Ventilation & Attic Systems Flashcards

What is the minimum net free area (NFA) of ventilation required per 150 square feet of attic floor space when there is no vapor barrier?

Answer: 1 square foot per 150 sq ft

Building codes typically require 1 square foot of NFA per 150 square feet of attic floor space when no vapor retarder is installed.

Which type of attic ventilation system uses both soffit vents and a ridge vent to create airflow through natural convection?

Answer: Balanced ventilation system

A balanced ventilation system pairs soffit (intake) vents with ridge (exhaust) vents so cool air enters low and hot air exits high via natural convection.

GAF's Cobra® Ridge Vent products are designed primarily to function as which component of attic ventilation?

Answer: Exhaust ventilation

GAF Cobra® Ridge Vents are exhaust ventilation products installed at the ridge to allow hot, moist air to escape from the attic.

What problem can result from having more exhaust ventilation capacity than intake ventilation capacity in an attic?

Answer: Short-circuiting where air is pulled in through exhaust vents

When exhaust exceeds intake, the system can short-circuit by drawing outside air back in through the exhaust vents rather than pulling it from the soffits.

According to proper ventilation principles, what percentage of the total NFA should be allocated to intake vents versus exhaust vents?

Answer: 50% intake, 50% exhaust

Best practice is a 50/50 balanced split between intake and exhaust net free area to ensure proper airflow through the attic.

Which condition in an attic is most commonly caused by inadequate ventilation during winter months?

Answer: Ice dam formation

Inadequate attic ventilation in winter allows heat to escape through the roof deck, melting snow that refreezes at the cold eaves and forms ice dams.

When installing a GAF ridge vent over a shingle roof, what must be cut along the ridge to allow proper airflow?

Answer: A slot through the roof deck on both sides of the ridge

A slot must be cut through the roof deck on each side of the ridge to create the opening that allows hot attic air to escape through the ridge vent.