Building Energy

ModelingModeling

Michael Andelman, P.E.

Andelman and Lelek Engineering, Inc.

� Fundamentals of Building Energy Modeling� Objectives� Available tools� Process

� eQUEST Overview

Learning Objectives

� eQUEST Overview

� Energy Modeling and the Design Process

� LEED Energy Modeling and ASHRAE Appendix G

� Strategies to Reduce Energy Use

� Reviewing Modeling Results

� Common Problems and How to Avoid Them

Fundamentals - Objectives

� Whole building design

� LEED EA Credit 1

� Code compliance analysis � Code compliance analysis

� Utility Incentives

� Predict operating costs

� Federal Tax Credits

Whole building design

� Right-sizing of mechanical systems/equipment

� System optimization; comparing alternative

building /system designs� Building geometry/location/orientation

� Walls/roofs/windows construction materials

� HVAC system/equipment

� Control strategies

� Lighting and lighting controls

� Utility selection (electricity, gas, oil, district steam, etc.)

Whole building design (cont’d)

� Life cycle costing of alternatives

� Determine interactivity of proposed alternativesalternatives

LEED EA Credit 1

� Baseline model per ASHRAE App G

� As-designed model per final construction documentsdocuments

� LEED template/ supporting documentation

Code compliance analysis

� MA Energy Code-Building Design by Systems Analysis

�ASHRAE Energy Cost Budget Method�ASHRAE Energy Cost Budget Method

� Pollution generation/reduction analysis

Predict operating costs

� Entire building

� Individual building components or end uses (chillers, pumps, lighting system, etc)

� Seasonal operating costs and patterns� Seasonal operating costs and patterns

� Building load analysis� Hourly/daily/weekly/monthly load profiles

� Seasonal/annual load profiles

� Peak load; design load

� Individual zones/systems or entire building

Fundamentals- Tools

� DOE-2 based tools� eQUEST

� VisualDOE

� Energy-10

� Other

� Energy Plus � Energy Plus � Design Builder

� Google sketch-up interface

� EcoTec

� Other� BLAST

� Carrier HAP

� Trane Trace/System Analyzer

� TRNSYS

� IES

Fundamentals - Process

� Define scope and set priorities

� Gather data

� Create baseline model

�Existing building�Existing building

�New building – code/ ASHRAE App G base

� Calibrate model (for existing buildings)

� Model alternatives

Process - Required Data

� Architectural Plans� Building geometry

� ACAD floor plan drawings

� Walls/ windows

� Elevations/ wall sections

� Operating Schedules� Operating Schedules

� Mechanical Plans� HVAC drawings/ system descriptions

� Equipment schedules and specs

� Controls specs or interview building operator for existing building

� Electrical Plans� Lighting fixture layout and schedules - COMCHECK or conduct

lighting audit of existing facility

� Lighting controls type/ location

eQUEST Overview

� DOE2.2 with GUI

� Hourly building energy simulation

� Heating/ cooling loads calculated using � Heating/ cooling loads calculated using transfer function methodology

� Separate calculations for loads, HVAC systems/ central plant equipment, and economics

� Building envelope� Building location� Building geometry� Walls/roofs/floors construction materials� Windows (glass, frames, exterior or interior shading devices)

Loads

� Windows (glass, frames, exterior or interior shading devices)� Large library of manufacturer’s glass selection

� Infiltration

� Internal loads� Occupants� Plug loads� Lights� Other (manufacturing/process equipment, etc.)

� Schedules (internal loads, infiltration, shading devices, etc)

� HVAC system� Type/size/performance – DX/chilled water, constant

volume/VAV, terminal units, etc.� Control strategies – temperature control, fan control, schedules,

setpoints, OA control, etc.

Systems

� Physical plant� Equipment selection (type, size, performance) – chillers, boilers,

cooling towers, pumps, heat exchangers, district steam/CHW, DHW heaters, etc.

� Process loads – type (steam, hot water, chilled water, other), size, schedule, etc.

� Utility rates/structure� Electricity (demand charges, energy charges,

summer/winter rates, time-of-use energy charges, ratchets, etc.)

