NC-v2.2 EQc2: Increased Ventilation

  • NC22_EQc2_IncreasedVentilation Diagram
  • More fresh air means healthier buildings

    More fresh air means healthier buildings. Building on EQp1: Minimum Indoor Air Quality Performance, this credit calls for exceeding by 30% the minimum outside air requirements set by ASHRAE 62.1-2004. This credit applies only to occupied spacesOccupied Spaces are defined as enclosed spaces that can accommodate human activities. Occupied spaces are further classified as regularly occupied or non-regularly occupied spaces based on the duration of the occupancy, individual or multi-occupant based on the quantity of occupants, and densely or non-densely occupied spaces based upon the concentration of occupants in the space. of the building unlike EQp1, which applies to all the rooms as per by ASHRAE 62.1. This increased ventilation helps reduce concentrations of carbon dioxide produced by occupants, and pollutants produced by off-gassing of construction materials and furnishings. By addressing these problems, increased ventilation can help mitigate occupant health problems.

    There may be an energy tradeoff

    Your mechanical system may already be designed to accommodate increased ventilation, but in other cases, this credit may represent a tradeoff in energy consumption (conditioning more air along with increased fan power to distribute it), and may reduce overall energy consumption as measured in EAc1: Optimize Energy Performance. Projects that use displacement ventilationA system in which air slightly cooler than the desired room temperature is introduced at floor level and is lifted up by warmer air to exhaust outlets at the ceiling, increasing air circulation and removal of pollutants., including underfloor air distribution, are often able to achieve the credit with minimal increase in energy use. Demand-controlled ventilation systems are also a good way to minimize the energy cost, and also work well with EQc1: Outdoor Air Delivery Monitoring.

    Tough to do with natural ventilation

    For projects relying on operable windows to provide fresh air, this credit is largely unattainable because you cannot usually guarantee a 30% increase in fresh air without mechanical means. However, projects using natural ventilation do have a compliance path and a reference standard they can use to attempt compliance. Increased ventilation in general as well as natural ventilation strategies are best implemented in mild, relatively dry climates where relatively little energy is needed to condition outside air.

    Carbon Trust guide out of circulation

    Even though the official LEED-NC v2.2 credit language hasn't been updated to reflect this, the Carbon Trust guide that is used for natural ventilation projects has been removed from circulation and can no longer be used for project teams that don't already have a copy. Instead, you can use the LEED-NC 2009 IEQc2 requirements as an alternative compliance path.

    Which code?

    For EQp1, project teams must use whichever is the more stringent code—ASHRAE 62.1 or the local code. However, for EQc2, the 30% increase is always based on ASHRAE 62.1, not the local code (even if it is more stringent).

Legend

  • Best Practices
  • Gotcha
  • Action Steps
  • Cost Tip

Pre-Design

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  • Evaluate and select ventilation strategies—natural, mechanical, or mixed-mode—during the pre-design phase


  • Evaluate each space in the building separately in order to determine air requirements. 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 room require more fresh air than other spaces. Explore whether individual spaces should be ventilated mechanically, naturally or mixed-mode.


  • Consider the potential cost implications of natural ventilation. This may reduce or eliminate the need for fans and mechanical systems, but will require operable windows and a floor plan—probably a relatively open one—that is conducive to passive ventilation. 


  • Analyze life-cycle cost tradeoffs between natural and mechanical ventilation systems. 


  • Naturally ventilated buildings may find this credit relatively difficult to achieve. If considered early in design, it’s possible to achieve the credit, but may take a concerted effort to increase the amount of outdoor air intake using larger and more numerous operable windows, and more sophisticated designs such as wind chimneys.


  • Mechanical Ventilation


  • Review the Ventilation Rate Procedure methodology in ASHRAE 62.1-2004 Section 6.2 and the associated Table 6-1.


  • ASHRAE 62.1 recognizes two procedures to demonstrate 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.


