Gravity Vents

  • gravity vents GI GR
  • gravity vents PR
  • gravity vents TR
  • gravity vents TRE
  • gravity vents LSUG
  • Standard Construction Features
  •  Certifications Logo

Gravity vents GI GR

Gravity vents RR

Gravity vents TR

Gravity vents TRE

Gravity vents LSUG

Standard Construction Features

Standard Construction Features

AMCA-Sound & Air Cert. logo

ISO 9001, US-Green logos -by model

LOREN COOK COMPANY Gravity Ventilation units are designed for industrial and commercial applications requiring building ventilation, either natural or mechanical. All units are produced in an ISO 9001 certified facility.

 

Related Documents

See the Downloads tab for specifications, submittals and FanDrafter files

  • GI / GR

  • PR

  • TR

  • TRE

  • LSUG

  • Selecting

  • Downloads

GI

All sizes are available with express service. Read more.

GI / GR

Gravity Vent

  • High efficiency gravity roof ventilators designed using the latest Computational Fluid Dynamic (CFD) and Finite Element Analysis (FEA) software packages
  • Bases are manufactured with a rounded flange around the throat that decreases pressure losses due to turbulence. (See CFD Models Below)
  • Available with throats in widths from 12” to 72” and unlimited length starting at 12”.
  • Units come standard with integral lifting lugs.
  • Tie down points are standard to allow for additional restraints to be added in the field as required.
  • Rain gutters are standard to help eliminate rain infiltration.
  • Roll formed hood panels provide excellent strength characteristics as well as creating a unit that is architecturally pleasing.
  • Units are designed to exceed 30 lbs./ft2 snowload rating.
  • Hinged hoods are standard on GR units with less than a 73” throat length and GI units with less than a 61” throat length.

Designed with the latest in computer aided engineering software.

The new COOK GI and GR Gravity Ventilators were designed using the latest Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA) software. This allowed our engineers to optimize the geometry of the throat and hood to reduce pressure losses and increase efficiency, while maintaining structural integrity. Once the design was optimized, physical prototypes verified the performance and durability of the design. The result is the most efficient Gravity Ventilator in the industry.

CFD Simulation

The figures above depict the relative turbulence of each unit and illustrate the improved airflow achieved by the new COOK design.
As can be seen in the figures, the radius throat design significantly reduces turbulence as compared to the typical square throat design.

Description: Unit shall be a hooded high efficiency roof mounted gravity ventilator.

Construction: The unit shall be of bolted and welded construction utilizing corrosion resistant fasteners. The hood shall be constructed of minimum 18 gauge aluminum, bolted to a minimum 8 gauge aluminum support structure. A radius throat must be provided for optimum performance. Lifting lugs shall be provided to help prevent damage from improper lifting. A rain gutter shall be provided to prevent rain infiltration. The base shall have continuously welded curb cap corners for maximum leak protection. Birdscreen constructed of 1/2” galvanized mesh shall be mounted in the hood. Unit shall bear an engraved aluminum nameplate and shall be shipped in ISTA Certified Transit Tested Packaging.

Product: Units shall be model GI and GR as manufactured by LOREN COOK COMPANY of Springfield, Missouri.

Intake Hood Velocity Notes

Velocity to 500 FPM: Velocity below 500 FPM provides for a level of protection against the influx of airborne mist or debris.

Velocity 500 FPM to 1000 FPM: Within this velocity range there is a possibility that fine, airborne mist will be carried into the building through the vent. Care should be taken in the location of the unit if airborne mist is a problem.

Velocity Greater Than 1000 FPM: Velocity in this range is not recommended unless special means are taken to prevent the influx of airborne matter and large droplets of moisture into the interior of the building. Velocities shown are to be used as a guide only. Final application and conditions will be a governing factor.

Dimensions (Inches)

dimension drawing

PR

All sizes are available with express service. Read more.

