The ASHRAE GreenGuide: One Means of Establishing a Link between Sustainable Design Practitioners John Swift 1, Thomas M. Lawrence 2 1 Cannon Design, Boston, MA USA 2 University of Georgia, Athens, GA USA Corresponding email: JSwift@cannondesign.com SUMMARY The paper discusses the newly revised ASHRAE GreenGuide, particularly as it relates to the topic of indoor environmental quality. The updated Guide includes a new chapter on LEED Guidance for Mechanical Engineers and a new chapter on building systems Impact on the Local Environment- both indoor and outdoor. This chapter is intended to describe how HVAC systems interact with the building indoor and outdoor environment, and includes (among others) sections dealing with indoor environmental quality, cooling tower systems and chemical water treatment, acoustics, and the science of designing healthy buildings. One of the more useful concepts in the Guide is the inclusion of Green Tips, which are sidebar summaries of specific technologies that can be used to design a high-performance (green) building. Three building specific Green Tips are discussed, with particular emphasis on topical areas related to indoor air quality concerns. INTRODUCTION The ASHRAE Green Guide (Guide) [1] is a primary reference for mechanical engineers working on high performance building projects in the United States. The original edition of the Guide was released in January of 2004, and the second edition was introduced at the U.S. Green Building Council s Greenbuild Conference in Denver, CO, USA in November, 2006. The Guide is intended to be a living document and the process is in place to maintain this with new editions that will contain updated material. The Guide is not intended as a complete compilation of all interactions that buildings, and heating, ventilation and air-conditioning (HVAC) systems in particular, have on and with the environment. Many of the issues are common knowledge as being important to green building design among engineers and lay people alike; such areas as energy consumption, location of buildings and the construction process are prime examples. The Guide is primarily intended to convey ideas on how to improve buildings and their systems. There are, however, some areas that are either not intuitively obvious as being potential impacts of HVAC systems, or are items that are some may not consider to be truly sustainability issues. While not being the sole target market, the Guide is written such that practitioners in the early stages of their career will particularly benefit. Regardless of your definition of sustainability or the various labels and compartmentalization, it is assumed that the reader of the Guide is interested in designing buildings and their systems that provide for the needs of the occupants while minimizing the their adverse impacts. Therefore, the chapter on local environmental impacts provides examples of several areas that
the HVAC engineer may not initially think are important when minimizing environmental impacts, but truly are significant. This paper discusses the importance of continuing to build a link between ASHRAE, REHVA and other global building engineering design associations. Important differences in the integrated design process will be identified from a U.S. perspective. The issues will be evaluated and discussed with the goal of working toward the optimization of the high performance building design process globally. The example presented for this discussion is the Second Edition of the ASHRAE Green Guide. What is New to the GreenGuide The updated Guide includes a new chapter on LEED Guidance for Mechanical Engineers and a new chapter on building systems Impact on the Local Environment- both indoor and outdoor. This chapter is intended to describe how HVAC systems interact with the building indoor and outdoor environment, and includes (among others) sections dealing with indoor environmental quality, cooling tower systems and chemical water treatment, acoustics, and the science of designing healthy buildings. One of the more useful concepts in the Guide is the inclusion of Green Tips, which are sidebar summaries of specific technologies that can be used to design a high-performance (green) building. Some of the chapters from the First Edition have been reorganized in an attempt to more accurately mirror the path that an actual project would take from Pre-Design to Post Occupancy. Content has been added and edited in all of the chapters, with significant updates in the subject areas of Building Automation Systems, Renewable Energy Options, combined heat and power and ground-source heat pump systems. The Second Edition