Outdoor air delivery monitoring ensures that the ventilation system, whether natural or mechanical, provides enough fresh air to occupants. The credit requires carbon dioxide (CO2) and outdoor airflow monitors that signal when fresh air is needed according to minimum set points defined by ASHRAE 62.1-2007. Typical ventilation design (without monitors) tends to encourage increased ventilation that may result in increased energy use and added cost for conditioning increased amounts of outside air. However, the addition of sensors and monitors allows ventilation to be delivered on demand only when required, potentially saving a lot of energy during unoccupied hours in spaces with varying occupancy.
A space with high-density occupancy at different times of day can be a great fit for this credit.
For buildings with varying occupancy rates and centralized mechanical systems, like offices and schools, the added cost should be minimal, and the systems will probably reduce energy bills, offering good return on investment. High-density areas like conference rooms, theaters, and congregation spaces are a particularly good match for this credit.
In multifamily or hotel projects, or any building with numerous isolated mechanical systems or natural ventilation, more sensors will be needed, making this credit relatively expensive to pursue.
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. #2099, issued 4/24/2008, allows the use of circuit transducers that measure fan status of 100% outside air and constant volume fan systems as an alternative to an airflow measuring station for this credit. For constant volume and 100% outside air systems that have been accurately balanced, monitoring the fan status is adequate to maintain proper outside air volumes. This is not an appropriate strategy for variable volume systems.
Determine the best ventilation strategy for your building: natural, mechanical, or mixed-mode ventilation. The choice of ventilation system is more likely to be shaped by the LEED minimum ventilation prerequisite (IEQp1) and increased ventilation credit (IEQc2), not this credit.
Consider incorporating CO2 sensors or outdoor airflow monitors into the building design, as required by the credit. Discuss with the project team the indoor air quality (IAQ) and energy benefits of installing monitoring devices in the project.
Outdoor airflow monitoring devices are the single most costly component of this credit, ranging from $1,000–$5,000 per monitor, depending on size of the ducts and product type. You can reduce this cost by minimizing the number of supply ducts coming into the building. Centralized systems minimize these ducts, thereby minimizing cost.
CO2 sensors are not standard practice and typically cost $500–$1000 per sensor including installation. Installing CO2 sensors is becoming more common and this price may come down, however. Costs can add up quickly if several sensors are required. In applications with many densely occupied spaces and isolated mechanical systems, like hotels and multifamily, providing CO2 sensors and the associated controls for each unit could become costly, without much added benefit. However, in applications with larger, densely occupied spaces served by centralized mechanical systems—such as office spaces—CO2 sensors become significantly more cost-effective, as ventilation demand is matched to occupancy and the HVAC system operates only when the room is occupied or to meet established set points.
CO2 sensors are not the same as CO sensors. CO (carbon monoxide) sensors are much more common, inexpensive, and do not need to be hard wired. Make sure this distinction is clear when talking with the owner, mechanical engineer, and building operator.
Consider the impact of monitoring devices on space and design requirements. Issues to consider include the location of CO2 sensors, the inclusion of outdoor air monitors when designing the mechanical system, and whether to use a building management system (BMS), which allows your ventilation system to automatically respond to changing indoor situations.
Demand Control Ventilation (DCV) in conjunction with CO2 sensors can serve the dual purpose of energy conservation and improved indoor air quality. They provide the option of additional ventilation only when CO2 sensors indicate that it is necessary.
Outdoor air can contain contaminants that lead to unhealthy working or living conditions. You may need to assess the quality of the local outdoor air before bringing it indoors. HHigh efficiency MERV filters (13 or higher) are one solution to treating poor-quality outdoor air before supplying it to the indoors. This can be part of a strategy for achieving IEQc5: Indoor Chemical and Pollutant Source Control.
Continuous airflow and CO2 monitoring is required. Air balancing measures such as total airflow measurement and static pressurization measurements do not comply with the credit requirements.
Projects without ducted make-up air must follow Option 2 for natural ventilation, and should weigh the costs and benefits of installing monitoring devices. For example, in multifamily projects and hotels where outside air is only supplied through pressurized hallways and operable windows. Every apartment or unit will need one CO2 sensor per unit, and many projects find this to be too costly. Mechanically ventilated common areas such as hallways and lobbies will require outdoor airflow monitors instead of CO2 sensors.
CO2 sensors do not provide the same benefit in non-densely occupied spaces as they do in densely occupied spaces. It is important to remember that CO2 sensors measure only CO2 generated by human occupants and they are typically not a good way to indicate indoor air quality in non-densely occupied spaces. CO2 monitors cannot replace outdoor air monitors and are often incorrectly preferred because they are less expensive than outdoor air delivery monitoring.
