Tools of the Trade

Written by R. Kirk Johnson, AIA, LEED AP

As designers, we approach effectual architectural design by understanding and interpreting a variety of elements such as the building program, project budget, construction schedule, climate, project context, available materials, aesthetic expression, owner vision, energy impacts, and considerable other elements.  As we build our repertoire of designing ecologically friendly designs, a broader comprehensive perspective of energy influences becomes much more paramount than earlier precedents.  As these energy ingredients are quickly emerging as essential foundations for building analysis, new understandings, reflecting a broader comprehension of building behavior is crucial to our developing appropriate facility designs.  One such elemental methodology is an adoption of Building Performance Modeling into the sustainable design process.

 

BUILDING PERFORMANCE MODELING

What is building performance modeling analysis (BPM)?  At a basic intrinsic look at the issue, building performance modeling analysis is the creation of a digital definition, description, and simulation process of a building behavior.  In essence, it illustrates performance and operational components of a facility prior to the construction of the building.  It particular investigates the analysis of building performance behavior- such as How it performs?  How well it does it?  What areas can be optimized?  The analysis is most influential when used during the early design stages but can equally provide valuable understanding in a lessons learned study after the facility has been constructed and occupied.  When utilized after this time duration, the model can be updated to match actual building performance using energy consumption and utility records similar to the requirements of one of the measurement and verification options contained within the LEED Rating System.

A common misunderstood assumption of building performance analysis is an equivalency comparison to energy consumption.  This is understandable given that the energy component is obviously a primary ingredient of the process.  However, whole building performance modeling analysis involves much more than simply energy simulation but also entails a more comprehensive understanding of supplementary items such as the building envelope, daylighting, views, winds, ventilations, acoustics, occupant egress, and other related components that may be part of a broad sustainable analysis.

However, a primary measured goal of building performance analysis is to use a digital building model to assist, illustrate, inform, and document the whole building thus providing a sustainable facility meeting the project program, goals, vision, regulations, and budget.  An additional hierarchical step includes the addition of an integrated project delivery design process (IPD).

Numerous entities have written copious listings, charts, papers, and blogs of the importance of the use of building performance analysis in the sustainable design process.  However, this article concentrates primarily on a digital BPM approach specifically to energy performance analysis and secondarily discusses some of the rationales in pursuing a performative design approach.  Readers are encouraged to explore the additional writings of sustainable conditions in order to gain a more comprehensive understanding of the linkage between the two concepts.  

PURPOSE

As an introductory orientation to this foundational concept, one of the primarily purposes of building performance analysis is to inform designers and occupants of the facility during the design process.  In other words, the goal is to understand building behavior and effects prior to construction and occupation.  This intention is particularly important as an understanding of building behavior will ultimately influence design energy optimization.

Residually, the overall building behavior will be influenced by numerous climate parameters, including sun, wind, water, and geotechnical factors.  The sun influences shading, orientation, and views of the building.  Wind introduces concepts of protection, shelter, and energy capture.  Water influences the consumption, respite, and distribution systems within a facility.  The earth influences topography and power opportunities for a project.  These components of sun, wind, water, and earth all influence the building design, construction, and occupation process.  In turn, they all affect building proportion, orientation, and function.

IMPROVEMENT

An inherent benefit from understanding building simulation and behavior is the opportunity to substantially improve energy and occupant performance.  This can be in the form of conservation, preservation, consumption, or generation. Conservation allows resources to be made available to other generations, preservation maintains healthy present conditions and resources, and generation explores using alternative energy to generate power via sun, wind, or earth strategies.  All three of these are linked together and are important.

However, in order to adequately understand the criteria involved in building performance analysis, it is also important to comprehend a broader perspective of building performance analysis by recognizing the primary agencies that currently influence the sustainable process and to understand their role in reaching these sustainability goals.  Some of the primary players in the arena are the United States Green Building Council (USGBC), American Institute of Architects (AIA), various governmental agencies, independent building regulators, and several facility standards.  The identification and influential roles of each of these are discussed below.

