Demystifying Energy ModelingWorkshop #2 of 4Performance Analysis & ToolsEarly Design Phase
Learning ObjectivesIdentify a range of building performance models and howthey are used to make sustainable design decisions.Recognize the benefits of using modeling analysis tooptimize sustainable design performance and meet aprojects sustainability goals.Learn how models can be used to win contracts bydemonstrating a firms commitment to performance-based sustainable design.Realize how building performance models can helpproject teams determine the best route for achievingLEED points on a project.
Overview Loads Energy Cost A Simplified Example 100,000 Units of Load x 80% HVAC Efficiency = 125,000 Units of Energy x 20 cents per Unit Energy = $25,000 Energy Cost
Overview Loads Energy Cost What is a Load? Heating Load: The amount of heat energy added to a building by HVAC equipment to maintain indoor design temperature at worst case conditions. Cooling Load: The amount of heat energy removed from a building … ”
OverviewWhat creates a Load?Heating Load Components Cooling Load ComponentsWindow Heat Loss External GainsOpaque Envelope Heat Loss Window SolarInfiltration Window Conduction Opaque Envelope Conduction Exfiltration Dehumidification Internal Gains Lights Equipment People
OverviewDefining Peak Demand vs.Total Consumption Ymax defines Chart area Peak Demand defines Total Consumption 80 70 60Thousands of kBtuh 50 40 30 20 10 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Heating Cooling
OverviewMechanical Engineer Models vs.Sustainability Consultant Models Mechanical Engineer Model Sustainability Consultant Model Calculates two “peak” points in time Calculates peaks and annual consumption 80 80 70 70 60 60 50 50Thousands of kBtuh Thousands of kBtuh 40 40 30 30 20 20 10 10 0 0 Heating Cooling Heating Cooling
Overview Early design focuses on load reduction 1. Reduces the amount of heating/cooling supplied to each space, reducing fan and duct size 2. Reduces plant size of boilers and chillers 3. When combined with optimizing schedules and controls, total consumption is also reduced
Understanding Climate // Weather DataWeather data not pre-installed in softwareavailable at DOEEERE websiteDownload ZIP for FortCollins, Colorado Google: “energyplus weather” Or go to: http://apps1.eere.energy.gov/buildings/energyplus/weatherdata_about.cfm
Understanding Climate // Weather Manager & Weather ToolOpen AutodeskEcotect WeatherManagerWe will learn toload/convert a customweather fileThen open AutodeskWeather Tool
Understanding Climate // Sun Position & Façade DesignChart three times of the dayto visualize solar azimuthand altitude referencedaround a building at thecenter of the sky dome:09:00 Sep 2112:00 Sep 2115:00 Sep 21This defines the averageannual day.
Understanding Climate // Sun Position & Façade DesignAltitude represents the verticalangle the sun makes with thehorizontal ground plane.Azimuth represents the horizontalangle of the sun relative to truenorth.
Understanding Climate // Sun Position & Façade DesignSummaryIdentify non-occupancy hoursand hours with altitudesmasked by site contextIdentify East façade exposure,135 deg Azimuth as a pivotpointIdentify South façade exposure,(-)135 deg Azimuth as a pivotpointIdentify West façade exposure,limited by occupancy hours orsite context
Understanding Climate // Sun Position & Façade Design 80Is Sep 21 the correctdesign day for solar 70studies? 60 Thousands of kBtuh 50Use the Autumnal Equinox 40when a loads model is notavailable 30 20When a loads model isavailable, find transition points 10between cooling and heating 0seasons Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Heating Cooling
Understanding Climate // Comfort (& Discomfort)Factors which determine comfort1. Metabolic rate Activity Level2. Clothing insulation3. Air temperature Low: Seated, relaxed or reclining.4. Radiant temperature5. Air speed Sedentary: Office workers, houses,6. Humidity schools and laboratories. Minor physical tasks. Light activity: People moving; washing, dressing, shopping, light industry. Medium activity: Ironing, brick-laying, other aerobic workouts. Heavy activity: Running, ice skating, shoveling, working with a sledge hammer.
