Protect Your Roof and Your Wallet With an Attic Ventilation System

Having a proper ventilation system in your attic can protect and extend the life of your roof while lowering your energy bills. In fact, good ventilation is the single most important factor in determining how long your roof lasts. Given that a new roof can cost anywhere from $20,000 and up, an investment in a good attic ventilation system makes a lot of sense.

How They Work

Ventilation systems can be active or passive. In a passive system, air is allowed to flow in at the eves of the roof (through soffit vents) and out through vents installed along the peak. These vents keep air circulating and ensure that the attic doesn’t turn into an oven in the summer. In the winter, hot moist air from the living space can condense in the attic when it meets colder air, leading to water damage and mold. If vents are properly installed, then moist air is able to travel through the attic to the outdoors before condensing.

In active systems, a fan pulls air through the attic to improve ventilation. Active systems are necessary when passive ventilation is not enough to get the job done. In general, you don’t want the temperature in your attic to vary too much from the temperature outside. If passive ventilation can’t keep attic temperatures close to outdoor temperatures, then you will need to install an active ventilation system.

Is Your Attic Ventilation Adequate?

The easiest way to determine if your attic ventilation is appropriate is to measure the temperature in your attic on a hot day. If it is more than 10 degrees above the outside temperature, you probably don’t have enough ventilation. If you want to get technical about it, then use the following calculation, which depends on a standard ratio whereby ventilation space must be 1/150th that of your attic floor space.

To do the calculation, start by calculating the square footage of your attic. You can determine square footage by multiplying width and length together. Whatever number you get should be divided by 150. This new number will be the number of square feet of ventilation you need. To determine the square footage of your ventilation system, measure the width and length of your ridge vents. If this measured areas is below the number just determined, your attic ventilation is not adequate. Note that if you don’t have soffit vents, it does not matter if you have ridge vents because no air flow will occur. Even if your ridge vent area meets ventilation requirements, you will still need to install soffit vents in the eves.

Of course, the easiest way to determine if attic ventilation is adequate is to call a professional. They can tell you if the ventilation is adequate and give you solutions to fixing any problems. They will be able to give you price estimates as well so that you have a good idea of what the project will cost.

Choosing a Venting Solution

Venting solutions include ridge vents, soffit vents, insulation baffles, attic fans, gable vents, and an almost endless list of additional options. In general, ridge vents are always necessary, even if you have active ventilation. Ridge vents are the single most important component of attic ventilation, but they can’t do the job alone.

For passive venting, soffit vents must be combined with ridge vents in order to ensure that air flows at a reasonable rate. Gable vents can be used in lieu of or in addition to soffit vents in some settings, though they generally provide inferior ventilation. It is important to note that gable vents are more likely to allow moisture into the attic than soffit vents.

For active venting, a fan will be necessary. It can be manually controlled via switch or automatically controlled via thermostat. Fans are generally installed at gables, though they can be put in other locations. Most attic fans come with motorized louvers that prevent rain and moisture from entering when the fan is not running. Look for attic fans with a solar panel connection to reduce energy costs.

The Bottom Line on Roofs

An attic must be ventilated in order to prevent roof damage. The easiest way to assess your house for adequate ventilation is to look at the eves for soffit vents. If those don’t exist and you know you don’t have gable vents or a fan, then you have a ventilation problem. Beyond that simple assessment, you will need to take the measurements listed above or call a professional. While not fun, ensuring that you have adequate attic ventilation can save you tens of thousands of dollars down the road.

John Young refurbishes houses. He enjoys blogging about construction projects and simple ways to improve home efficiency and value.