Google Answers Logo
View Question
Q: Self-tinting windows? ( Answered 5 out of 5 stars,   0 Comments )
Subject: Self-tinting windows?
Category: Family and Home > Home
Asked by: nak-ga
List Price: $5.00
Posted: 30 Jun 2002 11:30 PDT
Expires: 30 Jul 2002 11:30 PDT
Question ID: 35202
I'm looking for windows that can tint themselves, either in sunlight
or under operator control.  The product I have in mind would use
something like a liquid crystal (not an LCD, exactly, since the whole
pane would be one 'pixel') or that film they put on eyeglasses to make
them dark in the sun.

My question(s):
- does such a thing exist?  What's the proper name for it?
- where can I buy windows like this (or the precursors to contruct
them myself)?
- how much do they cost (US or Canadian suppliers preferred)?
Subject: Re: Self-tinting windows?
Answered By: huntsman-ga on 30 Jun 2002 22:05 PDT
Rated:5 out of 5 stars

I have been wanting to look into this technology myself, and your
question has given me a good reason to do so.

There are several types of high-technology "smart windows" (or
"switchable glass") that promise many home benefits, including:

- Automatic dimming of bright sunlight
- Better indoor temperature control throughout the year
- Reduced heating and cooling costs
- Reduced fading of carpets, furniture, and artwork
- Reduced dependence on artificial lighting
- Additional privacy with brighter interiors

In a fully computerized "smart home", I imagine that smart windows
could also be controlled according to the time of day, season, outdoor
temperature, or even the number of occupants.

Smart glass comes in several varieties which can be loosely divided
into two categories:

- Electrochromic [EC] glass
- Non-Electrochromic [non-EC] glass 

"Electro" refers of course to electricity, and "chromic" refers to a
reversible change. With "Electrochromic" glass, its opacity is
controlled by a low-voltage electrical current.

One example of residential EC technology is "SageGlass", a
glass-coating process being developed by Sage Electrochromics, Inc. in
Faribault, Minnesota. Several layers of transparent, electrically
conductive films are sprayed onto sheets of glass which are then baked
at high temperature. The resulting EC glass can be cut and assembled
into standard double-insulated residential windows. To avoid scratches
or abrasions from cleaning, the EC films are placed on the internal
surfaces of the window.

Although they may not be considered true EC glass, "Liquid Crystal"
[LC] and "Suspended Particle Device" [SPD] windows also use
electricity to adjust glass opacity. A layer of liquid crystals or
particles is suspended in clear plastic between panes of glass, and
controlled by electrical current. SPD windows become clear when
electrified and (partially or fully) opaque when turned off, and may
also be known as "PDLC" (Polymer Dispersed Liquid Crystal) windows.

SPD glass technology is being developed by Research Frontiers, Inc. in
Woodbury, New York. The ABC News SCi Tech "Sun Too Bright?" article
noted below features their product.

Other types of Non-EC glass technologies include "Photochromic" glass
coatings, which react passively to the amount of incoming ultraviolet
in sunlight. As sunlight gets brighter, these UV-sensitive coatings
get darker, but there is no way to manually adjust their opacity.

While photochromic coatings are widely used on "PhotoGray" and
"Transitions" eyeglasses, they are not scratch-proof or long-lasting
enough for use on residential windows. While they could make your
house cooler in summer, they would also reduce the amount of desirable
sunlight entering your house in winter.

The last general type of smart glass is "Thermochromic", which reacts
to the amount of infrared radiation striking the glass. Its primary
purpose is to reduce the amount of heat entering your home.

Due to the high technologies involved, smart windows are (or will be)
several times more expensive than standard windows. One hopeful
estimate for SPD windows suggests they might be four to five times
more than regular glass. Due to their complicated and more delicate
nature, smart glass will cost more to make, ship, and install. With
electrically-controlled windows, you (or preferably a qualified
electrician) will also have to wire in a power source for each one.