PR

Spun Aluminum
Gravity Vent

  • Spun aluminum intake/relief ventilator designed for use in both gravity and mechanical ventilation systems.
  • Compact, durable and efficient.
  • Bases are manufactured with a fully developed inlet to provide the most efficient and weather resistant path for both supply and exhaust applications.
  • Available in 9 sizes from 8 to 48 inches.

Description: Unit shall be a spun aluminum, roof mounted gravity ventilator.

Construction: The unit shall be of bolted and welded construction utilizing corrosion resistant fasteners. The spun aluminum structural components shall be constructed of minimum 16 gauge marine alloy aluminum, bolted to a rigid aluminum support structure. The aluminum base shall have continuously welded curb cap corners for maximum leak protection. The spun aluminum baffle shall have a rolled bead for added strength. Birdscreen constructed of 1/2” mesh shall be mounted across the air opening. Unit shall bear an engraved aluminum nameplate. Nameplate shall indicate design CFM and static pressure. Unit shall be shipped in ISTA Certified Transit Tested Packaging.

Product: Unit shall be model PR as manufactured by LOREN COOK COMPANY of Springfield, Missouri.

Dimensions (Inches)

dimension drawing

Size A Dia. B Dia. C D G T Sq Roof Opening Approx. Ship Wt.-Lbs.
8 8-5/-8 18-3/4 4/5/2008 3-1/4 2 18 13-1/2 13
12 12-1/2 27-3/4 5/1/2016 3-1/2 2 20 15-1/2 20
16 16-1/2 27-3/4 5-1/16 5-3/4 2 28 23-1/2 25
20 20-1/2 36-5/8 6-3/4 4-7/8 2 32 27-1/2 40
24 24-3/4 42-3/4 8 6-1/2 3 36 31-1/2 127
30 30-3/4 52-5/8 17-1/4 6-1/4 3 42 37-1/2 183
36 36-3/4 62-5/8 17-1/2 7-1/4 3 48 43-1/2 255
42 42-3/4 73-5/8 14 8-1/4 3 54 49-1/2 287
48 48-3/4 73-5/8 14 8-1/4 3 60 55-1/2 288
TR

All sizes are available with express service. Read more.

TR

Spun Aluminum Tiered
Gravity Vent

  • Spun aluminum ventilator designed for use in both gravity and mechanical ventilation systems.
  • Provide an increased intake area by utilizing two spun aluminum tiers and therefore, provide lower intake velocities reducing the introduction of airborne particles or moisture into the building.
  • Bases are manufactured with a fully developed base venturi to provide the most efficient and weather resistant path.
  • Available in 9 sizes from 8 to 48 inches.

Description: Unit shall be a tiered spun aluminum, roof mounted gravity ventilator.

Construction: The unit shall be of bolted and welded construction utilizing corrosion resistant fasteners. The spun aluminum structural components shall be constructed of minimum 16 gauge marine alloy aluminum, bolted to a rigid aluminum support structure. The aluminum base shall have continuously welded curb cap corners for maximum leak protection. The spun aluminum baffle shall have a rolled bead for added strength. Birdscreen constructed of 1/2" mesh shall be mounted across the air opening. Unit shall bear an engraved aluminum nameplate. Nameplate shall indicate design CFM and static pressure. Unit shall be shipped in ISTA Certified Transit Tested Packaging.

Product: Unit shall be model TR as manufactured by LOREN COOK COMPANY of Springfield, Missouri.

