by Scott Robbins
Scott Robbins
Student Unions have significantly evolved over the past several years. What was once a simple cafeteria and gathering space has become more of an architecturally-defined interaction space. Students Unions have become the heart beat of a campus; where students gather to study, socialize, relax, and of course – dine. Cooking areas are very complex from an equipment and systems perspective. Where there use to be only one large back of a house kitchen, there are now multiple cooking areas as students enjoy the experience of watching a chef prepare their meal. There are also now many choices of cuisine. Sloppy Joes may still be on the menu, but so are sushi, roasted chicken, risotto, and farm to plate selections. These different menu items require more cooking space. Not only are there more cooking areas, but they are now distributed throughout the student union.
These complex kitchens also require systems to function properly and these supporting systems require more space than has been historically required. This can be particularly challenging when the student union project is a renovation with low floor to floor heights. There are code requirements which dictate how the systems need to operate and what is required for the kitchens. For example, sinks being used for hand washing and triple pot sinks for cleaning need to be provided. Sinks require water, and more importantly sanitary lines which need to be pitched. These complexities in turn require an increased level of experience and coordination to ensure that the construction and subsequent kitchen operations are smooth and uninhibited.
Certain types of cooking require grease exhaust hoods. Grease exhaust ductwork has a number of code requirements to provide enhanced safety. Many fires have occurred over the years, in kitchens, due to the poor exhaust systems and surrounding construction techniques. Code requirements, as well as good industry practices surrounding the design and installation of kitchen grease exhaust, often have appreciable impact on the building design. Such designs need to be reviewed and accounted for early in the project to mitigate adverse impacts on space planning.
Here are a few examples of these items and how they impact the building design.
1) Number of Hoods/System – multiple hoods can be on one (1) exhaust fan, as long as they are located on the same floor, are located in the same room or adjoining rooms, do not penetrate fire resistance related assemblies, and do not serve solid fuel fired appliances.
2) Grease Duct Clearances – must have no less than 18 inches of clearance to combustible construction and no less than 3 inches to non-combustible construction.
3) Grease Duct Pitch – grease duct must be installed with a pitch (2% slope) for horizontal runs under 75 feet. More than 75 feet of horizontal run requires an 8.3% slope.
4) Cleanouts – cleanouts are requires on horizontal sections of ducts, no more than 20 feet apart and at all turns. The opening dimensions must be a minimum of 12 inches on each side. These cleanout locations cannot be obstructed.
5) Grease Duct Risers – each riser must be enclosed within its own shaft (or 2 hour wrap) and shall not contain other ducts, piping or wiring systems.
6) Roof Termination – exhaust outlets, on the roof, must be a minimum of 40 inches above the roof.
Grease exhaust can cause a visual and odor issue around the campus. Air purification units can be installed in order to capture the grease and odor from the kitchen hoods, prior to discharge. These units are large and take-up space on the roof or penthouse. They require regular maintenance for cleaning and filter replacement.
Kitchen hoods require a significant amount of make-up air; therefore energy efficiency needs to be considered. Whenever air is exhausted, an equal amount of outside air must be brought into the building. One way to reduce energy loss is to provide make-up air at the hood. This air can be delivered with less stringent temperature standards saving energy, rather than using fully conditioned air to be brought into the space. There are other opportunities to reduce the operating energy (fan energy, tempering, hood selections, and kitchen physical arrangements) and they should be explored on each project.
Fundamentally, grease can be very dangerous when not properly handled via a properly designed and constructed grease exhaust systems. What’s cooking?
Scott Robbins, PE, CEM, LEED AP BD+C, is an Associate Principal at Vanderweil Engineers in Boston.