also provides a more global perspective with a specific section titled International Perspective, along with SI/IP dual units provided for all. METHODS Developing a guideline on Indoor Environmental Quality (IEQ) intended for a broad audience while still technically sufficient can be a difficult task. One weakness of the original edition of the Guide was a lack of information on IEQ, and this has been corrected with the new second edition. This section first presents a summary of the IEQ information content in the new Guide and how it relates to other chapters within the Guide. Next, a description is given of three examples on how information contained in the Guide can be applied. The terms indoor environmental quality (IEQ) and indoor air quality (IAQ) are sometimes confused as being one in the same. In reality, IEQ is a broader, more encompassing concept which includes IAQ as one of the key factors. Other areas are also considered key to providing good overall IEQ, such as: Air quality and ventilation Thermal comfort Acoustics and noise Lighting levels Visual perception Building materials and envelope When considering indoor air quality, the outdoor environment can have a negative impact on the building HVAC and the indoor environment, or vice-versa depending on the specific
situation. Location of outdoor air intakes near a known contamination source (such as a loading dock with potential idling engines) can seriously degrade the indoor air quality by introducing, rather than removing, contaminants. Similarly, building exhausts can contaminate the local area near the exhaust discharge, making this air unsuitable for human exposure or re-intake into the building. Chapter 44 of the 2003 ASHRAE Applications handbook [2] (Building Air Intake and Exhaust Design) contains more information on this topic. Assuming no contamination of the local air surrounding the building, then good indoor air quality is possible by providing adequate ventilation and distribution within the space; for example if the design met the requirements as specified in ASHRAE Standard 62.1 [3]. Similar to lighting levels, thermal comfort affect the occupants and overall building indoor environmental quality. Thermal comfort of the occupied space is covered in Chapter 7 of the Guide. The interaction with the local environment has minimal impact on thermal comfort. The acoustical environment can also be an important factor in determining good indoor environmental quality. Sound and vibration are the often unheralded contributors to occupant comfort and health that should be an integral part of green building design and should not be forgotten. While noise is not always an obvious problem, human productivity and performance can be impacted by the acoustical environment. Adequate lighting levels are required for the building occupants. Lighting levels required vary according to the design purpose of the room or building zone. The local environment, in the form of trees, landscaping or other buildings, can influence the lighting that may enter the space and hence affect the lighting levels inside. Lighting and its impact on HVAC load determination is discussed in more detail in Chapter 6 of the Guide. This is another area that influences how a person perceives the indoor environmental quality. Rarely would the HVAC system interact with visual perception of the indoor space, with one possible aspect being exposed ductwork. Any HVAC system interaction with visual perception will likely be dealt with by the project architect. The Guide addresses these issues in Chapter 4. Recent years have seen a marked increase in recognition of the impact that building materials (envelope, furniture, paints, flooring, etc.) have on indoor air quality. This was the primary reason for changes to the ASHRAE Standard 62.2 outdoor air ventilation requirements to include an allowance for the building area and not just total number of occupants. The indoor air quality can be negatively affected by off-gassing of chemicals building materials or chemicals used during the construction or fabrication of the components. The LEED program contains a number of credit point items that related to reducing the introduction of potentially harmful materials into a building environment. It also describes methods to help ensure that key HVAC components, such as ductwork, do not become contaminated during construction and act as a source of indoor pollution after occupancy. Focusing on the Indoor Air Quality concept and how the Guide can assist in advancing the latest design concepts that optimize air quality, several example are given indicating how the Guide would be used.
