Schools-2009 IEQc6.2: Controllability of Systems—Thermal Comfort

  • NC CS Schools EQc6.2 Thermal Comfort Diagram

  • What schools need to do

    All multi-occupant spacesConference rooms, classrooms and other indoor spaces used as a place of congregation for presentations, trainings, etc. Individuals using these spaces share the lighting and temperature controls and they should have, at a minimum, a separate zone with accessible thermostat and an air-flow control. Group multi-occupant spaces do not include open office plans that contain individual workstations. (like classrooms or auditioriums) must have at least one occupant comfort control.

    For individual spaces or open-plan offices, at least 50% of occupants must be able to control their individual comfort conditions.

    A lot of options

    Multi-occupant spaces like classrooms need at least one comfort control. Operable windows are a common way to meet this requirement.Multi-occupant spaces like classrooms need at least one comfort control. Operable windows are a common way to meet this requirement.The credit defines comfort according to the four primary comfort criteriaComfort criteria are specific design conditions that take into account temperature, humidity, air speed, outdoor temperature, outdoor humidity, seasonal clothing, and expected activity. (ASHRAE 55–2004) identified by ASHRAE 55-2004:

    • Air temperature
    • Radiant temperature
    • Humidity
    • Air speed.

    A comfort control meeting the credit requirements needs to only address one of these four. Common ways to meet the credit include:

    • installing heating radiators or radiant panels with individual temperature controls;
    • operable windows;
    • or adjustable local air diffusersIn an HVAC context, diffusers disperse heating, cooling, or ventilation air as it enters a room, ideally preventing uncomfortable direct currents and in many cases, reducing energy costs and improving indoor air quality (IAQ). In light fixtures, diffusers filter and disperse light..

    Choosing your ventilation system

    You can meet this credit with either naturally or mechanically ventilated buildings.

    Projects using natural ventilation need to provide access to operable windows for at least 50% of occupants in individually 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.. An occupant has access to an operable window if their desk is located within 20 feet of a window to the inside, and 10 feet from side to side.

    It is more difficult to achieve credit compliance with mechanical systems like forced air because the controls typically serve a large area. You can provide a greater level of thermal comfort with underfloor air distribution that provide easily controlled diffusers. 

    Thermal comfort controls like thermostats are a common way to earn this credit, but make sure you choose a mechanical system that allows for that level of variability.Thermal comfort controls like thermostats are a common way to earn this credit, but make sure you choose a mechanical system that allows for that level of variability.For constant-air-volume systems that do not allow individual control, you may need to add an additional unit, such as a reheating coil at the diffuser or perimeter baseboard heating, to achieve the credit’s intent. 

    Heating or cooling

    For mechanically ventilated spaces, previous LEED-certified projects have complied with the credit by providing occupant controls for heating or cooling only. For example, a building providing controls adjusting heat within a certain temperature range can comply with the credit, even if controls are not providing for the cooling season.

    Approaching the credit by building type

    One control in each classroom, and controls for 50% of offices and individual workspaces. 

Legend

  • Best Practices
  • Gotcha
  • Action Steps
  • Cost Tip

Pre-Design

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  • Early during pre-design the owner identifies occupant comfort and control goals in the Owner's Project Requirements for commissioning in EAp1 and EAc3.

  • Assess your climate and your ability to provide occupant-controlled interventions for different comfort criteria. These may include: 

    • operable windows for air speed and temperature
    • air conditioning for temperature and humidity 
    • ceiling fans for air speed
    • desiccant dehumidification 
    • radiators for air temperature
    • air diffusers for air speed.

    Desk fans are not considered an acceptable strategy according to LEED Interpretation #1722, although USGBC has not officailly applied that Interpretation to LEED-2009 rating systems.

  • For commercial buildings, systems like fan coils paired with dedicated outdoor air systems can help provide local control to occupants, while reducing first-cost expenses like duct-work.

  • Operable windowIncluding operable windows in the building can reduce dependence on specific mechanical system designs. Positioning as many occupant spaces near operable windows as possible can make this credit easier to achieve.

  • Some conventional systems typically rely on central control, and multiple controls may be difficult to incorporate. Underfloor air distribution, on the other hand, is designed for flexibility and individual control in a way that naturally supports this credit. 

  • The required comfort control has to address only one of the four primary comfort criteria identified by ASHRAE 55-2004: air temperature, radiant temperature, humidity or air speed. You may address multiple criteria, but aren’t required to do so.

  • The comfort system does not have to be especially expensive or complex. It may simply be, for example, localized air conditioning with occupant controls. 

