Impact of Window Energy Efficiency and How to Make Smart Choices

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Center for Energy and Environment
Innovation Exchange October 3, 2013
Impact of Window Energy
Efficiency webinar
October 3, 2013
11:00 – 12:00
Hover your cursor at the top of your
screen to access the WebEx menu
bar and open your Chat box.
Technical questions: ajursik@mncee.org

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Discovering
the next generation of
energy
SOLUTIONS

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PRESENTATION TITLE HERE
The Impact of Window Energy Efficiency &
How to Make Smart Choices
Targeted Audiences
John Carmody | Center for Sustainable Building Research
University of Minnesota
Kerry Haglund | Haglund Design Inc.
October 3, 2013
• Design and development professionals
• Energy service professionals
• Facility management
• Utility and energy conservation management

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Continuing Education Credits
This webinar meets the GBCI requirements
for self-reporting continuing education credit.
Save an image of the registration page online for your
own personal records.

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1. Describe the Façade Design Tool and the benefits of using
this online tool early in the design process.
2. Compare the performance of a building with a large
window-to-wall ratio with that of a small window-to-wall ratio to see
the benefits of high-performance windows.
3. Identify and compare the impacts of windows with external
shading devices to unshaded high-performance windows.
4. Learn features of the COMFEN user interface and understand its
results of energy, peak demand, and thermal and visual comfort.

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The Impact of Window
Energy Efficiency and
How to Make Smart
Choices
John Carmody
Center for Sustainable Building Research
University of Minnesota
Kerry Haglund,
Haglund Design, Inc.

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Energy Use
Buildings are responsible for 48% of
energy consumption.
(Architecture 2030)
Building operation is responsible for
75% of all power plant-generated
electricity.
(Architecture2030)
53% of the primary end use of
commercial buildings is attributed to
lighting, space heating and space
cooling.
(U.S. DOE, Department of Energy Efficiency and Renewable Energy)
Research estimates that windows are
responsible for 39% of commercial heating
energy use and 28% of commercial cooling
energy use—34% of all commercial space
conditioning energy use. This is equivalent to
1.48 quads of space conditioning energy use—
almost 1.5% of the total U.S. energy
consumption. (Apte and Arasteh, 2006)

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Efficient Windows Collaborative
Residential Tools and Information
• Third edition of book: “Residential
Windows: A Guide to New Technology
and Energy Performance”
• EWC web site: www.efficientwindows.org
(reached 230,000 visitors in 2012)
• Fact sheets for 100 cities
• Education and training materials
• Product database for EWC members
(NFRC and ENERGY STAR participants)

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Measuring Window Energy Performance
U-Factor Visible Transmittance
(VT)
Solar Heat Gain Coefficient
(SHGC)
The rate of heat loss is indicated in
terms of the U-factor (U-value). The
lower the U-factor, the greater a
window’s resistance to heat flow and
the better its insulating properties.
The SHGC is the fraction of incident
solar radiation admitted, both directly
transmitted and absorbed and released
inward. SHGC is expressed as a
number between 0 and 1. The lower a
window’s solar heat gain coefficient,
the less solar heat it transmits.
The visible transmittance (VT) is an
optical property that indicates the
fraction of visible light transmitted.
While VT theoretically varies between 0
and 1, most values are between 0.30 and
0.80. The higher the VT, the more light
is transmitted.

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Commercial Tools & Information
•Book: “Window Systems for High
Performance Buildings”
•Web site: www.commercialwindows.org
featuring the Façade Design Tool
•Education and training materials
•Promotion of COMFEN
•Promotion of CMA
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What Makes an Energy-Efficient Window?
• Warm-edge spacers
• Gas fill
• Low-E coating
Characteristics of Low-E Coatings
Long-wave radiant heat is reflected, giving an improved U-factor and
reduced winter heat loss.
Higher temperatures on the interior glass surface contribute to greater
comfort and less condensation in winter.
Visible transmittance is only slightly affected.
With high-solar-gain coatings, solar heat is transmitted.
With low-solar-gain coatings, solar radiation is reflected back toward
the exterior.
Characteristics of Gas Fills
Thermal resistance is increased with argon and krypton gas fills,
reducing winter heat loss and summer heat gain through conduction.
Higher temperatures in winter on the interior glass surface contribute
to greater comfort and less condensation.
Visible transmittance is not affected.
Characteristics of Thermally Improved Spacers
Overall U-factor is improved because heat loss at the glass edges is
reduced.
Higher temperatures on the glass edges produce less condensation.

