Make-up Air & Kitchen Ventilation

June 12, 2023

Mrinmoy Dey

With modern construction techniques making the buildings tight, the make-up air unit is becoming increasingly indispensable to balance the outflow and inflow of air in the kitchen.

Ventilation is the single most important factor in the design, construction and operation of any kitchen. Without the right ventilation, it can be very difficult to operate in a kitchen. Effective kitchen ventilation has to balance the airflow in and out of the kitchen. The general ventilation introduces sufficient clean, cool air and removes excess hot air for the occupants to breathe adequately and remain comfortable. It also provides sufficient air for complete combustion, especially inside appliances. Failing to do so can lead to chronic debilitating carbon monoxide poisoning.

The amount of ventilation required in any particular kitchen depends on various factors like the kind of food being cooked, the structure of the cooking area and the type of equipment being used for cooking. Depending on the kind of cooking that is going to take place, the ventilation system will dilute and remove odours, vapours and steam from the cooking process. It would also protect the residents from any health hazards arising from some cooking fumes. A poor ventilation system will also result in more grease on appliances and countertops and hence increase the overall maintenance of the property.

Make-up Air

The key component for ventilation is the exhaust system. However, in kitchen exhaust systems there are a number of interdependent units namely, the exhaust hoods, exhaust fans, makeup air units, and HVAC (Heating Ventilation Air Conditioning) units. They all need to operate within defined parameters to make the exhaust system effective.

Of all the elements in the kitchen ventilation system, makeup air is often the neglected or overlooked element in kitchen designs. Make-up air is designed to “make up” the air in the interior space that has been removed by exhaust fans. This type of HVAC solution pulls in fresh, tempered air from outside the building to replace existing air that cannot be recirculated.

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Balancing airflow

A make-up air solution is often recommended by architects and designers for buildings where environmental conditions warrant a greater need for ventilation. It not only improves the quality of air within the building but also protects the health of the residents by bringing in fresh air.

From an architectural perspective, makeup air can be a concern for kitchens that are significantly tighter i.e. there are lesser openings for the air to get in. The need for makeup air units has risen in recent times because range hood fans have been getting significantly more powerful to accommodate a growing trend toward putting large commercial-style ranges in residential kitchens. Large range hoods can draw out air at the rate of 1200 CFM or more which is roughly a small roomful of air every 60 seconds.

In addition to the safety concerns, the downside of depressurisation includes a big energy penalty from exhausting air that has been heated or cooled by the residents. When a kitchen with a powerful range hood or exhaust does not have a proper makeup air unit then the airflow inside the room cannot be controlled which results in drafts, which in turn can make people uncomfortable. If the incoming air is humid, it can bring unwanted moisture into the house. In a cooling climate, that moisture can condense against the back side of cool, air-conditioned walls and cause concealed mould and rot.

Depressurisation is a potential problem, especially in modern constructions. Earlier makeup air units were not necessary as air would leak in through nearby windows and doors, and even through walls, to make up the pressure difference caused by the exhausted air. But with tight houses, makeup air units, to balance the outflow and inflow, have to be incorporated in the kitchen design. In a kitchen, the exhaust and makeup air systems have to be connected. When the range hood is turned on, it will send a signal to a damper in the makeup air duct, which will open to allow air to flow in. When the range hood shuts off, the damper will close, blocking the infiltration of unconditioned air.

Things to keep in mind

While designing a makeup air system, designers suggest that the makeup air unit should not be placed too close to the range hood itself. Then the air may be drawn directly into the hood and the air rising off steaming pots will spill into the room instead of being sucked into the hood. Care has to be taken in deciding where the make-up air will be released to make people inside the least uncomfortable.

Installing a makeup air unit may seem costly or unnecessary for some residents. However, monthly energy bills can get high if the ventilation systems and their different units are not functioning at their peak performance. When the ventilation system struggles to maintain good airflow, it will consume more and more electricity. A make-up air damper can provide the fresh, cool air that it needs to optimise the kitchen ventilation system.

[The article was published in the January-March 2023 issue of Kitchen Ideas magazine.]

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