Current primary regulators in the sustainable building industry are the United States Green Building Council (USGBC), ASHRAE, International Code Council (ICC), and the Illuminating Engineering Society of North America (IESNA).  Each of these institutions have developed either independently or collectively a series of standards to follow, such as the USGBC LEED Rating Systems, DOE Energy Star Program, ASHRAE 90.1 Standards for Buildings, the DOE Comcheck programs, the new USGBC/ASHRAE/IESNA proposed Standard 189P intended for usage at the building code level, International Energy Code, and various congressional legislation.

Governmental agencies occur at the federal, state, and city levels.  At the federal level, the primary players are the Department of Energy (DOE), the Environmental Protection Agency (EPA), the Energy Star initiative, and the GSA.  Most of the states follow the federal directives leaving the implementation to the individual cities.  At the local level, the Mayor Initiative is the primary influencing entity as a large majority of cities have begun or have implemented the U.S. Mayors Climate Protection Agreement, which has received full support from the American Institute of Architects (AIA).

The AIA is primarily an influencing agency with several divisions focusing upon sustainable design such as the 2030 Challenge, the Committee on the Environment (COTE), and the Integrated Practice Committee (IP).   According to the AIA, the goal is listed in the following. “Promote integrated/high performance design including resource conservation resulting in a minimum 50% or greater reduction in the consumption of fossil fuels used to construct and operate new and renovated buildings by the year 2010 and promote further reductions of 10% or more in each of the following 5 years.”

ARCHITECTURE 2030 CHALLENGE

One overriding element within the agencies, congress, corporations, and a large majority of individual citizens is the desire to control our own energy destination.  One such aspect is carbon neutrality as defined in the 2030 challenge covering such questions as the definition of carbon neutrality, how to measure consumption, how to improve the levels, and where is it going.  Basically, the intent is to generate the same amount as consumed- in other words to be neutral or equal.  According to Architecture2030.org, the 2030 Challenge targets are listed below.

• All new buildings, developments and major renovations shall be designed to meet a fossil fuel, GHG-emitting, energy consumption performance standard of 50% of the regional (or country) average for that building type.
• At a minimum, an equal amount of existing building area shall be renovated annually to meet a fossil fuel, GHG-emitting, energy consumption performance standard of 50% of the regional (or country) average for that building type.
• The fossil fuel reduction standard for all new buildings shall be increased to:
  • 60% in 2010
  • 70% in 2015
  • 80% in 2020
  • 90% in 2025
• Carbon-neutral in 2030 (using no fossil fuel GHG emitting energy to operate).
• These targets may be accomplished by implementing innovative sustainable design strategies, generating on-site renewable power and/or purchasing (20% maximum) renewable energy and/or certified renewable energy credits.
• Energy Reduction- 30 percent reduction from present standards goal with the 2030 challenge.

All of these institutions, regulations, standards, and targets are increasingly being connected influencing design, construction, and building performance modeling analysis.

GENERAL DESIGN RECOMMENDATIONS

One of the most obvious starting points for any energy simulation modeling or analysis is to identify the appropriate benchmark to meet.  This is particularly imperative in meeting the 2030 Challenge identified earlier and is analogous to a “knowing where you are going in order to get there” approach to traveling.  However, this simple rudimentary fundamental step is where a large majority of projects simply fail to capitalize on energy optimization opportunities.  Instead the approach in too many projects is one of following previous precedents and simply documenting the results.  This approach is flawed and dysfunctional.

A better way to approach energy efficiency opportunities is to identify energy reduction goals before embarking on the energy optimization journey.  As assistance to the later mindset, the following seven items are general recommendations for an appropriate starting point in the sustainable design energy reduction opportunity process.