  • Consider the potential cost implications and benefits of supplying an additional 30% of outdoor air. This may bring additional costs in the form of increased energy demand for conditioning greater air volumes and upsizing HVAC systems and fans. It is intended to bring more fresh air to occupants, potentially increasing their comfort and productivity.


  • Demand-controlled ventilation can significantly reduce energy use while providing large amounts of fresh air to occupants.


  • Natural Ventilation: Option 1 – Prescriptive


  • Review the requirements of the Carbon Trust Good Practice Guide 237 (1998) and the flow diagram process shown in Figure 18 of the Chartered Institution of Building Services Engineers (CIBSE) Applications Manual 10-2005, Natural Ventilation in Non-Domestic Buildings.


  • The Carbon Trust guide offers guidelines on window sizes, spacing and placement for non-residential buildings. These guidelines can be used as a great starting point to ensure sufficient fresh air is provided to the building with natural ventilation. Reference the guide early in design will help maximize benefits and ensure compliance.


  • Natural Ventilation: Option 2 – Modeling


  • Review the air-flow modeling methodology and requirements in Volume A of the CIBSE Guide and ASHRAE 62.1-2004, Section 6.2. This section of ASHRAE 62.1 offers the modeling protocol for simulating air movement within the building. It is not difficult to follow and may be familiar to modeling consultant.


  • Use Computational Fluid Dynamics (CFD) modeling to determine the proper sizes for windows and openings and ensure proper air movement through interior spaces. Some energy modeling programs also have CFD analysis capabilities.


  • Early air flow modeling will help the team create the most effective ventilation design. This data can inform the team on space planning and building envelope design, among other things.


  • There may be upfront modeling fees for CFD modeling. However, CFD can help design a better natural ventilation system that will deliver short-term payback and long-term savings.

Schematic Design

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  • Determine the required ventilation rates for indoor spaces based on occupancy and space types. ASHRAE 62.1-2004 tables 6-1 and 6-4 list minimum ventilation rates for particular spaces.


  • Begin preliminary ventilation rate calculations during project programming to help set goals for ventilation quality goals in particular spaces.


  • An integrated design approach among the mechanical engineer, architects, owners and end users will facilitate more informed decisions that can impact the mechanical system design. For example, space planning decisions will impact the architectural programming as well as access to natural ventilation. 


  • For mixed-mode and naturally ventilated spaces, it is up to the mechanical engineer to calculate the outdoor airflow rate and communicate with the architect on application of CIBSE guide for naturally ventilated spaces.


  • Increased ventilation rates come with long-term cost benefits. Well-ventilated spaces bring a premium in rents as well as the benefits of having healthy, productive occupants.


  • Mechanical Ventilation


  • Create separate zones in buildings with mixed-mode ventilation systems—one for natural ventilation and one for mechanical ventilation—and follow the appropriate compliance path for each area.


  • If you choose to pursue EQc5: Indoor Chemical and Pollutant Source Control, relatively high MERV 13 filtration is required. Pursuing both credits may require you to increase duct size and fan power, and may even affect your system selection.


  • Natural Ventilation


  • Determine the ratio of floor area to operable wall or roof openings for naturally ventilated spaces to see what floor areas can be ventilated by operable windows.


  • If using air flow modeling (Option 2), select a natural ventilation modeler and for the project and consult with them.


  • Space planning, building envelope and orientation to breezes will impact the effectiveness of natural ventilation systems.


  • At the first integrated design meeting during schematic design, develop a detailed natural ventilation strategy that includes goals for windows, building orientation, space planning and other sources of natural ventilation. In larger buildings, consider using an atrium to use the “stack effect”—allowing air to enter the building through exterior windows, cycle through the building into the atrium space and out through the top of atrium, using the natural buoyancy of warm air. Fans can be added, if necessary, to assist with stack-effect exhaust.


  • Multifamily residential projects may find it difficult to meet the credit unless the units are supplied with fresh air. Typically multifamily projects are naturally ventilated, and they can meet the IEQp1 requirements with operable windows. However, the additional outside air required for IEQc2  compliance may be difficult to provide unless they also duct in extra outside air.

