6420 Thermal Analysis of Buildings

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6420

 

Thermal

 

Analysis

 

of

 

Buildings

Rules of Thumb Design Model Christoph Reinhart Energy Considerations Christoph Reinhart Analysis

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Course Objectives

This seminar will introduce students to manual and computer‐based calculation methods to evaluate the thermal/energy performance of buildings. The course will also discuss non‐

technical aspects of using whole building energy simulation during building design,p g g gy g g g , retrofitting and operation. The primary simulation tool used will be

DesignBuilder/EnergyPlus. We will also be working on an EnergyPlus plug‐in for Rhino.

Rules of Thumb

Energy Energy

Revised Design DesignDesign Simulation analysis.

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Learning Objectives

‰ Learn how to carry out an energy analysis of an envelope-dominated

building.g

‰ Develop an intuition of when to use energy simulations as opposed

to manual methods to manual methods.

‰ Understand how simulations results can be effectively used during

building design and operation building design and operation.

‰ Learn how to set up a parametric energy modeling script using

Rhi G h d E Pl

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Course Philosophy

‰ An informed decision is a better decision.

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‰ Simulations as a pedagogical means to bring building physics to life.

‰ Current user interfaces for energy simulations are at a point at which

d i / i k i f l d l ? (If th d t d th designers/novices can make meaningful models? (If the user understand the modeling assumptions.)

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Why should I take this course now?

‰ New generation of design tools.

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Mechanics

‰ Meet once a week on Fridays 10.00 to 13.00. There was a request

to move the class up one hour to 9AM to noon.p

‰ First half lectures, second half practical exercises

‰ Prerequisites: 6205 or equivalent

‰ Bring your laptops to class

‰ Bring your laptops to class.

‰ Course open to all GSD students

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Course Overview

Fundamentals

Jan 29 Course Introduction

Feb 5 Manual Methods ‐ Balance Point

Feb 12 Numeric Methods I – Response Functions, HVAC

Feb 19 Numeric Methods II – Radiation Exchange, Surface Convection, Daylight Feb 25 Manual vs. Numeric Methods – Analysis of selected US‐DOE energy

benchmark buildings

Mar 6 Natural Ventilation ‐ Air Flow networks and Manual Methods

Applications

Mar 12 Practical Exercise ‐ Modeling a Small Building; Zoning Mar 26 Professional Practice I – ASHRAE 90.1 and LEED

f l b l h

Apr 2 Professional Practice II – Costs, Liability, Ownership, Commissioning, BIM Apr 9 Good Friday – Individual Group Meetings with Instructor

Apr 16 Building Simulation – Modeler Perspective (Guest Lecture)

A 23 St d t P t ti C St di d P t i E M d li Apr 23 Student Presentations ‐ Case Studies and Parametric Energy Modeling

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Assignments

Feb 5 1. Individual: Work through ‘Tutorial 1: Getting Started with DesignBuilder EnergyPlus’ and submit results for Boston.

Feb 12 2. Individual: Work through ‘Tutorial 2: Load Schedules’

Feb 19 3. Individual: Work through ‘Tutorial 3: Construction Assemblies, Load Reduction & Shading’

Feb 25 4. Group Presentation & Report: Compare manual and numeric methods for one of the DOE Energy Benchmark Buildings

Mar 12 5. Natural Ventilation Exercise

Mar 26 6. Group Presentation: Design a Residential Home I

A 9 7 G P t ti D i R id ti l H II

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Course Projects

Two types of project:

‰ Case Studies on the use of energy models in building design

‰ Case Studies on the use of energy models in building design.

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Last Year’s Project - Model Gund Hall

Collect weather data Build an energy model Survey occupant behavior Collect weather data Build an energy model Survey occupant behavior

Measure Energy Use

Compare predicted versus measured energy use

ARUP prize for the best paper out of 208 submission on the application of building performance simulation in the 

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Results – Electricity & Thermal

y

‰ Electric: Significance of installed electric lighting power densities ‰ Heating Energy: Significance of Infiltration Ratesg gy g

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Results – Cooling

‰ Chilled water meters have been replaced. ‰ Benefit of an energy model for building

Initial Results for 2007/2008 Historic Cooling Data for Gund Hall

‰ Benefit of an energy model for building

operation (continuous commissioning)

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Conclusions from previous Seminar

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‰ Design students are capable of learning to model a large ‰ Design students are capable of learning to model a large

complex building.

‰ Students had confidence in their results for comparative ‰ Students had confidence in their results for comparative

analysis purposes for smaller buildings.

