3.7.3.1 Baseline Fan System Summary

The baseline building fan system is summarized in this section. See Table 3.1-1 for the HVAC baseline building system mapping.

Total baseline building fan system power for the baseline building fan systems is given in Table 3.7.3-1. In this table, "cfms" is the supply fan air flow at peak design conditions. This is calculated for the baseline building with the sizing procedure described in Figure 2.4-1. This brake horsepower includes the supply fan, the return fan, and exhaust fans. Exhaust fans include kitchen hoods, toilets, fume hoods, and other miscellaneous fans that operate at design conditions.

Table 3.7.3-1: Building Descriptor Applicability for Fan Systems

Inputs	Supply Fan	Return/Relief Fan	Exhaust Fans (Hoods)
Modeling Method	Yes	Same as supply	Yes
Air Rated Capacity	Yes	Yes	Yes
Plenum Zone	Not applicable	Yes	Not applicable
Return Air Path	Not applicable	Yes	Yes
Fan Control Method	Yes	Same as supply	Yes
Brake Horsepower (bhp)	Yes	Yes	Yes
Static Pressure	Yes	Yes	Yes
Fan Efficiency	Yes	Yes	Yes
Fan Motor Efficiency (hm)	Yes	Yes	Yes
Fan Position	Yes	Not applicable	Not applicable
Motor Position	Yes	Yes	Not applicable
Part-LoadFan Power Curve(W)	Yes	Yes	Yes
Fan KW	Yes	Yes	Yes

Table 3.7.3-2: Baseline Building Fan System Details

Baseline System Type	Baseline Break Horsepower	Baseline System Fan Power	Baseline Motor Efficiency
1 PTAC	n. a.	P = 0.3 x CFM_s	n. a.
2 PTHP
3 PSZ-AC	bhp = CFM_s Í 0.00094 + A	P = (bhp x 746) / h_m	See Table 3.7.3-4
4 PSZ-HP
5 PVAV	bhp = CFM_s Í 0.0013 + A
6 PVAV / PFP
7 VAV
8 VAV / PFP
9 HV Furnace	n. a.	P = 0.3 x CFM_s OR P = 0.054 x CFM_nmc	n. a.
10 HV Electric
11 SZ-VAV	bhp = CFM_s Í 0.00062 + A	P = (bhp x 746) / h_m	See Table 3.7.3-4
12 SZ-CV-HW	bhp = CFM_s Í 0.00094 + A
13 SZ-CV-ER
P Total baseline fan power to be distributed among the supply, relief, and exhaust fans in the same proportion as the proposed design. bhp The baseline building break horsepower (applicable to systems 3-8 and 11-13). A A break horsepower adder due to special conditions. See Table 3.7.3-3. CFM_s The air volume in cubic feet per minute delivered by the supply fan. CFM_nmc The air volume in cubic feet per minute delivered by the supply fan for non-mechanical cooling systems (applicable to systems 9 and 10). h_mThe baseline system fan motor efficiency taken from Table 3.7.3-4.

Table 3.7.3-3: Baseline Building: Fan Power Limitation Static Pressure Adjustment

Source: Table 6.5.3.1-2 of Standard 90.1-2016

	Device	Adjustment (A)
Credits	Fully ducted return and/or exhaust air systems	0.5 in. w.c. (2.15 in. w.c. for laboratory and vivarium systems)
	Return and/or exhaust airflow control devices	0.5 in. w.c.
	Exhaust filters, scrubbers, or other exhaust treatment	The pressure drop of device calculated at fan system design condition
	Particulate Filtration Credit: MERV 9 through 12	0.5 in. w.c.
	Particulate Filtration Credit: MERV 13 through 15	0.9 in. w.c.
	Particulate Filtration Credit: MERV 16 and greater and electronically enhanced filters	Pressure drop calculated at 2× clean filter pressure drop at fan system design condition
	Carbon and other gas-phase air cleaners	Clean filter pressure drop at fan system design condition
	Biosafety Cabinet	Pressure drop of device at fan system design condition
	Energy Recovery Device and other Coil Runaround Loop	(2.2 × Energy Recovery Effectiveness) - 0.5 in w.c. for each airstream
	Coil Runaround Loop	0.6 in. w.c. for each airstream
	Evaporative humidifier/cooler in series with another cooling coil	Pressure drop of device at fan system design condition
	Sound Attenuation Section	0.15 in. w.c.
	Exhaust Systems serving fume hoods	0.35 in. w.c.
	Laboratory and Vivarium exhaust systems in high-rise buildings	0.25 in. wc./100 ft. of vertical duct exceeding 75 ft.
Deductions	Systems without central cooling device	-0.6 in. w.c.
	Systems without central heating device	-0.3 in. w.c.
	Systems without central electric resistance heat	-0.2 in. w.c.