The first example presented is how green practices can be applied in general to laboratory buildings. Building-specific Green Tips have been included in the Second Edition of the Guide. The Green Tip for Lab Buildings indicates a number of design concepts for consideration as they relate to IEQ issues. The second example is a summary of the Green Tip for Healthcare Facilities, and the final example is a similar compilation of techniques as applied to the specific design challenges of a university student residential facility. The strategies outlined can also be applied to hotels and multi-unit residential complexes, including luxury condominium developments. RESULTS Example 1: Laboratory Buildings One of the user friendly features of the Green Guide are the Green Tips. If used, these tips can help the designer make informed decisions on what systems may be properly integrated on a specific project. These tips also allow the engineer to identify benefits and costs in order to work with the constructors and the owner to implement concepts that best suit the needs and ideals of the project. Building-specific Green Tips have been included in the new Second Edition of the Guide. The Green Tip for Laboratory Buildings focuses on safety, energy and occupant comfort considerations. The following design concepts are given for consideration as they relate to IEQ issues: Safety 1. Fume hood design and associated air distribution and controls must be designed to protect the users and the validity of the laboratory work. 2. Pressurize rooms consistent with the ASHRAE Laboratory Design Guide and any other code required standards. Utilize building pressurization mapping to develop air distribution, exchange rate and control strategies. 3. Optimize air exchange rates to ensure occupant safety while minimizing energy usage. 4. Chemical, biological and nuclear storage and handling exhaust and ventilation systems must be designed to protect against indoor pollution, outdoor pollution and fire hazards. 5. Intake/ exhaust location strategies should be modeled to ensure that lab exhaust air is not reintroduced back into the building air handling system. Energy Considerations 1. Heat recovery for spaces served by air handling units with 100% outside air capability or over 50% outdoor air component. The Guide contains several Green Tips associated with air-to-air energy recovery covering heat exchange enthalpy wheels, heat pipe systems and run-around systems. 2. Utilize variable air volume (VAV) systems to minimize air exchange rates during unoccupied hours. 3. Consider low flow fume hoods with constant volume controls where this concept can be properly applied. 4. When appropriate, consider decoupling outdoor air conditioning from the space loads by using chilled beams.
Occupant Comfort 1. Air systems should be designed to allow for a collaborative working environment. Acoustic criteria should be adhered to in order to maintain acceptable levels of noise control. 2. Day light and views should be considered where lab work will not be adversely affected. Figure 1. Conceptual diagram indicating optimization of indoor air quality and minimization of cooling loads for a proposed project in Algeria. Example 2: Healthcare Facilities Healthcare facilities are infrastructure intensive and include many different types of spaces. The HVAC systems for these different types of spaces must be designed to address the specific needs of the spaces being served. The first considerations should always be safety and infection control. In addition, optimizing energy efficiency and positively affecting the patient experience should also be important design team goals. A summary of the key points contained in the Guide s Green Tip for healthcare facilities is given in the following topical sections. Safety and Infection Control 1. Consider HEPA (high-efficiency particulate air-filter) filtration for all air handling equipment serving the facility. 2. Consider air distribution and pressurization strategies in operating and trauma rooms that balance air flow zones from most clean to least clean. The order of zone cleanliness starts at the operating and thermal plume location at the patient, then moves to the zone around the doctors, the zone around the room, and then the zone outside of the room. 3. Pressurize rooms consistent with American Institute of Architect (AIA), ASHRAE or other local or national codes and guidelines. 4. Provide air exchange rates in excess of AIA guidelines in operating rooms, intensive care units, isolation rooms, trauma rooms, and patient rooms. 5. Redundancy of equipment should be designed for fail-safe operation and optimal full and part load energy efficient operation.
6. Intake and exhaust location strategies should be modeled (computational fluid dynamics or wind tunnel) to ensure no re-introduction of exhaust into the building. Energy Considerations 1. Heat recovery for spaces served by air handling units with 100% outside air capability. 2. Utilize VAV systems in non-critical spaces working in conjunction with lighting occupancy sensors. Occupant Comfort 1. Acoustics of systems and spaces must be designed with patient comfort in mind. 2. Daylighting and views should be provided but design to minimize the HVAC load impact of these benefits. 3. Provide individual temperature control of patient rooms with capability of adjustment by patient. 4. Building pressurization relationships/ odor issues should be carefully mapped and addressed in the design and operation of the building. Figure 2. CFD results showing particle path tracing in an operating room. (UMass Memorial Lakeside Addition, Worcester, MA, USA) Key Elements of Cost 1. HEPA filtration costs are significant in both first cost and operating cost. The engineer should work closely with the infection control specialists at the healthcare facility to determine cost/ benefit assessment of the filtration strategies. 2. Heat recovery strategies should be assessed using life cycle analyses. All components of the strategy must be taken into account, including the negative aspects, such as adding fan static pressure, and therefore, using more fan energy, when heat wheel or heat pipe strategies are considered.
