Thermally broken aluminum windows increasing?

[Paul Tillson]

It seems to me that the number of makers of thermally broken aluminum windows is increasing. Is this true and if so does anyone know the reason why?

[randy]

Thermally broken aluminum windows hold up better in extremely hot climates. Here in Houston, some vinyl windows begin to sag within 12 months of installation. (crowning, bowing, distorting)

The only trade-off, in terms of efficiency, is in U-Value, and since the SHGC is of primary concern down here, it is a minor concession.

If I lived in Chicago, Minneapolis, Kansas City, or any other city North of the Texas border, I would use vinyl with no concerns whatsoever. This is strictly a regional issue, with localized concerns.

It must also be noted, that some vinyl window issues could be eliminated, or at least minimized, with exceptional installation techniques, which are rarely utilized in Texas. Setting a vinyl window onto a crowned brick sill, will inevitably, lead to a crowned vinyl window sill and air leaks in the corners beneath the sash.

[Paul Tillson]

Now that I have time to think about it I am leaning towards a aluminum window for the added strength. I am not that concerned about heat transfer through the frame. The biggest problem I face is heat gain through true south facing windows with nothing to block the sun.

[randy]

I would only recommend that you make sure the aluminum window has both a thermally broken frame as well as thermally broken sashes. This will keep the heat from transferring through the frame on you.

[Paul Tillson]

It seems to me the most important area will be the glass for bloocking the sun's heat. Can a frame transmit a significant amount of heat?

[randy]

Yes, the glass package is extremely important, but an aluminum window that is not thermally broken will transmit the outdoor heat straight through to the interior.