Importance of Home Roof Ventilation
Proper attic ventilation is critical to the longevity of your roof system. In fact, having improper or inadequate roof ventilation can cut the life of your roof system in half. Because you can not see ventilation, roof ventilation often gets overlooked by the contractor and the homeowner. When roof ventilation components have been installed, we often see not enough ventilation for the size of the house, or even too much ventilation – Both of which can cause damage to your roof system and home. This article will discuss the different types of roof ventilation, how roof ventilation should be installed, and the metrics to determine how much roof ventilation should be installed.
Proper roof ventilation should provide benefits in all seasons, not just during warmer months. Ventilation should provide cooler temperatures during summer months, and help keep attic spaces dry during winter months. In the summer, a lack of ventilation can cause excessive heat in the attic space, reaching temperatures above 150 degrees F. This heat can migrate to living space inside the home, and also cause premature damage to the roof system. In the winter, a lack of ventilation can cause condensation in the attic space as warm air from the home rises. This moisture can create mold in the attic space and damage the roof system above. Sound ventilation promotes a homeostatic environment in your attic, and home, despite seasonal temperature changes.
Benefits of Proper Attic Ventilation
- More comfortable inside the home, year-round
- Helps prevent premature aging to roofing materials
- Helps reduce energy bills
- Promotes air circulation in attic space, keeping the roof deck dry year-round
A well-designed roof ventilation system should allow air to flow through attic space in a “balanced” fashion. This means intake and exhaust need to be evenly distributed. If your roof has exhaust ventilation (ridge vent, power attic fan, solar fan, gable vent, etc.), but no intake ventilation, your attic space is not being vented properly. We see exhaust ventilation without intake ventilation often. This gives the illusion of adequate roof ventilation to the homeowner, when in fact, nothing is happening. The attic space has stagnate, hot (summer) or moist (winter) air.
Ventilation works by prompting air to move. In a roof system, air movement is caused by a uniform movement of both intake and exhaust ventilation. It’s important that the ventilation system is currently sized and placed to achieve consistent air flow in all seasons. Air movement in a roof system can be manipulated mechanically or naturally, depending on the size and shape of the roof.
Types of Mechanical Ventilation
The (2) most common types of mechanical ventilation on residential roofs are power attic vents and power gable vents. Both of these fall in the exhaust category of attic ventilation, and use a motor to pull hot/humid air from your attic space. These fans have a thermostat controlled setting that can be adjusted fairly easily. The thermostat range is usually 60-120 degrees – the fan turns on when the ambient temperature in your attic reaches the selected temperature (we usually set our fans at 90 degrees).
In terms of volume of air, attic fans pull the most out in the shortest amount of time. However, because they rely on a motor, maintenance is required. Depending on where your home is located and what temperature setting you have on the fan, expect to change the motor out every 5-7 years.
Types of Natural Ventilation
Most attic ventilation falls in the natural, non-mechanical category. Natural ventilation requires little to no maintenance, and is suitable for a large variety of home types. Almost all intake ventilation is natural. Intake ventilation is found at the eaves of the house, either through soffit, or incorporated at the eave of the roof assembly. The most common types of intake vents are the following:
- Underave vents, located on the underside of the eaves
- Continuous soffit vents, located on the underside of the eaves
- Roof deck vents, incorporated in the roof assembly, usually within the first few rows of roofing material
There are several different types of natural, exhaust ventilation depending on the shape and size of the house. Most of these require no maintenance, but do require wind flow to be effective. The most common types of exhaust vents are the following:
- Ridge vent
- Gable vents
- Solar vents
- Louver vents
- Turbine fans
If applicable, it’s best to use only one form of exhaust ventilation. The type of exhaust ventilation is largely determined by the shape and size of the house. For instance, houses with continuous ridges are best suited for gable vents or ridge vents, while houses with limited ridge space are better suited for louver vents, turbine fans or attic fans (mechanical).
Requirements for Adequate Attic Ventilation
Requirements for attic ventilation vary by region and local codes. Most shingle manufacturers require attic ventilation to meet the International Building Code or local building codes. These standards normally require 1 square foot of net free ventilation area for every 150 square feet of attic floor space, which should be evenly distributed between intake and exhaust. A balance system is critical to proper attic ventilation, however, if a balance system is not applicable because of the size and shape of the attic space, it is better to have more intake ventilation.
Each type of ventilation application carries its own net free ventilation capacity. It’s important that the roofing contractor and/or homebuilder understands how much ventilation is needed, and how to calculate the ventilation output of each ventilation system.
Importance of Proper Attic Ventilation
When getting roof replacement estimates, attic ventilation is usually one of the last components discussed, if discussed at all. This is a problem. Proper attic ventilation is one of he best indicators of the longevity of your roof system, not to mention the energy savings over the years. A well ventilated roof should function all year – not just during summer months. Also, most shingle manufacturers will void manufacturing warrantees if the attic space is not properly ventilated.
You have lots of options when choosing a roofing contractor. Unfortunately, it’s often up to the homeowner to bring up proper ventilation. Every roof replacement project is different, the size and shape of the roof are the determinate factors in the type of ventilation system that should be applied. Make sure that your roofing contractor explains their approach to ventilation before signing the roof contract.