Specifying Demand Control Kitchen Ventilation Systems: Top 10 Best Practices

For many of us in the commercial kitchen ventilation industry, we have seen major evolutions in Demand Control Kitchen Ventilation (DCKV) over the last 20+ years. Some have been good – codes once prohibiting automatic variable-speed fans now allow them and often even require them. And some have been bad – several manufacturers have gone down-market to the point their controls are saving very little energy if any at all.

Cook using DCKV with visual optics to adjust fan speeds based on his cooking activity.

The general trend has been positive though because DCKV is no longer a niche but a mainstream solution across the U.S. and increasingly around the world. Running exhaust and make-up air fans at 100% speed all day long regardless of the actual cooking load is antithetical in the sustainability and IoT age in which we now live. As buildings, cars, and everything else get smarter and more efficient, it is only logical that kitchen ventilation systems do as well.

As the original pioneer and market leader of demand control kitchen ventilation since the early 1990’s, we at Melink Corporation want to continue helping building owners save energy – safely, cost-effectively, and efficiently. Having installed over 15,000 systems worldwide, we have assessed the most common problems in the marketplace and feel uniquely qualified to provide the following Top 10 Best Practices for specifiers.


1. Unless the foodservice consultant has knowledge and experience with fans and motors, he/she should consider letting the consulting engineer specify the hoods and DCKV system. The reason is, DCKV is a control system for the exhaust and make-up air fans on the roof. Though the kitchen hoods are ducted to these fans, they are comparatively simple stainless-steel boxes that only contain the rising heat and smoke from the cooking operations. The actual work of removing this heat and smoke is performed by the fans and motors on the roof along with their controls. Foodservice consultants, of course, provide a vital service in specifying the kitchen equipment below the ceiling, and this can still include the kitchen hoods and DCKV system if they have the requisite knowledge and experience of the rest of the ‘system’ above the ceiling. Otherwise, costly errors such as those described below are apt to occur.

2. The DCKV drives must match the fan motor ratings on the roof. If the foodservice consultant cannot obtain the voltage, phase, and frequency information from the ‘M’ drawings, or provide the fan package along with the hoods to ensure a proper match, the wrong drives can be specified and sent to the jobsite. This often causes frustration, time delays and extra costs. Moreover, the DCKV drives should come from tier 1, brand-recognizable manufacturers that have enough confidence in their product to offer a 3-year warranty. These highly sophisticated electronic devices are the beating heart of every DCKV system and therefore should not be selected based on low cost only. Performance and reliability should be the top consideration.

3. The DCKV system must be compatible with the make-up air heating (and cooling, if applicable) system. If the foodservice consultant does not communicate the minimum speed setting of the drives or provide the fan package with the hoods to ensure proper matching, the wrong type of make-up air system can be specified and sent to the jobsite. Not all make-up air systems are capable of heating and/or cooling at low-to-medium speeds and therefore the assumed energy savings by the foodservice consultant will not be achieved for his/her customer. This often causes frustration to everyone involved, and most importantly buyer angst and future bad-will because the purpose in he/she agreeing to buy the DCKV system was to maximize energy savings.

4. The specifier should weigh the risks vs benefits of adding modulating dampers inside the grease ducts for the following reasons: a) Dampers are obstructions inside grease ducts and such ducts are better designed to be completely open for the easy removal of heat and grease/smoke; b) These obstructions add resistance to airflow which force the fan motors to work harder and expend more energy, not less; c) Modulating dampers add another level of moving parts to the system which require regularly scheduled maintenance; d) These dampers are mounted inside the duct and above the ceiling where they are either likely to be damaged by hood cleaners or never seen again and maintained; e) When–not if–these dampers fail, the consequences can be serious if the heat and grease/smoke accumulate to the point of causing a fire; f) These dampers are often used in high-rise applications where only one duct can be run up to the roof and connected to one fan – making the consequences of a fire all the greater because there is more property and human life at stake; g) If more than one damper closes, the fan can cause such a severe negative pressure inside the grease duct that it collapses and renders the entire system unusable and in need of replacement (yes, we have seen this before). Most all engineers agree these risks are not worth the potential benefits.

Please see the photo below of a damper causing almost 100% blockage inside a grease duct. Also see the photo of a hood collar and fire suppression system coated in grease which can act like a ‘glue’ to the dampers above.

