3.6.5.3 Zone Exhaust

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

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 zone or multiple thermal zones. Energy is summed for the exhaust system level, not the thermal zone 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	This input defines the style of the kitchen hood
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 6.5.7.2.2 of Standard 90.1-2019
Units	List: Light Duty, Medium Duty, Heavy Duty, Extra Heavy Duty
Input Restrictions	As designed
Baseline Building	Same as the proposed design

Kitchen: Exhaust Airflow Rate

Applicability

Exhaust fans in spaces of type kitchen

Definition

Rate of exhaust from a thermal zone. Standard 90.1-2019, Section 6.5.7.2.2, requires each hood in a kitchen/dining facility with a total kitchen hood exhaust airflow rate greater than 5,000 cfm to have an exhaust rate that complies with Table 39. 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 39 values for the highest appliance duty rating under the hood or hood section.

Table 39. Maximum Net Exhaust Flow Rate, cfm per Linear Foot of Hood Length

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

The exhaust air flow rate for the baseline building should be equal to the exhaust flow rate prescribed in Table 39

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. Exhaust fans controlled with a demand ventilation system with a minimum flow no more than 50% shall be modeled as running at 75% during all exhaust fan operating hours.
Baseline Building	Same as proposed except fan speed would not be reduced due to demand ventilation systems

Laboratory: Exhaust Minimum Airflow Rate
Applicability	All laboratory zones
Definition	Rate of exhaust from a zone
Units	cfm
Input Restrictions	As designed
Baseline Building	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 airflow, the minimum outdoor airflow rate, or the airflow rate required to comply with applicable codes or accreditation standards. Baseline systems serving only laboratory spaces that are prohibited from recirculating return air by code or accretion standard, the baseline system shall be modeled with 100% outdoor air.

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

Exhaust Fan Operation Schedule
Applicability	All HVAC zones
Definition	Schedule indicating the pattern of use for exhaust air from the thermal zone. For laboratory exhaust hoods, 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 Building	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 airflow, the minimum outdoor airflow rate, or the airflow rate required to comply with applicable codes or accreditation standards

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 zone or multiple thermal zones.

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	This input defines the style of the kitchen hood
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 6.5.7.2.2 of Standard 90.1-2019
Units	List: Light Duty, Medium Duty, Heavy Duty, Extra Heavy Duty
Input Restrictions	As designed
Baseline Building	Same as the proposed design

Kitchen: Exhaust Airflow Rate

Applicability

Exhaust fans in spaces of type kitchen

Definition

Rate of exhaust from a thermal zone. Standard 90.1-2022, Section 6.5.7.2.2, requires each hood in a kitchen/dining facility with a total kitchen hood exhaust airflow rate greater than 5,000 cfm to have an exhaust rate that complies with Table 42. 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 42 values for the highest appliance duty rating under the hood or hood section.

Table 42. Maximum Net Exhaust Flow Rate, cfm per Linear Foot of Hood Length

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

Same as designed not exceeding the maximum allowed CFM from Table 42 (for projects following Standard 90.1-2022 Section G3.3 this maximum only applies to exhaust systems included in the scope of the retrofit and only if, based on Standard 90.1-2022 Section 6.1.4 language, the 90.1-2022 Section 6.5.7.2.2 requirements are applicable.).

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	G3.2 New Construction/Major Alterations Not applicable. G3.3 Minor Alterations The baseline shall be modeled as minimally compliant with 90.1-2022 Section 6.5.7.2.3 using the same strategy as specified in the proposed design. Where the proposed design does not include one of these strategies it is recommended that 90.1-2022 Section 6.5.7.2.3 option b be modeled in the baseline. Standard 90.1-2022 Section 6.5.7.2.3 requirements translated into modeling requirements are as follows. If a kitchen/dining facility has a total kitchen hood exhaust airflow rate greater than 5000 cfm then it shall be modeled with one of the following strategies: a. At least 50% of all replacement air is transfer air that would otherwise be exhausted. b. Demand ventilation systems on at least 75% of the exhaust air. Such systems shall be modeled to provide at least a 50% reduction in exhaust and replacement air system airflow rates. c. With an energy recovery device that results in a sensible energy recovery ratio of not less than 40% on at least 50% of the total exhaust airflow. A 40% sensible energy recovery ratio shall mean a change in the dry-bulb temperature of the outdoor air supply equal to 40% of the difference between the outdoor air and entering exhaust air dry-bulb temperatures at design conditions. Exception: the system should be modeled the same in the baseline and proposed if, based on the requirements of 90.1-2022 Section 6.1.4 and the scope of the alteration, the 90.1-2022 Section 6.5.7.2.3 requirements are inapplicable.

Laboratory: Exhaust Minimum Airflow Rate
Applicability	All laboratory zones
Definition	Rate of exhaust from a zone
Units	cfm
Input Restrictions	As designed
Baseline Building	G3.2 New Construction/Major Alterations 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 airflow, the minimum outdoor airflow rate, or the airflow rate required to comply with applicable codes or accreditation standards. Baseline systems serving only laboratory spaces that are prohibited from recirculating return air by code or accretion standard, the baseline system shall be modeled with 100% outdoor air. G3.3 Minor Alterations The baseline shall be modeled as minimally compliant with 90.1-2022 Section 6.5.7.3 using the same feature as specified in the proposed design. Where the proposed design does not include one of these features it is recommended that 90.1-2022 Section 6.5.7.3 option a be modeled in the baseline. Standard 90.1-2022 Section 6.5.7.3 requirements translated into modeling requirements are as follows. Buildings with laboratory exhaust systems having a total exhaust rate greater than 5000 cfm shall be modeled with at least one of the following features: a. VAV laboratory exhaust and room supply system modeled to reduce exhaust and makeup airflow rates and/or incorporate a heat recovery system to precondition makeup air from laboratory exhaust that meets the following: A + B × (E/M) ≥ 50% where A = percentage that the exhaust and makeup airflow rates can be reduced from design conditions B = sensible energy recovery ratio E = exhaust airflow rate through the heat recovery device at design conditions M = makeup airflow rate of the system at design conditions b. VAV laboratory exhaust and room supply systems shall be modeled to reduce exhaust and makeup airflow rates to 50% of the zone design values or the minimum required to maintain pressurization relationship requirements during unoccupied periods. c. Modeled such that direct makeup (auxiliary) air supply is equal to at least 75% of the exhaust airflow rate, heated no warmer than 2°F below room set point, cooled to no cooler than 3°F above room set point with no humidification added, and no simultaneous heating and cooling used for dehumidification control. Exception: the system should be modeled the same in the baseline and proposed if, based on the requirements of 90.1-2022 Section 6.1.4 and the scope of the alteration, the 90.1-2022 Section 6.5.7.3 requirements are inapplicable.

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

Exhaust Fan Operation Schedule
Applicability	All HVAC zones
Definition	Schedule indicating the pattern of use for exhaust air from the thermal zone. For laboratory exhaust hoods, 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 Building	G3.2 New Construction/Major Alterations 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 airflow, the minimum outdoor airflow rate, or the airflow rate required to comply with applicable codes or accreditation standards. G3.3 Minor Alterations Same as proposed except where a modeled efficiency/control strategy necessitates the use of an alternative baseline schedule for when complying with the baseline building requirements for the Kitchen: Demand Ventilation and Laboratory: Exhaust Minimum Airflow Rate descriptors above.