glass technologies to improve sustainable performance bob schrock architectural services ppg...
TRANSCRIPT
Glass technologies to improve sustainable performanceBob Schrock
Architectural ServicesPPG Architectural Coatings Mobile: 513-543-2555
E-Mail: [email protected]
PercentTransmittance
Wavelength (NM)
0
10
20
30
40
50
60
70
80
90
100
300 500 700 900 11001300 1500 1700 1900 2100
UV VISIBLE IR
UV3%
VISIBLE44%
INFRARED53%
SPECTRAL DISTRIBUTION OF SOLAR ENERGY
AT THE SURFACE OF THE EARTH
Short-Wave Solar Energy Spectrum
The Solar Energy Spectrum & Glass Performance Measures
Ideal Glass
Ideal Glass
Allow as much visible light as possible
Keep out Infrared Energy, especially Short Wavelength
How Low-e Coatings Impact Glass Performance
Coated Glass Terms
Visible Light Transmittance (VLT): A measure of how much light passes through a window. VLTs range from 0 (no light) to 1 (all light).
Solar Heat Gain Coefficient (SHGC): The fraction of incident solar radiation admitted through a window, both directly transmitted and absorbed and subsequently 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.
NOTE: Shading Coefficient is a similar measure to SHGC and not used interchangeably. SHGC is 86% of Shading Coefficient. Clarify which measure is being used.
U-Value: A rating given to a window based on how much heat loss it allows. U-values generally range from 0.2 (very little heat loss) to 1.2 (high heat loss).
Visible light, SHGC and U factors are optimized by low e coatings
How Low-e Coatings Impact Glass Performance
Types of Coated Glass
Non Low-e Glass: Tinted glass or reflective coating provide some degree of energy management
Passive Low-e: Mostly pyrolytic, hard coat coatings that have lower performing SHGC and therefore allow free heat in the winter
Solar Control Low-e: Mostly MSVD Magnetron Sputter Vacuum Deposition, soft coats. These are the highest performing low e coatings. They have low SHGC to keep solar energy out, have high visible light to let light in, and reflect heat back into the interior space.
Bill and Melinda Gates FoundationArchitect: NBBJ
How Low-e Coatings Impact Glass Performance
Performance Glazing
Reflective Coating:
Solar reflective coatings
Block direct solar heat transmission
Provides enhanced design aesthetics
Can be used with tints
May reduce visible light
SHGC down to .23 in clear
Reflective properties
Interior
Exterior
PercentTransmittance
Wavelength (NM)
0
10
20
30
40
50
60
70
80
90
100
300 500 700 900 1100 1300 1500 1700 1900 2100
UV VISIBLE IR
Reflective Glass
Ideal Glass
Reflective MSVD
“Reflective Glass
Passive Low-e: Pyrolytic Coatings
Hard coat:. Coating is applied to molten glass and becomes integral with the glass. Very durable, can be uses as monolithic pane
Passive glass: Allows higher levels of solar energy through the glass to take advantage of winter warming. Provides some U factor to reduce heat loss through the glass
Range of performance:
Visible Light Transmittance (VLT) – 54%-74%
Winter Night U-Value – .33-.37
Solar Heat Gain Coefficient (SHGC) – .45-.66
Light to Solar Gain (LSG) – 1.09-1.25
Performance Glazing
PercentTransmittance
Wavelength (NM)
0
10
20
30
40
50
60
70
80
90
100
300 500 700 900 1100 1300 1500 1700 1900 2100
UV VISIBLE IR
Passive Low-E Coatings
Pyrolytic Coatings
“Moderate” Glazing
Ideal Glass
“Passive Solar” Low-E Coatings
Solar Control Low-e: MSVD Coating Process
Also called“soft coat”, must be sealed in an IGU
Superior solar control, SHGC down to .27 in clear
Good U factor performance to reduce heat loss
High visible light with low reflectance is possible
Total thickness of low-e coating – 150 nanometers
Applied in layers. Double and Triple Silver Low e
Performance Glazing
150 nm
zinc stannate
silver
zinc stannate
titaniumzinc oxide
zinc oxide
silver
zinc stannate
titanium dioxide
titaniumzinc oxide
zinc oxide
PercentTransmittance
Wavelength (NM)
0
10
20
30
40
50
60
70
80
90
100
300 500 700 900 1100 1300 1500 1700 1900 2100
UV VISIBLE IR
Double Layer
Solar Control Low e Glazing
Ideal Glass
“Solar Control” Low-E Coatings
Triple layer
U-Values
Improving U-Values
Reduces heat loss through the fenestration
Optimize gas cavity, ½” optimal size for air filled units
Using noble gas. Argon or Krypton improves16% and 27% respectively.
