Subject: Double low-e glass with inert gas filling

From: Mother Jones <[email-masked]>
Date: 6 May 1996 01:16:25 GMT

We are about to replace a bunch of single pane windows with double pane 
window units. We want noise reduction, and in at least some of the windows 
we want UV filtration because we have fading. These windows are on the south 
side of the house where the sun is quite bright, and that part of the house 
gets quite hot in summer. (However, we live in coastal Southern California, 
so extreme heat and cold are not really a major issue, compared to other 
climates.)

We know that dual-glazing will give us noise reduction, along with 
temperature insulation, and we like that. For the fading and heat problem we 
were planning to get dual-low e glass also, but we've heard that the low-e 
coatings that have been around for a while are now showing that they don't 
actually last. Does anyone have any info about this? Should we go for low-e? 
Why or why not?

We'd also like to know about the argon and other inert gas fillings that are 
often used in dual low-e. How worthwhile is this feature? Is dual low-e 
worthwhile without inert gas filling?

For the windows that are not exposed to direct sun, is there any reason to 
have low-e panes -- with or without inert gas?

Gila Jones     -----     [email-masked]

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From: [email-masked] (Duncan Noble)
Date: Fri, 10 May 1996 16:42:39 -0400

> worthwhile without inert gas filling?

You may want to read some of the information published by the DOE on this
topic at:

http://www.nrel.gov/documents/erec_fact_sheets/erec.html

Keep in mind that the low-e is meant to block heat radiation ("southern"
low-e blocks heat radiation from entering your house; "northern" low-e
blocks heat radiation from leaving your house.)

Argon is the only cost-effective inert gas for most applications (as far
as I know). Argon increases the insulation value of your window, against
heat loss or gain by conduction.

To answer your question properly, you would have to consider how much
energy/$ you spend annually heating and/or cooling your house. If the
amount is small, you  won't be saving much in the way of $, but you may
make your house more comfortable. Dual low-e may be overkill, but single
low-e with with argon fill will only add about 5-8% to the cost of a good
quality window, not counting installation costs.

> have low-e panes -- with or without inert gas?

I'm not sure about that for Southern California. Up here in the north, the
answer would be yes, since the low-e and argon fill block heat loss from
the house, which is more an issue on the north side of the house. 

-- 
Duncan Noble, Noble Consulting
Ottawa, Ontario, Canada

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From: Dermot Lennon <[email-masked]>
Date: 12 May 1996 23:08:32 GMT

Enert gases are usually used to enhance the insulation effect of insulated 
glass units by reducing convection currents between the panes .I do not 
know about their effect on reducing radiation thro the unit.
Superior sound insulation insulation can also be achieved by using a 
laminated glass as one of the panes within the double glazed unit.