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ASHRAE Standard 62.1 and LEED Certification
Ventilation for Acceptable Indoor Air Quality
Stephen Haines, EIT, LEED AP JBA Consulting Engineers Mechanical Engineering
What is ASHRAE Standard 62.1? The Industries Ventilation
Standard
Purpose: “… to specify minimum ventilation rates and other measures intended to provide indoor air quality that is acceptable to human occupants and that minimizes adverse health effects.”
Scope: All commercial, institutional and high-rise residential buildings (excludes low-rise residential)
History of ASHRAE Standard 62.1
1970 1980 1990 2000 2010
1973 First Issued (Office – 15 cfm/person)
1984 Steve’s birthday
1981 Lower Rates
(Office – 5 cfm/person)
1989 Higher Rates (Office – 20 cfm/person)
1999 Little Change
2001 More Mandatory Language
2004 Key Changes:
Ventilation Rate Procedure
2007 Corrections,
Clarifications
2010 Most Current
Key Changes in 62.1-2004 Area-related and occupancy-related ventilation components
Minimum Ventilation Rate Table revised to apply only to non-smoking areas (smoking areas are still not addressed)
Appendix G – Existing Buildings Additions, Equipment replacements, Substantial alterations
Indoor Air Humidity (65% max) and pressure requirements (positive when dehumidifying)
Requirement to deliver outside air directly to occupied spaces
Why is ASHRAE 62.1 Important? It is the basis for many ventilation codes
More stringent than codes in some cases and helps establish the “standard-of-care”
Compliance with ASHRAE Standard 62.1-2007 is a prerequisite for any LEED-NC credits
Two Paths to Compliance Ventilation Rate Procedure Most commonly used method Table 6-1 Minimum Ventilation Rates in Breathing Zone Need to determine the zone air distribution effectiveness (Ez) LEED requires this method for compliance
Indoor Air Quality Procedure Designed to maintain specific contaminant levels Mass balance analysis Methods used in similar buildings Validation by contaminant monitoring verification
Ventilation Rate Procedure
Ventilation Rate Procedure
Note the following rooms do not require area-based ventilation per ASHRAE Standard 62.1-2007: Electrical equipment rooms Telecommunications/data rooms Elevator machine rooms Other similar non-occupied spaces
Clarified under Interpretation IC 62.1-2007-17 approved on January 23, 2010
Correction made for Standard 62.1-2010
Ventilation Rate Procedure
Note the following rooms do not require area-based ventilation per ASHRAE Standard 62.1-2007: Electrical equipment rooms Telecommunications/data rooms Elevator machine rooms Other similar non-occupied spaces
Clarified under Interpretation IC 62.1-2007-17 approved on January 23, 2010
Corrected in the 2010 version of the Standard
Classroom Example Single Zone - 62.1-2007
High School Classroom 35’ x 35’ (30 people)
Breathing Zone Outdoor Airflow (Vbz) = RpPz + RaAz
Occupancy component - 10 cfm/person – 10 x 30 people = 300 cfm
Area component - 0.12 cfm/ft2 – 0.12 x (35’ x 35’) = 147 cfm
Zone Outdoor Airflow (Voz) = Vbz/Ez
Voz = (300 + 147)/1.0 = 447 cfm or 14.9 cfm/person
Be careful with Ez values! Most of the time Ez = 0.8 in heating mode which yields a higher ventilation rate requirement. Reference Table 6-2!
