Triple pane vs. double pane in Phoenix
Im at the point where I have to narrow down my material choices for my new home build. Im in PHX, living in a home built like this : https://www.greenbuildingadvisor.com/blogs/dept/qa-spotlight/why-are-houses-built-way . And its driving me nuts having to pay my electric bill every summer ($500 a month and thats with solar!!). Currently I have spec’d Intus triple pane windows (Vinyl Arcade line, not the higher end Eforte) for their U Factor (high 0.10’s). I’m the opposite of most as I am trying to block the introduction of heat through thermal transfer not the loss of it. Of course I will have as low of a SHGF as possible (Intus is 0.23). Speaking with a well respected window dealer in town, triple pane windows are almost none existent with locally available windows. Looking at Milgard’s exterior fiberglass, interior wood double pane windows, they seem very solid and are quite attractive. U-Factor in the high 0.20’s and a SHGF of 0.21. Pricing favors the top of the line Milgard windows by a couple thousand dollars. My question is, am I placing too much value on the triple pane window for my environment? The effort required to get the Intus window (12-14 week lead time) is a negative. Milgard’s lifetime warranty is also appealing, but Intus has quite the cult following due to their performance and quality.
As for my construction details, I will be full sheathed with particular attention to air sealing (hopefully can find a Fluid applied WRB installer) and will have a conditioned attic space.
As always, any opinions are much appreciated.
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Replies
Jeffrey,
In your geographical location, there really isn't any justification for triple-glazed windows, unless you need to address noise (as might be the case if you live near an airport). What you need are double-glazed windows with a low SHGC.
If you can save a couple of thousand dollars by selecting low-solar-gain double-glazed windows instead of triple-glazed windows, you should. Use the money you saved to install exterior shading devices to protect the windows on your house that get the most sun.
Or use the money you saved to perform blower-door directed air sealing work.
Jeffrey,
Here are links to two articles that you may want to read:
All About Glazing Options
Hot-Climate Design
What he-said- double panes with a heat rejecting soft-coat low-E is the TYPE of window you're looking for.
But the bigger issue is the total amount of window area soaking up that gain, and in particular the total amount of hard-to-shade west facing window area. A lot of west facing glass can double the peak cooling loads, since the solar gain through those windows occurs after the exterior materials of the house have soaked up a lot of heat over the course of the day, and the outdoor temperatures in the afternoon & early evening are much higher than before noon on most days.
I love my Intus windows, but chose them in large part because we have a good local dealer. And as Martin and Dana point out, you porobably don't need triple panes. And as everyone always says, use the money you save for envelope improvement (or shading out the sun.)
Thank you for the answers. I do have minimal west facing glazing, most are under a 10.5 wide covered porch and the rest will be under 2.5' overhangs and individual awnings. I will be planting Afghan Pines (desert pines that can reach 75 feet) to shade the western side of the home. Not to mention the west side of my home has Phoenix style mountains. The south side of the home is all garage with no windows.
Thanks again!
Nice choice with the Afghan Pines. I live in New Mexico and love those things! Such versatile desert shade trees.