Question

I am considering Visions 3000 with Zo-e-shield for vinyl replacement windows, but I can't find evaluations. What do you think?

Asked by Dawn Gardner
Flagstaff, AZ

I live in Flagstaff, Arizona, a cooler mountain climate, and plan to choose windows based on cost, "green" considerations, and the federal tax credit.

Answer

Florian Speier

Answered by Florian Speier

San Francisco, CA

Zeitgeist Sustainable Residential Design

April 27, 2010

A quick look at the specifications of Visions 3000 Zo-e-shield shows the following NFRC values: a U-value of 0.28 and an SHGC of 0.22.

  • Compare that to their regular Low-E2 glass with a U-value of 0.29 but an SHGC of 0.33.
  • The difference in U-value is negligible, but the difference in SHGC is tremendous.

The U-value is the insulation value (it's the inverted figure of the R-value); the SHGC is the percentage (0.33 means 33%) of the energy in a sun ray that is allowed to pass through the glass and heat the interior.

What's best for your home?

Whether you want a low or high SHGC depends on the design of your home. In a well-designed passive solar home you would always want the lowest U-value but highest SHGC possible, unless you live in a climate where you only need to cool and not heat.

To figure out the right answer for your house, think of whether the sun's warmth that comes in lowers your energy bill or makes it higher.

  • Does your house overheat in summer due to sun shining in and you need to run air conditioning a lot? Go for the Zo-e-shield.
  • Are these windows south-facing and you need to heat in winter? You probably do not want the Zo-e-shield.
  • Are both statements true? You need longer overhangs, but no Zo-e-shield.
  • For north-facing windows, you would not want Zo-e-shield either, as it makes the room about 10% darker (comp. Vision 3000 tech specs, visible light transmission, 0.57 for low-e, 0.51 for Zo-e-shield).

Casement vs sliding windows

As for the window frames, the quality of the seal is most important.

Typically, this means that casement windows are more energy efficient than any sliding windows (because the seal has to be loose enough for you to slide the window).

I hope this gives you some guidance in your decision. I could only give you the final answer if I had more details of your house, but you are welcome to contact me and discuss this further.


For more information:

To learn more about energy-efficient replacement windows, read Susan Davis's Ask A Pro Q&A, "Should I choose vinyl or non-vinyl replacement windows?"

Tagged In: energy efficient window

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