Roof Sailing Roof Ventilation and Attic Systems 2 — Questions and Answers
Question 1: What is the maximum recommended attic temperature for preserving asphalt shingle life during summer?
- 100°F
- 120°F
- 140°F (Correct answer)
- 160°F
Correct answer: 140°F
Industry guidelines suggest that attic temperatures above 140°F accelerate the thermal aging and granule loss of asphalt shingles; proper ventilation should keep peak attic temperatures below this threshold.
Question 2: What causes ice dams on roofs and how does proper ventilation help prevent them?
- Ice dams form from rain freezing; ventilation has no effect
- Ice dams form when heat escapes through the roof, melts snow, and refreezes at the cold eave; proper ventilation keeps the deck cold uniformly (Correct answer)
- Ice dams form from condensation; ventilation adds moisture
- Ice dams only form on poorly insulated roofs regardless of ventilation
Correct answer: Ice dams form when heat escapes through the roof, melts snow, and refreezes at the cold eave; proper ventilation keeps the deck cold uniformly
Ice dams occur when attic heat warms the upper roof deck, melting snow that then refreezes at the cold eaves; proper ventilation removes attic heat so the entire deck stays uniformly cold, preventing the melt-refreeze cycle.
Question 3: What is the minimum clearance required between the tops of attic insulation and the roof deck sheathing for proper airflow?
- 1/2 inch
- 1 inch (Correct answer)
- 2 inches
- 4 inches
Correct answer: 1 inch
A minimum 1-inch clear airway between the top of the insulation and the underside of the roof deck sheathing must be maintained from eave to ridge to ensure adequate ventilation airflow.
Question 4: Which type of attic ventilation uses mechanical power to increase air exchange?
- Ridge vent
- Soffit vent
- Powered attic ventilator (PAV) (Correct answer)
- Gable louver
Correct answer: Powered attic ventilator (PAV)
A powered attic ventilator (PAV) uses an electric or solar-powered fan to actively draw hot air from the attic, providing much higher air exchange rates than passive vents alone.
Question 5: What ventilation problem occurs when both ridge vents and high gable vents are used together?
- Over-ventilation of the lower attic
- Short-circuiting — air flows directly from gable vent to ridge vent, bypassing the lower attic (Correct answer)
- Excessive intake at the eave
- Pressure equalization issues
Correct answer: Short-circuiting — air flows directly from gable vent to ridge vent, bypassing the lower attic
When gable vents and ridge vents coexist, air takes the shortest path from gable to ridge, short-circuiting the system and leaving the lower attic unventilated where moisture and heat accumulate.
Question 6: What is the recommended ratio of intake vent area to exhaust vent area in a balanced attic ventilation system?
- 2:1 intake to exhaust
- 1:1 (equal intake and exhaust) (Correct answer)
- 1:2 intake to exhaust
- 3:1 intake to exhaust
Correct answer: 1:1 (equal intake and exhaust)
A 1:1 ratio of intake to exhaust ventilation is the standard recommendation, ensuring that for every cubic foot of air exhausted at the ridge, an equal volume of fresh air enters at the soffit.
Roof Sailing Roof Ventilation and Attic Systems 2
What is the maximum recommended attic temperature for preserving asphalt shingle life during summer?