MAKEUP AIR FOR KITCHEN EXHAUST FANS
Today’s new homes are built with energy efficiency in mind, and with modern construction methods and materials allowing for much tighter construction, very little outdoor air can infiltrate a home. Exhausted air must always be replaced by an equal volume of “makeup air”; if makeup air is insufficient, a number of problems can occur. Such issues are common in new energy-efficient homes where powerful kitchen range hoods are installed, which is why New Jersey requires makeup air systems for exhaust fans above 400 CFM.
An exhaust fan can only remove as much air as is occupying a space. If there isn’t enough air to draw from, a drop in pressure will cause a severe decrease in airflow rate and the fan cannot adequately push out heat, odors, and contaminants. More importantly, use of a high-cfm fan where there is insufficient makeup air can lead to a dangerous phenomenon known as backdrafting in which negative pressure can halt or reverse the flow of air or harmful gases in flues and chimneys, causing unsafe levels of carbon monoxide to accumulate in the home.
N.J. code requirement IRC M1503.4 dictates the following: Exhaust hood systems capable of exhausting in excess of 400 cfm (0.19 m3 /s) shall be provided with makeup air at a rate approximately equal to the exhaust air rate. Such makeup air systems shall be equipped with a means of closure and shall be automatically controlled to start and operate simultaneously with the exhaust system. This can be accomplished with the Fantech Makeup Air System (MUAS). When the exhaust fan is activated, the MUAS damper opens and the fan powers on, speeding and slowing in unison with the exhaust fan to modulate air flow in direct proportion to the exhaust. The makeup air is filtered before it is delivered to the home, and cold outdoor air can be tempered with an optional heater kit. Since it is fan-forced, the MUAS can be ducted wherever it is most suitable. The MUAS can be programmed by the installer for slightly negative, slightly positive, or balanced pressure scheme depending on specific need.
E.P. Homiek Sheet Metal Fabrication & HVAC Supply is a certified Fantech dealer and can assist contractors with makeup air needs of up to 2,000 cfm. For more information on the Fantech Makeup Air System, call or stop in to EPH today.