Dimensions (Inches)

dimension drawing

Size A Dia. B Dia. C D G T Sq Roof Opening Approx. Ship Wt.-Lbs.
8 8-5/8 18-3/4 8-3/16 3-1/4 2 18 13-1/2 16
12 12-1/2 27-3/4 8-5/8 3-1/2 2 20 15-1/2 20
16 16-1/2 27-3/4 8-5/8 5-3/4 2 28 23-1/2 25
20 20-1/2 36-5/8 12-1/16 4-7/8 2 32 27-1/2 45
24 24-3/4 42-3/4 14-3/16 6-1/2 3 36 31-1/2 133
30 30-3/4 52-5/8 30-13/16 6-1/4 3 42 37-1/2 220
36 36-3/4 62-5/8 32-5/16 7-1/4 3 48 43-1/2 282
42 42-3/4 73-5/8 24-9/16 8-1/4 3 54 49-1/2 290
48 48-3/4 73-5/8 24-9/16 8-1/4 3 60 55-1/2 303
PR

All sizes are available with express service. Read more.

TRE

Extruded Tiered
Gravity Vent

  • Tiered aluminum intake/relief ventilator designed to be one of the most flexible designs on the market.
  • Can be tailored specifically to meet most building exhaust and intake applications.
  • The tiers are constructed of high quality extruded aluminum and provide for clean lines that can meet the requirements for even the most demanding architectural applications.
  • Available with throat dimensions from 12” x 12” to 60” x 120”

Description: Unit shall be an extruded aluminum, roof mounted gravity ventilator.

Construction - The unit shall be manufactured of 0.081 gauge extruded aluminum tiers welded to a minimum 8 gauge aluminum support structure. The aluminum hood shall be constructed of minimum 0.063 aluminum and provided with a layer of anti-condensate coating. The aluminum base shall have continuously welded curb cap corners for maximum leak protection. Birdscreen constructed of 1/2" galvanized mesh shall be mounted across the relief opening. Unit shall bear an engraved aluminum nameplate. Nameplate shall indicate design CFM and static pressure. Unit shall be shipped in ISTA Certified Transit Tested Packaging.

Product: Unit shall be model TRE as manufactured by LOREN COOK COMPANY of Springfield, Missouri.

Intake Hood Velocity Notes

Velocity to 500 FPM: Velocity below 500 FPM provides for a level of protection against the influx of airborne mist or debris.

Velocity 500 FPM to 1000 FPM: Within this velocity range there is a possibility that fine, airborne mist will be carried into the building through the vent. Care should be taken in the location of the unit if airborne mist is a problem.

Velocity Greater Than 1000 FPM: Velocity in this range is not recommended unless special means are taken to prevent the influx of airborne matter and large droplets of moisture into the interior of the building. Velocities shown are to be used as a guide only. Final application and conditions will be a governing factor.

Dimensions (Inches)