Zone Air Distribution Effectiveness
Ventilation Rate Procedure
Multiple Zone Recirculating Systems
Vou = ∑(RpPz + RaAz) for all zones – Uncorrected Outdoor Air Intake
Vot = Vou/Ev – Outdoor Air Intake
To determine the System Ventilation Efficiency (Ev), use Table 6-3 with the Zone Primary Outdoor Air Fraction Zp
Primary Outdoor Air Fraction Zp
Zp = Voz/Vpz
Voz – Zone outdoor airflow
Vpz – Zone primary airflow (for VAV systems Vpz is the minimum expected primary airflow for design purposes)
Multiple Zone Example Office 15’x10’
1 Occupant 100 cfm SA
Office 15’x10’
1 Occupant 100 cfm SA
Storage 10’x10’
0 Occupants 50 cfm SA
Office 18’x10’
2 Occupants 150 cfm SA
Office 18’x10’
2 Occupants 150 cfm SA
Break Room 10’x20’
4 Occupants 200 cfm SA
Corridor 4’ wide
0 Occupants 150 cfm SA Office
10’x20’ 2 Occupants 150 cfm SA
Conference 12’x12’
6 Occupants 150 cfm SA
Note: supply airflows are heating minimum values
Multiple Zone Example Vou = ∑(RpPz + RaAz) for all zones – uncorrected outdoor air intake
Offices 15’ x 10’ x (0.06 cfm/ft2) + 1 person x 5 cfm/person = 14 cfm OA 10’ x 20’ x (0.06 cfm/ft2) + 2 people x 5 cfm/person = 22 cfm OA 18’ x 10’ x (0.06 cfm/ft2) + 2 people x 5 cfm/person = 21 cfm OA
Office total (14 cfm) x 2 + 22 cfm + (21 cfm) x 2 Office total = 92 cfm OA
Multiple Zone Example Vou = ∑(RpPz + RaAz) for all zones – uncorrected outdoor air intake
Break Room 10’ x 20’ x (0.06 cfm/ft2) + 4 people x 5 cfm/person = 32 cfm OA
Conference 12’ x 12’ x (0.06 cfm/ft2) + 6 people x 5 cfm/person = 39 cfm OA
Storage 10’ x 10’ x (0.12 cfm/ft2) = 12 cfm OA
Corridor 296 ft2 x (0.06 cfm/ft2) = 18 cfm OA
Multiple Zone Example Vou = ∑(RpPz + RaAz) for all zones – uncorrected outdoor air intake
Office total – 92 cfm
Break room – 32 cfm
Conference – 39 cfm
Storage – 12 cfm
Corridor -18 cfm
Building total = 92 + 32 + 39 + 12 + 18 = 194 cfm … BUT WAIT!
Multiple Zone Example Building total = 194 cfm OA
But Vou is the “uncorrected” outdoor air intake – we also have to account for the System Ventilation Efficiency (Ev)
What exactly is the System Ventilation Efficiency?
Here is where it can get a little tricky!
System Ventilation Efficiency The System Ventilation Efficiency (Ev) increases the outside air at the
system to account for the critical zones
Example The critical zone is a conference room where the zone requires 50%
of the minimum supply air to be outside air Based on the building area and occupant requirements for ventilation,
the % outside air at the air handling unit is only 15% The critical zone will always be underventilated under these conditions
ASHRAE says we need to increase the outside air at the unit to compensate for this
How does this affect our Multiple Zone Example?
Multiple Zone Example Lets calculate the Zone Primary Outdoor Air Fraction for each zone
Zp = Voz/Vpz
Office 1 – 15’ x 10’ Zp = (18 cfm OA)/(100 cfm SA) = 0.18
Office 2 – 10’ x 20’ Zp = (28 cfm OA)/(150 cfm SA) = 0.19
Office 3 – 18’ x 10’ Zp = (27 cfm OA)/(150 cfm SA) = 0.18
Multiple Zone Example Zp = Voz/Vpz
Break Room Zp = (40 cfm OA)/(200 cfm SA) = 0.20
Conference Zp = (49 cfm OA)/(150 cfm SA) = 0.33
Storage Zp = (15 cfm OA)/(50 cfm SA) = 0.30
Corridor Zp = (23 cfm OA)/(150 cfm SA) = 0.16
Multiple Zone Example Office 1 – Zp = 0.18
Office 2 – Zp = 0.19
Office 3 – Zp = 0.18
Break Room - Zp = 0.20
Conference - Zp = 0.33
Storage - Zp = 0.30
Corridor - Zp = 0.16
Highest Zp – Conference – 0.33
Multiple Zone Example Vot = Vou/Ev – Outdoor Air Intake
Using Table 6-3 with Zp = 0.33 and by interpolating, Ev = 0.82
Vot = (194 cfm)/0.82
Vot = 236 cfm OA required
Will use 240 cfm OA
0.82
Multiple Zone Example Now what happens if we increase the VAV box minimums on the critical zones?
