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What Homeowners Need to Know About Soffit Ventilation

Soffit ventilation
The soffit is the piece of material under your eaves between the siding and the fascia board, and it is typically vented to keep your roof healthy. The ventilation system works in a number of ways, from installing special pest-proof vents to using a perforated soffit board.

Here's what you as a homeowner need to know about your soffit ventilation.

Soffit Ventilation Works in Tandem With Ridge Vents

Ideal roof ventilation systems use soffit vents and approximately equally sized ridge vents. These vents allow all the air that enters the soffit vents to be drawn up the underside of the roof to the ridge vents. Along the way, this air picks up excess heat and moisture and then carries it out of the attic.

This process works especially well to cool the roof down in summer, because the slope of the roof guides the hot air under the roof's surface upward to the ridge vents. Hot air rises naturally, so this warmer air keeps flowing out the ridge vents, drawing the outside air in through the soffit and allowing ventilation to occur even when there's no wind.

Soffit Vents Should Be Larger Than Ridge Vents

When the respective areas of soffit ventilation and ridge ventilation aren't correctly calculated, problems can occur. You need to have more ventilation area at the soffit.

Some homeowners are dazzled by the "turbine" style of ridge vent, because it can draw air so powerfully that they feel adding one must improve ventilation, and indeed it can increase the area of ridge vents. However, in some cases, this powered fan simply draws air in through nearby ridge vents, bypassing the parts of the roof that really need to be ventilated.

This effect can make the turbine vent worse than useless because it prevents the other ridge vents from venting air out, since they're forced to provide inflow instead. So in some cases, the air under the roof can stagnate. Or the turbine could simply create a vacuum that draws air from the house's living space through chinks and crannies, resulting in energy loss.

Insufficient Soffit Ventilation Can Lead to Mold and Rot

If there's not enough soffit ventilation to keep up with the ridge ventilation (such as is the case when a turbine vent draws too much air and shorts the airflow patterns), undesirable results can occur. When the roof deck doesn't have a constant stream of fresh air attending it, more heat damage can occur. Condensation also tends to build up, which can lead to mold and rot.

A turbine isn't the only reason soffit ventilation can be insufficient, however. The sizes of the ridge vent versus the soffit vents could possibly be calculated incorrectly, causing the ridge vent to need more air inflow than the soffit vents provide (this can cause a ridge vent to short out even without a turbine vent). Soffit vents can also be blocked by insulation or pest nesting.

Soffit Vents Can Suffer From Pest Intrusion

Different types of soffit vents have different types of pest vulnerabilities. Some types of soffit vents are specifically designed to keep squirrels and similar pests out, but may still allow termites in. Perforated soffit board, on the other hand, can be relatively easy for raccoons to rip through on their way in, especially if it's structurally compromised by water damage.

Keeping your soffit boards protected by a correctly installed drip edge can be a big help in preventing attack by pests, and using small wire mesh can exclude termites. However, mesh with very small holes can actually inhibit airflow, which in some cases may mean you need to install additional vents, so check with your contractor before deciding on a mesh size.

These basics will help you care for and use your soffit boards and soffit vents in an educated fashion. If you need help with soffit vent installation and repair, condensation problems with your roof, or other construction projects, contact Lane's Contracting, Inc. today.