residential window energy use residential heating energy use of windows is about 2 quads / year...
TRANSCRIPT
Residential Window Energy Use
• Residential Heating Energy Use of Windows is about 2 Quads / year
• Total energy consumption in US is about 100 Quads / year
• All Energy Star windows, still 1 Quad
• Goal: Zero Energy Windows
Performance Goals
Heating Climates: - static high solar, hi-R (U=0.1 Btu/h-ft2-F) can meet ZEH goals
- dynamic solar gain (.6<SHGC<.15) and U<.2 also meet ZEH goals
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Minneapolis, MN - Com bined Annual Heating and Cooling Energy (MBtu)
w indow s use energy
w indows provide energy
Com
bine
d A
nnua
l Hea
ting
and
Coo
ling
Ene
rgy
(MB
tu)
doub le clear
low ga in low -e A r double ,h igh ga in low -e A r double
sing le clear
low ga in low -e A r trip le
target perform ance reg ion
typ ica l Energy S tar
m oderate ga in low -e K r trip le (acrylic center layer)
Heat Transfer in Windows
Conduction
Radiation
Conduction
Convection
Low-e coatings
Special gas fillsMultiple cavities
Low conductance spacersBetter frames
Background
• Vacuum windows, aerogels high-risk strategies
• Current technologies for highly insulating products use multiple layers of low-e and gas fill – All glass is heavy– Thin film products expensive – Multiple spacers can lead to gas leakage– Market share is low (<1%)
• This research aims to develop lower-cost, non-structural center layers– Utilize available low-e and gas-fill
technologies– Research novel center layer designs and
materials
2 sealed gas gaps at different temperatures and pressures
with standard glass, unit is thicker and heavier
low-e
thin glass or plastic held by spacer
spacer
low-e
only 2 paths for gas loss
Prototypes
• Utilize available low-e and gas-fill technologies• Research novel center layer designs and
materials• Develop interests from industry partners who
would supply new components
Bent edge insert prototype
Alternative Designs
Acrylic in GrooveSpec 6
Angled AcrylicSpec 7
Two Layer TeflonSpec 8
One Layer TeflonSpec 13, 16
Alternative Designs
Acrylic Insert on standoffsSpec 10, 17
Partial TripleSpec 11
Screen InsertSpec 9,15
Results
Simple insert performs as well as fixed layer
Angular Selective Center Layers
High Angle summer sun blocked
Low Angle winter sun admitted
Conclusions to Date
• Possible to get very close to “net zero energy windows”– Climate based– No single, ideal, cost-
effective window
• Performance potentials of various insert materials studied
• High-performance frames still necessary
Picture of a zh