Some utilities offer rebates for installing CO2 sensors in conjunction with demand-control ventilation. For example, the New York State Energy Research and Development Authority (NYSERDA) and Florida Power & Light have offered such incentives. Check with your local utility or DSIRE to see if rebates are available in your area (see Resources).
CO2 sensors will provide the highest return on investment in areas where the occupancy is intermittent or unpredictable. Examples include conference rooms and auditoriums, where ventilation rates will need to be high only when close to full occupancy and where ventilation rates can be low when the spaces are unoccupied.
Fees for engineering services may increase due to this credit, because of the need to develop controls sequences. That premium can be reduced if the engineer has experience with the credit in similar applications.
The cost of alarms and BMS equipment varies greatly and is dependent on the complexity of the system.
The project team and contractor work together to determine the feasibility and rough cost increase of including CO2 sensors or outdoor airflow measurement devices.
The owner, mechanical engineer and building operator should determine the best option for corrective action in the project. Options for corrective action include opening windows, adjusting air-handling units, alerting tenants, and increasing ventilation flow rates.
Use ASHRAE standard 62.1-2007 to determine outside air requirements.
The mechanical engineer and architect identify densely and non-densely occupied spaces as defined by LEED and determine the quantity and locations of all monitoring devices, and integrate them into the HVAC system. The mechanical engineer should verify that the monitors are designed to interface with a BMS system or trigger an audible or visual alarm if CO2 concentrations or ventilation rates fall outside of the required range.
Not all conference rooms are densely occupied spaces! Densely occupied spaces are defined as having 25 people per 1,000 square feet of space.
All monitoring devices must be able to trigger an alarm or automated response when actual measurements vary by 10% or more in either direction from the design set points. The signal or alarm is most often relayed to a building management system that balances supply and return air volumes, monitors and controls minimum fresh air volumes, and provides a reliable reference point for commissioning of VAV systems. The alarm can be audible or visual and be relayed to building facility staff or directly to the occupants, to alert them to open windows.
The benefits of any monitoring device depend on the communication system, response and corrective action. Facility operators often find it very beneficial to automate the response by installing demand-control ventilation, which automatically regulates airflow as needed.
CO2 sensors can 1) measure the indoor concentrations of CO2 and compare them against ASHRAE 62.1-2007 limits or, 2) measure the indoor concentrations of CO2 and compare them against outdoor CO2 concentrations. If you choose the second option, you will need to install outdoor CO2 monitors as well.
All occupied spaces in naturally ventilated buildings require the installation of at least one CO2 sensor. The number of CO2 sensors depends on the project’s design and should be calculated by the mechanical engineer. Projects can use one CO2 sensor for multiple spaces only if the project is ventilated by an approved “engineered natural ventilation system” according to ASHRAE 62.1-2007 requirements and if it does not require occupant intervention. This type of ventilation system connects adjacent spaces via air pathways that utilize the stack effect, or passive air movement from openings at a lower level than the point of exhaust. A single CO2 sensor can be used in these connected spaces. To meet the credit requirement, an engineer must demonstrate that the natural ventilation system can maintain adequate ventilation rates.
All densely occupied spaces in mechanically ventilated buildings require the installation of at least one CO2 sensor per space. Non-densely occupied spaces require an outdoor airflow (OA) monitoring device. For mechanically ventilated spaces, the CO2 sensor has to be installed for the zone being served by one ventilation system. The credit requires only one sensor per space, but installing multiple sensors within a large space helps measure varying concentrations of CO2. For example, if the sensor is located in one location, while people are congregating in another corner of the same space, the sensor will not recognize the high CO2 concentrations. Spread the sensors out to accommodate for more uses of the space. Also, use at least one sensor per ventilated zone, for a large space being served by multiple zones. Consult the mechanical engineer on the quantity and placement of CO2 sensors.
For mechanical ventilated spaces that are installing a BAS or BMS, the system should be capable of integrating with the CO2 sensor and outdoor air flow monitors for immediate response with increased fresh air, such as demand-control ventilation.
Airflow measurement devices are installed as part of the air duct system and are designed to measure airflow and transmit a signal when airflow deviates from established set points. Two common types of these devices are those that measure intake volume directly by measuring air velocity (advanced thermal dispersion) and those that measure differential pressure across a fixed opening (pitot arrays and flow-rings). Both can provide the accuracy required for the credit. Advanced thermal diffusion is more accurate and requires less maintenance, but is more expensive.
CO2 monitors installed in return-air ducts (in the ceiling or floor) will not meet the credit requirements, as monitors are required to be placed 3–6 feet above the floor in all densely occupied spaces.