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Glazing
Types
Layers
Tints
Low-ECoatings

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Tools to Determine Window Performance
Developed by: Lawrence Berkeley National Lab
CGDB
(Complex
Glazing
Data Base)
calculationon
to
stics)
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to
stics)
on
to
stics)
calculationcalculation
Design /
Simulation Tools
DOE-2, EnergyPlus
Radiance
IGDB
(Specular
Glass Data
Source)
Optics
(Window
Glass)
RESFEN
(Whole Building
Residential)
WINDOW
(Whole Window)
COMFEN
(Whole Building
Commercial)
THERM
(Window
Frame)
Optics
Analyze glazing optical properties
IGDB (International Glazing Database)
Database of glazing materials
CGDB (Complex Glazing Database)
Database of complex glazing materials
THERM
Analyze two-dimensional heat transfer through
building products
WINDOW
Analyze window thermal and optical performance
RESFEN
Calculate the heating and cooling energy use of
windows in residential buildings
COMFEN
Calculate the heating and cooling energy use of
windows in commercial buildings, as well as evaluating
daylighting and thermal comfort

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The Façade Design Tool
The Facade Design Tool lets you
choose the design conditions of a
window and rank and compare
the performance data in terms of
annual energy, peak demand,
carbon, daylight illuminance,
glare, and thermal comfort.

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Façade Design Tool
Location: 21 Cities
Building Type: Office Zone / Classroom
Orientation: North, East, South, West
CHOOSE LOCATION & BUILDING TYPE
Select a location, building type, and
zone orientation from the drop-down
lists below. My city isn't listed»
"Refine & Explore" first lets you
choose the available design
parameters then you can refine and
explore the ranked results. Use this
exploratory method if parametrics are
unknown or to determine the optimal
design from various scenarios.
"Compare 5 Scenarios" lists the
design parameters for 5 scenarios for a
quick comparison. Use this comparison
method if many of the design
parametrics are previously determined.
Location 6A: MN Minneapolis
Building Type Office
Zone Orientation South
1 2REFINE & EXPLORE -OR- COMPARE 5 SCENARIOS
1: REFINE & EXPLORE:
Use this exploratory method if
parametrics are unknown or to
determine the optimal
performance of various scenarios
for a particular orientation.
2: COMPARE SCENARIOS:
Use this comparison method if
many of the design parametrics
(window area, shading, glass type,
lighting controls) are previously
determined.

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*The webinar broke to a web-based demonstration at this time.
The following series of slides cover the information
that was demonstrated.

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Façade Design Tool: Window Area Study

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Façade Design Tool: Window Area Study

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Façade Design Tool: Shading Study

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*The web-based demonstration ended here.

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COMFEN
For use early in design process to
provide design guidance on
commercial building façade and
glazing options.
Graphical and tabular format of
results in a simple user interface for
comparative designs.
Uses EnergyPlus as simulation engine.
Zone modeler with 5 building types
(office, mid-rise residential, hotel,
retail, and classroom).
Outputs information on energy
consumption, peak energy demand,
and thermal and visual comfort
Free download at:
windows.lbl.gov/software/comfen/comfen.html

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COMFEN: Graphical User Interface

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COMFEN: Projects

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COMFEN: Scenarios

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COMFEN: Libraries

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COMFEN: Calculate Scenarios

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COMFEN: Calculate Scenarios

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COMFEN: Compare Scenarios

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COMFEN: Compare Scenarios-Summary

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COMFEN: Compare Scenarios-Energy

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COMFEN: Compare Scenarios-Glare

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COMFEN: Other Features
• Customize scenarios for comparative analysis
• Import and analyze climate data
• Import glazing systems (from WINDOW) or design
systems within COMFEN
• Ability to import project definition from a CSV file
• Export results in CSV format
• Version 5 integrates limited cost information
• Includes dynamic systems (ie: electrochromics)

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Sources and Links
Center for Sustainable Building Research
www.csbr.umn.edu
Center for the Built Environment
www.cbe.berkeley.edu
COMFEN
windows.lbl.gov/software/comfen/comfen.html
Efficient Windows Collaborative (EWC)
Window Selection Tool
www.efficientwindows.org
ENERGY STAR
www.energystar.gov
National Fenestration Rating Council
(NFRC)
www.nfrc.org
RESFEN
windows.lbl.gov/software/resfen/resfen.html
US Department of Energy
Energy Efficiency and Renewable Energy
www.eere.energy.gov
Window Installation
Water Management Guide by Joseph W. Lstiburek
www.eeba.org
Windows and Daylighting
Lawrence Berkeley National Laboratory
windows.lbl.gov
Windows for High Performance Commercial
Buildings
Façade Design Tool
www.commercialwindows.org

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Presenter Contacts:
John Carmody: carmo001@umn.edu
Kerry Haglund: khaglund@umn.edu
Find Webinar Recording and Q&A
Visit: http://www.mncee.org/Innovation-Exchange/Resource-Center/
Webinar Questions:
Megan Hoye mhoye@mncee.org
EfficientWindows
@EWCwindows
PRESENTER RESOURCES

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Contact & Media Information
John Carmody: carmo001@umn.edu
Kerry Haglund: khaglund@umn.edu
www.facebook.com/EfficientWindows
www.linkedin.com/groups/Efficient-Windows-Collaborative-4286505
twitter.com/EWCwindows

Impact of Window Energy Efficiency and How to Make Smart Choices

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