VENTILATION101

PRESENTATION BY

Nick Kress CRA, UDCPBuilder Account Manager

More often than not, homeowners have either NEVER USED the hoods that exist in their kitchens or in the case of older homes, NEVER HAD A SYSTEM of removing moisture and heat produced when cooking in the kitchen.

Today hood manufacturers not only offer a multitude of SIZES, STYLES and SHAPES, but also they are able to provide the POWER required for efficiently removing heat and moisture. This can be achieved with NOISE LEVELS that begin as low as 0.08 sone.

The KEY TO PROPER HOOD SELECTION depends on many variables which should be evaluated and discussed with homeowners before they embark on the appliance selection process.

Always follow manufacturer recommendations and local codes.

Determine cubic feet of kitchen area for initial cubic feet of air movement recommended

Calculate additional cfm recommended based on the size and fuel type of cooking appliance

Design and measure the duct run and determine your EDL (Equivalent Duct Length)

Consider air capture of hood based on design and location of the hood.

Consider additional variables in the kitchen design

Provide make up air when required

Determine

CFMfor kitchen area

Let’s assume this kitchen is 9 FEET WIDE (X)10 FEET LONG (Y)with a ceiling height of 8 FEET TALL (Z)

1. Determine the cubic feet (CF) within the kitchenX x Y x Z = CF9 x 10 x 8 = 720

2. Multiply the CF by the recommended air changes per hour (ACH) for a kitchen (which is 15)720 x 15 = 10,800

3. Divide that number by 60 minutes10,800 ÷ 60 = 180 CFM

EXAMPLE

Determine CFMrequired for cooking surface

FUEL TYPESIZE

FEATURES

Add 100 cfm for every 10,000 BTU (British Thermal Unit) of heat produced on cooking surface.

EXAMPLE 6 burners x 15000 BTU each = 90000 BTU90k / 10k = 900 cfm

NOTE If the cook top has a grill or griddle, add 500 cfm for every 12” of each

6 burners x 15000 BTU each = 90000 BTU90k / 10k = 900 cfm

GAS COOKING

Add 100 cfm for every 10” of cooking surface.

EXAMPLE On a 36” induction cook top36/10 x 100cfm = 360 cfm

On a 36” induction cook top36/10 x 100cfm = 360 cfm

ELECTRIC / INDUCTION COOKING

Calculate

EDLEquivalent Duct Length

DEDUCT 1 cfm for every foot of duct run PLUS 20 cfm for every elbow PLUS 30 cfm for the wall cap

EXAMPLE A duct run is 20’ with two 90 degree elbows (radius turns) and one 45 degree elbow ending at the wall cap. Calculation:20 cfm + 60 cfm + 30 cfm = 110 cfm (EDL or Equivalent Duct Length). This should be added to the previously determined amounts for the total requirement for the hood.

20 cfm + 60 cfm + 30 cfm = 110 cfm

CALCULATE THE DUCT RUN REQUIREMENT

RECAP

Kitchen area9 feet wide (X)10 feet long (Y) 8 feet ceiling height (Z)

Cooking surface36” gas cook top four 16K BTU burners &a 12” grill

A duct run 15’ with one 90 degree elbow (radius turns) and two 45 degree elbows ending at the wall cap.

LET’S DETERMINE THE CFM REQUIRED FOR THE FOLLOWING EXAMPLE

Room cfm requirement:9 x 10 x 8 = 720 cubic feet720 x 15 = 10800 ACH / 60 min =

Range top cfm requirement:16K x 4 = 64K BTU64K BTU / 10K = 640 cfm + 500 cfm (grill) =

Ducting cfm requirement:15 x 1 = 15 + 60 + 30 =

TOTAL RECOMMENDED CFM =

CALCULATIONS

180 cfm

640 cfm1140 cfm

1425 cfm

105 cfm

Variablesto Consider

when Making theFinal Selection

Location of cooking surface – wall or island. Consider increasing coverage for an island hood.

Cooking appliance manufacturer recommendations for ventilation.

Hood manufactures required distance from cooking surface.

Ceiling height and mounting options.

Width and depth of cooking surface

Design of hood chosen and depth of hood sump.

Type of blower –internal, in line or external remote blower.

Noise level of selected hood on lowest speed and highest speed.

Hood lighting and “Green Features”

Only use downdraft ventilation when recommended by the manufacturer. Only 2 manufacturers of pro style ranges and range tops approve their own downdraft products for select models.

Make Up Air

2012 IRC CODES REGARDING MAKE UP AIR

Makeup air requirements associated with vented kitchen range hoods:(IRC M1503.4, M1501.2, G2447.6)

Three code provisions can trigger the need for makeup air in this situation. The bottom line is that makeup air is always required for high-volume hoods (> 400 cfm) and may be required for lower volume hoods when natural-draft appliances are used.

M1503.4 requires makeup air for kitchen hoods which exhaust more than 400 cfm. The makeup airflow rate must equal the exhaust flow rate and an intake damper on the makeup air duct must be interlocked with the control for the fan.

M1501.2 requires that “ducted exhaust systems” (such as kitchen hoods, bath fans, clothes dryers) not induce negative pressure in excess of negative 3 Pascals at the location of a natural draft combustion appliance. This provision applies regardless of the rated airflow of the exhaust system.

G2447.6 reinforces M1501.2, more explicitly for vented kitchen hoods. This provision is independent of the rated airflow through the hood.

A pressure test is required to demonstrate that the depressurization level is within the 3 Pascal limit. If the depressurization limit is exceeded, makeup air is one potential solution.

There is no requirement to temper makeup air.

REASONS TO HAVE MAKE UP AIR

•Recommended by hood manufacturer•HEALTH - Carbon Monoxide, contaminants•SAFETY - fireplace ambers•Avoiding negative air pressure•Local building codes

Verify the dampers operate properly.

Do not oversize the exhaust fan

Make Up AirSystems

VentilationSystem Noise

What can increase the noise level of the hood?

BLOWER MOTOR: TYPESingle phase - Three phase - Linear

LOCATION

FILTER: TYPEMesh - Baffle - Channel - Recirculating - Downdraft

DESIGN: HOOD DUCT

length, turns, interior obstacles

NOISE SUPPRESSION SYSTEMSIn line silencers

EXAMPLES

Well Matched Hoods& Cooking Surfaces

EXAMPLES

Approved Kitchen Ventilationalthough not always recommended

EXAMPLES

Unique Kitchen Ventilation Designs

The Bloopers

Kitchen Ventilation Selections