In laboratory and health care facilities, consider continuously measuring additional air quality factors such as TVOCs, carbon monoxide, and other small airborne particulates to reduce ventilation rates down to two air changes per hour (ACH), as conditions permit, in order to save energy.
Integrating an ERV or HRV into a system that meets the Outdoor Air Delivery Monitoring credit can be particularly cost-effective with large centralized systems.
Demand-control ventilation can help reduce peak load allow you to select smaller mechanical systems, minimizing upfront costs.
Include CO2 sensors and outdoor air delivery monitoring devices on the project plans and Equipment Schedule. Also highlight the interface between monitors and BMS or alarm on project plans.
Review drawings to ensure that all densely occupied spaces contain CO2 sensors.
Detailed construction instructions with locations of monitoring devices help to ensure that these devices are installed correctly.
Outdoor airflow monitors may be integrated within AHUs and ventilation equipment specifications.
The monitoring and alarm systems need to be included in the commissioning plan for EAp1: Fundamental Commissioning with the appropriate sampling rate.
The outside air delivery monitoring device should be specified along with the Air Handling Unit (AHU) equipment package.
Ensure that monitoring devices are included in budget estimates from the beginning to avoid any surprises.
Document credit compliance on LEED Online. This credit has an LPE path for Professional Engineers where project plans, drawings, and other information is not necessary for upload. For the full documentation path you will need to complete the following:
Contractor installs the monitoring devices as recommended by product manufacturer and mechanical engineer. Verify that all alarms have set points complying with ASHRAE 62.1-2007.
Verify that CO2 sensors are 3–6 feet off the floor.
The commissioning plan should include HVAC, monitoring, and alarm systems, with the appropriate sampling rate.
Integrating an automated BMS requires a highly skilled construction team. The BMS is a complex tool requiring skilled personnel who understand the controls and settings as applicable to the project.
Ensure that CO2 sensors and outdoor air monitors, and installation costs are incorporated into the detailed budget from the bid documents through final contracts. CO2 sensors are not common, and although the mechanical engineer is responsible for accounting for them on drawings, they could be a forgotten detail.
During the buyout phase, ensure CO2 sensors are included in the mechanical or controls contractor’s scope of work.
Monitor and recalibrate the monitoring and alarm systems as specified by the product manufacturer.
Occupant behavior is likely to evolve over the first few months of occupancy. If the building has a BMS, the control sequence, timers, thermal setpoints and other parameters might need to be tweaked for some time. Use the outdoor air monitoring and CO2 sensors to maintain good indoor air quality as well as efficiency.
Train facilities personnel to use systems as intended. Facilities personnel should be given all appropriate product data.
When alarms are activated by CO2 monitoring devices, facilities personnel and building occupants, if appropriate, need to be aware of the needed corrective measures, such as opening windows or changing AHU settings. The alarm should be visible enough to be noticed.
Include the alarm system in the occupant survey for IEQc7.2: Thermal Comfort—Verification to determine its effectiveness.
CO2 sensors and outdoor air flow monitors will need recalibration and maintenance, which will bring a minimal additional cost. If they are not recalibrated, there is potential for overventilation or underventilation, and consequently, unnecessary energy consumption or reduced indoor air quality.
Excerpted from LEED 2009 for New Construction and Major Renovations
To provide capacity for ventilation system monitoring to help sustain occupant comfort and well-being.
Install permanent monitoring systems to ensure that ventilation systems maintain design minimum requirements. Configure all monitoring equipment to generate an alarm when the airflow values or carbon dioxide (CO2) levels vary by 10% or more from the design values via either a building automation system alarm to the building operator or a visual or audible alert to the building occupants.
Monitor CO2 concentrations within all densely occupied spacesDensely occupied spaces are areas with a design occupant density of 25 people or more per 1,000 square feet (40 square feet or less per person). i.e., those with a design occupant density of 25 people or more per 1,000 square feet (95 square meters). CO2 monitors must be between 3 and 6 feet (between 1 and 2 meters) above the floor.
Provide a direct outdoor airflow measurement device capable of measuring the minimum outdoor air intake flow with an accuracy of plus or minus 15% of the design minimum outdoor air rate, based on the value determined in IEQ Prerequisite 1: Minimum Indoor Air Quality Performance, for mechanical ventilation systems where 20% or more of the design supply airflow serves non-densely occupied spacesNon-densely occupied spaces are areas with a design occupant density of less than 25 people per 1,000 square feet (40 square feet or more per person).".
