I am doing consumer research on replacement windows for my home. We are looking at triple glazing with 2 layers of low E coating and Argon gas. What is the best energy efficient and strongest window frame on the market today? (Wood, PVC or Fiberglass) Which glass manufacturer has the highest R-value and clarity of vision? Which has the most energy efficient spacers? Have the new non-metal spacers had problems maintaining the seals? How long have they been in use?
In my opinion, good, better, best would be PVC, Wood with aluminum exterior, Fiberglass. Considering your options, glass with Low E Squared with Argon will give you a R4.17. Triple glazing will give you more. Look for a minimum 10-year warranty on glass.