Low-E glass

Does anyone check the presence of low-e on glass? I have a detector and I check every window for it. I inspected a house a couple of weeks ago in which EVERY window was reversed (low-e on inside) and one window was clear. I noted this in the report but for a second there I thought my detector was broken. I’ve never seen every window incorrect with the low-e. Any comments from those of you who have experience with it?

The only person I know that knows anything about this is Dan Harris… I know of no one in the NACHI ORG that knows anything about this…


Inspect AZ
Dan Harris (480) 756-9064

The low-e coating is reversed depending on if you are in a primarily heating or primarily cooling climate. Perhaps the windows you saw were shipped from the other climate zone than you are located. Up here, they are aways on the inside.

Low E coatings vary depending on the type of window that was purchased.

They are not all on the outside, some are vacuum sealed inside…




This movie clip from Cardinal Glass that I visited in Wisconsin a few years back, might be found interesting also.


Marcel :slight_smile: :slight_smile:

Low E coatings vary depending on the type of window that was purchased.

They are not all on the outside, some are vacuum sealed inside…


Usually no Low E coatings are exposed to the exterior elements or the interior of the building since the coating will be sloughed off by any of a number of actions from washing to rain and wind. By industry convention, each surface of glass is numbered from the outside inward so that everyone will know which surface is being talked about. A double glazed sealed glass pane will be: (1) outside surface of outer glass layer, (2) inside surface of outer glass, (3) outside surface of inner glass, (4) inside surface of inner glass.

In heating climates, the Low E is applied to surface (3) while in cooling climates, it is applied to surface (2). The fact that it may be applied to the wrong layer for the particular climate does not negate all its energy conserving effects but will decrease the efficiency.

thanks for all the replies. I was taught that, at least with this climate anyway, the low-e application should be on the outer pane to reflect the solar energy out and not let it into the home. When the low-e is on the inside pane, it allows the solar energy to pass through. While this is above and beyond the SOP, I want to make sure I understand this if I am going to continue to report this condition as I see it.


Just goes to show there are always going to be many different types, styles, improvements, to any product in the race to attract customers and that once again…one size does not fit all. I believe the old axium, believe nothing you hear and only half of what you see.

A related link from the above site lists the follwing R values for various configuations:


  • Single Pane regular glass
    Clear Insulated Glass 7/8 inch overall thickness
    Hard Coat Low-E insulated glass
    Hard Coat Low-E insulated glass with argon
    Soft Coat Low-E insulated Glass
  • Soft Coat Low-E insulated glass with argon
    These appear to be “center-of-glass” values as they seem a bit high. When you take into account the old aluminum rectangular dessicant filled edge spacer (you have here a glass/metal/glass low R sandwich), the overall window R value usually falls about 1. This spacer sandwich with low R is also why the condensation begins at the edges of the window…it’s much colder there.

There are much better “warm edge” spacers in the market now. Here’s an online booklet written for the general public in Canada that some of my first year archtectural students found “a bit too technical” when I used it as an introduction to windows in the first year Building Science course I taught:


Scott, What instrument do you use for this?


here is a link to a website that you can buy it from. It also gives an explanation on how to use it


Nick the inspector tool guy that gave the moisture meter presenation at your last meeting has them in stock and sells them for about $50 less than any body else that I know of.
In AZ… The coating should be on the inside of exterior panel,
when testing them, verify by testing both sides before writing up if it shows missing or reversed,
The most common place I find reversed low e is SGD panels, missing low e on windows that were broken and replaced during construction.
1- if the gap between the panes is too wide it may not registar as being present on other panel,
2- I’ve seen the coating installed on both panels
3- if the builder or customer installed a refelive coating it will also identify as a coating.
4- most builders do not install low e on french doors, if purchased seperatly from the window package, and now state that in the purchase contract.

Another thing I found interesting. Two windows side by side in direct sun , 1 with low e, 1 with out,there was an apx 15 degree difference when scanned with an infrared camera.

Nick the inspector tool guy

Would that be Nick Amoroso @ http://www.hi-essentials.com/ ?

Great guy, stands behind his products.

You find it, he’ll match or beat it, even special orders in most cases.

If you talk to him tell him I said, HI!

I like the pen-type http://www.mlmenterprisesinc.com/tdg.html

Yea that’s him… I will…
He’s also very knowelgable and supportive of our profession.
I recently bought an electrical tester and a couple telescoping ladders from him, saved $30.00 on the tester and over $100 on the ladders when comparing to other company’s

I like the pen-type http://www.mlmenterprisesinc.com/tdg.html

This one looks like you have to contact the panel with coating, for 2 story homes and windows with screens, I found for a few bucks more the other brands work better for double pane wdos as they identify the other window pane as well.

Scott, what kind of detector do you use and what do they cost?


scroll up and you will see a link that I provided.


That unit you are refering to uses a radio frequency to sense a conductive coating. A non-invasive (pinless) type moisture meter works on the same principle. I have used my moisture meter many times to determine if low-e was present. One less tool to buy. One less tool to carry.

I thought my windows had low-e but when I phoned the Microsoft support line they didn’t know what I was taking about. :|.)

Good one Paul!!


Although the moisture meter will tell the PRESENCE of low-e, will it also tell on which side of the glass it is installed?