Monitor CO2 concentrations within all naturally ventilated spaces. CO2 monitors must be between 3 and 6 feet feet (between 1 and 2 meters) above the floor. One CO2 sensor may be used to monitor multiple nondensely occupied spaces if the natural ventilation design uses passive stack(s) or other means to induce airflow through those spaces equally and simultaneously without intervention by building occupants.
Install CO2Carbon dioxide and airflow measurement equipment and feed the information to the heating, ventilating and air conditioning (HVAC) system and/or building automation system (BAS)A building automation system (BAS) uses computer-based monitoring to coordinate, organize, and optimize building control subsystems, including lighting, equipment scheduling, and alarm reporting. to trigger corrective action, if applicable. If such automatic controls are not feasible with the building systems, use the measurement equipment to trigger alarms that inform building operators or occupants of a possible deficiency in outdoor air delivery.
1 Project teams wishing to use ASHRAE approved addenda for the purposes of this credit may do so at their discretion. Addenda must be applied consistently across all LEED credits.
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.
I-BEAM is a comprehensive tool for building professionals and others responsible for indoor air quality in commercial buildings; it provides state-of-the-art guidance for managing Indoor Air Quality in commercial buildings.
ASHRAE 62.1-2007 should be referenced when designing outdoor airflow monitoring devices.
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.
This guide is for preventing, identifying and resolving 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. problems in existing commercial and public buildings.
A study on the compatibilities and tradeoffs between energy and ventilation, which gives an idea of strategies that best meet both objectives.
This journal presents research to help designers, owners and operators provide healthy buildings.
This database shows state-by-state incentives for energy efficiency, renewable energy, and other green building measures. Included in this database are incentives on demand control ventilation, ERVs, and HRVs.
Use a narrative to describe how your project meets the requirements for outside air monitors and carbon dioxide monitors.
Use manufacturer cut sheets to find credit-compliant products and to document compliance when necessary.
Sample LEED Online forms for all rating systems and versions are available on the USGBC website.
Documentation for this credit can be part of a Design Phase submittal.
In a mixed use building, the residential dwelling units are being provided outdoor air via PTAC systems (apartment size determines the number of PTAC units). However, I just wanted to clarify whether or not EACH PTAC unit would require an outdoor air flow monitor in order to achieve this credit?
You need to monitor the airflow of any OA intake unless you are using a constant volume DOAS. In your case, I believe that you would need to monitor every one.
Can natural ventilated stairs and lift shaft excluded from requirements of this credit? If not, how can these spaces comply with this credit? Is required CO2Carbon dioxide sensor installed on each Landing?
These spaces are not regularly occupied spacesRegularly occupied spaces are areas where one or more individuals normally spend time (more than one hour per person per day on average) seated or standing as they work, study, or perform other focused activities inside a building., so they do not require additional monitoring.
Thank you Andrew.
We thought as you say, but the IEQ Space Matrix requires IEQ credit 1 compliance for stairways and corridors and for IEQ credit general requirements specifies "naturally ventilated spaces: 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.".
Our office building has two naturally ventilated stairways.
Hence our doubts.
Understood. I have had success in explaining that stairs are required emergency exits and that the primary means of vertical travel is an elevator.
Thanks to the valuable suggestion.
1. CO2Carbon dioxide sensors are installed in our project, but not interconnected with fresh air fans. CO2 sensors will only monitor the CO2 levels and raise an alert when the levels are increased. Operable windows are available and will be opened whenever there is an alert. Is this type of system enough to achieve this credit?? Or else, is it compulsory to connect the CO2 sensor with fresh air fans to achieve this credit??
2. In one of our submitted projects, there is no occupied warehouse room. But the reviewer is suggesting to give CO2 sensors in the unoccupied warehouse room. As per IEQ matrix,CO2 sensor is not needed in unoccupied warehouse room. How to address this issue?
Your CO2Carbon dioxide sensors do not need to be programmed to change anything on your systems. For your second question, you need to just decide on that with the owner, it is not a LEED issue.
We have a lab classroom building that is served by an 100% OA unit. It maintains 6 ACHAir changes per hour: The number of times per hour a volume of air, equivalent to the volume of space, enters that space. in all the lab spaces for ventilation while in use. This is obviously much higher than would be necessary for CO2Carbon dioxide control. I don't think you could fit enough people in the space to go over the 1100 ppmParts per million. setpoint. Has anyone every argued that CO2 sensors are not necessary in a scenario like this?
I have designed many labs with LEED certification. I have never designed a lab that met the requirements for dense occupation though. Typically, the amount of lab casework per person prevents this. That being said, if you have a densely occupied lab and do not find a 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 allowing the monitors to be excluded, then you can either submit a CIR or provide CO2Carbon dioxide sensors. I would opt for the sensors.
