Help with low e coating windows WITHOUT green hue

2 years ago

We are shopping for replacement Pella widows with low-e coating 270 on front and 366 on back of house which is very bright. Are these compliant with NC residential code? (can't find anything to clarify). More importantlly, how can I avoid the green hue that my neighbor has? I see they list gray as an option but can't find clear data on VLT and other factors. I found one thing that suggests the VLT goes from 45-50%ish for green to 25-30% VLT for the gray. I've called Pella and Cardinal and cannot get a clear answer from anyone. Has anyone installed the gray lowE or know how they compare. Please help! I don't know why such an expensive project should be so hard to research.

Featured Answer

oberon476

2 years ago

last modified: 2 years ago

I am a little confused reading your question, so I am going to reply as I think it's asked....

LoE-270 a dual silver coating, meaning it tends toward purple although that's hard to see and it really looks more of a neutral gray when installed.

LoE-366 is a triple silver layer coating that has the green hue that you are concerned about. If you are asking if you can get a gray version of 366, then no you can't since all triple silver coatings, no matter the manufacturer, have a slight greenish hue. It's a performance balance between required energy performance and maximum VT.

Otherwise, who is listing a gray option? Do you mean Pella?

There are tinted LowE coatings, but those are generally darker specialty products. There is also tinted glass that is not LowE coated, but can be used either with or without a LowE coating on the clear lite, or in some cases on the tinted lite depending on manufacturer of the coating (no window companies make their own coated glass, they all source it from a coated glass manufacturer).

For comparison, standard gray tinted glass (no coating) has VT of 44% or 28%, depending on the product/ level selected, while bronze is 52% VT and green 73% (recall that triple silver coatings get maximum VT at the performance level they require - green hue). LoE 366 has 66% VT and 270 has 70% VT. Add tinted glass as the second lite in an IG along with LowE and VT plummets rapidly.

What exactly do you mean by "gray LowE" would be my first question back to you.

And finally I gotta ask was "... but can't find clear data on VLT ..." an intentional pun? Whether it was or not, I think it was a good one!

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Comments (6)

PRO
M. ASSOCIATES
2 years ago
from my point view: one option for 1" insulated glass unit : 1/4" clear tempered + 1/4" bronze tempered+ Low E coating. Or 1/4" bronze tempered + 1/4" bronze tempered + Low E for more dk shade.
moneypit321 thanked M. ASSOCIATES
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moneypit321
Original Author
2 years ago
Thank you oberon476 and kevin-door and window. Oberon, pun was unintentional but i'll take credit anyway. So the Pella Impervia has a line item that says vent with tinted glazing and lists

--Gray advanced low-E IG" with a VLT of .29--big drop as you suggested

--Green advanced low-E IG" has a VLT of .45.

Section without tints show:

--Vent advanced low-E IG glazing with VLT of .53 (I believe this is the 270).

--The SunDefense IG (assuming this is the triple coating) shows VLT of .49.

To further complicate things, there is a SunDefense + IG that is VLT of .47 and show it to be energy star compliant.

Bottom line--I want to be compliant with code but limit the green hue. Adding the gray tint to low E coating drops VLT too much. We are on the lake and do get bright sun on one side and had after market tint by vista applied in gray but understand that would not comply with new windows. How can I best meet my goal--would 270 work on the whole house or do I just need to suck it up and accept the green to meet code?
oberon476
2 years ago
last modified: 2 years ago
Are you locked into the idea of using Pella? The Impervia is not highly regarded in general by many professional window folks when compared with fiberglass from other companies. There are other options to consider if you are not 100% set on Pella Impervia.

In NC, unless you are in the far western part of the state, you are needing a low solar heat gain and moderate U factor to meet code. While U factor is easy, trying to meet the lower SHGC is why you are seeing the tinted glass included in the package.

Based on how Pella describes their LowE coatings on the website, Advanced LowE is 270, AdvancedComfort LowE is 270 with i89 on surface 4, Sun Defense is 366, and Natural Sun is 180.

I would have suggested that you look at LoE-452, a relatively newer coating that is great for a cooling dominated climate and while it's darker than 366, it has a neutral gray hue and no green in the mix....however Pella doesn't appear to offer it that I recall.

Do you know what your required SHGC is?
moneypit321
Original Author
2 years ago
The SHGC is 0.30
oberon476
2 years ago
Since the SHGC of 270 is 37%, the immediate reaction would be that it doesn't meet code, but that's not how it works.

SHGC is based on the window performance, not just the glass. Window SHGC includes frame, sash, any bars or grids that cover part of the glass -- they are all part of the equation and their input to the total is zero.

If the percentage of frame/sash/etc. to glass is 20% of the total area, using 270 leaves you with a WINDOW SHGC of 29.6%, so within spec.

It is possible, depending on the window, that 270 could get you below the .30 that you need.