How To Install Makeup Air For Range Hoods

Makeup Air for the Range Hood

A range hood won't work well in a tight business firm without make-up air.

My own house is pretty tight — about 1.5 ACH50 — and when I run the range frazzle fan, I can hear air whistle in through the door gasket. The FHB Firm is even tighter — 0.39 ACH50 — and then I knew going in that we had to make provisions for brand-upwards air when the range exhaust is operating. Make-up air needs to be introduced into the kitchen but not too close to the range hood itself or the air volition be drawn directly into the hood and the air ascension off steaming pots volition spill into the room instead of being sucked into the hood. But on the other paw, I am reluctant to dump make-up air into the room where information technology may feel uncomfortable.

I opted to run a 6-in. duct through the get-go floor organization, alongside the exhaust duct, and terminate information technology in the kitchen cabinet toekick space only to the left of the range. In that location's a space between the toekick and the bottom shelf of the cabinet, so air tin can freely menstruum out from the toekick area. exhaust2016-12-26 17.11

A 6-in. intake duct is a big pigsty in a tight house and one that I want to control to prevent oestrus loss.
exhaust2016-12-26 17.29 So nosotros installed an automated mechanical make-up air damper (Broan). The half-dozen-in. damper fits inline on the intake duct and has a small low-voltage motor that opens a gasketed damper valve. The motor opens the valve when air menstruum is sensed by a venturi switch mounted to the side of the exhaust duct.

The microwave / exhaust is ducted through a wall shared with a closet, and so I installed a pocket-sized snap-in admission panel where the venturi switch in mounted. That way if there is always a problem with the switch it can be easily accessed.

exhaustIMG_4962 — Baseline Pressure level

exhaustIMG_4971 — Max depressurization before mechanical damper opens

exhaustIMG_4966 — Negative pressure level after mechanical damper opens fully and exhaust fan operates at high speed

To get a sense of whether there was any pressure level differential inside to outside the firm when the arrangement was operating I used a manometer to measure the baseline pressure and compare information technology to the pressure level differential when the exhaust was operating. The baseline pressure level differential was about -0.4 Pa. When the exhaust fan was turned on and before the mechanical damper opened the pressure dropped to -28 Pa. This shows that the exhaust fan was depressurizing the house quite a bit for a few seconds while the damper opened. Once the damper was fully open the pressure deviation settled at -7.6 Pa. So the exhaust fan put the firm under a slight negative pressure level.

exhaustIMG_4986 And how does the frazzle fan perform? To test information technology I put a menses hood over the exhaust vent to see how many CFM were exhausted. For a baseline I opened a door and then the exhaust fan had all the makeup air it needed. The hood measured a period of 101 CFM. Next I measured the menses with all the doors and windows closed and got a 87 CFM reading. This shows that at that place is some restricted makeup air flow that reduces fan operation. All the same, even at 87 CFM, the range exhaust fan is evacuating plenty of air to keep virtually of the cooking fumes and moisture vapor from lingering in the firm.