This prerequisite establishes a baseline for providing a minimum amount of outdoor air to buildings in order to maintain good indoor air quality and keep occupants comfortable and healthy. This prerequisite references ASHRAE 62.1-2007 (with errata but without addenda) and is often more stringent than local building codes, although it is not likely to entail any added costs.
The compliance paths for mechanically ventilated and naturally ventilated spaces, Case 1 and Case 2, are somewhat different and you may need to follow both paths for the same building. Naturally ventilated spaces must follow the distinct requirements set out in Case 2, even if other spaces in the same building are mechanically ventilated and are following Case 1. Mixed-mode spaces (with both mechanical and natural ventilation) must follow the compliance path for mechanical ventilation, Case 1.
New construction additions will need to confirm that any ventilation systems serving the project meet the ventilation rates required by ASHRAE 62.1 2007, even if the ventilation system design itself is outside the scope of the project. If base building systems do not meet the standard’s requirements, you will need to either modify the base building system or provide detailed analysis documenting the constraints and explaining why the base building systems cannot be upgraded.
The 2007 edition of ASHRAE 62.1 combines 62.1-2004 and the eight approved and published addenda to the 2004 edition. The new edition does the following:
If the building relies on the fans for daily ventilation, it is considered a mechanically ventilated building.
Testing in naturally ventilated spaces is not required per 62.1-2007 Sections 4-7 if the outdoor air quality adequately meets 62.1-2007, Table 4-1.
Both operable windows and vents can be used, but only the operable area within those elements can be counted towards the minimum percentage (4%) of net occupiable area.
Determine likely ventilation strategies during preliminary programming: natural, mechanical, or mixed-mode ventilation. This prerequisite is attainable with any of these strategies.
This prerequisite is paired with IEQc2: Increased Ventilation. If ventilation rates are targeted above the 30% ASHRAE requirement, projects can gain both the prerequisite and a point for EQc2. Projects pursuing IEQc2 may follow the compliance path for natural ventilation found in Chapter 2 of The CIBSE Applications Manual 10 (AM10) for both the prerequisite and for the credit.
Many of the strategies that contribute to meeting this prerequisite also support earning other indoor environmental quality credits and should be explored as integrated solutions. See LEEDuser's guidance on the rest of the IEQ section for ideas.
Natural ventilation strategies can reduce costs. Natural ventilation in particular can reduce the need for mechanical equipment as well as operational costs. Displacement ventilation, in which air is delivered at or near floor level at a low velocity, can also reduce ducting and improve equipment efficiency. In choosing a system, analyze life cycle cost tradeoffs.
Check local building codes to determine requirements. The project must either meet ASHRAE 62.1-2007, or local codes if they are more stringent. Since ASHRAE 62.1-2007 is often more stringent than local codes, be sure to review and be familiar with its requirements.
This prerequisite is not likely to require added costs.
Review the Ventilation Rate Procedure methodology in ASHRAE 62.1-2007 Section 6.2 and the associated Table 6-1.
ASHRAE 62.1 recognizes two procedures to prove IAQ compliance: the IAQ Procedure methodology and the Ventilation Rate Procedure. The Ventilation Rate Procedure is easier to apply and is the prescribed path for this LEED prerequisite.
If you are pursuing IEQc5: Indoor Chemical and Pollutant Source Control, you must incorporate MERV 13 filters into your filtration system. These relatively tight filters may affect the fan power and fan sizes necessary to provide the required quantities of air. Involve the engineer early if pursuing IEQc5.
Demand-controlled ventilation can greatly reduce energy use while providing large amounts of fresh air to occupants.
Determine whether natural ventilation is feasible based on the project type, use, and climate. Study the natural conditions of the site, such as prevailing wind direction, and orient the building to maximize airflow.
Review the prescriptive requirements for natural ventilation in ASHRAE 62.1-2007 Paragraph 5.1 (with errata but without addenda).
An integrated design meeting will help determine whether natural ventilation is a high priority and should be a primary driver of the design process.
Airflow modeling early in the design process can help teams create a more effective natural ventilation design. If the data is used early in the design to help inform team on such thing as space planning and building envelope design. An airflow modeling professional may add some upfront costs, while likely improving system efficiency and effectiveness.