ENERGY REDUCTION RECOMMENDATIONS

1. Define the Energy Reduction Target- Use Energy Star EUI Data
   •    Energy Reduction and Energy Use Intensity Targets
   •    Corresponding to 2030 challenge
2. Analyze Proposed Design Building Performance
   •    Conceptual
   •    Refined, Detailed
3. Reduce Building Energy Loads
   •    External. Shading. Orientation. Proportion
   •    Internal Lighting
   •    Process Loads
   •    Load Shifting (off-peak)
4. Increase Thermal Envelope Values
   •    Heat Island Reduction Roofing (Cool Roof. Green Roof)
   •    Thermal Value Increase.
5. Increase System Efficiencies
   •    Fans
   •    Pumps
   •    Drives
   •    Economizers
   •    Chillers
   •    Capacities
6. Harvest Resources
   •    Sunlight. Daylight
   •    Renewable Energy
   •    Solar
   •    Wind
   •    Geothermal
7. Recover Waste Energy
   •    Exhaust Air
   •    Heat Recovery
   •    Cogeneration

Once overall project energy goals are delineated, an effectual plan for approaching project building performance analysis is to identify the design process method into two distinct phases- Conceptual exploration and Detail refinement.  At a cursory level, the exploration phase looks at energy modeling in a conceptual method, concerned more about the overall parameters than the individual spatial details and the refinement phase completes the model with additional design details that more accurately describe the building design.  
Exploration phase efforts seek to optimize building orientation, glazing percentage amount, building proportion, and other similar components.

Refinement phase goals seek to identify the effect of a particular glazing type, sunscreen system, cool roof, occupancy sensors, and variable fan drives.  To phrase another way, the conceptual exploration phase explores overall building massing issues, and the detail refinement phase investigates the effect of the individual elements.  The following sections describe recommendations for both of the building performance modeling design directions.

CONCEPTUAL ENERGY MODELING

Developing the Building Performance Energy Model

It is commonly understood that approximately 75% of the design decisions that impact building performance are made in the early stages of project development.  Therefore, it is recommended to start energy simulation modeling as early as possible during this process.  The building performance model at this juncture can be quite conceptual as it is interested primarily in the overall volumetric thermal massing.  The purpose is to broadly identify energy optimization opportunities.  Simplistic geometry is needed during this phase rather than precisely detailed digital building information models.  

Remember, the primary goal of conceptual energy modeling is to initiate the process in order to inform and influence the design process.  This involves, at a minimum, at least two components in the building performance model- a perimeter zone and a core zone.  An optional third zone can be the demarcation of a secondary inner core to simulate items such as stairs, elevators, fan rooms, and similar support spaces.  However, in the majority of cases this may not be necessary with preliminary conceptual building performance modeling.

Perimeter zone areas can conceptually be viewed as a single offset of the exterior envelope boundary definitions.  Typically, this zone is between 15 ft. to 20 ft. (or 2.5 times the exterior wall vertical fenestration height) from the exterior wall construction.  The core zone will be all of the remaining spatial area.  It is important to note that in the conceptual analysis that these thermal zones are large blocks of massing space rather than precisely defined programmed architectural room definitions.  Think of these as thermal block and stack diagrams.  By utilizing this conceptual methodology, numerous what-if scenarios can be performed quite expeditiously and efficiently.  The results can then be compared to an energy goal for the project such as the Energy Use Intensity (EUI) measures defined by the Energy Star Target finder.

DETAILED ENERGY MODELING

Refining the Building Performance Energy Model

A detailed building performance model can be provided at any time during the design and documentation process.  However, it is recommended to provide the information when the building design is developed to sufficiently define and analysis spatial content.   Common intervals for developing and updating a detailed Building Performance Model are at the end of Schematic Design, Design Development, and 50% + 100% Construction Documentation phases.  A detailed digital energy model defines the building design elements, such as walls, doors, glazing, roofs, envelope, system loading, and other similar items.

After the definition of these elements, ideally through the usage of Building Information Modeling, the Building Performance Model analyzes the energy consumption, patterns, effect, scheduling and influential elements of the design.  This can be used to influence building design decisions and to refine building design elements.  The design process is similar to the conceptual energy modeling approach described above, with greater detailed information utilized to more accurately describe the building design and its associated environmental impact.