Apply low-e coatings to 2nd as well as 4th surface
Low thermal transmitting spacers, Warm Edge
Triple-glazing
U- Values
Improving U-Values
Triple Glazing
More energy efficient
Thermal insulation benefit
Acoustic performance
Higher cost
Framing considerations, glass thickness, weight etc.
Benefits of Low-e Glass
Benefits of energy efficient glass:
Low infrared heat gain
High visible natural light transmittance.
Less artificial lighting
Reduction of long wave heat gain/loss
Increased comfort/productivity
Results:
Overall reduction in energy usageLow-e, ½” airspace, ¼” clear VLT SHGC U-Value LSG
Pyrolytic 54% – 74%
0.45 – 0.66 0.33 – 0.37 1.09 – 1.25
Double-Silver MSVD(High VLT/Low Reflectance)
53% – 70%
0.28 – 0.39 0.29 – 0.29 1.76 – 1.98
Triple-Silver MSVD(High VLT/Low Reflectance)
61% - 64% 0.27 – 0.30 0.28 – 0.29 2.17 – 2.37
Other methods for Reducing Heat Gain
• Darker glass or tints
• Overhangs
• Exterior Shading Devices
• Interior shading devices
• Ceramic frit
• Tinted laminate
• Dynamic Glass
Many of these options also reduce visible light. Some still need low e coatings
Methods for Reducing Heat Gain
Dynamic Glass technology
Thermochromic materials for use in variable tinting windows can adapt to changing sunlight intensity to reduce heat load in buildings
Electrochromic Switchable technology using voltage to switch between is between a clear and transparent tinted state with no degradation in view,
Photochromic materials change their transparency in response to UV light intensity. Not commercially available
Gasochromic gas is introduced into the cavity Exposure to oxygen returns the window to its original transparent state.
Polymer Dispersed Liquid Crystal thin layer of liquid crystals is between two transparent electrical conductors. Also called Liquid Crystal Device.
Suspended Particle Device electrically controlled film utilizes a thin, liquid-like layer in which numerous microscopic particles are suspended
Methods for Reducing Heat Gain
Darkening glass activated by heat, Thermochromic
As the sun heats the glass the special coating darkens, then as the sun moves away the glass cools and returns to clear
Dynamic Glass
• Minimize SHGC
• Maximize daylighting
• Reduce glare, fading and noise
• Increase safety
• Still requires a low e coating
The middle glass does not have the heat activated coating
Electric current is applied to a special coating to control the level of tinting in stages from clear (60% VLT) down to 1%
It takes less than a 60 watt bulb to control 2,000 sq ft of glass
It can be automatically or manually controlled. Can be controlled in zones or individually.
The coating can perform as low e glass with SHGC around .41 for clear down to .09 for full tint. U factor needs to be considered.
Dynamic Glass
Darkening glass activated by electric current, Electrochromic
• Darkening glass activated by light, photochromic
As light (UV) hits the glass the special coating darkens,
like Transitions lenses in sunglasses
Dynamic Glass
Darkening glass, electric activated Suspended Particle Dispersion SPD
Electrically controlled film
Microscopic particles are suspended in thin, liquid-like layer
In unpowered state the particles are randomly oriented and partially block sunlight transmission and view.
When electric field to be applied to the dispersed particle film, the particles align and raise the transmittance
Polymer Dispersed Liquid Crystal and Liquid Crystal Device are similar technology.
Dynamic Glass
Many innovative solutions to managing energy and daylighting in commercial buildings