Key Factors in Selecting a Roof Mounted Kitchen Exhaust Fan

Installing a properly sized and designed roof mounted kitchen exhaust fan is one of the most critical elements for managing air quality and safety in a commercial kitchen. This heavy-duty appliance sits on the roof, drawing heat, smoke, steam, grease, and odors up from the cooking equipment below while ejecting it away from the building. With such an important role, it's vital to select the right exhaust fan model for your unique kitchen layout, ventilation needs, menu, climate, and compliance requirements.

Roof Mounted Exhaust Fan Basics

Roof mounted exhaust fans contain a powerful fan motor and precisely angled blades encased in a durable weatherproof housing. The sloped fan casing and elevated roof curb allow grease to drain off easily without pooling or sticking to surfaces. The entire fan structure rotates to discharge fumes vertically away through an exhaust duct or stack.

Unlike wall-mounted fans limited by the roofline, the rooftop location provides a shorter, straighter duct run. This greatly reduces static pressure, enhances efficiency, and enables the fan system to overcome heavy cooking loads from massive appliances like charbroilers or fryers. Key components like spun aluminum dampers, grease filters, and fire-rated curbs and roof jack flashings integrate with the fan for seamless operation.

Benefits of Roof Mounted Kitchen Exhaust Fans

• Increased ventilation capacity and efficiency
• Better smoke and odor removal
• Lower noise levels with less obstruction
• Improved fire safety with mesh screens and separation from flames
• Easier cleaning and maintenance access from the roof

Sizing the Fan Correctly

The first step is calculating your kitchen's air ventilation and extraction requirements measured in cubic feet per minute (CFM). Commercial kitchens must maintain 25-30 air changes per hour to properly manage heat, smoke, and emissions. An undersized fan fails to draw out contaminants, while an oversized option wastes energy.

Consider the room dimensions, number and type of cooking appliances, if appliances vent automatically or manually, if you plan to add more equipment, and if heavy cooking occurs seasonally. An exhaust fan should operate at full speed for at least 20-30 minutes after cooking ceases to clear residual heat and odors.

Use sizing guidelines from ventilation experts along with your peak operating conditions to determine the recommended CFM. Then match a roof mounted fan's airflow capabilities for optimal performance.

Kitchen Size, Layout and Configuration

Carefully evaluate the kitchen's footprint and configuration to select a fan dimensioned for sufficient coverage across all cooking equipment. Measure duct runs and note obstructions to size curbs and fans appropriately. Consider potential future kitchen expansions as well to avoid costly upgrades later. Streamlined layouts enhance ventilation efficiency.

Key Performance Factors

Commercial kitchen exhaust fans bear strict performance testing certifications for optimal operation, low emissions, and sound ratings. Assess key specifications like:

Capacity - CFM Ratings

Match the rated airflow volume (CFM) to your kitchen's needs for smoke and odor removal. Balance capacity relative to static pressure restrictions.

Power - Horsepower & Efficiency

Select an energy efficient fan motor with sufficient horsepower to generate the required airflow. Larger kitchens need more powerful fans.

Airflow & Pressure Capabilities

Determine the static pressure loads based on ducting length and layouts. Then size the fan to overcome that resistance while producing essential air velocity and circulation.

Discharge Velocity

Higher discharge velocities propel gases further away from the building. Consider public areas or operable windows situated downwind.

Operating Temperature Range

The fan must withstand cooking equipment exhaust temperatures up to 158degF indoors and 104degF outdoors. Arctic weather units are necessary in cold climates.

Construction and Build Quality

Commercial kitchen exhaust fans endure immense loads. Lifecycle operation costs make durable construction vital. Seek features like:

• Reinforced welds
• Corrosion-resistant housings
• Spark-proof impellers
• Stainless steel fasteners
• Sturdy curbs and frames

Units with the longest warranty demonstrate the manufacturer's faith in reliability. Well-engineered fans operate consistently for over a decade before major repairs arise.

