Why Install Roof Vents?

What is a roof vent and what is it used for?

A roof vent is an engineered structure that is typically rigid and has two primary functions. First, to allow air to travel through it, and second to prevent insects, rain, snow and any wind-blown debris (including burning embers) from passing through it.

Roof vents are used for the purpose of air intake and air exhaust. Having vents of both types installed is required by IBC International Building Code and all local municipalities for steep slope roofs.

The goal of roof ventilation is to provide a means of allowing outside air to enter and exit attics and ventilated spaces, so that heat and moisture can leave the building envelope.

What are (air) intake roof vents?

Air intake vents are used to allow outside air to enter into attics. Intake vents should be located along the lowest eave or soffit of the roof assembly. Intake vents are best when used in conjunction with roof exhaust vents.

(Source: NRCA)

Below are names and pictures of commonly used air intake vents:

Common problem with soffit vents (most popular air intake design)

All intake vents should be installed on the low end of the roof or under the eaves. Since soffit vent are installed under the eaves they run the risk of being blocked off on the interior side of the vent by attic insulation. This problem can be averted by doing a visual inspection of the attic from the inside to make sure that all soffit vents are not blocked off by insulation, storage items and or other materials.  original image

Another way to avoid soffit vents from being blocked is to install baffles. Baffles are placed between rafters keeping insulation from blocking air from the soffit vent below.  original image

In general intake vents should be designed and installed to prevent precipitation, animals and insects from entering the attic space.

NRCA does not recommend the use of drip edge vents as intake vents in northern climates where there is a likelihood of ice damming.

(Source: NRCA)

What are roof exhaust vents?

Roof exhaust vents allow for hot air from the attic below to pass through them so that heat and moisture go directly to the outside, leaving the building envelope completely. In order for roof exhaust vents to work efficiently they must be located at or near the roof peak since hot air rises.

What is roof ventilation (for steep slope)?

Proper roof ventilation consists of air intake at low points and air exhaust on the high points of the roof. This design system works off of nature’s thermal dynamic, a process called Diurnal Convection.  original image

(Source: ResearchGate)

• Static Vents: Are roof vents that are non-motorized vents can be used as a roof exhaust vents or roof intake vents depending where on the roof they are installed. For roof exhaust they are placed near the peak of the roof and for intake they are placed on the lower portion of the roof.
  Below are pictures of common static roof vents also called passive roof vents and gravity roof vents.  original image  original image  original image

Turbine Vents: Turbine vents and other similar vents rely on wind to rotate the turbine’s fan blades. The spinning of the blades by design rotate to keep out rain and snow, not to expedite the ventilation capacity like may people believe.  original image

(Source: NRCA)