Building Energy Modeling

8/2/2019 Building Energy Modeling

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Bui ld ing Energy Model ing

An Overview of Available Softwareand Modeling Strategies

Aleka Pappas

Fall Conference, 21 September 2007

Creating energy and resource efficient buildings

What is a Model?

A model is a pattern, plan, representation,or description designed to show thestructure or workings of an object,system, or concept. Wikipedia

A simplified representation (usuallymathematical) used to explain theworkings of a real-world system orevent. Wictionary

What makes a good model?

What are the desired results; what design questions do you want toanswer?

How expensive/ time consuming can it be to get results?

Good to define these things specifically before you start, then decide thebest way to achieve your goals.


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Physic a l Models

Le Corbusiers UnitedHabitation, Berlin-Tiergaten, 1957-1958,maquette d'tude (studymodel) of wood (solidand sheet), 55 x 122 x90 cm, GeorgesPompidou Center, Paris

How did this model help the design team?

Could there have been a better way?Could a computer model have provided better design assistance?

Did Corbu have lots of cheap intern labor?


Impac t on Arch i tec tu re

Antoine Predocks Spencer Theater for thePerforming Arts, Alto, New Mexico

Does your modelinform yourdesign or designor control it?


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What Answ ers can a Model Provide?

Schematic architectural Building form, orientation, window areas/ shading Who should be modeling for this? How to communicate the

information?Detailed architectural Glare, quality of light Glass & frame specifications Optimize insulation levelsHVAC System type selection in response to building loads Specific design decisions (i.e. equipment efficiencies) Air distribution system designWhole building energy

Annual energy cost Carbon emissions

Others???


Bui ld ing Energy Model ing Tools

Daylighting/ lighting modeling

Computational fluid dynamics(CFD)

Building component analysis

HVAC analysis

Building thermal analysis

Whole building energysimulation programs (BESP)

Packages with combinations ofthe above


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Diffuse surface models

The modeler defines a number of surfaces,

assumed uniform

Good for determining overall illuminance levels and glare ina space

Ray tracing models

Traces rays of light from your eye to the source (sun, lamp)

Realistic renderings

Dayl ight i ng & L ight ing Models

MITs heliodome


Diffuse Surfac e Models

Relatively easymodels to build,fast run times

Tools:

AGI32

Ecotect

DOE2

IESLumen Micro


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Ray Trac ing Models

Much longer computation time Also used for medical imaging, video game

graphics, animation

Tools: Radiance, AGI32

SLS Lighting, H2O Store, Vancouver BCErnst Holzapfel, Residence, Italy


Comput at ional Flu id Dynamic s

Very detailedairflowpatternsimulation


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Bui ld ing Component Analys is

THERM, WINDOW (LBNL)


Whole Bui ld ing

Energy Sim ulat ion Program s (BESPs)

Bin analysis (spreadsheet tool)

Load calculation software (Tranes Trace)

Hourly building energy simulation programs

Simplifies a building into a number of energy flows &systems, and performs a calculation for each hour ofthe year along with weather data

Most detailed building energy analysis


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Most Widely Used Ho urly BESPs

DOE2 Good, free interface for detailed modeling available (eQuest)

Well validated with research

EnergyPlus More advanced modeling capabilities Modular programming structure

Free software (DOE funded)

No interface thats quite there yet

TRANSYS Pretty difficult interface, very detailed modeling options

Ecotect Reasonable 3D modeling interface, imports dxf files

Nice graphical results viewing Export to powerful simulation tools (Radiance, EnergyPlus)

Good for schematic, conceptual design (no real HVAC analysis) Energy10

Good for small, 1-2 zone buildings

Conceptual design tool


Resident ia l Bui ld ing Analys is

Simplifies user inputs with many defaults oftypical residential buildings

Much faster than using a commercial building

BESP

REM/ Design, REM/ Rate

Code compliance: REScheck


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DOE2.2/ eQues t

Quick whole building energysimulation

Capabilities of a very detailedprogram


EnergyPlus

Significant technical advantages over DOE2in simulation capabilities

Easier to add additional modules

Still very difficult and time consuming to usein practice to model a whole building

Interfaces in development

Sketch-up/Energy Plus

Design Builder


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ECOTECT

Shading, solar geometry, lighting & daylighting,natural ventilation, passive solar thermal

Export to Radiance, EnegryPlus

Great for passivedesign analysis

Really cool resultsvisualization

No HVAC analysis


In ter faces and Sof tw are Pack ages

Translate between the user and thesoftware

There are always trade-offs between

accuracy and detail of analysis and user-facility

What is important? Depends on the usersarea of expertise and what results are

required.


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IES

System of integrated building analysistools

CapabilitiesThermal analysis

Daylighting

HVAC

CFD

Solar geometry

Uses ApacheSim for thermal simulation

http://www.iesve.com


Green Bui ld ing St udio

Web-based interface that translates from 3Darchitectural rendering to energy simulationprogram

http://www.greenbuildingstudio.com


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The Future of Energy Model ing

Links to building information models (BIM)

Autodesks Revit MEP with IES

Graphisofts ArchiCAD with Ecotect

Microstation

Will software start to redefine rolls on a designteam?

How will these new tools begin to really

influence the design process?


- Thank You

Documents

Building Energy Modeling