Ventilation & Insulation
Attic ventilation ratios, ridge vents, soffit vents, power vents, ice dam prevention, and energy efficiency.
- State the recommended minimum attic ventilation ratio
- Describe the function of ridge vents, soffit vents, and power vents
- Explain the causes and prevention of ice dams
- Identify the causes of shingle blistering, cupping, and wind damage
- Describe proper ventilation balance between intake and exhaust
Lección 1
Ventilation Principles & Ratios
Why Ventilation Matters
The purpose of roof ventilation is to remove excess heat and moisture from the attic space to prevent condensation damage, ice dams, and premature shingle deterioration. Proper ventilation extends the life of both the roofing materials and the roof structure.
The recommended minimum attic ventilation ratio is 1:300 - meaning 1 square foot of net free ventilation area for every 300 square feet of attic floor space. If the vapor barrier is inadequate, the ratio increases to 1:150.
Balanced Ventilation
Effective attic ventilation requires a balance between intake and exhaust vents. The ideal split is 50% intake (at soffits) and 50% exhaust (at ridge or near peak). If the system is unbalanced, slightly more intake than exhaust is preferred to maintain positive pressure in the attic.
Ventilation Balance Rule
Never combine ridge vents with power vents on the same roof. The power vent can short-circuit the ridge vent, pulling conditioned air from the living space instead of drawing fresh air from the soffits.
The minimum attic ventilation ratio is 1:300 (1 sq ft of vent per 300 sq ft of attic floor). Ventilation must be balanced with 50% intake at soffits and 50% exhaust at the ridge. Never combine ridge vents with power vents.