Could a presure deferential sensor used as outdoor air monitoring devise?. It is a DOAS with diferential presure sensor wich will control the speed fan in order to deliver the same outdoor air when the filter gets old and the the presure increased.
This is not an acceptable solution for a variable volume system. If you are using a constant volume system, you may use a system status as a monitor.
Hi Andrew, it is a constant volume system. The diferential pressure sensor and the VRF adjust the fan speed in order to mantain the same cfm. As the filter gets dirty the pressure will increase and the fan will speed up to maintain the same air flow.
Just use the VFDA variable frequency drive (VFD) is a device for for controlling the speed of a motor by controlling the frequency of the electrical power supplied to it. VFDs may be used to improve the efficiency of mechanical systems as well as comfort, because they use only as much power as needed, and can be adjusted continuously. status to comply with the credit.
So a project can use the VFDs to monitor fan status (at 100% outside air at constant volume) and not have to include CT monitors? Thanks
If it is a constant volume system, the VFDA variable frequency drive (VFD) is a device for for controlling the speed of a motor by controlling the frequency of the electrical power supplied to it. VFDs may be used to improve the efficiency of mechanical systems as well as comfort, because they use only as much power as needed, and can be adjusted continuously. has a CT built in for status.
I'm working on a residential project hat has mixed-mode ventilation, partial mechanical and operable windows in units. What are the requirements in terms of CO2Carbon dioxide and OA sensors for mixed-mode ventilation? Also, do CO2 monitors need to be wired to the BMS? Thank you
If you are using mixed mode, then you should comply with both requirements for natural and mechanical monitoring (AFM and CO2Carbon dioxide). The sensors are not required to be wired to the BAS as long as they provide an alarm to the building occupants.
For Case 1, Type 2, where at least 20% of the system serves non-densely occupied zones, we have a situation where (1) dedicated outside air system (DOAS) serves several smaller heat pumpA type of heating and/or cooling equipment that draws heat into a building from outside and, during the cooling season, ejects heat from the building to the outside. Heat pumps are vapor-compression refrigeration systems whose indoor/outdoor coils are used reversibly as condensers or evaporators, depending on the need for heating or cooling. In the 2003 CBECS, specific information was collected on whether the heat pump system was a packaged unit, residential-type split system, or individual room heat pump, and whether the heat pump was air source, ground source, or water source. (HP) zones, by ducting the conditioned OA directly into the return ducts of the HP zones. Can we use just one outside air flow monitoring station in the DOAS system, or do we need an air flow monitoring station at each HP connection?
Reading thru the comments, it appears we can get away with just the (1) AFMS at the DOAS. However, the LEED form under Table IEQc2-1 that "System names and numbers must correspond with IEQp1". For credit IEQp1, we had to list all the individual HP zones, as some of the were single zone, and some were multi-zone. Can we just list the DOAS system under Table IEQc2-1, even though it doesn't correspond with IEQp1, which lists the individual HP units? If not how, are we supposed to deal with this?
How did you end up pursuing this credit? I am looking for answers to the same question. Thanks
The project I am working on has large laundry area with outside air provided for makeup air for the dryer exhaust. The system is designed to modulate based on the amount of exhaust caused by the dryers. When the dryers aren't running the DOAS will not run. Would OA air monitoring be required for the Makeup air units serving the laundry?
Joe - good question.
If your make up to the laundry was connected directly to the machines then I would call that "process" make up. In that case you wouldn't have to monitor it. But if you are supplying to the laundry area where people are folding clothes/putting in laundry and that is your only form of ventilation then you need to monitor it. If you have natural ventilation or another system that provides ventilation - then perhaps you could call it "process" again.
we have a project of around 20,000 sft and floor height 14 ft. its a textile project. 210 people work there. the space is ventilated by evaporative cooling system. how many CO2Carbon dioxide sensors do I need to place for CO2 monitoring?
In my opinion one (1) sensor is sufficient if the space is open (there are no impediments to the diffusion of the gas) and there are no local concentrated point sources of CO2Carbon dioxide generation other than the occupants.
You don't need any CO2Carbon dioxide sensors if it is one big space. You only need CO2 sensors in densely occupied spacesDensely occupied spaces are areas with a design occupant density of 25 people or more per 1,000 square feet (40 square feet or less per person).. For units serving spaces that are at least 20% not densely occupied you need to provide outside air flow monitoring to achieve this credit.