Understanding Climate // Passive StrategiesSummaryPsychrometric analysisprovides the comfort impactof different passive designstrategies for a givenperiod of time, e.g. an entireyearSupplement psychrometricanalysis with additional tools asneeded:1. Vasari climate analysis2. DView3. Climate consultant4. VE-toolkits5. Spreadsheet analysis
Understanding Climate // Wind Speed Conditions Force Name knots km/h m/s mph on Land 0 <1 <2 <1 <1 Calm Smoke rises vertically. 1 1–3 1-5 1–2 1–4 Light air Smoke drifts and leaves rustle. 2 4–6 6 – 11 1–3 5–7 Light breeze Wind felt on face. 3 6 – 10 12 – 19 3–4 8 – 11 Gentle breeze Flags extended, leaves move. 4 11 – 16 20 – 29 5–7 12 – 18 Moderate breeze Dust and small branches move. 5 17 – 21 30 – 39 8 – 10 19 – 24 Fresh breeze Small trees begin to sway. Large branches move, wires whistle, 6 22 – 27 40 – 50 11 – 13 25 – 31 Strong breeze umbrellas are difficult to control. Whole trees in motion, inconvenience 7 28 – 33 51 – 61 14 – 16 32 – 38 Near gale in walking. Difficult to walk against wind. Twigs 8 34 – 40 62 – 74 17 – 20 39 – 46 Gale and small branches blown off trees. Minor structural damage may occur 9 41 – 47 76 – 87 21 – 24 47 – 54 Strong gale (shingles blown off roofs). Trees uprooted, structural damage 10 48 – 55 88 – 102 25 – 28 55 – 63 Storm likely. 11 56 – 63 103 – 118 29 – 32 64 – 73 Violent storm Widespread damage to structures. Severe structural damage to 12 64+ 119+ 33+ 74+ Hurricane buildings, wide spread devastation.
Understanding Climate // WindSummer WindsWind direction is variant,though the primary directionis wind from the northWind velocity is 10 - 20 km/hfor a higher frequency ofhoursThis translates to a gentlebreeze and comparable tothe downward flow of aceiling fan (+/- 2 m/s)
Understanding Climate // Wind Case StudyA long, slender tower to take advantage of wind-driven cross-ventilation.More information: http://btus.lbl.gov/HPCBS/pubs/E4P21T1a3_LBNL-51134.pdf
Understanding Climate // WindWinter WindsWind direction again isvariant, divided fairly equallybetween North, East andSouth directions
Understanding Climate // WindWind EnergyWind velocity increaseswith turbine placementheight, size and isdependent on turbulencefrom site obstructions
Understanding Climate // Wind Summary Summer Wind analysis used to determine the availability of winds for natural ventilation Winter Wind analysis used to determine discomfort areas for building entryways, outdoor spaces and pedestrian pathways Energy Direct relationship between wind availability, velocity and energy potential
Understanding Climate // Temperature and HumidityThe green band designates arange of comfort Requires CoolingSpace conditioning is notneeded when within this range ComfortableA majority of temperaturevalues above or below thegreen band determine a Requires Requires“heating dominated” or “cooling Heating Heatingdominated” climateThis does not account for heatgenerated by internal heatsources
Understanding Climate // Temperature and HumidityDaily conditions shown in thelower right define the “diurnalswing”Swing = Daily High – Daily LowMinimum swing of 10-15 F recommendedfor related passive strategies
Understanding Climate // Temperature and HumidityThe pull-down menu provides aselection for visualizingtemperature, humidity, radiationand cloud cover
Understanding Climate // Temperature and HumiditySummaryTemperature graphs provide asnapshot of seasonal and dailyconditions to inform a strategy forenvelope system selection andclimate dependent mechanicalstrategies such as economizersand resets and other strategiessuch as night-time purgeHumidity graphs provide a checkagainst the suitability of strategieslike natural ventilation andevaporative cooling; a 40%-60%RH range is desirable
Design ProblemYour team is designing a free-standingwelcome center connected to an existinguniversity building with a skywalkThe owner would like guidance on twobuilding placement optionsFrame the analysis using Vasari and noteyour observations
Building Placement Options Option 1 Option 2 45’x45’ Proposed Existing New 30’ 90’x45’ Existing 90’x45’ 30’ 45’x45’ North
Building Placement Options // Modeling Method Model 2nd In “Design Option 01” Model 3rd : 45’x45’ Duplicate “Design Option 01” Save As “Design Option 02” Move Location of Mass 90’x45’ 90’x45’ 45’x45’ Model 1st In “Main Model”
