The argument that one spacer system is inherently superior to another or all others  is ripe with the possibility of misinformation, misunderstanding, and certainly a great deal of emotionalism. Each system has its proponents and its detractors. SuperSpacer uses an organic as the primary moisture and gas seal. It uses an acrylic as the primary structural seal. Unlike other systems, SS is "backwards" in that it places the structural seal inside of the moisture seal. The primary structural component of SuperSpacer is silicone - which is neither moisture nor vapor resistant, so the silicone is wrapped with a moisture barrier to prevent air and other gasses from passing thru the silicone. Does this make SS an inferior product? Nope, not in the leastÂactually SS outperforms every other system on the market in energy performance numbers. What EdgeTech (makers of SS) does really well is market their product (for example "Health Smart Windows" is primarily a marketing tool). They have what may be an excellent product, but they also have a marketing program that totally kicks butt! They have opened areas of discussion that really didnÂt exist prior to their introduction of itÂthey have emphasized SSÂs inherent advantages while ignoring any potential disadvantages (which is what marketing folks do, of course). They have "invented" new ways to categorize window spacer systemsÂheck, they have introduced IGU spacers to the general public. For an example of longevity, EdgeTech advertises that their system goes 80+ weeks in a P1 test chamber (a standard for testing dual pane windows). They advertise that the "Stainless Steel" systems go 40+ weeks in the P1 chamber. What they donÂt advertise is exactly how long is the "plus" in the 40+ weeks of the "metallic" systemsÂhow about 80 weeks for a PIB / silicone dual seal stainless steel spacer system. By the way, at 80 weeks or so the glass begins to break down and the seal tends to be lost at that point because of glass rather than spacer issues. The hot melt systems used with the SuperSpacer system also have a very specific application temperature range of about 275º  325º. If the applied material is outside of this range, then the P1 chamber testing can be significantly reduced  to as little as two to three weeks to seal failure. What happens in the field in this case? Only time will tell. Am I slamming SuperSpacer? Nope, not a bit. When manufactured to strict quality control standards and exactly as specified by the manufacturer, then SuperSpacer really is a very good, even superior, product. Energy performance and durability are what these things are ultimately about. How do different systems compare? As I mentioned, SuperSpacer is on top  at the edgeÂand TPS is second, by about ½ of a degree or so. The Stainless Steel systems (there are a couple of different ones) tend to be about a degree or so lower  about equal to Swiggle (again, at the edgeÂthe difference may not have much of an impact on the overall U value depending on the construction of the window). Drop another degree or so to Intercept and about another 8º for an aluminum spacer. Using a LowE coating will have more of an effect on the overall window temperature than does the choice of one of the "warm edge" systems. Of course using a LowE coating with SuperSpacer and with Swiggle still keeps SS a couple of degrees warmer at the edge. BUT, these are also ratings of the "raw" IGUÂwhat happens when the unit is in a frame? Well, how about this for thought: Conclusion The thermal resistance of the spacer bar material influences the glass temperature at the edge-of-glass region of an IG unit. Based on the limited testing performed at IRC and computer modelling at EMPA Switzerland, the spacer bar with the highest thermal resistance shows the warmest glass temperature on the warm side and the coldest temperature on the cold side of the glass at a distance 5 to 60 mm from the edge of the IG unit. But the effect of the type of spacer bar on the overall thermal resistance (and tote heat loss) through windows depends heavily on the window design and material. Therefore, the full impact of thermal characteristics of the spacer bar material on the thermal resistance and the condensation resistance of a window should only be determined by testing complete window assemblies. Interesting concept  testing complete systems.

They both work quite well. Fiberglass is typically chosen out of aesthetic considerations (ability to paint or stain) rather than performance characteristics.

Well engineered windows of any type will do fine in your climate region. I have seen fiberglass, aluminum, or even vinyl. As a matter of fact, my Aunt has vinyl windows in her home (I supplied them) and they are doing fantastic in her application. There is a good resource in the DFW and Houston area that posts on here by the name of Randy (UltraWindows). He might be a good point of contact.

Impervia good window, warranty sucks. to many fine prints. If not mistaken the window is mechanically fasten. Which gives it a not so good air infilteration rating and it has weeping holes. Any window has weeping holes means that water gets in their framing. which means water has to come out those weeping holes. Which means that tempature outside(hot or cold) can blow in your framing and into yor house. Look into a uipvc vinyl window with fiberglass reinforcement,and also are fuse welded on outside and inside(no weeping holes.