dimension drawing

Throat
Size
No.
of
Tiers
Hood Size
Ht. Curb Cap
Size
Throat
Area
  Static Pressure Drop (in W.G.)
Ducted 0.02 0.055 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.5
Non-Ducted 0.028 0.068 0.134 0.198 0.264 0.325 0.39 0.455 0.52 0.645
Hood
Area
Shipping Weight CFM
12 x 12 2 23.75 x 23.75 9 17.5 x 17.5 1 2.3 47 324 513 725 888 1026 1147 1256 1357 1451 1622
12 x 14 2 23.75 x 25.75 9 17.5 x 19.5 1.2 2.4 50 365 577 817 1000 1155 1291 1414 1528 1633 1826
12 x 16 2 23.75 x 27.75 9 17.5 x 21.5 1.3 2.5 52 404 638 902 1105 1276 1427 1563 1688 1805 2018
12 x 18 2 23.75 x 29.75 9 17.5 x 23.5 1.5 2.6 54 440 696 984 1205 1391 1556 1704 1841 1968 2200
12 x 24 2 23.75 x 35.75 9 17.5 x 29.5 2 3 61 541 856 1210 1482 1711 1913 2096 2264 2420 2706
14 x 14 2 25.75 x 25.75 9 19.5 x 19.5 1.4 2.5 52 409 646 913 1119 1292 1444 1582 1709 1827 2043
14 x 16 2 25.75 x 27.75 9 19.5 x 21.5 1.6 2.6 54 449 710 1004 1229 1420 1587 1739 1878 2008 2245
14 x 18 2 25.75 x 29.75 9 19.5 x 23.5 1.8 2.7 56 487 770 1089 1334 1540 1722 1886 2038 2178 2435
14 x 24 2 25.75 x 35.75 9 19.5 x 29.5 2.3 3.1 63 592 936 1323 1621 1872 2092 2292 2476 2647 2959
14 x 30 2 25.75 x 41.75 12.5 19.5 x 35.5 2.9 5.1 69 855 1352 1912 2342 2704 3023 3312 3577 3824 4275
16 x 16 2 27.75 x 27.75 9 21.5 x 21.5 1.8 2.7 56 491 776 1098 1345 1553 1736 1901 2054 2196 2455
16 x 18 2 27.75 x 29.75 9 21.5 x 23.5 2 2.8 58 530 838 1186 1452 1677 1875 2054 2218 2372 2652
16 x 24 2 27.75 x 35.75 9 21.5 x 29.5 2.7 3.2 65 638 1008 1426 1746 2016 2254 2469 2667 2851 3188
16 x 30 3 27.75 x 41.75 12.5 21.5 x 35.5 3.3 5.3 83 932 1474 2085 2554 2949 3297 3611 3901 4170 4662
16 x 32 3 27.75 x 43.75 12.5 21.5 x 37.5 3.6 5.4 86 978 1547 2187 2679 3093 3458 3788 4092 4374 4891
18 x 18 2 29.75 x 29.75 9 23.5 x 23.5 2.3 3 61 571 902 1276 1563 1804 2017 2210 2387 2552 2853
18 x 24 2 29.75 x 35.75 9 23.5 x 29.5 3 3.3 67 680 1975 1520 1861 2149 2403 2632 2843 3039 3398
18 x 30 3 29.75 x 41.75 12.5 23.5 x 35.5 3.8 5.4 86 1004 1587 2244 2748 3174 3548 3887 4198 4488 5018
18 x 32 3 29.75 x 43.75 12.5 23.5 x 37.5 4 5.6 88 1051 1661 2350 2878 3323 3715 4070 4396 4699 5254
18 x 36 3 29.75 x 47.75 12.5 23.5 x 41.5 4.5 5.9 93 1143 1807 2555 3129 3614 4040 4426 4780 5110 5714
24 x 24 3 35.75 x 35.75 12.5 29.5 x 29.5 4 5.4 86 1033 1634 2311 2830 3268 3653 4002 4323 4621 5167
24 x 30 3 35.75 x 41.75 12.5 29.5 x 35.5 5 5.9 93 1191 1884 2664 3263 3768 4213 4615 4984 5329 5957
Propeller Hooded H Series Fans

All sizes are available with express service. Read more.

LSUG

Low Silhouette Upblast
Gravity Vents

  • LSUG is a low silhouette, gravity relief, upblast ventilator designed for use on vertical high velocity exhaust systems.
  • LSUG units include damper doors and a high volume rain gutter to prevent water infiltration.
  • LSUG units are available in 7 sizes from 24 to 60 inches.

Description: Unit shall be a low silhouette gravity upblast ventilator

Construction: The unit shall be of bolted and welded construction utilizing corrosion resistant fasteners. The fan housing and base shall be minimum 14 gauge and the baffle shall be a minimum 18 gauge steel. Unit shall have built-in butterfly dampers of aluminum or steel construction (aluminum on sizes 24-36, steel 42-60). Curb cap corners shall be continuously welded for maximum leak protection. The wind band shall be continuously seam welded with rolled flanges on each end for strength.

Coating: All steel fan components shall be Lorenized® with an electrostatically applied, baked polyester powder coating. Each component shall be subject to a five stage environmentally friendly wash system, followed by a minimum 2 mil thick baked powder finish. Paint must exceed 1,000 hour salt spray under ASTM B117 test method.

Product - Unit shall be model LSUG as manufactured by LOREN COOK COMPANY of Springfield, Missouri.