Consider the cost implications of natural ventilation. Passive strategies may reduce or eliminate the need for fans and HVAC equipment, but they may also require high quantities of operable windows and a floor plan that is conducive to passive ventilation. Natural ventilation often requires the cooperation of occupants, to open and close windows when appropriate, for example, be sure that your project is likely to succeed in this respect.
Determine the required ventilation rates for indoor spaces based on occupancy and space types. ASHRAE 62.1-2007 tables 6-1 and 6-4 list minimum requirements for particular spaces.
Separately evaluate each space to determine air requirements and what type of ventilation will be best. Metabolic rate of the space activities and the occupant density are factors that determine the amount of fresh air needed in a space. For example, exercise rooms and conference rooms require more fresh air than offices.
An integrated design approach among the mechanical engineer, architects, owners and occupants will facilitate design decisions that impact the HVAC design. For example, space planning decisions will impact the architectural programming of the space as well as access to natural ventilation.
Increasing a project’s ventilation rate brings long-term cost benefits. Good indoor air quality can lower operational costs by increasing occupants’ health and productivity as well as the value and marketability of the building.
The mechanical engineer begins preliminary ventilation rate calculations during project programming in order to set ventilation quality goals for particular spaces and occupancies. The area of a given multi‐zone system should be broken down by ventilation zones, and all zones within that system must meet the minimum breathing zone ventilation air requirements as per ASHRAE 62.1‐2004. For a typical office space, the mechanical design consists of multiple ventilation zones for which compliance would need to be shown on an individual basis.
For mixed-mode and naturally ventilated spaces, the mechanical engineer should calculate the outdoor airflow rate and communicate the area requirements for operable wall or roof openings to the architect.
For mixed-mode ventilation, zone the plan into areas—mechanically ventilated and naturally ventilated—and follow separate compliance calculations for each area.
Determine the applicable floor area for operable wall or roof openings according to ASHRAE 62.1-2007 section 5.1.
Consider using Computational Fluid Dynamics (CFD) modeling to determine proper opening sizes and ensure proper airflow. Some energy modeling programs also have CFD analysis capabilities.
Expect upfront modeling fees for Computational Fluid Dynamics (CFD), but also consider the benefits of CFD modeling: a better-designed natural ventilation system that can bring short-term payback from reduced mechanical systems, and long-term operational savings.
At the first integrated design meeting during schematic design, develop a detailed natural ventilation strategy involving goals for windows, building orientation, space planning, use of atriums, and other access to natural ventilation. Natural ventilation systems may require a more robust and intense integrated design process, of several focused workshops analyzing several alternatives. Computer modeling may be necessary to test various design alternatives to determine which is most effective and efficient.
Hotel and multifamily projects may have difficulty achieving this prerequisite if they are naturally ventilated and have interior spaces that are further than 25 feet from an operable wall or roof opening. These projects might consider increased window areas, shallower floor plates, or using mixed-mode ventilation so that mechanically supplied outdoor air can support areas outside the 25-foot natural ventilation boundary.
The mechanical engineer continues to run ventilation rate calculations during the mechanical design process to inform design development and confirm compliance with this prerequisite. The ventilation rate procedure is explained in section 6 of ASHRAE 62.1-2007. See the attached 62MZ calculator.
Continuing to use an integrated design approach among the mechanical engineer, architects, owners and end users will facilitate design decisions that impact the mechanical design. For example, space planning decisions will impact the architectural programming of the space as well as access to natural ventilation.
Strategically locate air intakes for mechanical or natural ventilation systems to avoid taking in contaminants and odors like vehicle exhaust from parking lots or fumes from garbage storage areas.
Incorporating operable windows into the design for natural and mixed-mode ventilation can help with an additional LEED point for EAc6.1: Controllability of Systems—Thermal Comfort.
Continue running ventilation rate calculations during the mechanical design process to confirm compliance with this credit and to inform the design. The ventilation rate procedure is explained in section 6 of ASHRAE 62.1-2007. See the 62MZ calculator.
Implement energy recovery systems, economizers, low-pressure-drop design, and efficient fans as appropriate to support ventilation rates meeting or exceeding the referenced ASHRAE standard without compromising energy performance.
Avoid oversizing mechanical equipment. Oversized equipment will often increase operating costs and reduce operational efficiency. The correct equipment size will depend on a number of factors, including local climate, total building area, insulation levels, air filtration medium, number of windows and doors, and occupant comfort preferences.