Analysis StepsDesign Problem1. Model existing building and proposed optionsA university library is looking to add awelcome center which wind resources and note2. Analyze site solar and is free-standing butconnected to the existing building with a observationsskywalk.3. Run DOE-2 simulation for each option and note observationsWhere should the welcome center beplaced?4. Discussion about lessons learned, simulation capabilities and limitations
Summer Winter Option 1 Primary opportunity for Propose landscaping to natural ventilation protect plaza space and Exercise through west facade entriesSummary Secondary opportunity Existing building for natural ventilation protects addition, through south/east provide supplemental facade landscaping Option 2
Option 01 9 AM 12 PM 3 PMEvaluating use of theexisting building forshading outdoorground plane areasand building surfacesas desirable Option 02 Autumnal Equinox Tested
Option 01 Optional 01 uses the existing building to shade area between buildings most of the day, providing a comfortable outdoor space in hotter months. The negative impact on passive winter gain would need to be tested. ExerciseSummary Optional 02 less effectively shades the area between buildings, but the positive obstruction of western exposure in hotter months would need to be confirmed. Option 02 Test for other times of the year based on anticipated occupancy schedules
On ScreenRadiation ExerciseNote:1. Switch “primary” designation on each design option to analyze2. Vasari’s radiation calculation is suitable for early comparisons but values are not accurate enough for design calculations; perform those calculations with engineering tools like SunCast
Exercise // Radiation SummaryWestern Season Option 01 Option 02 Reduction (Btu/ft2) (Btu/ft2) (% Difference)Exposure Summer 141 135 4% Vernal/Autumnal 25 25 No Change Winter 18 34 NegativeSouthern Season Option 01 Option 02 Reduction (Btu/ft2) (Btu/ft2) (% Difference)Exposure Summer 96 96 No Change Vernal/Autumnal 32 39 Negative Winter 48 96 NegativeEastern Season Option 01 Option 02 Reduction (Btu/ft2) (Btu/ft2) (% Difference)Exposure Summer 147 147 No Change Vernal/Autumnal 23 23 No Change Winter 39 39 No Change
Exercise // Radiation Summary: What does it all mean?Western Season Reduction Comments (% Difference)Exposure Summer 4% Existing building blocking afternoon summer sun in Option 02. Existing building blocking Vernal/Autumnal No Change early afternoon winter sun in Option 01. Winter Negative Option 02 favorable for cooling reductionsSouthern Season Reduction (% Difference)Exposure Summer No Change Existing building blocking both winter and vernal/autumnal season sun in Option 01. Vernal/Autumnal Negative Summer sun altitude too high to block. Winter Negative Option 01 favorable for heating reductionsEastern Season Reduction (% Difference)Exposure Summer No Change No existing building impact on the East façade. Vernal/Autumnal No Change Both options require architectural Winter No Change intervention to mediate Eastern solar exposure
Exercise // Radiation Summary: What does it all mean? 120 Reducing Monthly Cooling Load Components = Reducing Annual Energy Consumption 250 105 200 90 Walls Plug Load 75 Window Conduction 150 LightingMBtu Mbtu/h Window Solar Boilers 60 Occupants Chillers 45 Light Fixtures 100 Fans and Pumps Misc. Equipment Heat Rejection 30 50 15 0 0 May Feb Nov Jul Mar Aug Sep Oct Jan Apr Jun Dec
Exercise // Radiation Summary: What does it all mean? 120 Reducing Monthly Cooling Load Components = Reducing Peak Demand Charges & HVAC Capacities 12000 105 10000 90 Walls 8000 Demand (kBtu/h) 75 Window ConductionMBtu 60 Window Solar 6000 Occupants 45 Light Fixtures Misc. Equipment 4000 30 2000 15 0 0 May Feb Nov Jul Mar Aug Sep Oct Jan Apr Jun Dec
On ScreenThermal ExerciseNote:1. Change existing building to “phase created-existing”2. Select proposed massing and add “mass floors”3. Click “Enable Energy Model”4. Click “Energy Settings”
Exercise // Energy Parameters and Known LimitationsVasari Parameter Comments/Known LimitationsParameter ValueCommon Packed into a “Building Type” are assumes about schedules and diversity factors forBuilding Type School or University people, lights and equipment. These may or may not match your project A dataset from the weather station nearest toLocation Fort Collins, CO, USA specified site location is selected. The same datasets are used by all simulation program. Allows for identifying basement levels, however does not allow for specification ofGround Plane Level 1 slab and foundation insulation options which is a major factor in low-rise construction
