More fresh air means healthier buildings. Building on IEQp1: Minimum Indoor Air Quality Performance, this credit calls for exceeding by 30% the minimum outside air requirements set by ASHRAE 62.1-2007. 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.
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. 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 IEQc1: Outdoor Air Delivery Monitoring.
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.
Each space must be provided with a 30% increase in ventilation rate.
Based on the definition provided for occupiable spaces and 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 62.12007) in ASHRAE 62.1 Section 3, electrical rooms, telecommunication/data rooms, elevator equipment rooms, storage rooms and similar spaces would not require the per square foot ventilation indicated in Table 6-1 to be delivered to the space since they are unoccupied the majority of the time.
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.
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 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.
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.
Review the air-flow modeling methodology and requirements in Volume A of the CIBSE Guide and ASHRAE 62.1-2007, 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.
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 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.
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 IEQc5: 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.
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.
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.
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 62.1-2007.
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.
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.
Hotel and multifamily projects may have difficulty achieving this credit 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 can support areas outside the 25-foot natural ventilation boundary.
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.
For mechanically ventilated spaces, run final ventilation calculations to verify that the design exceeds ASHRAE 62.1-2007 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 credit form 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:
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.
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.
Excerpted from LEED 2009 for Schools New Construction and Major Renovations
To provide additional outdoor air ventilation to improve 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.) for improved occupant comfort, well-being and productivity.
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 62.12007) 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 62.1-2007 (with errata but without addenda1) as determined by IEQ Prerequisite 1: Minimum Indoor Air Quality Performance. Projects outside the U.S. may use a local equivalent to ASHRAE Standard 62.1-2007, if the same is used for IEQ Prerequisite 1: Minimum Indoor Air Quality Performance.
Projects outside the U.S. may earn this credit by increasing breathing zone outdoor air ventilation rates to all occupied spaces by at least 30% above the minimum rates required by 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, as determined by IEQ Prerequisite 1: Minimum Indoor Air Quality Performance,
Determine whether natural ventilation is an effective strategy for the project by following the flow diagram process in Figure 2.8 of the Chartered Institution of Building Services Engineers (CIBSE) Applications Manual 10: 2005, Natural Ventilation in Non-domestic Buildings.
Show that the natural ventilation systems design meets the recommendations set forth in the CIBSE manuals appropriate to the project space.
Use CIBSE Applications Manual 10: 2005, Natural Ventilation in Non-domestic Buildings. Projects outside the U.S. may use a local equivalent.
Use CIBSE AM 13:2000, Mixed Mode Ventilation. Projects outside the U.S. may use a local equivalent.
Use a macroscopic, multizone, analytic model to predict that room-by-room airflows will effectively naturally ventilate, defined as providing the minimum ventilation rates required by ASHRAE Standard 62.1-2007 section 6 (with errata but without addenda), at least 90% of occupied spaces. Projects outside the U.S. may use Annex B of Comité Européen de Normalisation (CEN) Standard EN 15251: 2007, or a local equivalent to section 6 of ASHRAE Standard 62.1-2007 to define the minimum ventilation rates.
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 8 design steps described in the Carbon Trust Good Practice Guide 237:
This is a best-practice design guide to natural ventilation.
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
This site contains research data and considerations EPA uses to study sick building syndrome.
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.
Located in London, this organization publishes a series of guides on ventilation, including natural ventilation.
ASHRAE publishes widely used standards and publishes the ASHRAE Journal.
Labs21 is a voluntary partnership program dedicated to improving the environmental performance of U.S. laboratories.
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.
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.
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 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.
This Rocky Mountain Institute publication is a case study of the connection between worker productivity and indoor air quality.
Use this example ventilation rate table from 23 High Line as guidance when developing compliance documents for your project for credit compliance.
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.
