Insulated vs. non-insulated glass
Does insulated glass have a lower heat gain than non-insulated?
I just built a commercial building with all insulated low-e glass. The doofus that installed the glass used 1/4″ single pane glass on the door only. When the afternoon sun hits, it just bakes in there and it is 20-30 degrees outside. I’m going to have him change the glass to insulated but I was wondering if this will help with the greenhouse effect.
John
J.R. Lazaro Builders, Inc.
Indianapolis, In.
Replies
Insulated glass will tend to reflect more sunlight than single-layer glass, due to having twice as many reflective surfaces.
Keep in mind that because door glass must be somehow shatter-safe, insulated door glass is pretty expensive.
Thanks for the info. I just wanted to make sure that I was on the right train of thought. To me the extra cost will be offset by comfort and efficiency.John
J.R. Lazaro Builders, Inc.
Indianapolis, In.
John,
Insulated glazing (double glazing) can be ordered with a low solar heat gain coefficient (SHGC) or a high SHGC. The SHGC of double glazing is always lower than that of single glazing, but ranges from low (say, 0.30) to high (say, 0.60).
In your example, you want to specify double glazing with a low SHGC.
Isn't low vs. high SHGC relative to clear vs. Low-E glass?John
J.R. Lazaro Builders, Inc.
Indianapolis, In.
John,
The SHGC of any glass can be measured, whether or not it is low-e.
The SHGC is simply a way to describe the percentage of solar heat striking the glass that makes its way to the other side.
There are several types of Low-E coatings.The Efficient Windows Consortium has more information:http://www.efficientwindows.org/lowe.cfm
Jon Blakemore RappahannockINC.com Fredericksburg, VA
SHGC is not relative to clear single glass. It is relative to no glass. It is similar to the shading coeficient (SC) which did compare to single glass. SHGC doesn't do that.
Tinting alters the SHGC as does the type of low-e coating. If you have other windows on that same side of the building, you MAY not want to e.g. do tinted and/or reflective glass on the door only. But you can get a low SHGC w/ low-e ... just ask for their lowest SHGC value.
For a door it is tempered glass. If a relatively standard door size, the cost should be no big deal ... as they make insulated glass for that application in the millions ... even low-e. You can get SHGC as low as 0.10 for some combinations of tint/reflectivity and/or low-e.
You are right ... it will be well worth it. Good job!