Range Hoods Need Makeup Air
Range hoods suck unwanted air pollutants out of the living space, so we don't have to breathe them. At least range hoods that are ducted to the outside do. Recirculating rangehoods, affectionately referred to as forehead greasers by some engineers, attempt to clean the air instead of exhausting it. But range hoods that exhaust air are also doing something else: sucking air into the living space—unless they are outfitted with a make up air supply. Sucking air into the living space through holes in the walls, floors, and ceiling, means sucking in air filtered by mouse poop, radon, and squirrel carcasses—an IAQ nightmare.
Make-up air is fresh air brought into a building to replace the air exhausted by ventilation systems like range hoods or bath fans. Make-up air helps maintain proper air pressure within a building, preventing drafts and improving air quality.
In this excerpt from a Building Science Fundamentals class, taught by Dr. Joseph Lstiburek (STEE-brick), Dr. Joe gives the simple answer: do what restaurants do.
Transcript:
Bettsy Pettit (off camera), Sam's asking: "How would you install a range hood in a balanced ventilation system?"
Dr. Joe: With makeup air. You can actually get range hoods with makeup air. And what you end up doing is the way we do it in the—in the restaurant industry.
So if I’ve actually got a 600 CFM exhaust hood, I introduce 500 CFM at the toe kick.
I have pictures. I’ll show you.
More to explore:
- Whole-House Mechanical Ventilation: Exhaust, Supply, Balanced, and Backdrafting (ProTradeCraft)
- Mechanical Ventilation: 7 Minutes of BS (ProTradeCraft)
- Balancing Act: Exhaust-Only Ventilation Does Not Work. (buildingscience.com)
- The Hollow Building (buildingscience.com)