Hey Dylan! Spot on point. However I seem to remember that if you put CO2Carbon dioxide sensors in all spaces served by a system then you can meet the credit requirement without the airflow measurement even if the spaces aren't densely occupied. I used that for a project where we couldn't accurately measure the outdoor airflow. Does that compliance path ring a bell for you?
That'd be nice. But I don't think you'd get a good enough sample size in my opinion. CO2Carbon dioxide takes a while to mix.
I've heard of projects trying to put a CO2 sensor in the main return duct - which would be a better indication of average CO2 - but that hasn't been allowed as a replacement to the measurement by LEED in the past.
Yeah, return air is no good because if the outdoor air bypasses 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) it'll give you false sense of over ventilation when the opposite is true. I'm going to personally test the diffusion speed in a large volume space we're working on. Unfortunately I won't be able to do that until late 2016 probably.
when I have an addition project do I have to demonstrate compliance for the new addition and renovated areas or does it have to be applied to all areas? (existing to remain, renovated and new)
You need to demonstrate compliance for all areas within your LEED boundary. If part the building is existing to remain, it would be a good idea to leave that out of your LEED Boundary.
Hi, my project has PAU distributes 100% OA to AHUs so I want to ask if installing 1 OA meter at PAU is sufficient for the credit or I have to install meters at every AHU?
Thank you for your advice
It depends on whether or not the PAU is constant volume. If it is, then one AFS or CSR for that fan is allowable. If it is variable volume, then not only is it required for LEED, but it is good for building control.
Does CO2Carbon dioxide sensors that run by battery or powered by PC (USB port) count towards this credit for compliance? Please let me know.
The credit language says that permanent monitoring systems should be installed. I would not consider either of those to be permanent.
We are working on an office project. The typical floor will be a completely open space, with workstations and meeting spaces (not enclosed). This will not be a densely occupied space.
The design team proposes to install 4 CO2Carbon dioxide sensors through the space (approx. 1.400m2 of net area) to regulate the outdoor air supply of 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. based on CO2 levels.
This approach is choosen because outdoor air calculations are based on a high occupancy rate, but it is not sure if this occupancy will be achieved or will change during the building lifetime.
Would this approach meet credit requierements?
Is the building naturally, or mechanically ventilated?
Great. In that case, you will only need to measure the airflow at the unit level in order to monitor the status of the OA flow and provide an alarm if it is outside of the limits. I recommend that you provide a narrative and include your reasoning behind the design supply of OA as well as the CO2Carbon dioxide sensor control. The sensors will not be necessary for the credit, but they will probably wonder why they are there if you don't tell them ahead of time.
Your design approach sounds very good.
Thank you Andrew.
The CO2Carbon dioxide sensors alone would not be enough to comply with the credit?
If not, if we use 100% OA at unit level can we just monitor the operation of the fan?
If you want to consider the spaces as densely occupied, and the unit supplies less than 20% of its air to non-densely occupied spacesNon-densely occupied spaces are areas with a design occupant density of less than 25 people per 1,000 square feet (40 square feet or more per person).", then this approach will satisfy the credit. If you keep the spaces as non-dense, you will need direct flow measurement.
As for the fan status, that applies only to a constant volume dedicated OA unit. If you plan to vary the OA percentage, you cannot use that method.
Based on our control description, I assumed that you were monitoring the flow anyway. That way, when CO2Carbon dioxide levels are satisfied, you can set the flow to a minimum pressurization level.
Thank you Andrew for your response
I am working in a underground metro station which is aiming for LEED certification. I am facing difficulties with placing CO2Carbon dioxide sensors in breathing level in Public, Entrance, concourse and platform areas. this is a huge station and the client requirement is to consider 1 sqmt per person which is 10.76 sqft person considering it as a worst case scenario.
As per the credit requirement the density is lesser than 40 Sqft which leads to go for CO2 sensors in breathing level. as per the space matrix we need to consider all the transition areas if they have less than 40 Sqft per person (please confirm my understanding on this)
The problem here is how to place these sensors in these areas. these areas are huge and may require at least 60 to 70 sensors if i consider 200 Sq ft coverage per sensor and also we don't have many columns in these areas to fix these sensor to sense the CO2 concentration.
Our mechanical engineer says that we are considering 10.76 Sq ft per person as a worst case scenario and the chance for this situation is very meager and as per my understanding people will not stand or sit or do anything in these areas for an hour or more, they will move around continuously so there is no need to consider these space for the CO2 requirement. ( please clarify).
your inputs and suggestions are much appreciated.
How did you determine 200 sq ft/ sensor? You don't need "full coverage" for LEED. Just a sample size.
I'd say consider it a space that needs CO2Carbon dioxide and find strategic locations but much less. Even just a few for a large space is fine.