‰ St d t f t l l i PBS d d h l i it ‰ Student comfort levels using PBS dropped when applying it

to complex buildings (handover point to the mechanical engineers).

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G(SD)2 Rhino Toolbar

Radiation Maps

Rhino Model

Daylighting Metrics

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Round of Introductions

‰ Your name/program/year.

‰

‰ Have you any energy simulations in the past? (Which programs?)

‰ Other simulation experience?

‰What are your favorite CAD tools?

‰ Could you do Fridays 9AM to noon?

‰ Could you do Fridays 9AM to noon?

‰ Main interests for this course.

‰ Which type of course project are you spontaneously more drawn to (Case Study or Rhino Modeling)?

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Books and Publications

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Software

WE will be using the following software throughout the course. Please use the setup files form the course web site.

‰ DesignBuilder 2.1

‰ O St di (J 2010) ‰ Open Studio (January 2010) ‰ EnergyPlus 4.0

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Building Performance Simulation

Building Performance Simulation

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What is BPS?

Building performance simulation (BPS) is the attempt to model the

various energy and mass flows within a building in order to predict one various energy and mass flows within a building in order to predict one or several performance aspects of a building using computer

simulations.

Example performance aspects are energy, light, acoustics, LCA, structure, costs, …

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What are BPS used for?

‰ To compare different design variants

‰ To compare different design variants.

‰ To demonstrate code compliance (most difficult)

‰ To demonstrate code compliance (most difficult).

‰ To reduce risk through reduced planning uncertainty

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Who should ‘do’ PBS?

Who should do PBS?

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Architects! (At least some of them.)

Better interfaces. Faster computers.

To interactively improve your design at the schematic design stage.

To be able to engage in a dialogue with the HVAC engineer.

Competitive edge: high demand for simulationists

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Do today’s BPS ‘work’?

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Yes, but:

‰ You have to make sure that the tool that you are using hasy g

been validated for the specific task that you intend to use it for and that

‰ you know how to use it properly ‰ you know how to use it properly.

Energy BESTEST/ ASHRAE 140 Daylight: NRC Daylighting Test Cases

http://gundog lbl gov/dirpubs/rio4 pdf www autodesk com/us/3dsmaxdesign/B3241 MentalRayValidation v3 pdf

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“I have heard that LEED buildings, which receive a rating

that is partly based on BPS, do often not save as much

energy as predicted by the simulation.”

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Energy Performance of LEED Buildings

Measured energy use data from 100 LEED-certified commercial and institutional buildings were compared to the energy use of the general US commercial building stock. On average, LEED buildings used 18–39% less energy per floor area than their conventional counterparts. However, 28–35% of LEED buildings used more energy than their conventional counterparts. Further, the measured energy

performance of LEED buildings had little correlation with certification level of the building or the number of energy credits achieved by the building at design time building, or the number of energy credits achieved by the building at design time.

LEED building uses more energy than the reference building

LEED building uses less energy than the reference building

Newsham et al. Energy and Buildings 2009

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Measured Energy Performance vs. Energy

Credits (BPS)

Credits (BPS)

Newsham et al., Energy and Buildings 2009

‰ Poor correlation (lots of scatter in the data)

‰ Reasons can be attributed to differences ‘as designed’ vs. ‘as built’ vs. ‘as used’ ‰ Reasons can be attributed to differences as designed vs. as built vs. as used ‰ Despite these shortcomings, PBS is useful/required for the design of high

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BPS Requirements

q

Elements needed for BPS are a building model, a simulation program

(GUI & engine) and a suitable metric that is able to measure the

(GUI & engine) and a suitable metric that is able to measure the performance in question.

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Simulation Engine vs. GUI

Most building energy simulation programs come with a graphical user interface (GUI) as well as the actual simulation engine. The

g

( ) g

former is used to prepare simulation input files for the latter and to display simulation results once a simulation is complete.

While the choice of GUI determines the ease of use if a simulation program, it is ultimately the engine that determines how reliable simulation results are

simulation results are.

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Slide 30

MSOffice1 Inset slide:GUI and Simulation EngineExplain the difference (with a graph) and that an engine can have mutiple GUIs. Explain that the hcooice of simulation program should begin with the engine as results cannot be trusted otherwise. The (next slide) motivate our choice for EnergyPlus (what is it, what are its capabilties, accreditation etc. Active developer community with new modules being added contantly such as green roofs and phase change materials. There is also a growing user base.Explain strategy of USDOE to offer the engine for freree and have comercial comapnies devleop GUIS and provide software support. Explain that in he long run a tool will have most credivbility if the osurce code is avaialbe (external quality fcontrol.)now why design builder: commercial tool, currently most matured GUI. Offers flexible geometry input and extensive material librabies and load profiles.