5. The engineer should design a dedicated exhaust fan for each kitchen hood whenever possible to improve reliability and energy savings. This allows each hood/fan system to operate independently according to the actual cooking load. It also eliminates the risks of a multi-hood system connected to a single fan which include the following: a) There is no redundancy in the event the single fan goes down due to a fan, motor, drive, or belt failure; b) There is no justification to use modulating dampers inside the grease ducts to achieve energy savings (see above).

6. The engineer or consultant should specify direct-drive fans whenever possible to further improve reliability and energy savings. In the old days, fan and motor pulleys and belts were used to adjust the fan speed to achieve the proper airflows during the original air balance. But today, the DCKV drives can be programmed for a minimum and maximum speed and thereby eliminate the need for these pulleys and belts. This improves reliability because belts are the infamous weak-link in most every HVAC system; and it improves energy savings because belts just create additional efficiency losses in the system.

7. The specifier should consider DCKV systems with both temperature and optic sensors for maximum energy savings on Type I hoods. This is because there are two main by-products of most cooking processes: heat and smoke/steam. If the DCKV system only senses heat, it will not quickly respond to a fast-rising plume of smoke/steam into the canopy. As a result, the hood will ‘spill’ this smoke/steam into the kitchen space and cause comfort, health, and other concerns. The typical way to counter this problem is to program the demand control kitchen ventilation system at a high minimum speed of 80-90% with a low-temperature duct-stat so that the fans operate at 100% even with the slightest amount of heat. However, this eliminates most of the fan energy and conditioned air savings that your customers want during idle-cooking conditions.

We recommend both temperature and optic sensors–to detect both heat and smoke/steam. This allows the DCKV system to be programmed at a much lower minimum speed of 30-50% with a wider temperature span so that average fan speeds can be 60-80% and quickly go to 100% only when there is cooking smoke/steam present inside the hood. Though the optic sensor adds a slight cost premium, the additional operating savings will typically more than offset this cost within 1-2 years. If designed smartly, you will only need one optic sensor per hood, not one optic sensor per appliance. And if designed smartly, you will not have to worry about the optic sensor getting fouled with grease over time because it will be out of the air stream and protected by other capabilities (ie. air-purging, auto-calibrating) to ensure maximum energy savings each and every day.

Of course, if the cooking operations are mainly ovens and do not produce smoke/steam, then the optic sensors can be deleted from the specification to reduce first cost. But optic sensors would provide future flexibility in the event new and different appliances are installed. Moreover, optic sensors are fast-acting whereas temperature sensors are slow-acting, and this complementary combination makes for a safe and reliable control strategy. The lessons being learned from Boeing’s failure to use the right number and type of sensors as well as time-tested algorithms in its new 737Max airplanes are in some ways relevant to our industry. A first-cost obsession can be dangerous.

8. The specifier should be willing and able to logically argue against efforts to reduce the first cost of the DCKV system in the name of value-engineering. As indicated, we live in a world that often thinks in terms of first cost only rather than total life-cycle cost. And this means that sometimes the optic sensors, if not the entire DCKV system, get value-engineered out of the specification. This is another reason why the consulting engineer is often better suited to specify the demand kitchen control ventilation system. He/she is typically better able to make an informed argument to the architect and building owner that a well-engineered DCKV system is fundamental to the safety, health, comfort, and energy efficiency of a kitchen and these should not be compromised.

Having said this, we have also worked with highly-qualified foodservice consultants who have taken the time to learn the savings, costs, risks, and benefits of the various technologies and are just as capable of making this argument.

If a first-cost mindset continues to prevail, then the engineer or consultant should rely on the DCKV manufacturer to provide a comprehensive ‘energy savings report’ to show the expected financial payback and ROI based on the pertinent operating assumptions. The architect and building owner need to understand what they would give up in energy savings if they just install a code-minimum, auto on/off system. Fortunately, the world is increasingly trying to lower its carbon footprint – and this means maximizing energy savings, not just meeting code minimums for safety purposes.

9. Specify the DCKV system to be commissioned by the manufacturer or its trained/authorized representative for every installation prior to turnover to operations. It is our experience that too many systems have not been tested to ensure the owners will ever realize the energy savings they have been led to expect. Without this service, countless systems are operating at 100% speed all day long. We have found this problem at many locations where we are called to investigate as an independent commissioning firm. Invariably, the facilities managers state the systems have run this way for years. Verification and commissioning are essential.