90.1-2019

The baseline building fan system is summarized in this section. See Table 3 for the HVAC baseline building system mapping.

Total baseline building fan system power for the baseline building fan systems is given in the following sections as well as Table 53 and Table 54. Table 52 summarizes all descriptors for fan systems and their applicability to supply, return/relief, and exhaust fans.

Table 4 summarizes inputs for each of the three approaches for imputing system fan power (fan power method, brake horsepower method, and design pressure drop method).

In these tables, CFMs is the baseline fan supply fan airflow at peak design conditions.
The fan system power includes the supply fan, the return fan, and exhaust fans.
Exhaust fans include kitchen hoods, toilets, fume hoods, and other miscellaneous fans that operate at design conditions.

When the proposed design has return fans, exhaust fans (toilets or kitchens), or fume hood exhaust systems, the baseline building has the same systems. Fan power will be allocated to the baseline supply, return, and exhaust fans based on the Fan System Power described below and the ratio of each fans power in the proposed design to the proposed design fan system power.

Table 52. Building Descriptor Applicability for Fan Systems

Inputs	Supply Fan	Return/Relief Fan	Exhaust Fans (Hoods)
Modeling Method	P	Same as supply	P
Air Rated Capacity	P	P	P
Plenum Zone	X	P	X
Return Air Path	X	P	X
Fan Control Method	P	Same as supply	P
Brake Horsepower	P	P	P
Static Pressure	P	P	P
Fan Efficiency	P	P	P
Motor Efficiency	P	P	P
Fan Position	P	X	X
Motor Position	P	P	X
Part-Load Power Curve	P	P	P
Fan KW	P	P	P

Table 53. Baseline Fan System Details for Fan System Power

System	Fan Power Method (W/cfm)	Brake Horsepower Method (bhp/cfm)	Design Pressure Drop (DPD) Method	Fan Motor Efficiency ŋm	Fan Mech Efficiency	DPD (If no additional pressure drop credits)^(a)
1 & 2	0.3	W/cfm x ŋm x 0.00134	bhp/cfm x fan mech efficiency x 6356	80%	65%	1.33 in. w.g.
3, 4, 12. & 13	(bhp x 746)/ŋm	0.00094 x CFMs + A	bhp/cfm x fan mech efficiency x 6356	Standard 90.1-2019, Table G₃.9.1^(a)	65%	3.88 in. w.g.
5 through 8	(bhp x 746)/ŋm	0.0013 x CFMs + A	bhp/cfm x fan mech efficiency x 6356	Standard 90.1-2019, Table G₃.9.1^(a)	65%	5.37 in. w.g.
9 & 10 supply fan	0.3	W/cfm x ŋm x 0.00134	bhp/cfm x fan mech efficiency x 6356	Standard 90.1-2019, Table G₃.9.1^(a)	65%	1.33 in. w.g.
9 & 10 non-mechanical cooling fan^(b)	0.054	W/cfm x ŋm x 0.00134	bhp/cfm x fan mech efficiency x 6356	80%	65%	0.24 in. w.g.
11	(bhp x 746)/ŋm	0.00062 x CFMs + A	bhp/cfm x fan mech efficiency x 6356	Standard 90.1-2019, Table G₃.9.1^(a)	65%	2.56 in. w.g.
The term “A” for system types 3 through 8 is calculated based on equipment included in the proposed design using the procedure in Table 6.5.3.1.1 of ASHRAE Standard 90.1-2019 and the airflows from the baseline design. This accounts for various additional fan pressure drops associated with special conditions. (a) Fan motor efficiency is the efficiency from Table G₃.9.1 of Standard 90.1-2019 for the next motor size greater than the bhp. (b) This alternate equation is only used if there is a non-mechanical cooling fan in place in the proposed design. (c) If system qualified for additional pressure drop credits DPD should be calculated based on adjusted bhp.