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Simulation ‘Mindset’

‰ Use simulations to ‘create value’ for the design process.

‰ Have the end in mind before you start.

‰ Use a validated simulation tool.

‰ You have to understand the assumptions and limitations of the

underlying simulation models and performance metrics.

‰ Build you model as simple as your intended use allows. If possible

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Significance of building energy simulations?

Buildings consume roughly one-third of all the energy consumed nationally every year. Much of this energy is consumed maintaining the thermal conditions inside the consumed maintaining the thermal conditions inside the building and lighting.

Simulation can and has played a significant role in reducing the energy consumption of buildings

Energy savings should be realized through comparing competing design variants (link to LEED).

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Slide 36

MSOffice7 Inset slide:GUI and Simulation EngineExplain the difference (with a graph) and that an engine can have mutiple GUIs. Explain that the hcooice of simulation program should begin with the engine as results cannot be trusted otherwise. The (next slide) motivate our choice for EnergyPlus (what is it, what are its capabilties, accreditation etc. Active developer community with new modules being added contantly such as green roofs and phase change materials. There is also a growing user base.Explain strategy of USDOE to offer the engine for freree and have comercial comapnies devleop GUIS and provide software support. Explain that in he long run a tool will have most credivbility if the osurce code is avaialbe (external quality fcontrol.)now why design builder: commercial tool, currently most matured GUI. Offers flexible geometry input and extensive material librabies and load profiles.

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Simulation Engine vs. GUI

Simulation Engine vs. GUI

Most building energy simulation programs come with a

graphical user interface (GUI) as well as the actual simulation graphical user interface (GUI) as well as the actual simulation engine. The former is used to prepare simulation input files for the latter and to display simulation results once a

i l ti i l t

simulation is complete.

The developers of simulation engines and GUIs often work for different companies with the engine being developed at public organizations (government lab & universities) whereas GUIs are more often developed by commercial vendors. As a result p y there can be several GUIs for the same simulation engine.

While the choice of GUI determines the ease of use if a While the choice of GUI determines the ease of use if a

simulation program, it is ultimately the engine that determines how reliable simulation results are. A great GUI with a weak engine cannot yield reliable results!

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Slide 37

MSOffice6 Inset slide:GUI and Simulation EngineExplain the difference (with a graph) and that an engine can have mutiple GUIs. Explain that the hcooice of simulation program should begin with the engine as results cannot be trusted otherwise. The (next slide) motivate our choice for EnergyPlus (what is it, what are its capabilties, accreditation etc. Active developer community with new modules being added contantly such as green roofs and phase change materials. There is also a growing user base.Explain strategy of USDOE to offer the engine for freree and have comercial comapnies devleop GUIS and provide software support. Explain that in he long run a tool will have most credivbility if the osurce code is avaialbe (external quality fcontrol.)now why design builder: commercial tool, currently most matured GUI. Offers flexible geometry input and extensive material librabies and load profiles.

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Brief History of Simulation

1st Generation

handbook oriented, piecemeal (disparate simulation techniques) “easy to apply but difficult to interpret”

2nd Generation (mid seventies)

stress on temporal aspects of energy simulation; response functions (analytical solutions)

HVAC d li fi d t t d t t HVAC modeling confined to steady state

3rd Generation (mid eighties)

integration: only space time and climate are independent variables integration: only space, time, and climate are independent variables …

all other system parameters are linked and solved numerically … first GUIs

4th Generation (mid nineties)

4th Generation (mid nineties)

integration continued … data modeling and interoperability… user centered knowledge based GUIs and user-training

Ref. J Clarke

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Where are we now?

‰ Focus on integrated databases.

‰ Focus on modeling occupant behavior.

f f

‰ Use of parametrics and genetic algorithms to identify optimum

solutions.

‰ More quality control in simulations and enhanced workflows.

‰ M ki i l ti ibl t l di d t k t

‰ Making simulations accessible to larger audiences due to market

pressures.