10. Specify the DCKV system to have remote monitoring capabilities to ensure proper operation and energy savings for the life of the system. Like a car or any mechanical/electrical system, proper operation and performance are essential to ensuring a happy customer for life. And, therefore, remote monitoring is a highly beneficial and even necessary feature. Unfortunately, very few demand control kitchen ventilation systems are equipped with this capability and so the specifier and the customer need to know which ones are and are not. In this day and age every facility manager should be able to ‘see’ how his/her systems are performing online.

If you follow these Top 10 Best Practices, you will not only save significantly more energy for your customers and the world at large, you will likely improve your reputation as an expert and be more successful in growing your business. At the least, be mindful that DCKV systems ‘touch on’ multiple professions and trades and therefore we encourage you to help promote good communication between the foodservice consultant and consulting engineer.

Demand control kitchen ventilation as a technology has grown leaps and bounds over the last 20+ years. We hope you and your customers fully benefit from all these advancements well into the future.

Contact us here or call us if you have any questions at 513-965-7300.

Energy Conservation in Commercial Buildings

There’s no doubt that energy conservation in commercial buildings (or any building for that matter) is important.  Reducing operating costs are important for valuations, freeing capital up for other projects or simply reducing the carbon footprint of your building, or portfolio of buildings.  There are many different ECMs (energy conservation measures) available to companies to help achieve these goals, and almost always the decision to use certain measures comes down to “I have to be at 3 years or less for the simple payback”.   While financial metrics are important, I believe that this focus often obscures the soft benefits to the building’s occupants and workers.

 A noise study was recently completed where a corporate kitchen’s noise levels were measured before and after the installation of variable speed controls on both the hood exhaust and supply fans. Traditionally kitchen exhaust fans run at 100% speed for constant periods of time.  With the addition of a variable speed system, like Melink Intelli-Hood, fan speeds are reduced to slower speeds when cooking isn’t at its maximum.  From an energy savings perspective there are two buckets of operational cost reductions, fan energy and conditioned air.  The chart below shows that when the kitchen fans are operating at 100% speeds the decibel level is just short of what a fire alarm sounds like when activated.  With the addition of the variable speed controls, the site realized much lower average fan speeds, as well as a reduction in kitchen noise levels to just below conversational speech, or a reduction of 11 decibels. 

The financial metrics for this project met all approval hurdles and the site is very happy.  For a moment, think about the Chef and his staff.  Their work environment has now become much more quiet.  They can hear each other better when they’re coordinating and preparing meals for several hundred employees each day.  Shouting and miscommunication is greatly reduced, and their environment is more pleasant.  This particular improvement would be hard to show on an income statement…or would it? 

As one example, within Seniors Housing, Dining Services is consistently near, or at, the top in employee turnover percentages.  The current industry turnover rate is 36.91%, (McKnight’s Senior Living, Salaries and Benefits Report 2017-2018) with Certified Nurses Aids coming in a close second at 34%.  It will cost a facility approximately $2,500 in recruiting and training to backfill a single new employee.  Compound that amount with multiple hires each year and it gets expensive very quickly.  If along with reducing energy costs a site can also create a better work environment for its full time employees (FTE), then perhaps that large expense can begin to be reduced and more employees will remain on the payroll instead of seeking other places to work. 

See the full case study here or contact us today to learn more about Intelli-Hood and the benefit of kitchen hood controls.

Noise! Noise! Noise! Reduce The Noise!

The Holidays are upon us, with all the excitement and the parties. As the Grinch says, “And Then! Oh, the noise! Noise! Noise! Noise! There’s one thing I hate! All the NOISE! NOISE! NOISE! NOISE!”

Now, I am no Grinch about the holidays, but prior to my tenure here at Melink I worked for nearly 10 years as an Environmental Health and Safety Manager within a large chemical facility, and there were various work areas which exceeded noise thresholds requiring hearing protection. It was LOUD. This is where I became cognoscente of NIOSH (National Institute for Occupational Safety and Health) standards for hearing conservation,

NIOSH states continued exposure to noise above 85 dBA (adjusted decibels) over time will cause hearing loss. The volume (dBA) and the length of exposure to the sound will tell you how harmful the noise is. In general, the louder the noise, the less time required before hearing loss will occur. According to the NIOSH, the maximum exposure time at 85 dBA is eight hours.

