Roof Sailing Roof Ventilation and Attic Systems

Question 1

What is the minimum net free ventilation area required per square foot of attic floor space under the IRC?

Accepted Answer

1/300 of floor area

Answer

The IRC requires a minimum of 1/150 of the attic floor area in net free ventilation area when vapor retarder is absent, or 1/300 when a vapor retarder is present on the warm side of the insulation.

Question 2

What is the benefit of a balanced ventilation system (equal intake and exhaust) in a residential attic?

Accepted Answer

Creates consistent airflow that removes heat and moisture without short-circuiting

Answer

A balanced system with equal intake (soffit/eave) and exhaust (ridge/upper) vents creates continuous airflow that flushes out heat in summer and moisture-laden air in winter without drawing from unintended paths.

Question 3

Where should intake vents be located in a properly designed attic ventilation system?

Accepted Answer

At or near the eaves or soffits

Answer

Intake vents must be located at the lowest possible point — at the eaves or soffits — so that cool outside air enters at the bottom and warm, moist air exits at the ridge through exhaust vents.

Question 4

What problem can occur when attic insulation blocks soffit intake vents?

Accepted Answer

Reduced ventilation causing moisture buildup and heat accumulation

Answer

When insulation blocks soffit vents, intake airflow is eliminated, causing heat and moisture to accumulate in the attic, which can lead to ice dams, shingle deterioration, and mold growth.

Question 5

What device is installed at the soffit to maintain the airway between attic insulation and the roof deck?

Accepted Answer

Baffle (insulation dam / rafter vent)

Answer

Baffles (rafter vents or insulation dams) are channels installed between rafters at the eaves to keep the ventilation path open and prevent insulation from blocking the airflow from soffit vents.

Roof Sailing Practice Test

Roof Sailing Practice Test

Roof Sailing Roof Ventilation and Attic Systems