Example 3: University Residential Facilities Student residence halls are made up primarily of living spaces (bedrooms, living rooms, kitchen areas, common spaces, study spaces, etc.). Most of these buildings also have central laundry facilities, assembly/ main lobby areas, and central meeting/ study rooms. Some of these spaces also include classrooms, central kitchen and dining facilities. The strategies outlined below can also be applied to hotels and multi-unit residential complexes, including luxury condominium developments. Energy Considerations 1. Heat recovery for spaces served by air handling units with 100% outside air capability serving living units (exhaust taken from toilet rooms and supply air to occupied spaces). 2. Utilize VAV systems or induction systems for public spaces. 3. Investigate methods to provide natural ventilation or hybrid natural ventilation strategies, as appropriate to the local climate. An example airflow path of such is given in Figure 2. 4. Utilize electronically commuted motors (ECM) for fan coil units. 5. Utilize ground source heat pumps where feasible. Occupant Comfort 1. Systems should be design to appropriately control noise in occupied spaces. 2. Daylight and views should be optimized while minimizing load impact on the building. 3. Consider providing occupant control in all bedrooms, which will be a balance of cost impact with improved indoor environmental quality. Figure 3. Path of natural ventilation in high-rise atrium which also optimizes views while minimizing solar gain (Suffolk University Residence Hall, Boston, MA, USA).
Key Elements of Cost 1. While there is a premium to be paid in first costs for ECM motors, many utility companies have energy rebate programs that make this concept viable, even on projects with tight budgets. 2. Heat recovery strategies should be assessed using life cycle analyses. All components of the strategy must be taken into account, including the negative aspects, such as adding fan static pressure, and therefore, using more fan energy, when heat wheel or heat pipe strategies are considered. 3. Hybrid natural ventilation strategies could be utilized using operable windows, properly designed vents using venturi effect to optimize natural airflow through the building, and shut down of mechanical ventilation and cooling systems during ambient temperature ranges between 15 and 17 C. This will save significant operating costs. The costs of the operable windows and vents will need to be weighed against the energy savings. SUMMARY Indoor air quality is influenced by all of the inter-related aspects of building design. The ASHRAE Green Guide is a valuable tool for mechanical engineers striving to meet the goals of resource use optimization and a comfortable, healthy indoor environment through an integrated design team approach. Sources of Further Information The following are sources of further detailed information regarding the three Green Tip examples for different building types listed in this paper. ASHRAE Laboratory Design Guide, NFPA 45 Standard on Fire Protection for Laboratories using Chemicals, and Labs 21 Environmental Performance Criteria, http://www.labs21century.gov/ ASHRAE - HVAC Design Manual for Hospitals and Clinics, NFPA-99 Healthcare Facilities 2002, ASHE Green Guide for Healthcare, www.gghc.org BRESCU, BRE, "Natural Ventilation for Offices" Guide and CDRom, ÓBRE on behalf of the NatVent Consortium, Garston, Watford, UK, March 1999, Svensson C. and Aggerholm S.A., "Design tool for natural ventilation" Proceedings of the ASHRAE, IAQ AQ '98 Conference, New Orleans, October 24-27, 1998, ASHRAE Fundamentals 2005, Chapter 27, pages 25.10-25.12. REFERENCES 1. ASHRAE. 2006. ASHRAE GreenGuide, Amer. Society of Heating, Refrigeration and Air Conditioning Engineers, Atlanta, GA, USA, 393 pp. 2. ASHRAE 2003. Handbook, Applications. 3. ASHRAE 2004. Standard 62.1-2004, Ventilation for Acceptable Indoor Air Quality.