Although we may not be able to control the noise of the holiday party or the loud toys the children will receive on Christmas day, perhaps within the working environments of commercial kitchens we can make drastic improvements and reduce the overall noise level.

Studies have been conducted over the years and dependent on many variables such as the size of the kitchen spaces, the duration of peak activity, and other various factors the overall noise level at times approach or exceed the 85dBA level, sources show a typical restaurant operates at 80 dB, although this value does not trigger hearing protection, some restaurants are known to reach 110 dB at times which is the noise level of a jackhammer! Think of the last time you were at your favorite restaurant and seated near the kitchen entrance versus the opposite side of the room.

Demand control kitchen ventilation can help not just provide energy savings but also reduce the noise levels drastically, especially over an 8-hour timeframe for employees in the kitchen spaces. When researching kitchen exhaust fans one will find that the noise levels are reported as a “sone” which depending on the static pressure of the design the noise levels can vary. A sone is a unit of loudness, how loud a sound is perceived. Doubling the perceived loudness doubles the sone value. Within fan specs of kitchen exhaust fans manufacturers indicate the “Sones” level for example a 5hp kitchen exhaust fan has a sone level ranging from 16.5 to 26 sones dependent on duct design. Per the decibel level and sones conversion chart this is equivalent to around 68.3 to 74.9 dB!

Now considering utilizing a temperature and optic based demand control kitchen ventilation, such as Intelli-Hood, can reduce fan speeds by 30-45% average fan speed over a 24hr period consider the reduction of noise exposure this provides. It is not uncommon for customers post installation of a Melink Intelli-Hood system to recognize significant noise reduction, many times commenting that during food prep hours, although the fans are “turned on” they operate at a minimum speed and it sounds like they are not even operating!

Perhaps you are in a position of influence of the decision to retrofit Demand Control Kitchen Ventilation, or perhaps evaluating and analyzing the opportunity for a client. Remember that there is more savings than simply energy that can be considered when evaluating demand control kitchen ventilation.

The Culprit of Corporate Cafeteria Energy Consumption

Corporate cafeterias have taken off over the last decade, and the trend is not slowing. Businesses and building owners have been adding new cafeterias or expanding current ones to help with recruitment of the millennial generation, boost employee retention and satisfaction, and establish a more inviting work environment. While providing a value to employees, cooperate cafeterias are one of the largest operation costs within the building. After all, food service areas account for the highest energy cost per square foot in the commercial building sector.

Cafeteria Energy Consumption Culprit:

The expansion of cafeterias and new cooking techniques create new challenges for kitchen design, code compliance, and added ventilation among other things. A commercial building’s HVAC system accounts for about 29% of energy consumption, and up to 75% of the HVAC energy consumption is contributed to the kitchen hood ventilation system. Kitchen hoods normally run at 100% fan speed from open to close — sometimes even running for 24 hours a day. Even during slow hours of operation, the system is continuously running at 100%. Any time the fan is on, the kitchen hood’s exhaust fans are pulling perfectly good conditioned air out of the building. At the same time, the makeup air unit is trying to respond to this and is heating/cooling the air to redistribute it back into the kitchen. It is a vicious cycle of wasted energy and wasted money.


DCKV systems utilize optic and/or temperature sensors to actively modulate the exhaust and make up air fans based on the cooking activity within the fume hood. So what does this mean? If your kitchen has downtime and there is no active cooking, the fans will automatically lower their run speed to conserve energy. As cooking starts, fan speed will rev up appropriately until it hits the maximum speed of 100%, if necessary. This allows the highest energy savings, as well as increased comfort and safety for building occupants. DCKV is also easy to implement. It is a low-cost project that is equally effective in new construction or retro-fit during remodels. Savings from installing DCKV can be used to accelerate your payback for the addition of your corporate kitchen, making the cost of the kitchen less.

Interested in seeing how DCKV could benefit your company or commercial building? Contact us for a free energy savings report to see just how much you could save!

