John began his presentation by stating that poor working conditions within a kitchen drive good cooks and chefs to other more desirable locations. Every time a trained cook or chef is driven to leave by uncomfortable working conditions, the owner loses money.

Why not, he challenged, design the kitchen HVAC system correctly to begin with and eliminate costly high turnover. Employees are becoming increasingly educated to the fact that there is always another restaurant, often right around the corner that is much more comfortable to work in.

GENERAL DESIGN for COMFORT Criteria:

• Create a temperature range from 70 F winter to 80 F summer
• Humidity is not as important as a curtain of air in a spot cooling mode used to offset radiant heat from a particular device
• Add 10% to UL710 exhaust rates which are a minimum for capture and containment
• Use high ADPI (air diffusion comfort index) diffusers
• Use induction type area diffusers for the general kitchen (vane, plaque or slot type)
• Evaluate the common constant volume system vs. VAV
• Consider the use of perforated face diffusers
• AVOID 4 way diffusers in a kitchen, especially within 12’-0” of the hood(s)

KITCHEN COMFORT CONDITIONS

• Consider air conditioning the kitchen to retain trained staff
• Beware of creating draft conditions that disturb the hood capture
• Cool for radiation from equipment by creating a “good draft”
• Create high induction and good mixing for the general kitchen
• Provide laminar cooling draft for the cooking line

TEMPERATURE CONDITIONS

• Winter: 70 – 74 F.
• Summer: 85 – 88 F.
• Air conditioned or non air conditioned replacement air options include economizer, evaporative cooling and transfer air
• IMC Note: Temperature differential between replacement and air-conditioned air shall not exceed 10 F.
• Exception to above: Replacement air is part of the AC system and does not decrease comfort conditions

DRAFT CONDITIONS

• Occupied zone, ASHRAE:
  • 30 fpm (heating)
  • 50 fpm (cooling
  • This low range is “still air” at the occupied level of 6” AFF to 6’-0” AFF
  • Still Air is 50 fpm
• At the Air Terminal
  • Diffuser: Neck velocity 1000-1200 fpm (NC 35-40)
  • Displacement device: 75-125 fpm
  • Spot cooling, air curtain or laminar flow perforated plenum: 150-200 fpm
  • Plaque, induction/slots, neck velocity: 1000-1200 fpm

CODE REQUIRED EXHAUST & REPLACEMENT AIR

• Exhaust over cooking areas: 150-400 CFM/LF
• Dishwasher exhaust: 600-1200 CFM
• Heat and cool general kitchen area
• Replacement air: heated (50 F. min) and cooled as owner decides

BASIC KITCHEN DESIGN

• Require equipment list and layout from kitchen designer
• Include heat gain calculation
• Include heat rejection from freezers/refrigerators (reach-in & walk-in)
• Provide 12 to 15 air changes per hour
• Review exhaust requirements from manufacturers hood data
• Verify overhang of hood over deepest equipment item (6” min. required, 12”+ is desirable)(listed hoods are not penalized for additional CFM by greater overhang))
• Identify source of replacement air
• Include 20% transfer air

COMFORT DESIGN for the KITCHEN

• Cost vs. benefit with regard to cooling of replacement air.
• GOOD
  • Vane type ceiling diffusers
  • Tempered (heat) replacement air in the hood face
• BETTER
  • Vane type ceiling diffusers (heat and cool) in general kitchen area
  • Hood side curtains to reduce exhaust/replacement air
  • Perforated hood front face for heated replacement air
• BEST
  • High induction diffusers in general kitchen area
  • Hood side curtains
  • Plenum front of hood discharge
  • Back wall discharge (adjustable)

For questions, contact John Clark directly at JClark@hga.com