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History of Energy Modeling Tools

‰ BLAST at US-DOD, DOE2 at US-DOE, TRNSYS at University of

Wisconsin and ESP at Strathclyde University

‰ 2001: DOE2 and BLAST merged into EnergyPlus

‰ T d

‰ Today:

- several interfaces for DOE2: eQuest, Green Building Studio - several interfaces for EnergyPlus: DesignBuilder, Open Studio

ESP r has only a very basic interface - ESP-r has only a very basic interface - several interfaces for TRYNSYS

- IDA-ICE is gaining increased recognition in Europe - IES/VE uses proprietary APACHE engine

- IES/VE uses proprietary APACHE engine …

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U d

t

di

Understanding

Thermal Models

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EnergyPlus continued

EnergyPlus continued…

EnergyPlus is freely available for download. The program comes with ample documentations but without a GUI.

EnergyPlus’ capabilities are constantly being further expanded so that more recent modules might not be p g

accessible through any GUI. As a result advanced users often start editing their models manually using a text editor. Once any manual changes have been made to a model one usually any manual changes have been made to a model one usually cannot go back to the GUI.

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Other reasons for using EnergyPlus

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gy

It is a ‘Qualified Computer Software’ for Calculating Energy Savings for Purposes of the Energy-Efficient Commercial Savings for Purposes of the Energy Efficient Commercial

Building Tax Deduction under Internal Revenue Code §179D. Expert users can get access to the source code allowing for Expert users can get access to the source code allowing for third-party validation which adds to the software’s credibility and long term reliability.

EnergyPlus has been validated under the comparative

Standard Method of Test for the Evaluation of Building Energy

A l i C t P BESTEST/ASHARE STD 140

Analysis Computer Programs BESTEST/ASHARE STD 140.

The BESTEST (Building Energy Simulation TEST) is a comparative set of tests which has become one of the industry’s most accepted methods to validate and test the simulation capabilities of the exterior envelope portions of building energy simulation programs. More information at

http://gundog lbl gov/dirpubs/rio4 pdf http://gundog.lbl.gov/dirpubs/rio4.pdf

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We will be suing DesignBuilder as the

GUI for EnergyPlus

GUI for EnergyPlus

‰ Includes extensive default librariesc udes e te s e de au t b a es

‰ Emphasis on architectural concerns such as massing and building

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Why DesignBuilder?

Why DesignBuilder?

We chose DesignBuilder the tool for this tutorial as we found it to be a mature product which offers flexible geometry input and extensive material libraries and load profiles.p

EnergyPlus is integrated within DesignBuilder’s

i t hi h ll t t l t

environment which allows you to carry out complete simulations without leaving the interface.

INFO

When bringing whole-building performance simulation closer to designers it is key to make the process of setting up a model and populating it with technical data as simple as possible the process of setting up a model and populating it with technical data as simple as possible without compromising accuracy or rigor. Reliable data templates of libraries and

components (constructions, materials, schedules, HVAC system, activity profiles, etc) are extremely important in this process as they help designers set up their models in a

comprehensive and transparent way comprehensive and transparent way.

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Why DesignBuilder?

Why DesignBuilder?

Simulation results can be effectively displayed and Simulation results can be effectively displayed and analyzed. simulation data in a comprehensive manner.

DesignBuilder has quality control procedures which assure the accuracy of the results in comparison the assure the accuracy of the results in comparison the stand-alone EnergyPlus engine. e.g. As EnergyPlus, it has been tested under the comparative Standard

Method BESTEST/ASHARE STD 140 Method BESTEST/ASHARE STD 140.

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Software Limitations

Software Limitations

An advanced user might find the EnergyPlus An advanced user might find the EnergyPlus

simulation capabilities that are accessible form the DesignBuilder GUI limiting. In this case a user can export a DesignBuilder model into EnergyPlus ASCII export a DesignBuilder model into EnergyPlus ASCII files. Unfortunately, it is currently not possible to

import a modified model back into DesignBuilder. There are limitation for inputting complex geometry (e g geometries defined through smooth functions / (e.g. geometries defined through smooth functions / free forms)

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DesignBuilder GUI

DesignBuilder model of a small office building

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Installation

- DesignBuilder 2.0X (January 2010) - EnergyPlus 4.0 “6it4qjq9t”

-Open Studio “ch8tRaGu“

k h

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Assignment & Reading #1

‰ By Friday, Feb 5th: Work through the ‘Getting Started with DesignBuilder/EnergyPlus’ tutorial and submit your DesignBuilder file for

Assignment & Reading #1

DesignBuilder/EnergyPlus tutorial and submit your DesignBuilder file for Boston via the course’s Dropbox.

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Questions

Figure

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References

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