  • Providing occupant comfort controls can add some costs, but they can also save money and improve occupant comfort and productivity. Occupant comfort controls allow for the mechanical system to respond to conditions specific to different parts of the building, improving overall comfort while saving energy. Typically, a system under central control is sized and calibrated for the least comfortable space. For example, in cooling season overhead air conditioning is provided for the warmest space, while everyone else under the same AHU feels uncomfortably cold. By providing individual controls, everyone can adjust the cooling or air speed to their comfort needs. This control often directly translates to lower energy costs.  

  • Individual thermal comfort plug-in devices are allowed under IEQc6.2, as long as they are included in the design but not the baseline energy model.

Schematic Design

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  • Develop a list and number of all occupied spaces in the building, noting multi-occupant spaces. The number of individual occupant spaces and multi-occupant spaces should be the same between IEQc6.1 and IEQc6.2.

  • A multi-occupant space is space for group interactions, like classrooms, conference rooms, cafeterias, lobbies, warehouse loading areas, theaters, break rooms, commercial kitchens, retail stores, and exhibit spaces that expect large number of people to gather. 

  • Each multi-occupant space should have at least one comfort control that regulates air temperature, radiant temperature, humidity, or air speed in that room. 

  • For individually occupied spaces, identify the total number of workstations anticipated to be in each space per the project FTE count or based on the estimates listed in the Reference Guide Appendix 1. "Workstations" are referred here as places where full-time occupants spend majority of their time.

  • How many people per operable window? If using operable windows, locate as many people as possible close to them. Although strictly speaking it may make sense to count one person as needing one operable window, the experience of the LEEDuser team is that the credit has been approved by counting multiple people sitting close to a window as long as a person is within a 20-foot depth and a 10-foot length from one. The operable portion of the window must also be at least 4% of the size of the floor area of the space accessible to a given window, per ASHRAE 62.1-2007. For example, for a 5-foot-long window plus 10 feet on either side the total qualifying floor area would be 25 (5 + 10 + 10) multiplied by 20, or 500 ft2. At 4% of the floor area, the operable window area must be at least 20 ft2. Refer to the Documentation Toolkit for a diagrammatic representation of the window-area-to-floor-area relationship.

  • How many people per control? Even though the credit calls for individual comfort controls, projects often earn this credit by grouping occupants around a single operable window. Similarly, a single mechanical system control can serve up to two occupants, contributing to the 50% credit threshold.

  • If less than 50% of occupants have access to operable windows, add more operable windows, adjust the layout, or add ducts, baseboards or diffusers with controls to add individual comfort controls. Run calculations again and redesign till 50% of people have access to the controls. 

  • An open office space is individually occupied where each person has an individual desk and defined space. 

  • Individually occupied spaces are defined as the place where an occupant spends most of their time, such as a private office, reception desk, workstations or cubicles in open-plan offices. 

  • A control can be as simple as a switch to turn air conditioning on or off, changing temperature in a small permitted range using a thermostat, or closing a diffuser to reduce air flow. 

  • Providing comfort controls that allow an occupant to turn a system on only when using the space, and turn it off at other times, supports energy efficiency goals. Whether or not it can contributes to demonstrable energy reductions for EAc1: Optimize Energy Performance is another question. Except for operable windows, this would be difficult to demonstrate.  

  • Note the credit requirement is based on number of occupants for individually occupied and number of spaces for multi-occupants. Only half of the total building occupants must have controls in individually occupied spaces. However, each of the multi-occupant spaces must have independent controls. 

  • For example, a school has 10 classrooms with 20 students each, five private offices and one hallway reception desk. The individually occupied spaces are the offices and administration desks with total occupancy of 5 + 1 = 6 people. At least three of those occupants should have access to controls to meet the credit. The multi-occupant spaces are the classrooms, and each classroom needs at least one independent control. 

  • Facilities managers may have reservations about providing controls to users. The range of control can be limited to a certain range, however, and should be programmed to be reset at least at the end of the day with the building’s typical temperature setback. Be sure that occupants will be educated on how to use controls. 

  • Additional controls imply higher construction costs, with additional wiring, and maintenance for uninterrupted operations. There are low-cost options, such as baseboard heating radiators and heat pumps that are easy to operate and provide good local comfort. Compare the upfront costs of better controls to the long-term benefits of higher productivity, better test scores or hotel occupancy, plus savings in energy usage.

  • Underfloor air or ceiling-air plenum are common systems for allowing occupant comfort control. In addition, they can: 

    • allow for flexibility in layout and design, and ease of electrical wiring, installation of work stations, and arrangement of work spaces; 
    • realize first-cost savings in reduced duct work, lower floor height and possible an additional floor with more leasable space;
    • and enhance daylighting by creating higher floor-to-ceiling heights.

