Keeping Up With Codes
Vetting the information about minimum and maximum exhaust rates for commercial-kitchen-ventilation systems in this issue’s Focus, “The ABCs of CKV," has been, well, exhausting.
I’m not sure how foodservice facility designers keep up with standard building codes, energy-efficient building codes, code revisions or even code-enforcement authorities as they design CKV systems. If you’ve ever smelled the kitchen broiler from the dining room, you’ll know that some are better at it than others.
Back in the day, assorted code-writing organizations—such as the Building Officials and Code Administrators Int’l., Int’l. Association of Plumbing and Mechanical Officials and the Int’l. Code Council—set minimum exhaust volumes for CKV. They were generous rates, and it was easy to comply. Then UL 710 came along and established that a well-engineered CKV system could exhaust effluent at lower volumes than even the minimums. For years, those “UL-listed hood” rates were included in American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 154 in a handy table. It listed minimum exhaust rates for four kinds of hoods and four levels of equipment, from light to heavy duty. (The ASHRAE Handbook still includes the table; the current Standard 154 does not.)
Today, a newer standard is in use for buildings wishing to comply with energy-efficiency regulations. Currently, 16 states and Washington, D.C., officially have adopted ASHRAE Standard 90.1 into their energy codes (go to energycodes.gov/adoption/states) and more are following suit. Standard 90.1 sets maximum exhaust rates. These rates fall just about 30% lower than the high end of the exhaust ranges set up in the old Standard 154 table.
So what does this mean? As one manufacturer told me, if you’re designing a commercial kitchen, the first question you need to ask is, “What is the maximum amount of air I am allowed to take out of this kitchen?” Then design the CKV system accordingly, which means carefully. Too often, I’ve heard that the CKV system, much like storage space, comes toward the end of the design process. I don’t want to say it’s an afterthought, but it could be that just ramping up exhaust rates was relied on as a quick fix for pressure imbalances and hood performance issues. But if you’re limited in how much you can exhaust, then the way air is introduced, flows through and exits the space becomes paramount, and CKV engineering “best practices” become more important than ever.