Zp = Voz/Vpz
Conference (increased minimum SA from 150 cfm to 250 cfm) Zp = (49 cfm OA)/(250 cfm SA) = 0.20 (previously 0.33)
Storage (increased minimum SA from 50 cfm to 100 cfm) Zp = (15 cfm OA)/(100 cfm SA) = 0.15 (previously 0.30)
Using Table 6-3 with the max Zp = 0.20 and by interpolating, Ev = 0.95
Vot = (194 cfm)/0.95
Vot = 205 cfm OA required
Use 205 cfm OA instead of 240 cfm
0.95
Alternative Procedures Appendix A Another way to calculate System Ventilation Efficiency (Ev) other
than using Table 6-3 Ev = minimum (Evz) Evz = 1 + Xs – Zd
Xs is the Average Outdoor Air Fraction at the air handling unit Zd is the Discharge Outdoor Air Fraction at the zone
In our Multiple Zone Example, Ev = 1 + (194 cfm)/(1200 cfm) – 0.33 = 1 + 0.16 – 0.33 = 0.83 Vot = (194 cfm)/0.83 = 234 cfm – very similar result
All zone Zp values do not necessarily need to be calculated, just the “critical zones”
Title 24 Requirements But what about Title 24?
Based on Section 121 – Requirements for Ventilation
Mechanical Ventilation The conditioned floor area of the space times the applicable
ventilation rate from Table 121-A or 15 cfm/person times the expected number of occupants Cannot be less than the larger of the two!
Multiple Zone Example Area-based ventilation rate: Table 121-A for office space (other) is 0.15 cfm/sf Required OA = 1,600 sf x 0.15 cfm/sf = 240 cfm
People-based ventilation rate: 15 cfm/person Required OA = 18 people x 15 cfm/person = 270 cfm
Title 24 Ventilation – 270 cfm
ASHRAE Standard 62.1 Ventilation – 240 cfm
This result is not always the case!
Title 24 Requirements Section 144 (d) – Space-conditioning Zone Controls Minimizes reheating to reduce energy use The volume of primary air that is reheated, re-cooled, or mixed air
supply shall not exceed the larger of: 50 percent of the peak primary airflow, or The design zone outdoor airflow rate per Section 121
May not be possible to increase minimum zone airflows to reduce Zp in the critical zones
Title 24 Requirements Section 121 (c) – Operation and Control Requirements Required Demand Control Ventilation CO2 sensors required in densely occupied spaces (occupant
density greater than or equal to 25 people per 1,000 sf) May reduce OA for these spaces based on CO2 levels
Dynamic Reset not a requirement in ASHRAE Standard 62.1
CO2 sensors are required for LEED OA Delivery Monitoring credit
ASHRAE 62.1 Design Tips Identify the “critical zones” High occupant density and low airflow requirement (i.e. little to no envelope
load) Interior conference/meeting rooms Interior waiting/lobby areas Interior break rooms Not necessarily limited to interior zones (north-facing and no glass)
Increase VAV box minimum airflows in critical zones to reduce outside air where possible [ watch out for Title 24 Section 144 (d) ]
May use transfer fans to increase supply air to a critical space
ASHRAE 62.1 Design Tips May account for Occupant Diversity – the ratio of the system
population to the sum of the zone populations
Utilize calculation spreadsheet Spreadsheet provided with ASHRAE 62.1 User’s Manual Allows you to input only the critical zones Spreadsheet uses Appendix A approach
Caution! Don’t forget about building pressurization - a pressurization calc
should be done to ensure that the building is positively pressurized which could result in higher air quantities than ASHRAE 62.1 requires
Make sure heating minimum supply air values can handle the zone heat losses with the selected reheat coil
LEED Compliance LEED Version 3.0 requires that the design meet the minimum
requirements of Sections 4 through 7 of ASHRAE Standard 62.1-2007 IEQ Prerequisite 1 – Minimum IAQ Performance (mandatory) IEQ Credit 2 – Increased Ventilation (optional)
The Ventilation Rate Procedure must be correctly documented and uploaded to LEED Online for review
Best method – “62MZCalc” spreadsheet Pre-programmed spreadsheet template Accepted by USGBC Available with purchase of ASHRAE 62.1 User’s Manual Free through LEED Online under “Credit Resources”
LEED Compliance – 62MZCalc
System Ev = 0.84 Required Vot = 229 cfm
Critical Zone
Entered Values
LEED Compliance – 62MZCalc
“62MZCalc” spreadsheet tips Required only to input “potentially critical zones” Analyze all operating conditions Cooling mode Heating mode
Apply occupant diversity (D) where possible Check with Architect for a building program or design occupancy May be based on full-time equivalent (FTE) occupants