� Natural gas

Economics

� Natural gas

� Fuel oil

� Purchased steam

� Purchased chilled water

� Other

� Equipment cost – first cost, maintenance cost, major overhaul cost

eQUEST Wizard

� Up Side

� Import AUTOCAD floor plans to trace building

geometrygeometry

�Screens simplify defining building shell

components, schedules, and HVAC systems

�Create working model in minutes – useful for

early schematic phase

eQUEST Wizard (cont’d)

� Down Side

�Not all eQUEST options available through

Wizard screensWizard screens

�Schedules; lighting and equipment power

densities based on building type –

customizing easier in detailed mode

�Can’t switch from detail mode back to wizard

mode

eQUEST Model Limitations

� Daylight Analysis

� No light shelves

� No internal obstacles

� No daylight through interior windows

� Natural Ventilation

� No interzonal airflow

� Limited to simple systems

� Curtain Walls

� Must fit frame conductance/ width to overall U-value

eQUEST Model Limitations (cont’d)

� No air stratification

� Displacement ventilation modeled through work-

around

� Atriums modeled as multiple zones when required� Atriums modeled as multiple zones when required

� No ventilated double skin walls

� No radiant cooling system (modeled through

work-around)

� One HVAC system per zone

Energy Modeling and the Design

Process� When to Start

� Conceptual / early schematic (throw-away)

� Siting/ building shape analysis

� Early evaluation of HVAC systems alternatives

� Design Development� Design Development

� Evaluation of building shell/ HVAC system alternatives

� First pass estimate of LEED credit points

� Progress/ first final

� Estimate LEED credit points/ evaluate utility incentives

� Updating Model� Update model as design progresses

� Check impact of possible changes with model before implementing changes

LEED MODELING & ASHRAE APP-G� Create as-design model

� Create baseline model� ASHRAE 90.1 Appendix G

� Used for LEED analysis

� Very detailed – many requirements above code� Baseline HVAC system

� Pump power

� Plant equipment type and number� Plant equipment type and number

� Special requirements for central plant/ cogeneration

� Schedules same for baseline & as-designed

� Items to watch� Hours loads unmet� Heated only spaces� Glass overall U-value� Utility rates� Exceptional method calculations

Recommended Strategies

� Architectural� High performance glass (limit % glass)

� Passive Solar – south glass w/ shading devices – limited north glazing

� Mechanical� Mechanical� Energy efficient equipment

� Right sizing equipment

� Airside heat recovery (heat wheel) for VAV systems w/ ~40% OA or more (application specific)

� DOA system w/ chilled beams

� VFDs for fans/ pumps

� Demand ventilation or occupancy based controls

� Cogeneration

Recommended Strategies- cont.

� Electrical

� High performance lighting

� T-5 or ‘Super’ T-8

� LED downlights� LED downlights

� High bay T-5 or MH w/ electronic ballast

� Daylight controls

� Occupancy controls

Review Results

Electric Energy UseComponents

Fans

Equipment

4%

Cooling

Lights

15%

Fans

68%

Pumps & Aux.

10%

Heat Rejection

2%

Cooling

1%

eQUEST Graphic Output

Energy Modeling vs “Common

Sense”

� Lighting energy savings in electrically heated buildings

� VFDs for hot water pumps

� Optimizing windows for cooling and heating � Low SC reduces passive heating

White roofs – minimal impact in this climate� White roofs – minimal impact in this climate� Best suited for mild climates where Code insulation is low (e.g.

R-10 continuous)

� Heat Recovery � high parasitic losses� heating savings for VAV systems can be low if not 100% O.A. at

minimum flow� interaction with demand ventilation controls

� DOA Based Systems� Sensitive to supply air temperature� No airside economizer

Common Problems and how to avoid them� Excessive hours outside throttling range

� Check SS-R reports for problem zones

� Check reheat and or baseboard heat assigned

� Check zone cfm

� Pump/ auxiliary energy too high� Pump/ auxiliary energy too high

� Check PV-A report for pump sizing

� Check PS-C report for pump operating hours / part load operation

� Schedule CHW loop

� Change pump control to speed if pump has VFD

� Excessive winter cooling/ summer heating

� Check if airside economizer is called out

� Check minimum flow ratio for VAV system

� Check space temperature are properly applied

Common Problems and how to avoid them

� Excessive cooling / heating energy use

� Check PS-C for average equipment performance

� Resize equipment

� Change CHW loop/ CW loop controls� Change CHW loop/ CW loop controls

� Change default equipment performance

� Condensing boilers need custom curves� Change boiler aquastat setpoint

Where to Get More Information

� http://doe2.com

� http://gundog.lbl.gov

� http://lists.onebuilding.org/listinfo.cgi/bldg-� http://lists.onebuilding.org/listinfo.cgi/bldg-sim-onebuilding.org

Thank you!

� QUESTIONS?

Michael Andelman, P.E.Andelman and Lelek Engineering, Inc.1408 Providence HighwayNorwood, MA 02062

AndelmanLelek

Norwood, MA 02062(781)769-8773mike@andelmanlelek.com