Ventilation Engineering
Comprehensive technical specifications for attic ventilation systems and performance metrics.
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Airflow Dynamics
- NFVA Ratio: 1:150 to 1:300
- Stack Effect: 2-4 Pa/m height
- Wind Effect: 0.5-2.0 coefficient
- Air Changes: 6-10 ACH minimum
- Flow Rate: 700-1000 CFM typ.
- Pressure Drop: 0.1-0.25 iwc
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Vent Types & Specs
- Ridge Vent: 18 in² per foot
- Soffit Vent: 9 in² per foot
- Gable Vent: 144 in² each
- Turbine: 150-350 CFM rated
- Power Vent: 1000-1600 CFM
- Static Vent: 50-60 in² NFVA
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System Integration
- Intake/Exhaust Ratio: 50:50
- Cross Ventilation: 90° optimal
- Height Differential: 3' minimum
- Baffle Clearance: 1-2 inches
- Vent Spacing: 4-6 feet typical
- Screen Mesh: 1/4" maximum
Environmental Factors
Critical parameters affecting ventilation performance:
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Climate Considerations
- Hot Zones: +25% NFVA
- Cold Zones: Heat Dam required
- Mixed Climate: Balanced system
- Coastal: Corrosion resistant
- High Wind: Hurricane clips
- Snow Load: Ice shield needed
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Moisture Management
- Relative Humidity: 30-50%
- Dew Point Control: +4°F min
- Vapor Pressure: 0.5" WC max
- Condensation Risk: <5%
- Moisture Content: <19%
- Drying Capacity: 1-2 pints/day
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Thermal Performance
- Summer Peak: 140°F max
- Winter Delta-T: 10°F target
- Solar Heat Gain: 30-40%
- R-value Impact: -5% max
- Energy Savings: 10-15%
- Thermal Mass Effect: 4-6 hours
Installation Standards
Key specifications for proper ventilation system installation:
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Component Requirements
- Flashing: 4" minimum lap
- Fastener Spacing: 4-6 inches
- Sealant: 50-year rating
- Weather Strip: EPDM/TPE
- Metal Gauge: 26-gauge min
- Insect Screen: 18x14 mesh
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Safety Standards
- Fire Rating: Class A
- Wind Rating: 110 mph
- Load Capacity: 40 psf
- Electric: UL Listed
- Fall Protection: OSHA
- Access: 22x30" minimum
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Maintenance Specs
- Inspection: Bi-annual
- Cleaning: Annual
- Screen Check: Quarterly
- Motor Service: 3-5 years
- Seal Review: Annual
- System Test: Semi-annual