  • Chilled beams and radiant ceiling panels can provide individual temperature controllability. Given the appropriate climate, internal loads and envelope design chilled beams can be a good fit for this credit, especially if other options like operable windows are limited—for example in laboratory buildings.  

  • In the absence of operable windows, it is difficult to meet the 50% credit requirement unless the mechanical system is designed with zones to provide multiple comfort controls. 

  • Operable windows, although offering some energy and comfort benefits, have some drawbacks. They allow in outside air, which may not be of the highest quality, and also allow in outside noise. The unconditioned air they allow in can affect the operation of mechanical systems. 

  • Operable windows are generally higher in cost than fixed windows.

  • A mechanical system with more individual controls may cost more than a conventional system. This cost can be offset, though, by lower operating costs, a more flexible layout, and improved occupant productivity. 

Design Development

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  • If using a mechanical system, confirm that the project design is progressing with a system that allows for multiple controls.

  • Update the count of total individual workstations and those with controls. If the controls do not add to be 50% of total workstations then investigate the potential to add more controls or change the layout to make them more accessible to windows. 

  • Configure the mechanical system so that when windows are open, cooling is turned off to avoid wasting energy. You can accomplish this by hooking operable windows up to wireless sensors that communicate with the cooling system. 

  • Install a building management system that communicates with occupants to open operable windows when outside temperature and humidity are within comfort range as defined by ASHRAE 55-2004. 

Construction Documents

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  • If using operable windows, make sure the window schedule and all construction drawings include relevant details. Specify windows and window locations that make them easy to operate. 

  • Include all control locations and specifications in drawings and bid documents. Verify that the construction budget accounts for all thermostats, diffusers and a feedback system. 

  • Provide for the commissioning of control and response systems in the commissioning scope for EAp1. 

  • During the construction bidding phase, discuss the schedule to make sure correct control equipment is purchased and installed on time. The controls are only as good as the feedback and response system they are connected to. Explain the control sequence to the subcontractors to minimize confusion. 

  • If value engineering threatens comfort controls, remember their benefits—including energy savings and higher productivity.

Construction

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  • Ensure correct installation of all mechanical systems. 

  • Complete LEED Online documentation. Include mechanical system layout with controls schedule and cut sheets. 

  • List all spaces and occupancy types for the project on LEED Online. Mark the kind and number of controls available in each of those spaces. Select “None” if any of those occupants do not have individual controls. The online submittal form will automatically advise on number of required occupants with controls and those that are available. 

  • The commissioning agent should check and verify operation and setpoints of the controls. (See EAp1.)

Operations & Maintenance

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  • Educate occupants about the range of control adjustments available. Many air diffusers can open or close the air vent and change the temperature only within a limited range, typically within 5ºF–10ºF of acceptable comfort levels. For example, a heating system may allow a range from 68ºF–74ºF. Comfort controls may not allow larger changes or switching to air conditioning during the heating season, and it is helpful for occupants to understand this. Encourage occupants not to leave windows open when heating or cooling is on.

  • Train operations and maintenance staff to troubleshoot any problems, particularly if there is a BMS system that responds to user controls, with overrides for end-of-day setbacks.

  • Incorporate controls into the operations manual and training so that facility staff are aware of the controls mechanism and response system. 

  • USGBC

    Excerpted from LEED 2009 for Schools New Construction and Major Renovations

    COPYRIGHT © 2009 BY THE U.S. GREEN BUILDING COUNCIL, INC. ALL RIGHTS RESERVED

    IEQ Credit 6.2: Controllability of systems - thermal comfort

    1 Point

    Intent

    To provide a high level of thermal comfort system control1 by individual occupants or groups in multi-occupant spacesConference rooms, classrooms and other indoor spaces used as a place of congregation for presentations, trainings, etc. Individuals using these spaces share the lighting and temperature controls and they should have, at a minimum, a separate zone with accessible thermostat and an air-flow control. Group multi-occupant spaces do not include open office plans that contain individual workstations. (e.g., classrooms or conference areas) and promote their productivity, comfort and well-being.

    Requirements

    Provide individual comfort controls for 50% (minimum) of the building occupants in workspaces to enable adjustments to meet individual needs and preferences. Operable windows may be used in lieu of controls for occupants located 20 feet inside and 10 feet to either side of the operable part of a window. The areas of operable window must meet the requirements of ASHRAE Standard 62.1-2007 paragraph 5.1 Natural Ventilation (with errata but without addenda2).

    Conditions for thermal comfort are described in IEQ Credit 7.1: Thermal Comfort – Design and include the primary factors of air temperature, radiant temperature, air speed and humidity.