Design Development

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  • 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. 


  • Mechanical Ventilation


  • The mechanical engineer continues 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 62.1-2004.


  • 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.


  • Use building automation systems (BAS) to control mechanical systems efficiently and maintain desired ventilation rates while minimizing unscheduled maintenance.


  • 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 might want to separate a non-perimeter space even if it shares the same VAV controller.


  • The Ventilation Rate Procedure calculation includes occupancy counts based on space types.


  • Laboratory facilities generally require very high ventilation rates. Consider installing separate mechanical systems for lab spaces and other 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.


  • Natural Ventilation


  • Continue running ventilation calculations and develop flow diagrams to inform the design process and confirm credit compliance.


  • Natural ventilation systems may require a more robust and intense integrated design process, consisting 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.


  • 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 be equal to or greater than 4% of the total floor area that the design considers naturally ventilated. Multiple windows 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.

Construction Documents

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  • For mechanically ventilated spaces, run final ventilation calculations to verify that the design exceeds ASHRAE 62.1-2004 by 30%.


  • For naturally ventilated spaces, confirm compliance with the requirements of the CIBSE Applications Manual 10-2005, Natural Ventilation in Non-Domestic Buildings.


  • Fill out the LEED submittal template and upload all supporting documents to LEED Online


  • 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.


  • Use this checklist prior to construction for mechanical systems and credit compliance:

    • Using the mechanical equipment schedule, confirm that outside air is being supplied to mechanically ventilated spaces.  
    • Do you have calculations showing the outside air required by ASHRAE 62.1-2004 for mechanically ventilated spaces separate from naturally ventilated spaces?
    • Do outside air rates meet or exceed the calculated ASHRAE minimums?
    • Are all regularly occupied spaces listed in the ASHRAE calculations?
    • What is the desired MERV filtration? If using a high level of ventilation to meet EQc5, has the mechanical system been sized accordingly?

Construction

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  • Coordinate the installation of mechanical systems with the project’s commissioning process.


  • Use commissioning to confirm that installed systems are providing the outside air rates specified in the design.

Operations & Maintenance

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  • 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 over time.


  • 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.

  • USGBC

    Excerpted from LEED for New Construction and Major Renovations Version 2.2

    EQ Credit 2: Increased ventilation

    1 Point

    Intent

    Provide additional outdoor air ventilation to improve indoor air quality for improved occupant comfort, well-being and productivity.

    Requirements

    For mechanically ventilated spaces
    • Increase breathing zoneThe breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. (AHSRAE 62.1–2007) outdoor air ventilation rates to all occupied spacesOccupied Spaces are defined as enclosed spaces that can accommodate human activities. Occupied spaces are further classified as regularly occupied or non-regularly occupied spaces based on the duration of the occupancy, individual or multi-occupant based on the quantity of occupants, and densely or non-densely occupied spaces based upon the concentration of occupants in the space. by at least 30% above the minimum rates required by ASHRAE Standard 62.1-2004 as determined by EQ Prerequisite 1.
    For naturally ventilated spaces

    Design natural ventilation systems for occupied spaces to meet the recommendations set forth in the Carbon Trust “Good Practice Guide 237” [1998]. Determine that natural ventilation is an effective strategy for the project by following the flow diagram process shown in Figure 1.18 of the Chartered Institution of Building Services

    Engineers (CIBSE) Applications Manual 10: 2005, Natural ventilation in non-domestic buildings.

    AND

    • Use diagrams and calculations to show that the design of the natural ventilation systems meets the recommendations set forth in the CIBSE Applications Manual 10: 2005, Natural ventilation in non-domestic buildings.
      OR
    • Use a macroscopic, multi-zone, analytic model to predict that room-by-room airflows will effectively naturally ventilate, defined as providing the minimum ventilation rates required by ASHRAE 62.1-2004 Chapter 6, for at least 90% of occupied spaces.

