The glass cables ARE made from silica sand which is a safe and abundant natural resource.  Ultrex has all the characteristics that are crucial in Arizona’s extreme climate.  It’s as strong as steel, rigid, essentially no thermal expansion, heat resistant, non-corrosive, and capped with a patented exterior coating that is resistant



Ultrex is thin strands of strong glass cables, saturated with resins, and is pulled through a heated die. 

to fading and requires little to no maintenance.  The finished frame is free from volatile organic compounds (VOC’s).  Plastics use petroleum and other harmful chemicals in the manufacturing process. 

maintenance would be incredibly tedious because of our extreme heat. 


Window frame materials should be thought of in the same way.  Until recently, builders installed double paned aluminum framed windows as the standard.  To some extent, metal was the best material for Arizona because the heat did not break down the metal frames.  Unfortunately, metal frames allow the transfer of thermal energy and is a thermal conductor.  Let’s simplify this, aluminum framed windows help heat transfer in your home! 

Because heat reflects off concrete and pavers, the heat transfer can be much higher than the temperature outside.  It is common to see exterior temperatures of aluminum frames above 160° and interior temperatures of 150°.  Your air conditioner has to work overtime to compensate for this. 

Builders now install vinyl framed windows in new construction because they are the cheapest product available.  Unfortunately, the heat deflection point is far too low for a long lasting well-functioning window frame.  Andersen’s Fibrex® is not much better.  Infinity from Marvin’s Ultrex material can take much more heat.  View the chart below that compares the three products.


Residential building materials aren’t universally successful throughout the United States when extreme climates are considered.  In the Phoenix market, it is rare to see a vinyl, wood or synthetic wood sided home.  A vinyl or wood sided home will certainly not age as well as stucco or block and the

When considering the three most common window replacement frame options in the Phoenix market, vinyl, Fibrex® (Andersen’s composite), and fiberglass, Infinity from Marvin’s Ultrex fiberglass frame has quite an advantage.  It is a thermoset which means it becomes permanently hard and rigid when heated or cured and that process is irreversible.  Vinyl, which is 100% PVC plastic, and Fibrex® are thermoplastics.   Thermoplastics


have the property of softening when heated.  The softening will make the frame weak with constant glass pressure weight.  Ultrex is 8x stronger than vinyl and 3.5x stronger than Fibrex®.


The other tendency with thermoplastics is thermal expansion.  Thermal expansion is the continual expansion and

contraction with the frame as fluctuations in temperature take place.   This will create warping, sagging, cracking, and air leakage.  Infinity from Marvin’s Ultrex is as stable as the glass it supports. 


© 2019 by SI Phoenix, LLC.

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Si Phoenix, LLC

4014 E Broadway Rd,

Suite 408

Phoenix, AZ 85040