In addition to Dylan's appropriate response; when you do your design, you are allowed to do an occupancy average over a period of time based on the total volume of space. All of the equations are in ASHRAE 62.1 - 2007 chapter 6.
During one of our geek sessions the following conversation came up: would monitoring OA be allowed via a calculation? For example, say we’re monitoring supply air and return air. If we subtract the monitored return air from the monitored supply air doesn’t that yield the outside air? Do you think GBCIThe Green Building Certification Institute (GBCI) manages Leadership in Energy and Environmental Design (LEED) building certification and professional accreditation processes. It was established in 2008 with support from the U.S. Green Building Council (USGBC). would accept this approach, presuming it was well-documented? Thanks. David
This is more than likely possible. However, you will need to keep a few things in mind. Your AFMS's will need to be located such that significant duct leakage is negligible. In other words, if you were only taking the sums of a lot 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. supply and return boxes, I would not consider that to be very accurate. Also, I would imagine that you would be required to show that the compound error of the multiple sensors is still within the bounds of the credit requirement. I really do not see where this is a beneficial approach.
We are currently working on an office building, we want to achieve IEQ cr1, by installing C02 monitors in all spaces. (The building has rooms with mini-plits and windows so we will consider these spaces as naturally ventilated for this credit). The problem is the architect doesnt wants the monitors to be fixed to the walls due to esthetics. Can desktop C02 monitors, located in 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) count toward this credit? We will give each executive one to have in their shelves at about 4.5 feet.
I think that if you provide a narrative about how each sensor is placed, it is possible to meet the credit requirements. A few things to consider; the reviewer may challenge that the sensor will be moved elsewhere by the occupant, and thus you do not comply. Also, the sensors are required to generate an alarm to the building occupants. Unless you are using wireless transmission to the BAS, this will be a nuisance. I have seen sensors on desk generate readings of around 12,000 ppmParts per million. while occupants are within 36".
We have a project where in IEQ C1 was attempted when almost the construction was already completed. Now the client does not want the Co 2 sensors to be located within 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) of the rooms as it affects the aesthetics. Hence our HVAC engineers are proposing to place them within the return air grilles of the rooms. Since this approach would not be acceptable to USGBC they propose to decrease the Design Value (CO2Carbon dioxide ppmParts per million.) to make it even more stringent; so that it can accurately gauge the concentration levels within the breathing zone though placed at the return air grilles. Will this be a acceptable approach, please advice. Thanks.
No, this will not be acceptable. The owner should just be made aware of the consequences to LEED Certification.
We are working on a six story residential project. Each unit is cooled by ducted water source AC unit. AC unit does NOT have outside air connected to it. We are delivering pre-cooled outside air in the corridor of each level. This pre-cooled air will be transferred into each residential unit via 3/8" entry door undercut. Residential unit has toilet and dryer exhaust system, which works as "Push-Pull". Thus, there will be a continuous exhaust in the space 24/7. This will pull pre-cooled make up air from the corridor via door undercut.
Could we qualify this design as "Mechanically Ventilated" space?
You can, but be sure to have the exhaust running any time the room is occupied. Also, be sure to use the correct ventilation effectiveness fraction. If the exhaust is near the front door it will likely be 0.5. That means you will need to supply twice the calculated amount using area/occupant calculation.
In order to file compliance with IEQP1 & IEQc1: does the Airflow measuring devices need to be connected to BMS? Can they be standalone and programmed to generate an alarm?
Local alarms are allowed. Alarms should alert building occupants.
Thanks, can I clarify 2 more items:
1)if a meeting room is served by a dedicated FCU;
Does the meeting room require both the airflow measurement device as well the CO2Carbon dioxide sensors or just the CO2 sensor will do?
2) We have CO2 sensors in the return air duct that modulate the airflow based on occupancy. When there is less/no occupancy if modulates the damper to close In order to save energy.
Now when we program the airflow device serving the same space to maintain a minimum airflow, it does not complement each other. As airflow devices are programmed to maintain a minimum airflow even with no occupancy. How to resolve this?
We have a project with some areas served by AHUs and some areas served by contant volume FCUs. For the areas served by AHUs we have CO2Carbon dioxide sensors in the return air duct and not within the space.The FCUs delivers contant volume of air. Do we need to provide airflow measuring device? and do we need to provide CO2 sensors within the breathing zones?
CO2Carbon dioxide sensors in the return air duct does not meet the requirements of the LEED credit NOR does it meet the requirements of ASHRAE 62.1. To meet the LEED credit, the CO2 sensors must be within the densely-occupied zones and within 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) (3-6ft above the floor). The CO2 setpoint for each zone should be calculated individually based on the occupancy density and the expected occupant activity level (i.e., metabolic rate). Refer to Appendix C in the Standard for more on how to do this.