    Potential Technologies & Strategies

     

    For Mechanically ventilated Spaces: Use heat recovery, where appropriate, to minimize the additional energy consumption associated with higher ventilation rates.

    For Naturally ventilated Spaces: Follow the eight design steps described in the Carbon Trust Good Practice Guide 237 – 1) Develop design requirements, 2) Plan airflow paths, 3) Identify building uses and features that might require special attention, 4) Determine ventilation requirements, 5) Estimate external driving pressures, 6) Select types of ventilation devices, 7) Size ventilation devices, 8) Analyze the design. Use public domain software such as NIST’s CONTAM, Multizone Modeling Software, along with LoopDA, Natural Ventilation Sizing Tool, to analytically predict room-by-room airflows.

     

Technical Guides

IEQ Space Matrix - 2nd Edition

This updated version of the 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. Up to date, 2nd Edition.


Chartered Institution of Building Services Engineers (CIBSE) Applications Manual 10: 2005, Natural Ventilation in Non-Domestic Buildings

This is a best-practice design guide to natural ventilation.


ASHRAE 62.1 User's Manual

The ASHRAE User's Manual accompanies the 62.1 ASHRAE reference standard. The manual offers detailed plans and examples of the requirements spelled out in the reference standard. (With access to LEED Online, the 62MZ calculator and the 62.1 User


Building Assessment, Survey, and Evaluation Study (U.S. EPA)

This site contains research data and considerations EPA uses to study sick building syndrome.


The Carbon Trust Good Practice Guide 237 – Natural Ventilation in Non-Domestic Buildings – A Guide for Designers, Developers and Owners (1998)

This is a best-practice design guide to natural ventilation. The guide explores the benefits of natural ventilation and offers numerous case studies.


IEQ Space Matrix - 1st Ed.

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 is the 1st edition.

Organizations

CIBSE Applications Manual 10-2005

Located in London, this organization publishes a series of guides on ventilation, including natural ventilation.

Software Tools

62MZ Calculator: Ventilation Rate Procedure

This is a Microsoft Excel calculator that accompanies the ASHRAE 62.1 reference standard. The calculator allows users to plug in variables for specific project types and run the Ventilation Rate Procedure.


CONTAM 3.0 Multizone Modeling Software

Public domain software from NIST (National Institute of Standards and Technology) that has natural ventilation sizing tools, and flow models to analytically predict room-by-room airflows.


Loop DA Multizone Modeling Software

Public domain software from NIST (National Institute of Standards and
Technology) that has natural ventilation sizing tools, and flow models
to analytically predict room-by-room airflows.


ASHRAE 62.1 iPhone App

ASHRAE released an app for iPhone, iPod touch, and iPad that allows you to perform comprehensive minimum ventilation calculations for a wide variety of commercial buildings based upon Standard 62.1, using either I-P or SI units. This app is based upon the 62MZCalc.xls. Now, you can make calculations at a meeting and know if your project meets IEQp1 or IEQc2.

Ventilation Rate Table

Use this example ventilation rate table from 23 High Line as guidance when developing compliance documents for your project for credit compliance.

Air Riser Diagram

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.

Mechanical Systems Schedule

Use this example mechanical schedule created from 23 High Line for guidance when developing ventilation effectiveness compliance documents for your project.

LEED Online Sample Template – EQc2

This template is the flattened, public version of the dynamic template for this credit that is used within LEED-Online v2 by registered project teams. This and other public versions of LEED credit templates come from the USGBC website, and are posted on LEEDuser with USGBC's permission. You'll need to fill out the live version of this template on LEED Online to document this credit.

USGBC

Official LEED Online Forms

Design Submittal

PencilDocumentation for this credit can be part of a Design Phase submittal.

18 Comments

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Ashraf Nawaz Mr Saudi Binladin Group
Jan 28 2014
LEEDuser Member
12 Thumbs Up

0% Achievement

I was just wondering why the credit achievement rate is 0 on the top right corner of the webpage.

