventilation?

A: There is a 30% Federal Tax Credit available on the total install cost of solar powered ventilation products. In many cases, contractors can offset the difference in cost versus a passive venting system allowing homeowners to upgrade to a ventilation system that will keep attics drastically cooler than a passive system during the hottest times of the year, using the free source of the sun.

Robert Charanza has worked in the roofing and attic ventilation industry for close to 25 years and is currently a National Accounts Manager for Attic Breeze, a Texas-based manufacturer of solar-powered ventilation and tubular skylight products for residential and commercial markets.