US triple pane with uncoated glass?
Griffin728
| Posted in PassivHaus on
I’ve been thinking that for the shaded south side of my Minneapolis home, triple panes with no Low-E coating might be best. I’m looking for a US made window that’s decently insulated with high SHGC. I’ve asked a few manufacturers if they would make me a triple pane with clear glass, but I haven’t found anyone willing to do this. Would I be giving up too much insulating performance (or interior heat reflectivity) with clear glass, and is the a US maker who will do this?
Thanks,
Ryan
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Replies
Ryan,
Glass-only performance for triple pane IGU, 90% argon fill, 1/2" airspace, 3mm glass:
U - .29, SHGC - .70
Glass-only performance for dual pane IGU, Cardinal LoE-180 surface 3, 90% argon fill, 1/2" airspace, 3mm glass:
U - .26, SHGC .69
posted twice, likely operator error.
There are a variety of types of low-E coatings. Many are designed to reduce solar gain, but others are designed for high U value (good insulation), while also allowing high solar heat gain. Meanwhile, increasing the number of panes decreases solar heat gain. So double pane with a high SHGC low-E coating will have very similar SHGC to uncoated triple pane, and a better U value, as Greg's numbers show. And it's probably cheaper. Adding a coating should be cheap compared to adding a pane (unless you get take-out double pane windows and add storms you find in a dumpster.)
It can be a challenge is to find sources of windows with high solar heat gain low-E coatings, but it's more widely available than it used to be. Lots of other threads here list possible manufacturers, but to name three, Marvin, Loewen, and FiberFrame are worth considering.
The reality is that finding a US made triple pane window that has a high SHGC is not going to happen. The US window market is 20 years behind the curve when it comes to passive solar. For some reason Cardinal & US window manufacturers don't want to make triple pane windows with a high SHGC.
Best bet is to try a European triple pane window like Intus. They use Guardian glazing and offer SHGC as high as 0.63 in triple pane glazing.
I just installed Marvin (I wanted made in USA windows, also) triple-pane windows in my house.
The double-hung windows have the following performance:
U Factor = 0.23
Solar Heat Gain (SHGC) = 0.40
If you can use picture windows, Marvin has a triple-pane picture window:
U Factor = 0.19
Solar Heat Gain (SHGC) = 0.45
US made triple pane with high SHGC includes FiberFrame, Alpen, Eagle....but to meet the objectives of the original poster, double pane low-e high SHGC works and is more widely available.
And if you can't find it in the US there are lots of Canadian manufacturers to consider...going to Europe is not necessary.
Thanks everyone for the good information. Maybe I just need to be more realistic with my expectations. I have already spent way too much time trying to find the right window, and it's starting to show. Soo... If there is such thing as a US made casement with a U-value 0.60, I need to know about it!! Wait, I'm going to take it one step futher and say if you are aware of any CASEMENT meeting those specs, I need to know about it. Sorry, the casement part rules out Intus.
To the double pane advocates: A Kolbe VistaLuxe triple pane has a 0.23 U value and 0.47 SHGC when spec'd with a single LoE 180 layer on surface #5. That same exact window in a double pane is rated at 0.30 U-value and 0.52 SHGC with a LoE 180 layer on surface #3. Is it really worth it to give up 30% of the insulation value in order to get 10% more heat gain? If you are aware of any products that beat these numbers, please post specs for me.
Thanks!
Ryan