I guess we need an update on the webpage.

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Mar 07 2014 LEEDuser Moderator

Ashraf, that is fixed now. We had a little issue importing the data.

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Larry Storset LNS Engineers, Inc.
Sep 13 2013
Guest
8 Thumbs Up

IAQ Calculator

I understand that LEED has their own version of the ASHRAE 62_MZCalc, where can this be downloaded?

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Dylan Connelly Mechanical Engineer, Integral Group Sep 30 2013 LEEDuser Expert 6110 Thumbs Up

On the LEEDOnline (LEED v2009) site if you have a project registered there.

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Rick Servoss Mechanical Engineer
Nov 07 2012
Guest
361 Thumbs Up

Using V4 From

The IEQP1 V4 active form is very user friendly and familiar to the USGBC reviewers. Due to this, I was hoping to upload this completed form as my supporting documentation. There are differences between 62.1 2004 & 2007, but these difference can be overridden where necessary. Has anybody had success submitting the V4 IEQp1 form to show their V2.2 ventilation calculation?

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Hernando Miranda Owner, Soltierra LLC Nov 07 2012 Guest 5813 Thumbs Up

I have a v2.2 project where the engineer used an alternative software tool that based on calculations on ASHRAE 62.1-2007. A 2004 version was not available for the software. The LEED Reviewers accepted the 2007 calculations in lieu of the 2004 calculations. I would assume that using the LEED v4 form would be acceptable.

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Tom Hootman Director of Sustainability RNL
Jun 14 2011
LEEDuser Member
150 Thumbs Up

30% over ASHRAE 62.1 or the more stringent local code?

You state above under "which code?," that only ASHRAE 62.1 applies to this credit and not the local code (as in EQp1). I'm requesting clarification because there is one sentence on page 312 of the 2.2 reference guide under "Mechanically Ventilated Buildings," that states "exceed minimum rates required by ASHRAE 62.1-2004 or the applicable local code, whichever is more stringent, by a minimum of 30%." In looking at the reference guide for LEED 2009, it looks like they have taken out the sentence that says 30% over local code and it clearly states 30% over ASHRAE. This makes me believe that the 30% over ASHRAE would suffice.

We are working on a project that is registered under NC 2.2 and it's in California where the local code,Title 24, is more stringent than ASHRAE 62.1-2004. We need clarity on whether the requirement for EQc2 is 30% over ASHRAE and/or local code or just 30% over ASHRAE. We’d like meet the 30% over ASHRAE to earn the credit, and not have to meet the 30% over Title 24 which would have a large impact on our energy efficiency.

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Jul 12 2011 LEEDuser Moderator

Tom, I think you summarize things correctly. It's 30% above whatever is more stringent for v2.2, and 30% above ASHRAE for v2009. To my knowledge, you can apply the looser v2009 requirement to v2.2, however—that requirement has not been changed retroactively. However, has anyone had a different experience?

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Veronica Addison
Feb 03 2011
LEEDuser Member
166 Thumbs Up

Increased Ventilation Calcs

We just received the following comments from the reviewer after providing calculations for the critical zones:

The LEED Submittal Template has been provided stating that the project has increased breathing zoneThe breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. (AHSRAE 62.1–2007) outdoor air ventilation rates to all occupied spacesOccupied Spaces are defined as enclosed spaces that can accommodate human activities. Occupied spaces are further classified as regularly occupied or non-regularly occupied spaces based on the duration of the occupancy, individual or multi-occupant based on the quantity of occupants, and densely or non-densely occupied spaces based upon the concentration of occupants in the space. by 30% above the minimum rates required by ASHRAE Standards 62.1-2004 as determined by EQp1.

However, two issues are pending:
1. It is unclear if all zones are receiving the outside air required since a mechanical schedule has not been provided.
2. A 30% increase in outside air for compliance of this credit must be provided at the zone level to ensure that breathing zone outside airflow is increased adequately. Note that a 30% increase of OA at the system level is not allowed since it does not guarantee a 30% increase at the zone level.