Spreadsheet instructions Cell unlock code
LEED Compliance
LEED Documentation Materials IEQp1 Submittal Template (LEED Online form v3.0 or Template PDF v2.2) ASHRAE Standard 62.1 Documentation of the VRP “62MZCalc” Spreadsheet Trane Trace 700 Calculation Report Carrier’s HAP Calculation Report Other suitable analysis program
Equipment schedules identifying design OA for all systems Equipment submittals (if applicable)
LEED Compliance LEED Design Review Process Design Application Submission Design Application Review GBCI (25 business days) Final Design Review Appeals ($500 per credit)
Design Application Review Pending Issues “It is unclear…”
Technical Advice “Please provide revised VRP calculations demonstrating…”
Design Application Review Comments
The LEED Submittal Template has been provided stating that the project complies with the minimum requirements of ASHRAE Standards 62.1-2004. A narrative has been provided describing the project's ventilation system design. However, specific information regarding the fresh air intake volumes has not been provided.
TECHNICAL ADVICE: Please provide a more detailed narrative or resubmit the LEED Submittal Template to include a more detailed narrative that includes specific information regarding the fresh air intake volumes.
Design Application Review Comments
The LEED Submittal Template has been provided stating that the project complies with the minimum requirements of ASHRAE Standard 62.1-2004, Ventilation for Acceptable Indoor Air Quality, using the Ventilation Rate Procedure… However, two issues are pending: 1. The documentation and Ventilation Rate Procedure (VRP) calculations indicate an Ez value of 1.0 for all VRP calculations, and it is unclear whether the operating conditions represented in the calculations reflect the worst-case scenario. 2. It is unclear how the System Ventilation Efficiency (Ev) value has been determined. In addition, it is unclear which zone, for each unit serving multiple zones, is the critical zone. Therefore, it is unclear whether the critical zone has been used to determine the Primary Outdoor Air Fraction (Zp) and System Ventilation Efficiency (Ev) values. TECHNICAL ADVICE: 1. Please provide revised VRP calculations demonstrating that the values have been adjusted such that they are in compliance with ASHRAE Standard 62.1-2004, Table 6.2. Provide a detailed narrative including specific information regarding the selection of the worst-case design conditions for the VRP calculations. Alternatively, include information explaining the selection of an Ez value of 1.0 for all systems. 2. Indicate in the narrative how the Ev value has been determined, as well as the critical zone for each unit serving multiple zones. If necessary, provide revised calculations demonstrating that the critical zone has been used to determine the Primary Outdoor Air Fraction (Zp) and System Ventilation Efficiency (Ev) values.
Design Application Review Comments
The LEED Prerequisite Form has been provided stating that the project is mechanically ventilated and mechanically conditioned, therefore the project applies Case 1. The project has utilized the VRP Compliance Calculator. However, the tenant guidelines do not indicate the requirements of ASHRAE 62.1-2007 must be met and a copy of the legally binding document (e.g. lease, sales agreement), specifying minimum performance criteria for IEQp1 for the tenant work, has not been provided. TECHNICAL ADVICE: 1. Provide revised tenant guidelines to include a reference to meeting the minimum requirements of ASHRAE 62.1-2007 and ensure that a copy of the legally binding document (e.g. lease, sales agreement), explicitly stating the performance requirements for the tenant work is included.
Other Important Sections in ASHRAE 62.1
Minimum MERV ratings for filters (minimum MERV 6 upstream of cooling coils)
Exhaust rates (Table 6.4) Restrooms Copy/printing rooms Kitchenettes (break rooms) Chemical storage rooms (housekeeping)
Natural ventilation – specifies location and size of openings in lieu of or in addition to mechanical ventilation
Outside air intake minimum separation distances (Table 5.1)
References ASHRAE Standard 62.1
PDFs available of older versions of the Standard
ASHRAE 62.1 User’s Manual More detailed explanation of the Ventilation Rate Procedure Example problems
ASHRAE website
Questions?