Weather, Corrosion and Fire Resistance

Outdoor rooftop conditions require rugged weatherproofing including watertight seals and heavy-gauge anti-corrosive galvanized, stainless or aluminum construction. Opt for spark resistant polymer or stainless fan blades. Seek grease containment and runoff reduction to limit fire hazards.

Noise Reduction Features

Given the fan proximity to interior work areas, aim for sound ratings below typical ambient kitchen noise levels. Noise buffers like deep-drawn shrouds with rolled bead edges help dissipate vibration and sound.

Grease Handling and Cleanup

Choose self-draining housing and curb designs that deter grease adhesion while allowing easy wipe-downs when needed. Sloped planes paired with smooth welds and flanged edges facilitate runoff.

Additional Fan Features

Utility Sets

Utility set fans feature built-in flush lighting, receptacles, switches and accessories for rooftop HVAC equipment. The consolidated design reduces roof penetrations.

Speed Controls

Variable speed controls balance ventilation rates with energy savings. Pitched blades adapted to spin efficiently across a wide RPM range optimize performance.

Sensor Integration

Many fans now integrate sensors to monitor performance metrics like airflow, temperature, vibration, and more. Diagnostic feedback enhances operational efficiency and uptime.

Smart Monitoring Options

IoT enabled fans allow remote monitoring, preventative alerts, runtime tracking, and data benchmarking when paired to a WiFi gateway or building management system.

Accessories and Options

Curb Dimensions & Weight Ratings

Curbs elevate fans for proper ducting alignments. Choose durable curbs sized appropriately for the fan unit's measurements and mounting points. Confirm weight limits match the fan, accessories, and expected snow/wind loads.

Dampers

Butterfly dampers with weighted ends manual or automated by actuators control airflow. They facilitate system balancing and prevent backdrafts.

Roofing Integrations

Fans require proper roof construction to flashed, insulated curbs along with platforms to mount equipment without damaging the roof membrane. Fan curbs must synchronize precisely with the roof's foundations and membranes.

Kitchen Hood Compatibility

Fans link directly to hood plenums or vertical duct risers transferring heat, moisture and emissions up from cooking equipment. Verify fan dimensions and duct openings suit the planned hood configuration and anchoring.

Evaluating Compliance

Stringent health, safety, and fire codes apply given the fan's fire prevention role. Reputable third-party certifications validate ratings and construction quality.

Health, Safety, Building, and Fire Codes

Ensure the fan meets the latest local mechanical, energy, and plumbing codes. UL 705, 762, and CSA C22.2 standards guide hazardous electronics protections.

AMCA Sound and Air Ratings

AMCA certification marks guarantee manufacturer CFM airflow claims match real-world results plus reliable sound level testing.

UL / NSF Certifications

UL and NSF certify construction safely resists grease buildup and meets sanitation standards for food environment equipment.

Comparing Fan Models and Manufacturers

While comparing exhaust fans, balance acquisition costs against expected lifespan operation expenses and capabilities. Determine which performance factors and options provide the best value for your application.

Leading manufacturers known for quality products with robust warranties, timely availability and strong customer support offer peace of mind for a critical kitchen investment.

Top Brands & Buying Considerations

Among the top suppliers, Loren Cook, Greenheck, CaptiveAire, PennBarry, and Acme each offer strengths depending on product lines and configurations. Consider costs, construction, efficiencies, sound levels, climate suitability and certifications.

Installer Support & Warranties

Select an installer thoroughly familiar with roof curbs, ducting, and penetrations to integrate the fan properly avoiding leaks or air gaps. Manufacturer warranties ranging from 1 to 5 years demonstrate confidence while easing ownership risks.

Specifying the optimal roof mounted kitchen exhaust fan model involves balancing horsepower, airflow volumes, features, sound levels, durability, and budgets. Carefully tailor selections to the cooking equipment, peak conditions, space configurations, climate, and compliance demands. Investing in quality leads to superior ventilation, indoor air quality, safety, and reliability yielding substantial long term savings.