Replies

1. 
   CramerSilkworth | May 21, 2012 01:10pm | #1

   All the (European) triple glazed windows I've seen recently have SHGCs around 50%. You could find higher with double glazing, but it's more a matter of balancing solar gain with the heat losses. A well designed Passive House doesn't need massive solar exposures (like they used to do back in the 70s for "solar homes"), but they're also super air tight and have high-R enclosures, so the modest SHGC works just fine. What will your walls, roof, and foundation be?

2. GBA Editor
   Martin Holladay | May 22, 2012 05:25am | #2

   David,
   Whenever you specify glazing, you have to make a compromise. Compared to double glazing, triple glazing reduces solar gain. But triple glazing does a better job of retaining heat at night.

   Whichever type of glazing you choose, be sure to order high-SHGC glazing for your south windows. Be careful: not all types of double or triple glazing have a high SHGC. For more information, see these articles:

   All About Glazing Options

   High-Solar-Gain Glazing

   Choosing Triple-Glazed Windows

   To determine the best glazing specifications for your house design and your climate, you'll probably need to use an energy modeling program; one useful program is RESFEN.

3. 
   user-1081368 | May 23, 2012 12:27am | #3

   Thanks for the input. My insulation values are as follows. Basement slab and walls R-24, Framed walls R-36, Roof R-60.
   My proposed window supplier is suggesting the best Solar Heat Gain Coefficient I will get is 0.18 with a U factor of 0.27 from the tripple glaze that they offer. I have read that I should be getting near 0.20 with a SHGC of 0.40. Is this reasonable to expect?
   David

4. GBA Editor
   Martin Holladay | May 23, 2012 03:52am | #4

   David,
   The SHGC offered by your window supplier is ridiculously low. It is suitable for Florida, not Canada.

   Thermotech Fiberglass Fenestration sells operable casement windows with triple glazing with the following specs: 0.63 SHGC (glazing only), 0.44 SHGC (whole-window). More information here:
   http://www.thermotechfiberglass.com/case2.htm

   The same company sells fixed casement windows with triple glazing with the following specs: 0.65 SGHC (glazing only), 0.55 SHGC (whole-window). More information here:
   http://www.thermotechfiberglass.com/fixed3.htm

5. 
   user-1136025 | May 23, 2012 06:06pm | #5

   David,
   You are in southern BC, we are currently building on Vancouver Island and get our triple-glazed windows from Cascadia Windows in Langley. They manufacture fibreglass windows. In 1 3/8" triple-glazed you can get up to a SHGC of 0.56 with a U value of 0.13.
   Manfred

6. 
   [email protected] | May 25, 2012 11:43am | #6

   Manfred,

   Those look like center-of-glass values, not whole window. You might consider asking your supplier what their whole window values are for comparison.

7. 
   user-1136025 | May 25, 2012 09:35pm | #7

   Greg,

   That is right. According to a thermal performance data sheet from the Cascadia website, for their 300 series fixed and tilt& turn windows the thermal performance as per the EN ISO 10077-2 standard in the low-e 180 / clear / low-e 180 configuration, argon-filled, XL Edge spacer is:
   center-of-glass U-factor, fixed: 0.75 (metric) corresponding to 0.13 (imperial)
   total window U-factor, fixed: 0.96 (metric) corresponding to 0.17 (imperial)
   The SHGC also is for center-of-glass but I don't have figures for total window. The decisive factor for us was, we wanted tilt & turn windows in fiberglass and this limited the available selections from the start of course since we also wanted to source as local as reasonably feasible. And Cascadia fits the bill quite nicely.

   Manfred

8. 
   user-1081368 | May 30, 2012 01:51am | #8

   Manfred:
   I have made contact with the Cascadia rep. Thank you for your input.
   Are you able to contact me directly. I am building in Cobble Hill. email: [email protected]
   Thanks again
   David