Spaces served by the same VAV (variable air volume) controller can be grouped together in the 62MZ calculator, but grouped spaces should have similar exterior exposure. For example, you can group two perimeter spaces that share a VAV controller, but would want to separate a non-perimeter space even if it shares the same VAV controller.
Laboratory facilities generally require very high ventilation rates. Consider installing separate mechanical systems for lab spaces to maximize return-air mixing. Other strategies may include using a heat exchanger to capture energy from laboratory exhaust, using low-flow or variable-flow fume hoods, minimizing ventilation rates during unoccupied times, or using a dedicated outdoor air system.
Integrating building automation systems can control mechanical systems efficiently and maintain desired ventilation rates while minimizing unscheduled maintenance.
The Ventilation Rate Procedure calculation includes occupancy counts based on space types.
Continue to run calculations and develop flow diagrams to inform the design process and confirm compliance. If you are using a natural ventilation modeler for the project, use the model as a tool to inform design development.
The calculation for operable openings will only apply to the floor area adjacent to the window—25 feet to either side and in front of the opening.
The surface area of window openings must, for compliance with ASHRAE 62.1, be equal to or greater than 4% of the occupied floor area that the design considers naturally ventilated. Multiple windows in aggregate can provide the operable area needed to meet the requirements.
In naturally ventilated multifamily buildings, air infiltration from a pressurized hallway or corridor can contribute to the Ventilation Rate Procedure calculation for areas that do not meet the requirements of ASHRAE 62.1, as long as the corridor is pressurized with outdoor air.
For mechanically ventilated spaces, run ventilation calculations to verify that the final design meets the minimum outside air rates equal to or exceeding the ASHRAE 62.1-2007 minimum.
For naturally ventilated spaces, confirm compliance with the requirements of ASHRAE 62.1-2007 section 5.1.
If natural ventilation strategies are integrated into the design, ensure that key elements of the natural ventilation system, such as operable windows, window actuators, controls, operable atrium elements, and solar chimneys, are not compromised during value engineering. Educate decision-makers about the natural ventilation design and the importance of maintaining all the key components. If these elements are altered in a way that compromises natural ventilation rates, the mechanical system may no longer be sized appropriately.
Fill out the LEED credit form and upload all supporting documents to LEED Online.
Use this checklist for naturally ventilated spaces prior to construction to review plans for prerequisite compliance:
Use this checklist for mechanical systems prior to construction to check prerequisite compliance:
Coordinate the installation of ventilation systems with the project’s commissioning process.
Use commissioning to confirm that installed systems are providing the outside air rates specified in the design.
Monitor outdoor air delivery periodically to confirm that minimum ventilation rates are being maintained. Implement a maintenance program to ensure that mechanical system components are functioning properly.
Test all dedicated building exhaust systems including chemical areas, bathroom, shower, kitchen, and parking exhaust systems to confirm proper fan speed, voltage, control sequences, and set points as applicable. Provide operations and maintenance personnel with manuals and educate them about any atypical maintenance requirements.
Getting feedback on ventilation performance from occupants through surveys can help to identify potential problems that may become expensive if they go unnoticed.
A documented ventilation performance plan can help ensure that systems reach the expected ventilation thresholds.
In projects with operable windows, occupants may not know when conditions are best for opening the windows. Implement a system so that occupants are informed of when to open and close the windows to achieve designed performance and optimal comfort.
Maintain a building operating plan (BOP) that establishes operating schedules and set points and regularly review these parameters against actual building needs. When developing these parameters, consider both time-of-day and time-of-year variations in optimal temperature requirements and be careful to avoid over-conditioning the building spaces with more ventilation, heating or cooling than is necessary.
Adjust reset and setback temperature settings and calibrate controls and sensors. A Building Automation System (BAS) will allow building managers to adjust, monitor and control temperature set points and air volumes throughout the building from a central location. Direct digital controls (DDC) utilized by the BAS will function more efficiently than older pneumatic controls and help to avoid unnecessary use of HVAC equipment during non-business hours and holidays.
Develop and implement a comprehensive Indoor Air Quality Management Plan using the EPA’s “Indoor Air Quality Building Education and Assessment Model” (I-BEAM).
Following the initial audit, the IAQ manager must make periodic inspections to uncover new IAQ issues and monitor the status of previous issues. The I-BEAM tool supplies inspection forms that can be tailored to the project building to facilitate this process.