TECHNICAL ADVICE:
Please provide a mechanical schedule along with evidence that all zones are getting the required outside air, either by showing the critical zones or listing all zones.

Does anyone know if this means that we need to provide calculations for each zone? We did provide calculations for the critical zones. This has never been requested on previous projects.

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Nancy Henderson Managing Partner, ArchEcology Feb 03 2011 LEEDuser Member 604 Thumbs Up

Veronica - see my comment above. The reviewer gave clear steps for calculating the increase in OA required at the breating zone. I don't believe they want to see all the zones, but they want the OA requirement increased at the breathing zoneThe breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. (AHSRAE 62.1–2007), which in turn changes the ventilation efficiency Ev. My issue was there was no way to do this with the ASHRAE 62MZ, unless you have an unlocked spreadsheet. After some back and forth with my reviewer I was told to use the 62MZ spreadsheet but increase the system floor area by 30% to trick the spreadsheet into calculating the increased Vbz requirement. The reviewer later sent me the new LEED 2009 Retail sample form which has the proper calculation built into the form. I tried it out and it seems to work.

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Nancy Henderson Managing Partner ArchEcology
Jan 14 2011
LEEDuser Member
604 Thumbs Up

Increased Ventilation Calculation methodology

I recieved the following comments from a reviewer on how we should be calculating the 30% increase:
1. At the system level, the uncorrected outside air requirement for the system (Vou) must be multiplied by 130%.

2. For the critical zone, the outside air required at the breathing zoneThe breathing zone is the region within an occupied space between 3 and 6 feet above the floor and more than 2 feet from walls or fixed air-conditioning equipment. (AHSRAE 62.1–2007) (Vbz) must be multiplied by 130%.

3. For the critical zone, the zone ventilation efficiency (Ev) must be recalculated based on the revised values for Vou and critical zone Vbz).

4. At the system level, the total outside air intake required as a fraction of primary supply air must be recalculated using the new critical zone ventilation efficiency (Ev), and the new uncorrected outside air requirement for the system (Vou).

I have never seen this before, and have alway shown the percentage increase as a simple equation of (Provided OA-Required OA)/Required OA.

The only thing I can figure to do is manually adjust the Vbz number for the critical zone in the "Detailed Calculations" area which then adjusts Ev for the system and the total required OA Vot. Then multiply the new Vot by 130%. Does that make sense? Has anyone else had a reviewer ask for the calculation to be done this way? If so, where is the reference to it?

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Roger Chang Principal, Director of Sustainability, Westlake Reed Leskosky Jan 21 2011 LEEDuser Expert 3818 Thumbs Up

Nancy, the procedure described is correct. I think your interpretation is correct; different terminology is being used. You should focus on a 30% increase to Vbz values. For decoupled ventilation systems, the calculation is much more straightforward to demonstate. When dealing with a multiple-zone recircualting system (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.), the calculation becomes more challenging. I recommend having the project's mechanical engineer review the calculations.

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Nancy Henderson Managing Partner, ArchEcology Jan 21 2011 LEEDuser Member 604 Thumbs Up

Roger, I can see how this would result in better OA flow and is apparently the correct procedure - and yet this is not the procedure shown in the Reference Guide. In addition, the ASHRAE spreadsheet does not allow editing of the cells that would produce this calculation. How is it acceptable that design teams cannot rely on the guidance and examples provided?

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Roger Chang Principal, Director of Sustainability, Westlake Reed Leskosky Feb 26 2011 LEEDuser Expert 3818 Thumbs Up

Nancy, in the past, we've submitted stand-alone Excel spreadsheets documenting the ASHRAE 62 methodology in detail, rather than trying to show this within the letter template. The template is trickier to use with a building that has a lot of separate zones. Have you been using the 62 compliance spreadsheet developed by ASHRAE?