Dimensions (Inches)

 dimension drawing

Size A Dia B C L x W T Sq. Material Gauge Max. Motor Frame Roof Opening Square* Approx. Ship Wt.-bs. Less Motor
Base Hood
24 31-1/4 28 26 3 36 14 14 18 31-1/2 200
30 37-1/4 34 32 3 42 14 14 18 37-1/2 260
36 43-1/4 38 36 3 48 14 14 18 43-1/2 310
42 49-1/4 45 43 3 54 14 14 18 49-1/2 380
42 55-1/4 50 48 3 60 14 14 18 55-1/2 445
54 61-1/4 46 44 3 66 14 14 16 61-1/2 480
60 67-1/4 51 49 3 72 14 14 16 67-1/2 540

Selecting

Cook has 5 models and many sizes of gravity vents. Use the equations below to understand which is the best.

First calculate the temperature differential (TD)

The temperature differential (TD) is the indoor temperature (TI) minus theoutdoor temperature (To) in °F. Indoor temperature should be lower than the outdoor temperature
- = °F


Then, choose an application to find the airflow:

Heat removal

  • Heat load (HL) from sunlight, lights, motors, people etc. measured in BTU per hour.
    =
  • Airflow (Q) measured in cubic feet per minute (CFM) = HL / 1.1 x TD
    = CF

Dilution of contaminants

  • Building volume (BV) in cubic feet
    =
  • Air change frequency (AFC) in minute per change
    (Q) =
  • Airflow (Q) measured in cubic feet per minute (CFM) = BV / AFC
    = CF


Location & number

Once the required air volume is known, the locations of gravity ventilators and intake openings need to be determined. It is wise to disperse gravity vents over the roof surface to provide even ventilation. If all intake openings are located on one side of the building, typically the gravity vents would be located on the opposite side of the building to provide a sweeping effect across the space.


Finally, determine the size of gravity ventilators

  • Required airflow (Q) measured in cubic feet per minute (CFM). See above.
  • Wind velocity (V) in miles per hour. Most wind velocity data is taken from 33 feet above the ground. Wind velocity decreases closer to the ground. With any disruption, design wind velocity may be less than meteorological data. Typically half of the average wind velocity is a good design value.
  • Height of gravity ventilator above neutral pressure level (H) in feet. The height above neutral pressure level is assumed to be the distance above the centerline elevation of the largest opening in the side wall - often an overhead door. If the side wall openings are evenly spaced along the height of the side wall, the height above neutral pressure level would be half of the building height.
  • Gravity ventilator throat velocity (TV) in feet per minute
    equation
  • Total gravity ventilator throat area in square feet (A) = Q /TV
  • The throat area for each gravity roof unit in square feet = A / N

Look for vents with:
square feet

GI / GR: Up to 72 square feet throat area
PR & TR: Up to 12.9 square feet throat area
TRE: Up to 50 square feet throat area
LSUG: Up to 20.1 square feet throat area


Aspect ratio

Many selections are possible which will have an equivalent throat area. When making a decision on throat size, keep in mind that selections with an aspect ratio of 3:1 or less will perform the best. Aspect ratio is the ratio of the throat length to the throat width.

  • Example: a GI or GR 30" x 42" has an aspect ratio of 1.4:1 – well below 3:1.
  • PR, TR, & LSUG models always have a 1:1 ratio.
  • TRE modles are always 2:1 or lss.

Example

  • 90°F Indoor Dry Bulb Temperature
  • 80°F Outdoor Dry Bulb Temperature
  • 156,000 BTU/Hr Heat Load
  • 7 Gravity Ventilators
  • 5 MPH Wind Velocity
  • 15 ft Roof Elevation & 10 ft Overhead Door (Primary Intake)
  • throat area = 8.34
  • Select (7) LOREN COOK Model GR 30 x 42 (8.75 ft2 throat area).