No significant downfall to Low-e 180 on the other elevations, but no real benefit either.

An overwhelming majority of your passive solar is going to be the South facing elevation.

Thanks for the reply Windowsonwashington. I have followed many of your posts and have found answers to a lot of other questions I've had!

So are the 180 better overall than the low e II? Or is there a situation in which the low e II is better?

Thanks!

Did they explain what the actual difference is?

Low-e ll or 272 glass contains 2 coats of silver oxide on the glass. What the number 72 stands for is the visible transmittance which is basically clarity looking through the glass out of 100. You will typically get a better (lower) u factor with low-e ll or lll but only marginally.

So the 180 glass will have 1 coat of silver oxide and a VT of 80. It will also allow more solar heat gain but you will lose heat from the inside. My personal opinion is that low-e ll is better for areas with four seasons. Also besides keeping out heat the layers of silver oxide protect your floors, furniture, rugs etc from fading and discoloring. If you have furniture by a 180 window its going to take a beating.

That is a fantastic and nicely simplified answer for me. Thanks Window_Mike, very helpful!
(I must say that it's crazy how many different systems and materials, etc. I am trying to 'figure out' while building our home!)

Would you then put low e II on all windows in a four season area? (vs low e 180 on south windows?)

We are debating between saving about 25-30% by using a good quality, lifetime warranty, vinyl window with low e 180 (from a friend who is a supplier) vs going with Marvin Integrity wood-ultrex with low e II?!?!?! Ahhhhhh!!! Any thoughts on this would be very helpful too!

We are trying to find that perfect balance between form, function and cost!

A. You should be seriously considering triple pane in your climate.

B. There are triple pane windows with high SHGC and good U-Factors out there. That is the best combination of the two worlds. High SHGC on the South Facing while not sacrificing the thermal performance.

Combine that with some heavy drapes and insulating shades and you have the right combination.

Integrity does offer Low e 180, 272, and 366. They are not limited to just the low e II (272).

Okay, so the vinyl company we may use sources it's glass from the same company as Pella - is this good or bad!??!

I can get triple pane, or any of the other low e treatments. So, would you (WoW or eastbay or WindowsMike or ?) recommend double pane, low e 180 on south windows and then triple pane on all others? (what is the low e rating on triple pane windows - or do you choose that too?) Or maybe just triple pane on north wall (faces a lake)? Or....???

(We are doing full ICF for exterior walls, if that makes a difference?)

Triple pane on ALL windows seems a bit excessive and pricey??! We also have some really big windows, so I don't know about the weight of them (does that affect efficiency)?

I have been trying to find the U and SHGC numbers for the vinyls that we are looking at...haven't found them yet.

Thanks for your time, patience and help!

Triple pane is not excessive from an energy standpoint. What company "X" tries to charge for it may be a different story.

If you are building and ICF home, the windows are definitely the weak point in the wall assembly and you should be going for triple pane.

You can still go triple pane on the South facing windows as well as long as it is a high SHGC range coating.

Can you give me a range I should look for in U-factor and SHGC numbers? (i.e. good, better, best?)

Thank you!!!

U-Factor (total unit), I would look for sub 0.20.

SHGC (total unit), I would look for above 0.55