Lastly, airflow measuring devices are required for any system for where 20% or more of the design supply airflow serves nondensely 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.. So it depends on how you are providing the outdoor air to the zones served by the FCUs and AHUs. If you are using a central system to deliver the outdoor air to each FCU (i.e., not relying on the FCU fan to draw the outdoor air into the space) then a single airflow measuring device on the central system should be sufficient. Otherwise, you'll need a separate airflow measuring device on each FCU. Note, even with CO2 sensors in some zones served by the AHU, the AHU may need to have airflow measuring device as well.
Hope this helps.
My firm has had success not including CO2Carbon dioxide sensors in units of mid-rise residential project under LEED v3 NC. However, our new MEP team was recently required to install CO2 sensors in every unit, though they're technically low density spaces. The credit was ultimately dropped for the final design review due to cost. Our new project is using an individual aqua therm split system. Are we missing out on new requirements for CO2 sensors in low-density spaces for LEED v3 NC?
The "Document credit compliance on LEED Online" portion of the checklist provided above needs to be corrected to avoid further confusion.
1. References to ASHRAE 62.1 and OA ventilation rates are not relevant to this credit (or at least to LOL version 4 template)
2. There is no signatory for the ventilation or controls designer for this credit
3. There is no LPE for this credit.
If I am mistaken, please let me know.
We want to achieve this credit for a manufacturing facility. The air supplied to the production area is delivered through 26 propeller hooded roof fans and each one supplies 20,000 CFM to the ventilation zone. The ventilation rates supplied to the space are much higher than the ventilation rates stated by ASHRAE 62.1-2007, due the low occupancy. Therefore we would like to justify the credit monitoring the ventilation performance through the BMS to verify the correct performance without having the airflow measurement devices. If an equipment fails, an alarm will be send to the central monitoring and the maintenance department will be notified.
This is because the purpose of the credit is to avoid the CO2Carbon dioxide concentrations in the spaces, but evaluating the proportion of the space, the quantity of occupants in the area and the ventilation rates in the ventilation design this condition will not happen, and also the ventilation system will operate continuously during the occupation hours, this way we can corroborate that the outdoor air flow is according the project. Could this be acceptable for reaching this credit?
Thank you in advance.
Sorry, but you're not meeting the credit requirements by not providing either airflow monitoring or CO2Carbon dioxide sensors. That said, I see your predicament as it would be hard to install airflow monitoring on those fans. An alternative approach that I have seen used is to install CO2 sensors throughout the space (even though it is not densely occupied) and use that as the indicator of proper outdoor air delivery. Use Appendix C in ASHRAE 62.1-2007 as a guide on how to calculate the appropriate CO2 differential concentration.
As an aside, I like your plan to have the BMS alarm if the fan(s) fail to operate. Keep that even though it doesn't earn the credit. It's the right solution (in my opinion).
We are working on a project which is an industrial plant, the building will be mechanically ventilated. The manufacturing area is about 142,800 sf and this space will only have about 60 workers and it counts with 25 ceiling exhaust fans in the area, my question is, do we have to install one airflow measurement device for each one of the ceiling fans even though it is an open floor plant? or can we install only in half of them and connect the devices to the central system that can control all the ceiling fans and activate them if necessary?
I´m sorry, i meant supply filtered fans, no exhaust fans.
Since they are constant volume you are allowed to monitor fan status only.
Thank you Andrew, we will apply considering only the fan status monitoring.
We have a building with a large area of lockers/toilets. According to ASHRAE 62.1 these spaces do not require ventilation air. These spaces do require exhaust air.
Due to the large area of these spaces and minimal conditioning requirements, these spaces are being served by a dedicated 100% OA unit that heats and/or ventilates only.
Since these spaces are not required by ASHRAE 62.1 to be provided ventilation air, do these units need air flow monitoring? (The rest of the facility will have airflow monitoring as required). Yes, these serve non-densely occupied spacesNon-densely occupied spaces are areas with a design occupant density of less than 25 people per 1,000 square feet (40 square feet or more per person)." only.
If yes, CT's on the fans meet the requirements per 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 ID #2099, right?
If it is only for make-up air for the required exhaust, then it is not required.
We are working with a project that have a densely occupied meeting room. The walls of this room do not go from floor to ceiling and the room is located in a not densely occupied open office.
Do we need to install CO2Carbon dioxide sensors?
Thanks in advance,
How tall are the walls and what is the ceiling height?
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