Packaged Make-Up Air
Why Your Home Needs Make-Up Air
With a goal of greater heating and cooling efficiency, many new and remodeled homes are very well insulated and tightly sealed to reduce the infiltration of cold air. This means fresh air from outside cannot easily enter the home. When kitchen exhaust or bathroom vent fans are in use, especially those over 400 CFM, more air is removed from the home than is able to enter. This causes the home to experience negative pressure, where the air pressure inside the home is lower than the pressure outside the home. A home under negative pressure can experience dangerous problems that are sometimes not noticed until it is too late. In some homes, the outside air will enter and backdraft vents or exhaust ducts of atmospherically vented water heaters and furnaces, causing unsafe operating conditions and the potential for carbon monoxide poisoning. In colder climates negative pressure inside the home can cause colder outside air to find its way in through uninsulated openings, cracks, or open seems. This cold air contacting a warmer interior wall surface can result in dangerous mold growth. Homes with basements may see an increase in the infiltration of RADON gas through floor openings or drains.
Symptoms of a home with potential negative pressure issues could include unpleasant odors coming from a basement or crawlspace, random drafts, and doors that are difficult to open. Homes with wood burning fireplaces may experience drafting issues of the wood smoke or lingering smoke smells days later. In extreme cases a home may become “sick” and occupants may feel sick while in the home for a length of time with symptoms improving once they leave.
All of these issues are solved with the introduction of make-up air into the home. By introducing outside air into the home at nearly the same rate it is exhausted, there is very little chance the home will experience negative pressure.
International Residential Code (IRC) M1503.4 requires automatic make-up air in homes that have an exhaust fan greater than 400 CFM. This is commonly associated with the installation of a large kitchen exhaust hood. A make-up air system is installed to operate automatically when the kitchen hood is turned on. What some homeowners may not realize is that other fans in their home may also be the cause of negative pressure issues. When multiple bathroom fans and clothes dryer fans are running the total CFM exhausted could easily exceed 400 CFM.
How It Works
Electro Industries’ Packaged Make-Up Air utilizes current sensing technology to automatically activate when connected exhaust fans are turned on. A current sensor (included with each unit) is used to measure motor current from an exhaust fan. A two-wire signal from the sensor is wired to the make-up air unit. When the exhaust fan is turned on, the signal from the current sensor tells the make-up air to open its damper and activate the blower to bring in fresh air. A built-in filter will remove any debris such as bugs or small leaves. Heating elements, with our patented WarmFlo® technology, will heat the air to a pre-determined set point as required. This is very important in colder climates to prevent extra cold air from overloading the home’s heating system.
The Electro Packaged Make-Up Air has the ability to monitor multiple exhaust fans via individual current sensors. It can also vary its blower speed to closely match the changing speeds on a multi-speed exhaust fans. Whether multiple low speed fans or a single high speed fan, Electro’s Make-Up Air will recognize the CFM needed and change to meet the demand, always preventing the home from experiencing negative pressure.