What our research found: Pyrolitic or Hard-Coat Low-E coating are designed to reduce heat loss and to increase solar gain. This is great for areas needing a lot of winter warming and not a lot of summer heat. The SHGC is normally higher for this type. We were told that this is the older Low-E coating. Sputtered or Soft-Coat Low-E are designed to reduce heat loss and let in some solar heat, not as much as pyrolitic. This is OK for areas where there are both heating needs and cooling needs. Still good for cold winter area and mild summer area. This is Low-E II. Spectrally Selective Sputtered coating Low-E are designed to reduce heat loss in winter and also reduce heat gain in summer. THis is for area where we have cold winter and real hot summer. Another version of Low-E II. In Texas, I would definitely go with Low-E II, it is a no brainer. We live in CA where it gets downright cold, blasting rain and some snow and then searing hot summer. Low-E would have been insufficient so we have Low-E II. The difference in temperature, depending on insulation in the house wall, can be dramatic. We often are a cool 70-F inside while it is 105-F outside.

There are basically five types of LowE coatings currently on the market. Three are "sputter" or softcoats and two are "pyrolytic" or hardcoats. Of the three softcoat products, basic LowE would be considered a high solar heat gain product. LowE2 would be considered a low solar heat gain product, and LowE3 would be considered an even lower solar heat gain product. Andersen's LoE4 has a standard LowE2 coating between the lites and argon gas for energy performance, but it also includes a titanium dioxide coating on the exterior of the window that makes the glass "self-cleaning". Although some folks might cringe at the term self-cleaning, the coating does work quite nicely and you will notice a difference in how they look and in how often you will have to clean the glass. Finally, the "4th" feature of the LoE4 is a plastic film that is applied to the glass in the factory that protects it from dirt and debris and even minor scratches during shipping and handling and install. Andersen's SunII glass is a tinted LowE2 that has very nice solar heat gain blocking ability and also it is nice because it cuts down on glare as well. Milgard's SunCoat is a standard LowE2 product - much the same as the LowE2 that Andersen offers as their standard. SunCoatMax is a LowE3 product. The LowE3 product is very new and has only been around for maybe 3 or 4 months - this doesn't mean avoid it because it is new - it means that it is an advancement of a proven technology and it works really well. LowE3 has the same heat blocking ability as a tinted LowE2 (such as SunII), but with visible light transmittance very similar to a standard LowE2 product - without tint. In the case of a west-facing door that has both heat and glare issues, then you may prefer a tinted LowE but with the understanding that the view thru the door will be less. SunII has either 38% or 40% visible light transmittance (I forget which version they use) and SunCoatMax has 66% visible light transmittance - again with very comparable solar heat blocking capability. Standard LowE2 (including SunCoat) has about a 70-72% visible light transmittance. Standard LowE has about a 78% visible light transmittance, but it also passes significant solar heat which is an advantage in places other than where you live. I didn't mention anything about hardcoat coatings because none of the products you mentioned use them. Also, they are much less appropriate in your environment (primarily cooling) than are sputter coats. No LowE coating has an affect on sound propagation thru the glass.

Mike, Climaguard 55/27 is Guardian's low SHGC offering. The numbers relate to the VT and SHGC - 55% visible transmittance and 27% Solar Heat Gain Coefficient. It is a softcoat LowE2 product - which generically means that it has two layers of silver - with performance standards something of a mix between triple silver and double silver products. For example, comparing to Cardinal's LoE2-240 low solar heat gain coating and also to Cardinal's LoE2-270 and Viracon's E1-55 which are dual silver moderate solar heat gain products: Climaguard 55/27 - VT = 55, SHGC = 27, U (cog) = .29 Cardinal 240 - VT = 40, SHGC = 25, U (cog) = .30 Cardinal 270 - VT = 70, SHGC = 37, U (cog) = .30 Viracon E1-55 - VT = 49, SHGC = 36, U (cog) = .31 Technically, LowE and LowE2 are not the same thing, but the term LowE is often used generically to refer to any low emissivity product. A bit more precise would be to consider LowE as either a pyrolytic (hard) coat or single silver soft coat product - or typically high solar heat gain coatings - whereas LowE2 (versus LoE2, or correctly LoE squared, which is specific to Cardinal's coating terminology) refers to dual silver soft coats which can be either low or moderate solar heat gain (as noted earlier), and LowE3 refers to triple silver layer low solar gain coatings. I would suspect his reluctance to discuss technical details may be more his lack of product knowledge than any attempt to "hide" anything from you - IMO.

I would opt for the higher VLT if in your area. Michael