Establish protocols to manage all significant pollutant sources referenced in I-BEAM that are applicable to the project building.
Ensure that procedures are in place for receiving and responding to IAQ complaints from building occupants. The I-BEAM tool provides sample forms and logs for fielding and recording occupant complaints as well as information about key principles for developing effective communication with building occupants regarding IAQ issues. Strategies for investigating and resolving the issues that trigger occupant complaints are covered by a variety of I-BEAM guidelines.
Excerpted from LEED 2009 for Schools New Construction and Major Renovations
To establish minimum indoor air quality (IAQIndoor air quality: The quality and attributes of indoor air affecting the health and comfort building occupants. IAQ encompasses available fresh air, contaminant levels, acoustics and noise levels, lighting quality, and other factors.) performance to enhance indoor air quality in buildings, thus contributing to the comfort and well-being of the occupants.
Mechanical ventilation systems must be designed using the ventilation rate procedure as defined by ASHRAE 62.1-2007, or the applicable local code, whichever is more stringent.
Meet the minimum requirements of Sections 4 through 7 of ASHRAE Standard 62.1-2007, Ventilation for Acceptable Indoor Air Quality (with errata but without addenda1). Projects outside the U.S. may use a local equivalent to Sections 4 through 7 of ASHRAE Standard 62.1-2007.
Projects outside the U.S. may earn this prerequisite by meeting the minimum requirements of Annex B of Comité Européen de Normalisation (CEN) Standard EN 15251: 2007, Indoor environmental input parameters for design and assessment of energy performance of buildings addressing indoor air quality, thermal environment, lighting and acoustics; and the requirements of CEN Standard EN 13779: 2007, Ventilation for nonresidential buildings, Performance requirements for ventilation and room conditioning systems, excluding Section 7.3 – Thermal environment, 7.6 – Acoustic Environment, A.16, and A.17.
Naturally ventilated buildings must comply with ASHRAE Standard 62.1-2007, Paragraph 5.1 (with errata but without addenda1).
Design ventilation systems to meet or exceed the minimum outdoor air ventilation rates as described in the ASHRAE standard. Balance the impacts of ventilation rates on energy use and indoor air quality to optimize for energy efficiency and occupant comfort. Use the ASHRAE Standard 62.1-2007 Users Manual (with errata but without addenda1) for detailed guidance on meeting the referenced requirements.
1 Project teams wishing to use ASHRAE approved addenda for the purposes of this prerequisite may do so at their discretion. Addenda must be applied consistently across all LEED credits.
This spreadsheet categories dozens of specific space types according to how they should be applied under various IEQ credits. This document is essential if you have questions about how various unique space types should be treated.
This example ventilation rate table from 23 High Line provides guidance when developing prerequisite compliance documents for your project.
This example air riser diagram from 23 High Line shows the mechanical ventilation supply for the building. It is the ducted diagram showing how air will be supplied to building occupants. Use this as an example for how to document ventilation effectiveness compliance.
Use this example mechanical schedule created from 23 High Line for guidance when developing ventilation effectiveness compliance documents for your project.
The following links take you to the public, informational versions of the dynamic LEED Online forms for each Schools-2009 IEQ credit. You'll need to fill out the live versions of these forms on LEED Online for each credit you hope to earn.
Version 4 forms (newest):
Version 3 forms:
These links are posted by LEEDuser with USGBC's permission. USGBC has certain usage restrictions for these forms; for more information, visit LEED Online and click "Sample Forms Download."
Documentation for this credit can be part of a Design Phase submittal.
I am working on a school project. The ventilation is "Mechanical Ventilation 100% Outside Air" +natural ventilation in all of the classrooms. There are several multiple zone AHUs and several single zone AHUs.
I use v.4 of the online form.
I chechked the box "Mechanical Ventilation 100% Outside Air" and started filling in table IEQp1-A3.
Do I need to fill anything exept these tables?
I have noticed the following while filling in the IEQp1-A3 table:
There is NO fieled where one can fill in the Project Design Outdoor Airflow for EACH SEPARATE ZONE so that the table can compare the results zone by zone. At the bottom of the table there is the SUM of the Vot values for all zones and under it one is asked to fill in the Project Design Outdoor Airflow for the AHU.
In this case one can be below the Voz for several zones but still will manage to comply to the credit if he has more flow than the required in other zones of the same AHU.
Am I correct or do I miss something because this seems terribly wrong?