The LEED Reference Guide only addresses the increased ventilation calculation at the zone level, not the system level. I understand that the outdoor air supplied to each zone needs to be increased by 30% to obtain this credit. I found a way to do this on the 62MZ spreadsheet. What about at the system level? Vot (the amount of air the system needs to suppy, i.e. the corrected outdoor air) cannot simply be increased by 30%. It is dependent on Ev, which is dependent on the critical zone. I am finding that when I increase the outdoor air to each zone by 30%, the system outdoor air (Vot) increases by much more, as much as 55%. I am getting some units with very high outdoor air percentages. I can increase the supply air to the critical room, which increases Ev and therefore decreases Vot. But it seems arbitrary, and I am not convinced this is the correct approach. Has anyone had any experience with this?
Laura, I've asked around and haven't been able to gather any thoughts on your questions here. Have you learned anything more since posting this?
Hello Tristan, no, I did not, and in order to stay on schedule I had to make a decision and move forward with design. So what I did is increase the outdoor air to each zone by 30% (by multiplying the people and the area by 1.3), and let the system be whatever it is, even though it is higher. I felt this was the only way to make sure we meet the requirements. Thanks for asking around, anyway. If you do find any information, I would appreciate you posting so I know for future projects. Thanks!
I am having the same issue right now on a CI 2009 project, Increased Ventilation Credit submission. Mathematically, within the 62MZ spreadsheet, what you are saying makes sense. However, I get the impression that it is not the Intent of LEED for us to have to increase the outdoor air "requirement" in each zone by multiplying the people and areas. Rather, to me, their intent seems to be that we calculate the requirement, then increase the required amount of outdoor air by at least 30% and distribute it so that each zone gets at least 30% more "unused outdoor air" than it would have at the minimum outdoor air intake volume.
Some of the math seems to me to hinge on whether the extra 30% going to 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 62.12007) is now determined to be "used" and therefore is of no use to the other zones when it is recirculated. If you multiply the people and area by 1.3, then the extra air is considered used when it gets to the breathing zone of the space, and cannot be considered unvitiated when recirculated back as return air. But it doesn't seem like that is the LEED intent. For one thing, notice that the templates ask for the actual 62.1 breathing zone rates required; they don't check for the 30% factor until AFTER outdoor intake volume is calculated.
Nonetheless, I am still not sure how to calculate the outdoor intake volume provided for a specific zone, especially a non-critical zone.
I haven't submitted this yet, so I don't know what the response will be. Just letting you know my thoughts after hours of staring at spreadsheets Voz, Vot, etc.....
Laura and Tristan-
While I'm still inclined to argue as in my March 18th reply above, I did receive comments from my LEED reviewer indicating that your approach was what he/she wants to see, Laura. Here is the reviewer's comment on my submission:
"The LEED Credit Form 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 62.12007) 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 62.1-2007. However, the calculation has applied the 30% increase at the system level, and not at the zone level. To correctly determine the required outdoor airflow rate (Vot), the system ventilation efficiency (Ev) must be adjusted to reflect the 30% increase in the required breathing zone outdoor airflow rate (Vbz). TECHNICAL ADVICE: Please revise the calculation to determine the value of Vot as a result of the increased Vbz. This can be determined by any of the following:
a. Increasing the people and area outdoor airflow rate
values (Rp and Ra) by 30% in the calculation.
b. Increasing the Vbz at the system level by 30% in the calculation.
c. Increasing the uncorrected outdoor
airflow rate (Vou) at the system level, and Vbz at the critical zone by 30% in the calculation."
It's not worth it to try arguing to the contrary on this project. Maybe I will try it sometime in the future. To me, one key is whether the outdoor air "requirement" actually increases 30% as opposed to the "requirement" staying the same, but just providing 30% more to each zone than it requires.
Principal, Director of Sustainability
Westlake Reed Leskosky
Commissioning will verify that systems are operating efficiently and delivering required air volumes.
Mechanical system designs for effective ventilation will need to comply with requirements to stop
tobacco smoke exposure.
Supplying more fresh air reduces the buildup of carbon dioxide. A monitoring system can make
ventilation systems more effective and energy-efficient, when used with demand-control ventilation.
Increasing ventilation rates can increase energy demand. Use natural ventilation or effective ventilation design to offset this issue.
MERV 13 filtration required by this credit must be accounted for in fan power requirements, duct sizing, and equipment size and type, all of which must also be considered for increased ventilation.
If operable windows are part of a project’s natural ventilation design, they can count towards IEQc6.2.
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