Another problem is the additional time, labor, and money involved in
replacing or repairing one of these windows. The seals could fail, the
electronics could go bad, or the glass could be accidentally broken. A
home-run from the neighborhood baseball game loses some of its
innocent charm when batted through a multi-thousand-dollar window.

They may require unique installation methods and specially-trained
installers. Acceptance of these new windows by local Building
departments may also be a problem. It is usually difficult to
introduce new technologies in residential construction because no one
really knows how well they will hold up over time.

More traditional window treatments -- reflective and tinted plastic
films, window blinds, insulated window shades, awnings, etc. -- have
been proven over many decades of use and will probably remain the most
practical all-around window solutions for many years. They are more
readily available, cheaper, and easier for homeowners to install and

However, it is pioneers like yourself that help bring these new home
technologies into wider use. For more detailed information, please
browse through the links and sources listed below.

You may want to contact the manufacturers for brochures and any dealer
information. I would also ask them if there are any installations in
your area that you can see.

Thank you,

References - 
For a quick introduction:

Get Smart Windows
High-Tech Innovations For Windows Mean Energy Savings

This ABC article features the SPD window system from Research
Frontiers. BTW, after reading this history of "liquid crystals", you
may never look at your LCD watch (or laptop screen) in the same way

ABC News SCi Tech
Sun Too Bright? Just Dim The Windows

Easy explanations, interactive illustrations, and related links:

Marshall Brain's How Stuff Works
Question of the Day [Photochromic eyeglasses]

Marshall Brain's How Stuff Works
How Smart Windows Will Work

The details, pros, and cons of photochromic eyeglasses:

Eyewear Concepts
Lens Tints
Photochromic Lenses
- Note link near top of page

Smart windows information from government offices and labs:

California Energy Commission
Windows of the Future

Lawrence Berkeley National Laboratory
Windows & Daylighting

NASA Tech Briefs
Photoelectrochromic "Smart" Windows and Displays

Berkeley Lab Research News

Manufacturers and developers of smart glass:

"Night Vision Safety" Auto Mirrors
Gentex Corporation
600 North Centennial St.
Zeeland, MI 49464
Tel: 616-772-1800
Fax: 616-772-7348

SAGE Electrochromics, Inc.
2150 Airport Drive
Faribault, Minnesota 55021
Tel: 507-333-0078
Fax: 507-333-0145

SPD Windows
Research Frontiers, Inc.
240 Crossways Park Drive
Woodbury, New York 11797-2033
Tel: 1-888-773-7337, 516-364-1902 
Fax: 516-364-3798 

ThermoView, Inc. 
5611 Fern Valley Road 
Louisville, KY 40228 
Tel: 502-968-2020 
Fax: 502-968-7798 

For information about other smart window manufacturers in the United
States, contact this national association:

Window & Door Manufacturers Association
1400 East Touhy Avenue, Suite 470
Des Plaines, IL 60018
Tel: 800-223-2301
Fax: 847-299-1286

Search Terms & Google Results - 

smart windows

"smart windows" manufacturer

photogrey windows

photochromic windows

"liquid crystal" windows
nak-ga rated this answer:5 out of 5 stars
A thorough, thoughtful answer [ eBay equivalent: AAAAA+++++++ SMOOTH

Many thanks.

There are no comments at this time.

Important Disclaimer: Answers and comments provided on Google Answers are general information, and are not intended to substitute for informed professional medical, psychiatric, psychological, tax, legal, investment, accounting, or other professional advice. Google does not endorse, and expressly disclaims liability for any product, manufacturer, distributor, service or service provider mentioned or any opinion expressed in answers or comments. Please read carefully the Google Answers Terms of Service.

If you feel that you have found inappropriate content, please let us know by emailing us at with the question ID listed above. Thank you.
Search Google Answers for
Google Answers  

Google Home - Answers FAQ - Terms of Service - Privacy Policy