Exercise // Energy Parameters and Known LimitationsVasari Parameter Comments/Known LimitationsParameter ValueDetailed Model An architectural room is different from aExport Category Rooms mechanical zone which can comprise of multiple rooms, or fractions of a single room Including fine levels of geometric details like mullions in a thermal simulation can slow down the creation of solar shading masks withoutExport Complexity Simple with Shading Surfaces adding much value. Extended mullion which are a part of the shading strategy should be modeled explicitly or as shade elements in the next section Vasari does not calculate daylight dimming; this can be approximated in eQUEST once a results file is exported. An ideal workflow is toDaylighting N/A replace eQUEST dimming calculations using a simulation program called Radiance to generate dimming profiles
Exercise // Energy Parameters and Known LimitationsVasari Parameter Comments/Known LimitationsParameter ValueEnergy Model Creates perimeter zones (external gains)Perimeter Offset 15’-0” designating the remainder of floor area as a core zone (internal gains only) Generic, non-specific envelope properties limitConceptual Constructions Library options user ability to match actual design considerations Windows created as a percentage of total wallTarget Percentage Glazing 40% area An option to auto-create window overhangs. Custom shading elements should beGlazing is Shaded Yes/No geometrically constructed within the modeling environment
Exercise // Energy Parameters and Known LimitationsVasari Parameter Comments/Known LimitationsParameter ValueEnergy Model – BuildingServices Some functionality provided for specifyingBuilding Operating Library options occupancy schedules, however these may notSchedules be reflective of the actual building Some functionality provided for specifying HVAC systems, however these may not be reflective of the actual building. Vasari is bestHVAC System Library options used primarily for climate and site studies, and secondarily for load studies. Using Vasari for energy studies is not recommendedOutdoor Air Information Fresh air intake See above
Exercise // Deciphering ResultsComments1. Location assigns a weather file2. Average lighting power is assumed from specified “Building Type”3. People also assumed from “Building Type”4. Electrical cost and fuel cost assumed based on location
Exercise // Deciphering ResultsComments1. Review – EUI refers to “Energy Use Intensity”, which is total annual consumption divided by total building floor area2. kWh x 3.413 = kBtu
Exercise // Deciphering ResultsComments1. Life cycle assumptions in results unknown. A custom calculation would include first cost, operating cost, maintenance cost, discount rate and life span.
Exercise // Deciphering ResultsComments1. PV array size, mounting angle and spacing between modules assumptions unknown.2. Wind turbine placement turbulence, de-rating of efficiency not accounted for.
Exercise // Deciphering ResultsCommentsEnergy use isdependent on detailedmodeling inputs; useenergy results withcaution
Exercise // Deciphering ResultsCommentsLoad results can be appliedto design alternatecomparisons with lesscaution than energy resultsHowever, keep in mind theinput limitations: Light Fixture wattage/count Misc. Equipment wattage/count Occupant count Custom window and opaque construction specifications
Exercise // Deciphering ResultsCommentsWeather datavisualizations areaccurate; the sameweather datasets areused in detailedmodeling
Exercise // Sending Vasari Models to Revit and eQUEST eQUEST Export Vasari Results as DOE2 file (*.inp) Revit Vasari’s native file type is (*.rvt)
Exercise // Sending Vasari Models to eQUESTExported Vasari fileopens in eQUEST
Homework // Early Design Modeling PracticeAutodesk EcotectTraining PackagesRecommended1. Introductory2. Shading Device Design3. Shadows and ReflectionsOptional1. Daylighting2. Solar Radiation3. Visual Impact
Next Workshop:3:00 PM - 6:00 PM, Friday, November 2Bring your laptops with all software installed per technologypreparation instructions.Performance Analysis & Tools II: Schematic Design Phase1. Learn to reinterpret architectural geometry into thermal zones2. Learn to research and compile architectural model inputs assumptions