(I have asked this question in other section of the forum by mistake, sorry)
Each zone needs to comply with ASHRAE 62.1, even if the form does not ask for details on a zone by zone level. I suggest submitting a separate spreadsheet with your calculations for backup.
With the V4 form you are correct that you only need to enter in the total OA for each system, not each zone as in previous versions of the form and LEED. No need to submit additional backup calculations in this regard.
You are penalized in zones where you aren't providing as much OA with your Zp coefficient. The forms will only give you an error if you to have zones with a minimum SA that is lower than required OA requirements of that zone.
We are working on a university building wich has 2 underground floors, with mechanical and storage rooms in them, all these rooms are adjacent to the stairs. There are no means to provide natural ventilation to these rooms and they are not regularly occupied, only for inspections or maintenance. ASHRAE 62.1 - 2007, table 6-1, states "storage rooms" with it associated building component ventilation requirement, but in ASHRAE 62.1 - 2010, table 6-1, the definition is "occupiable storage rooms" and there is no occupancy category for unoccupied storage or mechanical rooms.
It doesn´t make sense to have a mechanical ventilation system operating continously in this rooms, considering the minimum 15 minutes occupation, the investment on duct work and air handler units, and the energy consumption of the system.
Are we forced to implement a mechanical ventilation system in these spaces? Should it be acceptable to implement louvers (dimentioned to comply with natural ventilation) in the partitions adjacent to the stairs to ventilate the rooms throught them, even tho the stairs don´t have mechanical or natural ventilation on these underground floors?
Rodrigo, this 62.1-2007 interpretation should be helpful. http://ashrae.org/File%20Library/docLib/Public/20100203_ic_621200717.pdf
It provides clarification regarding storage rooms.
I have received review comments from a LEED Review Team questioning the results of the 62MZ spreadsheet which identified a Storage Room as the "Critical Zone". The reviewer requests that I revise 62MZ spreadsheet indicating the "correct" critical zone. I have reviewed the imput cells in the spreadsheet and find no mistakes in the input values. The Storage Room which turned out to be the "critical zones" are large storage rooms within a relatively small air handling system. The outdoor air for Storage Rooms from Table 6-1 requires OA ONLY based on Area Outdoor Air Rate(0.12cfm/sq.ft.). No OA is required for occupants since space is normally unoccupied. Anyone else run across this or similar circumstance?? How do I effectively respond to reviewer given these circumstances?? I think providing a response that essentially tells the reviewer to read and understand ASHRAE 62.1-2007 and how results are determined when using 62MZcalc spreadsheet may not be well received.
Sometimes LEED review teams will question something that's not typical, even if the documentation is correct. Usually a conference room or other high density space will be the critical zone for a multi-zone system.
Has anyone had any experience with GBCI allowing the use of the IAQIndoor air quality: The quality and attributes of indoor air affecting the health and comfort building occupants. IAQ encompasses available fresh air, contaminant levels, acoustics and noise levels, lighting quality, and other factors. procedure rather than the ventilation rate procedure?
We are designing a school with 58 classrooms and are utilizing air purification units that lower the amount of outside air needed and increase the efficiency of the system. This method is allowed by ASHRAE 62.1 through the IAQ procedure and is preferable to our project as we are located in the southeast where humidity is a problem. We can provide documentation that the indoor air quality levels are acceptable.
Thanks for your comments.
Chad, could you provide more information on the air purification units specified?
We have been wondering the same thing, Chad. We are located in Texas, where humidity is also (usually) a problem, and our project team has data that shows schools that used the IAQIndoor air quality: The quality and attributes of indoor air affecting the health and comfort building occupants. IAQ encompasses available fresh air, contaminant levels, acoustics and noise levels, lighting quality, and other factors. Procedures are outperforming schools that used the Ventilation Rate Procedure in terms of indoor air quality. Results were measured by monitoring test scores and asthma inhaler use - the school using the IAQ Procedure had significantly reduced inhaler use and significantly higher test scores than the school using the Ventilation Procedure.
The ASHRAE 62.1-2007 User's Manual, p. 6-43, actually states, "The IAQP may also be used to achieve better air quality than the VRP (lower contaminant levels and/or higher perceived acceptabilty) with or withiout increasing first cost or maintenance cost." Yet LEED 2009 prescribes the Ventilation Rate Procedure, and the draft LEED 2012 prerequisite specifically prohibits using the IAQ Procedure.