Pressure Drop Adjustment
Applicability	Any system serving zones served by systems in the proposed design which qualify for pressure drop adjustments in Table 54
Definition	Adjustments to fan power limitations related to application-specific requirements as allowed by Standard 90.1-2019 Table 6.5.3.1-1
Units	List
Input Restrictions	As designed
Baseline Building	Calculated from Section 6.5.3.1-1 of Standard 90.1-2019 for baseline system fans. Pressure drop adjustment is based on the device from Table 54 being present in the proposed design.

Table 54. Baseline Building: Fan Power Limitation Pressure Drop Adjustment

Device	Adjustment
Credits
Return or exhaust systems required by code or accreditation standards to be fully ducted, or systems required to maintain air pressure differentials between adjacent rooms.	0.5 in. w.c. (2.15 in. w.c. for laboratory and vivarium systems)
Return and/or exhaust airflow control devices	0.5 in. w.c.
Exhaust filters, scrubbers, or other exhaust treatment	The pressure drop of device calculated at fan system design condition
Particulate filtration credit: MERV 9 through 12	0.5 in. w.c.
Particulate filtration credit: MERV 13 through 15	0.9 in. w.c.
Particulate filtration credit: MERV 16 and greater and electronically enhanced filters	Pressure drop calculated at 2x clean filter pressure drop at fan system design condition
Carbon and other gas-phase air cleaners	Clean filter pressure drop at fan system design condition
Biosafety cabinet	Pressure drop of device at fan system design condition
Energy recovery device and other coil runaround loop	(2.2 × Energy Recovery Effectiveness)—0.5 in w.c. for each airstream
Coil runaround loop	0.6 in. w.c. for each airstream
Evaporative humidifier/cooler in series with another cooling coil	Pressure drop of device at fan system design condition
Sound attenuation section	0.15 in. w.c.
Exhaust systems serving fume hoods	0.35 in. w.c.
Laboratory and vivarium exhaust systems in high-rise buildings	0.25 in. w.c./100 ft of vertical duct exceeding 75 ft.
Deductions
Systems without central cooling device	–0.6 in. w.c.
Systems without central heating device	–0.3 in. w.c.
Systems with central electric resistance heat	–0.2 in. w.c.

Fan Power Adjustment
Applicability	All fan systems qualifying for pressure drop adjustments as described above.
Definition	Standard 90.1-2019 specifies a “pressure drop adjustment” for fan systems with requirements for filtration or other process requirements.
Units	List
Input Restrictions	Derived from other building descriptors
Baseline Building	Pressure drop adjustment is calculated separately for each applicable device. Credit for each device is specified in the section above. A = sum of zones (PD_sum x CFM_{d_baseline}/4131) Where: PD = Each applicable pressure drop adjustment from the proposed design CFM_d = The design airflow through each applicable device in cfm from the baseline building Note: In scenarios where the proposed and baseline building have varying zone to system assignment, the pressure drop credit ‘A’ shall be calculated for each thermal zone in the proposed building, using the design flow rates in the proposed building design. For multi-zone systems in the proposed building, the pressure drop adjustment will be split for each zone based on the zone to system airflow ratio. The pressure drop adjustment for the baseline building will then be calculated by adjusting the calculated PDA by the ratio of baseline building design airflow rate to proposed building design air flow rate for each zone. The baseline system pressure drop adjustment will be a sum of the individual pressure drop adjustments of the applicable zones.

Supply Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust, or return fans
Definition	The ratio of supply fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions.
Units	Unitless fraction (0 to 1)
Input Restrictions	As designed
Baseline Building	Same as proposed

Return Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust, or return fans
Definition	The ratio of return fan brake horsepower in the proposed design to total fan system brake horsepower for the proposed design at design conditions
Units	Unitless fraction (0 to 1)
Input Restrictions	Derived from other building descriptors
Baseline Building	Same as proposed

Exhaust Fan Ratio
Applicability	Systems that serve thermal blocks that have exhaust, fume hoods, kitchen exhaust, or return fans
Definition	The ratio of exhaust fan brake horsepower in the proposed design to total fan system brake hp for the proposed design at design conditions. Exhaust fans include toilet exhaust, kitchen hoods, and other miscellaneous exhaust. For fan systems with multiple exhaust fans, the exhaust fan ratios shall be calculated separately for each exhaust fan.
Units	Unitless ratio
Input Restrictions	Derived from other building descriptors. In the event that a common exhaust system serves thermal blocks that are served by different HVAC systems, the brake horsepower shall be divided in proportion to design cfm.
Baseline Building	Same as proposed