Melink Corporation Awarded GSA Certification To Work Directly With U.S. Government Agencies

CINCINNATI, OH – Melink Corporation, a global provider of energy efficiency and renewable energy solutions, just announced it has been awarded a General Services Administration (GSA) Multiple Award Services 056 Contract. This 5-year contract will enable Melink Corporation to partner directly with U.S. government agencies to deliver Intelli-Hood®, their proprietary kitchen ventilation controls, for increased energy efficiency in cooking operations. .

The US Government has been making strides towards sustainability, adopting more products and services that will improve energy usage in their buildings. The US Army compiled research on exhaust air and makeup air hood optimization, showing both the energy and financial savings of using kitchen ventilation controls to regulate the fan speed found here. Melink Corp has worked on numerous US Government projects to date, with agencies such as DOD, DOE, VA Healthcare, GSA and others with cooking operations. This certification will make it easier for the government to implement Intelli-Hood into their projects and continue to make energy efficiency a priority.

“Melink is optimistic that this GSA contract award will increase opportunities for the Government to create more sustainable operations and eliminate barriers to purchasing our Intelli-Hood controls.” said Randy Miles, VP & General Manager of Intelli-Hood.

Since inventing the first demand control kitchen ventilation (DCKV) system over 30 years ago, Melink has created significant energy savings in over 30,000 hoods across the globe. Compatible with all manufacturers, Intelli-Hood can be used in both new construction and retro-fit projects. Unique dual sensors with self-learning algorithms ensure the safest environment and the highest energy savings.

To learn more about Intelli-Hood please visit Intellihood.com.

­­About Melink Corporation: A global provider of energy efficiency and renewable energy  solutions for the commercial building industry. With four business units and a singular energy mission, we help companies save energy, increase profits and make the world a more sustainable place.

Intelli-Hood Military Base Retrofit Case Study


In effort to evaluate the potential of Demand Control Kitchen Ventilation (DCKV) technology, the US Army Engineer Research and Development Center (ERDC) designed, executed, and evaluated a field study. Melink Intelli-Hood® was installed in four dining facilities at Department of Defense (DoD) locations in different climate zones across the United States. These kitchens typically serve a high volume of many meals in short time periods and are excellent candidates for DCKV kitchen controls equipment to reduce energy usage of kitchen hood fans. Baseline measurements were taken before the installations and the energy savings were determined after several months of data. There were two performance objectives: demonstrate a savings of at least 30% in energy usage and maintain or improve occupant comfort.


Both performance objectives were achieved with all four dining facilities saving more than 30% in energy usage as well as maintaining comfort and noise level. No complaints were reported. Further, the following parameters were found to maximize ROI:

  • Relatively large exhaust hood systems (min. of 5,000 CFM)
  • Climate requiring significant heating and/or cooling of makeup air
  • Relatively long operating hours
  • Med-High utility costs


The following is an excerpt from the ERDC report in section 8.3:

Procurement Considerations:
Some vendors offer systems that use only temperature sensors, i.e., they do not use optical or opacity sensors. This is not recommended since the opitcal sensors provide an indication of cooking when the exhaust air has not yet reached the set point temperature.  Thus, the hoods would continue to operate at a low exhaust rate and cooking effluent would spill from the exhaust hood. Temperature-only systems are usually set to higher exhaust rates to mitigate this issue.

The following is a summary table of the energy savings results:

Before/After Energy Savings Summary of Intelli-Hood

The following are before and after Intelli-Hood exhaust fan speed graphs:

Line graph

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Could Intelli-Hood be a fit for my project?

Are you curious how much energy Intelli-Hood could save within your commercial or industrial kitchens?  Submit an energy savings estimate request form at the bottom of our Intelli-Hood page to get started.


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Intelli-Hood Frankfurt Hotel Retrofit Case Study


In October 2012 the Radison Blu Hotel in Frankfurt installed their first Melink Intelli-Hood system. Following the success of this project another 7 installations followed throughout Germany, Switzerland, Austria and Poland. Additional opportunities in the portfolio are being reviewed as a result of the energy savings being realized at the existing properties. There is an established and dedicated network throughout Europe to ensure project support from concept to completion for commercial kitchen operations.


intellihood radison blu savings graphic



Are you curious how much energy Intelli-Hood could save within your commercial or industrial kitchens?  Submit an energy savings estimate request form at the bottom of our Intelli-Hood page to get started.