Does anyone know the reason for this? Why does LEED prohibit using the IAQ Procedure?
Just found this credit interpretation ruling, which was published in 2007. However, please note, according to the CIRCredit Interpretation Ruling. Used by design team members experiencing difficulties in the application of a LEED prerequisite or credit to a project. Typically, difficulties arise when specific issues are not directly addressed by LEED information/guide database, this ruling does NOT apply to LEED 2009 rating systems:
"LEED InterpretationLEED Interpretations are official answers to technical inquiries about implementing LEED on a project. They help people understand how their projects can meet LEED requirements and provide clarity on existing options. LEED Interpretations are to be used by any project certifying under an applicable rating system. All project teams are required to adhere to all LEED Interpretations posted before their registration date. This also applies to other addenda. Adherence to rulings posted after a project registers is optional, but strongly encouraged. LEED Interpretations are published in a searchable database at usgbc.org.
MPR/Prerequisite/Credit: IEQp1: Minimum Indoor Air Quality Performance
Posting Date: 5/15/2007
ID Number: 5053
Primary Rating System: New Construction v2.2
The CIR is inquiring if the IAQIndoor air quality: The quality and attributes of indoor air affecting the health and comfort building occupants. IAQ encompasses available fresh air, contaminant levels, acoustics and noise levels, lighting quality, and other factors. Procedure, as described in Section 6.3 ASHRAE Standard 62.1-2004, can be used in place of the Ventilation Rate Procedure of the same Standard to document compliance with the requirements of this prerequisite. The Ventilation Rate Procedure methodology found in Section 6.2 of ASHRAE 62.1-2004 is the required approach in EQp1, since it is prescriptive and therefore more straightforward to apply. The Ventilation Rate Procedure is based on contaminant sources and source strengths that are typical for common space types listed in the Standard. The Indoor Air Quality (IAQ) Procedure methodology found in Section 6.3 of ASHRAE 62.1-2004 and proposed by this project team is performance-based and relies on identification of contaminants of concern, sources for those contaminants, concentration targets, and perceived acceptability targets. The project-specific nature of the IAQ procedure methodology makes it less commonly used and more difficult for USGBC to evaluate. Therefore USGBC cannot allow its use to show compliance with LEED NC v2.2 EQp1. Please note that the intent behind this prerequisite is to encourage designers to take the most stringent and conservative prescriptive approach to providing fresh air. The language of the prerequisite asks designers to compare the rates recommended under Ventilation Rate Procedure with that required by their local code and to pick the most stringent. As for the project team's legitimate concern with energy efficiency, the "additive" Ventilation Rate Procedure adopted in the ASHRAE Standard 62.1-2004 reflects concerns for energy consumption with elevated ventilation rates. The recommended rate under the Ventilation Rate Procedure in ASHRAE Standard 62.1-2004, in many important occupancy types and projects can result in lower ventilation rates than those required by the earlier version of the Standard - Standard 62.1-2001."
I have an office room located inside a gymnasium space. The gymnasium is conditioned by an AHU1.Air-handling units (AHUs) are mechanical indirect heating, ventilating, or air-conditioning systems in which the air is treated or handled by equipment located outside the rooms served, usually at a central location, and conveyed to and from the rooms by a fan and a system of distributing ducts. (NEEB, 1997 edition)
2.A type of heating and/or cooling distribution equipment that channels warm or cool air to different parts of a building. This process of channeling the conditioned air often involves drawing air over heating or cooling coils and forcing it from a central location through ducts or air-handling units. Air-handling units are hidden in the walls or ceilings, where they use steam or hot water to heat, or chilled water to cool the air inside the ductwork., while the office room has an FCU.
For the office room, fresh air is not provided separately through a dedicated fresh air duct. Instead, the exhaust rate in the office is higher than the supply, causing a negative pressure in the office, and consequently air will flow from the ventilated gymnasium towards the office through infiltration/cracks.
If this infiltrated air is proven to include the minimum amount of fresh air required for the office space, is this scenario acceptable, or a separate fresh air duct is required in this case? Please note that I have around 16 cases similar to this one!
George, this is not permitted. You will need to provide a separate fresh air duct. The reasoning is that infiltration is uncontrolled and is not filtered.
