RE: [GBlist] Low E glass

["Ralph Bicknese" <ralph.bicknese@christnerinc.com>]

Alan:

Low e coatings are selective coatings.  That means one can choose coatings
with different properties.  Having various low e properties to choose from
gives a designer the option of specifying different glass for different
climates or at different orientations.  The "northern" and "southern"
designations are really just marketing buzzwords and I think confuse rather
than clarify the issue. The main difference between "northern" and
"southern" coatings is that the southern coating provides more shading and
less solar penetration through the glass.

Southwall Technologies offers glass with selective low e coatings with
various shading coefficients.  If a person wants a window with high solar
heat gain potential and high light transmittance to increase daylighting,
one would select a highly insulating glass with a low shading coefficient.
This will give a high solar heat gain factor. This type of window is often
used in passive solar heating applications.

So for house in a cold climate one may want a window with a low shading
coefficient on south, east, west and north facing glass.  For a hot southern
climate one would want to use a selective coating with a high shading
coefficient particularly on the east west and south orientations and might
want to choose a glass with a low shading coefficient on the north
orientation. Other considerations may take precedence for a building in a
swing climate or for buildings with high internal gains.  The ability to
utilize external shading devices may also influence glazing selection.

There are two ways to achieve various shading coefficients.  One is to use a
basically clear low e coating with different properties.  With this a window
with a high shading coefficient and a low one will look basically the same.
Another way to vary shading coefficient is to use tints on glass or colored
glass.

For more information about the products Southwall offers and a more detailed
explanation about how low e works see:
http://www.southwall.com/products/hm.html.  Click on "Heat Mirror explained"
and "Products".

Cheers,
Ralph Bicknese





-----Original Message-----
From: Alan Courtright [mailto:acourtri@linknet.kitsap.lib.wa.us]
Sent: Wednesday, January 02, 2002 11:24 AM
To: Ralph Bicknese
Cc: Richard Averett; greenbuilding@crest.org
Subject: RE: [GBlist] Low E glass

On Wed, 2 Jan 2002, Ralph Bicknese wrote:

> In most cases low e glass will permit a net gain in solar heating for the
> winter.  I have low e glass on my south windows and on a sunny winter day
> the heat gain is considerable even when it is only 10 or 20 degrees F
> outside.

On this list not too long ago there was mention of the existence of two
kinds of low-e glass: northern and southern.  What can anyone tell me
about the differences and where they'd be best applied?

                         -|//*Alan Courtright*\\|=
                                Poulsbo, WA
                             acourtri@krl.org



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