Zone Exhaust | COMNET

This group of building descriptors describes the rate of exhaust and the schedule or control for this exhaust. An exhaust system can serve one thermal block or multiple thermal blocks. Energy is summed at the exhaust system level, not the thermal block level.

Kitchen Exhaust Hood Length
Applicability	Exhaust fans in spaces of type Kitchen
Definition	The exhaust hood length
Units	ft
Input Restrictions	As designed
Baseline building	Same as the proposed design

Kitchen Exhaust Hood Style
Applicability	Exhaust fans in spaces of type Kitchen
Definition	The hood style as defined in Table 140.9-A of the Standards
Units	List: Wall-mounted canopy, Single Island, Double Island, Eyebrow, Backshelf/Passover
Input Restrictions	As designed
Baseline building	Same as the proposed design

Kitchen Exhaust Hood Cooking Duty
Applicability	Exhaust fans in spaces of type Kitchen
Definition	The hood cooking duty as defined in Table 6.5.7.1.3 of the 90.1 2010 Standards
Units	List: Light Duty, Medium Duty, Heavy Duty, Extra Heavy Duty
Input Restrictions	As designed
Baseline building	Same as the proposed design

Kitchen: Exhaust Air Flow Rate

Applicability

All Kitchen HVAC zones

Definition

Rate of exhaust from a thermal zone. Standard 90.1 2010 Section 6.5.7.1.3 requires each hood in kitchen/dining facility with total kitchen hood exhaust airflow rate greater than 5,000 cfm to have an exhaust rate that complies with Table 3.6.5-1. If a single hood, or hood section, is installed over appliances with different duty ratings, then the maximum allowable flow rate for the hood or hood section shall not exceed the Table 3.6.5-1 values for the highest appliance duty rating under the hood or hood section.

Table 3.6.5-1: Maximum Net Exhaust Flow Rate, CFM per Linear Foot of Hood Length

Source: Table 6.5.7.1.3 of Standard 90.1-2016

Type of Hood	Light Duty Equipment	Medium Duty Equipment	Heavy Duty Equipment	Extra Heavy Duty Equipment
Wall-mounted canopy	140	210	280	385
Single island	280	350	420	490
Double island (per side)	175	210	280	385
Eyebrow	175	175	Not allowed	Not allowed
Backshelf/Passover	210	210	280	Not allowed

Units

cfm

Input Restrictions

As designed

Baseline building

If the exhaust airflow rate of the proposed design is less than or equal to the exhaust flow rate prescribed in Table 3.6.5-1 above, then the baseline exhaust flow rate will be same as proposed. However, if the kitchen hood exhaust air flow rate for the proposed design is greater than the airflow rate prescribed, then the baseline buildings uses airflow rates equal to that in the table.

Kitchen: Demand Ventilation
Applicability	All Kitchen HVAC Zones
Definition	A demand ventilation system uses a light beam and a photo detector to detect the presence of smoke. It also has a temperature sensor to detect heat. The exhaust fan slows down below design levels and both exhaust and replacement airflow rates are reduced when the system detects no smoke or heat.
Units	Unitless
Input Restrictions	As designed
Baseline building	For proposed designs with exhaust air flow rate greater than 5000 CFM, baseline models is required to use demand ventilation system on 75% of the exhaust air and makeup air. Airflow will be reduced by 50% during 50% of kitchen occupied hours.

Laboratory Exhaust Rate Type
Applicability	All laboratory zones
Definition	The type of load that dictates lab exhaust rate requirements
Units	List, either: Hood dominated or Load dominated
Input Restrictions	As designed
Baseline building	Same as the proposed design

Laboratory: Exhaust Minimum Air Flow Rate

Applicability	All laboratory zones
Definition	Rate of exhaust from a zone
Units	cfm
Input Restrictions	Baseline Building
Baseline Rules	Same As Proposed except for the unoccupied periods, where systems serving laboratory spaces shall reduce the exhaust and makeup air volume during unoccupied periods to the largest of 50% of zone peak air flow, the minimum outdoor air flow rate, or the air flow rate required to comply with applicable codes or accreditation standards.

Exhaust Fan Name
Applicability	All HVAC zones
Definition	A reference to an exhaust fan system that serves the thermal block
Units	Text or other unique reference to an exhaust fan system defined in the secondary systems section.
Input Restrictions	As designed
Baseline Rules	Same as the proposed design

Exhaust Air Flow Rate
Applicability	All HVAC zones
Definition	Rate of exhaust from a thermal block
Units	cfm
Input Restrictions	As designed
Baseline Rules	Same as the proposed design

Exhaust Fan Schedule
Applicability	All HVAC zones
Definition	Schedule indicating the pattern of use for exhaust air from the thermal block. This input should consider the position of fume hood sash opening. For toilets and other exhaust applications, the schedule may coincide with the operation of the exhaust fan system.
Units	Data structure: schedule, fraction
Input Restrictions	As designed
Baseline Rules	Same as the proposed design