I have a VAVVariable Air Volume (VAV) is an HVAC conservation feature that supplies varying quantities of conditioned (heated or cooled) air to different parts of a building according to the heating and cooling needs of those specific areas. system for my school, with each AHU1.Air-handling units (AHUs) are mechanical indirect heating, ventilating, or air-conditioning systems in which the air is treated or handled by equipment located outside the rooms served, usually at a central location, and conveyed to and from the rooms by a fan and a system of distributing ducts. (NEEB, 1997 edition)
2.A type of heating and/or cooling distribution equipment that channels warm or cool air to different parts of a building. This process of channeling the conditioned air often involves drawing air over heating or cooling coils and forcing it from a central location through ducts or air-handling units. Air-handling units are hidden in the walls or ceilings, where they use steam or hot water to heat, or chilled water to cool the air inside the ductwork. feeding around 25 zones (classrooms and offices).
Each zone has a maximum primary air flow and an outdoor air intake flow (specified as per ASHRAE standard 62.1).
Taking the example of 1 zone:
The minimum ASHRAE required outdoor air intake flow is 800CFM, and the Design zone primary air flow is 2000CFM. If the cooling load in this zone drops, being a VAV, the supply primary air flow may get down to 1000CFM. However, since the fresh air and the recirculated air are being mixed in the AHU, the fresh outdoor air intake flow for out zone will drop down proportionally to 400CFM, which no longer complies with ASHRAE requirements!
How do you deal with this issue? Do you think that the fresh air minimum requirement must correspond to the minimum design primary air flow? In this way, if the zone load increased, the design primary air flow will induce a lot more fresh air than required by ASHRAE.
Thanks for your help!
This is one of the weak points of VAVVariable Air Volume (VAV) is an HVAC conservation feature that supplies varying quantities of conditioned (heated or cooled) air to different parts of a building according to the heating and cooling needs of those specific areas. systems. In order to guarantee proper ventilation at all conditions, the amount of outdoor air that needs to be brought in at the air-handling unit can be significantly higher than what's required if you just sum up the ventilation rate required for each zone. This is why decoupled ventilation systems are now preferred, especially for schools. A dedicated outdoor air system handles delivers only what is needed for ventilation to each zone, typically at neutral air temperature. Space sensible cooling and heating is provided by a recirculating VAV system (dual-duct), fan coil units, radiant panels, chilled beams, etc.
Does GBCI really require the template filled out? We have a spreadsheet exactly like your sample documentation documenting compliance, etc. This is for a school with over 150 spaces, and we'd just as soon not have to go enter 150 individual line items into the LEED template. Do they accept this means of documentation as an alternative compliance path, or are we forced to spend hours uploading this duplicative info into the templates?
Before LEED v3.0, we would submit our own spreadsheets with ventilation calculations and they were usually approved or we were given minor comments on adjustments to make during the review process. I think it is unreasonable to expect teams to completely duplicate this work on projects with a lot of ventilation zones. I would submit your spreadsheet, include a detailed narrative, and at least see what the review comments are. The worst outcome would be that they reject this approach and you then have to fill out the template. Please let us know what you end up doing and what the outcome is.
Dear Tommy & Roger,
Any reviews from the USGBC regarding submitting one's own spreadsheet?
We contacted GBCI and their help forum said we could submit our own spreadsheets. We did so in our design review response (after they initially rejected the submission w/o the info in the template). But with a copy of the email and clarification on the spreadsheets, they accepted it! Saved many, many hours of copying the same information into the template!
Here is the actual response we received (of course with the caveat that the following text represents staff opinion of a particular issue, and does not set any precedent, etc, etc:
The project team is inquiring as to whether or not providing a supplemental spreadsheet that contains the Ventilation Rate Procedure calculations for each zone under each outside air unit in lieu of completing the table on the LEED prerequisite Form is an acceptable alternative compliance path. This approach to the prerequisite is acceptable, so long as the supplemental calculations include all of the required information outlined in the LEED Prerequisite Form. Note that the form itself must contain all other required information, save the table calculations, in order to demonstrate prerequisite compliance.
Principal, Director of Sustainability
Westlake Reed Leskosky
Mechanical and natural ventilation designs must comply with requirements to mitigate environmental tobacco smoke.
The amount of fresh air the HVAC system is designed to process has a direct correlation to the buildup of carbon dioxide.
Increasing the ventilation rates 30% above the ASHRAE standard will help teams gain IEQp1.
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