    Provide comfort system controls for all shared multi-occupant spacesConference rooms, classrooms and other indoor spaces used as a place of congregation for presentations, trainings, etc. Individuals using these spaces share the lighting and temperature controls and they should have, at a minimum, a separate zone with accessible thermostat and an air-flow control. Group multi-occupant spaces do not include open office plans that contain individual workstations. to enable adjustments that meet group needs and preferences.

    Potential Technologies & Strategies

    Design the building and systems with comfort controls to allow adjustments to suit individual needs or those of groups in shared spaces. ASHRAE Standard 55-2004 (with errata but without addenda2) identifies the factors of thermal comfort and a process for developing comfort criteriaComfort criteria are specific design conditions that take into account temperature, humidity, air speed, outdoor temperature, outdoor humidity, seasonal clothing, and expected activity. (ASHRAE 55–2004) for building spaces that suit the needs of the occupants involved in their daily activities. Control strategies can be developed to expand on the comfort criteria and enable individuals to make adjustments to suit their needs and preferences. These strategies may involve system designs incorporating operable windows, hybrid systems integrating operable windows and mechanical systems, or mechanical systems alone. Individual adjustments may involve individual thermostat controls; local diffusersIn an HVAC context, diffusers disperse heating, cooling, or ventilation air as it enters a room, ideally preventing uncomfortable direct currents and in many cases, reducing energy costs and improving indoor air quality (IAQ). In light fixtures, diffusers filter and disperse light. at floor, desk or overhead levels, control of individual radiant panels, or other means integrated into the overall building, thermal comfort systems and energy systems design. Designers should evaluate the closely tied interactions between thermal comfort, as required by ASHRAE Standard 55-2004 (with errata but without addenda2), and acceptable indoor air quality as required by ASHRAE Standard 62.1-2007 (with errata but without addenda2), whether natural or mechanical ventilation.

    FOOTNOTES
    1.  For the purposes of this credit, comfort system control is defined as control over at least 1 of the following primary factors in the occupant’s
    vicinity: air temperature, radiant temperature, air speed and humidity.

    2.  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.

Articles

Daylighting in Schools: An Investigation into the Relationship Between Daylighting and Human Performance

Study examining the correlation of human performance benefits and daylighting in the classroom.

Organizations

ASHRAE 55-2004

This ASHRAE standard defines the criteria for human comfort that is followed to design mechanical systems.

ASHRAE 62.1 2007

This ASHRAE standard stipulates minimum outdoor air requirement and minimum window opening for naturally ventilated space. This formula is referenced in this credit where windows are used as control mechanism. 

Publications

National Review of Green Schools: Costs, Benefits, and Implications for Massachusetts

This seminal report documents the financial costs and benefits of green schools compared to conventional schools, specifically with reference to Massachusetts. Page six describes the benefits of ventilation controls on occupant productivity.

Operable Windows and HVAC Systems

Taylor Engineering lays out design guidance for integrating operable windows into an HVAC system, while also reducing energy consumption.

Integrated Design and UFAD

In this article from ASHRAE Journal, the authors outline the benefits of an integrated designAn integrated design process (also called "integrative" design by some proponents) relies on a multidisciplinary and collaborative team approach in which members make decisions together based on a shared vision and holistic understanding of the project. Rather than a conventional linear design process in which a design is passed from one professional to another, an integrated process has all key team members talking together through out the design and construction process as they share ideas and use feedback across disciplines to iteratively move toward a high-performing design. approach for underfloor-air distribution, and explain how UFAD can contribute to LEED credits including IEQc6.2. (Subscription Required)

Technical Guides

IEQ Space Matrix

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.

LEED Online Credit Form

Documenting this credit in LEED Online includes completing the table shown here (as samples), with occupancy types and thermal comfort control types indicated.

Operable Windows

Operable windows are an appropriate way to meet the requirements for this credit in many building types. A single operable window can serve multiple occupants, as shown here.

LEED Online Forms: Schools-2009 IEQ

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."

Design Submittal

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

3 Comments

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Erik Bergstrom Green Building Associate
Jun 08 2010
Guest
1318 Thumbs Up

Air Speed Control

Is a ceiling fan with individual control considered a thermal comfort control under IEQ6.1 for a multi-occupant space? (air speed)

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Tristan Roberts LEED AP BD+C, Editorial Director – LEEDuser, BuildingGreen, Inc. Jun 10 2010 LEEDuser Moderator

Yes, I would say so, based on the credit requirements as explained above. It would probably need to affect the air speed in the whole room, so it would have to be sized/designed properly.

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SERA Architects SERA Architects May 11 2011 Guest 184 Thumbs Up

Also, it depends on what is your heating and cooling strategy for the space. if ceiling fans is the only means of achieving thermal comfort, then ability to individually control them would be considered compliant. Hope that helps.

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