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Nancy Henderson Managing Partner, ArchEcology Feb 28 2011 LEEDuser Member 604 Thumbs Up

Yes we use the ASHRAE 62 compliance spreadsheet. We used it for the project referenced, however, in order to do the calculation they have asked for, we would need an unlocked ASHRAE 62 spreadsheet. We were ultimately told to increase the system floor area by 130% (and the zone popluation if not defaulted) to trick the spreadsheet into producing the correct cacluation. This means that separate forms are required for the prerequisite and the credit. We were also told that on V3 projects the ONLY form that has the correct calculation is the LEED-NC Retail. We were told to use the Retail sample form on our NC project and upload it separately. That worked mostly OK, but there is a bug in the form that will not allow use of actual occupants - only default. A mechanical engineer working on one of our projects told us he has been told by reviewers NOT to use the ASHRAE 62 spreadsheet on v3 projects, because the calculation is built into the form.

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Hernando Miranda Owner, Soltierra LLC May 26 2012 Guest 5813 Thumbs Up

"A mechanical engineer working on one of our projects told us he has been told by reviewers NOT to use the ASHRAE 62 spreadsheet on v3 projects, because the calculation is built into the form."

The reviewers are wrong to force the LEED form to be used.

For multiple systems and ease of use the LEED form is not the tool to use. PDF is and never will be a substitute for Excel or similar spreadsheet tools.

The v4 version of the form has some bugs when diversity is changed back and forth several times.

For a spreadsheet tool I developed I can enter the word "heating" or 'cooling" and have the tool automatically adjust the calculations by changing to the appropriate Ez. I can change diversity factor and have it auto-populate the spaces I want to take diversity credit for and not the ones I don't want or think it is appropriate to take the credit.

I can do both heating mode and cooling mode calculations and submit both to prove compliance no matter which demand the review makes (heating or cooling).

The LEED form tool has nowhere near the flexibility as the tool I developed on my own. The USGBC and GBCI are far from getting this one right.

As for the sample calculations being wrong in the Reference Guide, this is a long time uncorrected error by the USGBC. Why the the GBCI and USGBC wait to tell you until the time of review to use a different calculation method than published in the guide, long after you designed a project, is a severe problem.

I was the vice-chair of the LEED Indoor Environmental Technical Advisory Group (EQ TAGLEED Technical Advisory Group (TAG): Subcommittees that consist of industry experts who assist in developing credit interpretations and technical improvements to the LEED system.) when the requirements for this credit were invented. The additional ventilation was intended to be a per occupant increase at working area level. Not a system level OA bump. I stopped working for the EQ TAG more than seven years ago. Still, the problem hasn't been corrected.

The TAG did not write the reference guides. The TAGs are unpaid volunteer positions. The error is entirely the error of the reference guide authors. The TAGs never had control over the guides.

When the Reference Guide (publicly available) and Review Requirements (not publicly available) are in conflict the Reference Guide should take precedence until it is properly revised, meaning the information is publicly available.

The LEED review world does not the way I described. The reviewers are required to follow hard-core review rules invented by an entity called the LEED Department. As best I can determine the LEED Department is a USGBC entity, not a GBCI entity.

Why the USGBC and GBCI refuse to match the review requirements with officially published Reference Guide addenda is a mystery.

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mike diess Engineer LNI, inc.
Jul 01 2010
LEEDuser Member
317 Thumbs Up

Increased ventilation with a constant volume system?

In a CV system the OA is distributed evenly & is proportional to the SA delivered to the space. The only way I can increase the OA to a given room is by increasing the SA delivered. Sometimes this is impractical - I am wondering if GBCI ever overlooks an OA deficiency in a given room when the total being delivered from the 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. exceeds 30%?

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James Thornton Project Manager, Commissioning Group, ccrd Jul 01 2010 Guest 150 Thumbs Up

You can increase your fraction of OA for the entire system to raise your proportion of OA in a given room. Not a very energy efficient way of doing it, but it will meet the requirement.

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Apr 20 2014
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