Yolonda,

The four coatings that you mention all come from Cardinal Glass. Cardinal supplies the majority of LowE coatings to the residential window companies, but they aren't the only LowE supplier to that market.

Your primary concern is visible light transmittance, and while LoE-180 does have the best highest visible light transmittance of any of the coatings that you mentioned. You also noted that LoE-180 has 80% visible light transmittance - technically it's really 79% for a dual pane with 3mm glass - which is about the most VLT as you will get with any coating (dual pane without any coating is 82%).

LoE-180 has high visible transmittance because it's a HIGH solar heat gain coating - meaning that it lets the sun's heat through your windows and it keeps that heat inside. LoE-180 is a great choice if you live in Minnesota, or Maine, or North Dakota, but it's a very bad idea if you live in Houston, or anywhere where cooling is more important than heating.

LoE-180 has a single layer of silver in the coating stack. The number of layers of silver in the coating stack is directly related to how much direct solar heat is blocked by the coating, so a coating with two silver layers (270 and 272) block more solar heat than 180 and are known as moderate solar heat gain coatings, while coatings with three or more layers of silver in the coating are considered to be low solar heat gain coatings. There are also dark-tinted two layer and three layer LowE coatings that are intended for places with serious solar heat gain. Obviously these coatings have very low visible light transmittance, so not what you want.

Windows will have a VT rating for the entire window, not just the glass. Window VT will be much, lower than glass-only VT because it includes not just the glass, but the sash and frame plus any grills or anything else in the window that blocks visible light.

In Houston you want the lowest Solar Heat Gain Coefficient that you can find, but you also want the highest visible light transmittance that you can find. Unfortunately, physics is not on your side. Higher VT also means higher SHGC just as lower SHGC means lower visible light.

If code allows the higher SHGC, your best compromise among the coatings you mentioned would be LoE²-272. LoE²-272 is a neutral gray color so less noticeable than any of the triple silver layer products. It's pretty much the standard for people in moderate climate zones.

Tough to add anything to that. The master has spoken.

So true MWM. Might be stuff I know or have read previously...but nobody lays it out in as understandable a format as Oberon does.

We do mostly 272 and 366.,

Don't assume your trees will always be there! We have some beetle in our area that is attacking pine trees, very large pine trees. When the beetles take hold, the tree dies pretty quickly, the needles dry up and fall, and in no time there is no shade from those large pine trees.

Buy the right windows for your climate.

Yolanda, I hear you. I am sensitive to the terrible results that sometimes occur in rooms with low e glass. It often changes the color of paint on the walls and other materials in the room like rugs & seating. White walls often end up green and depressing.

I have bronze single-pane glass and wouldn't switch to the low e-glass no matter the savings on AC.

“It often changes the color of paint on the walls and other materials in the room like rugs & seating. White walls often end up green and depressing.”

I agree based on past experience. It can also make white window treatments look green from the exterior.

@chloebud and @BeverlyFLADeziner have either of you felt this way about LoE²-272 that was recommended to me in this thread as being the best compromise among the coatings? I could understand 366 turning things green but the google images show 272 as being somewhat neutral?

Thank you @oberon476 .Can I ask you Oberon, the North windows that never receive any direct sun : could those be clear glass to bring in the most light? Or would you still recommend a loE on them (or maybe code will insist on it, not sure), in which case, would 188 be the "brightest" option for a North wall if loE is required?

I was just going to suggest something similar. Use the higher numbers for south facing windows, and lower for north facing windows. And then turn on the lights. I don’t understand why people live in a box with a roof and expect all the lighting to come from the windows. Just flip the switch when you enter/exit a room. Lights will brighten up any room any time of the day or night.

I don't know your local codes, but I suspect that the emphasis is on keeping solar heat out of your home which would not allow the single silver coating because they are intended to pass solar heat through the glass into the home.

I understand that the north windows are the least concern about solar heat gain, but I don't think that the code would differentiate between what direction the windows are facing or make an exception specifically for north facing windows.

My house has windows which block bright light, direct sunlight. They were here when we bought the house 12 yrs ago. I have no idea what type they are. However, during the day, the outside of the glass looks like mirrors. You cannot see into the house from outside. I've asked people what type of windows they are and all said they block the heat from the sun. I live in Florida. The entire front of the house faces West and the whole back faces East.

I know they block the heat from the sun. The room never gets warm from the hours of direct sunlight. I have never noticed any color change to the greens or colors outside. I have trees, gardens with many colors and they all appear normal to me.

Personally, I have mixed feelings about the windows looking like mirrors when outside. You cannot see through them at all outdoors, but they appear totally clear in the house. At night, you can see through the windows so I know they weren't installed for privacy.

I do have skylights in most rooms except the bedrooms. My house is very bright.

I just don't like the mirrors outside.