Replies

1. GBA Editor
   Martin Holladay | Jul 22, 2009 01:58pm | #1

   Robert,
   Passive solar heating works best in a location with daily sunshine during the coldest months. Some areas of the U.S. — including parts of Colorado, New Mexico, and Arizona — see a fair amount of winter sunshine, making passive solar heating a reasonable option. Other parts of the U.S. — including Vermont — see very little sunshine during the winter.

   You may be interested in reading about another coastal Oregon house — the so-called Cannon Beach house. The GBA case study is here:
   https://www.greenbuildingadvisor.com/homes/trailblazing-solar-home-made-composite-icfs

   One of the consultants working on the Cannon Beach house, Charlie Stephens, noted that “the solar-thermal system isn’t contributing much when you really need it: during the winter, when there’s hardly any sun on the Oregon coast.”

   That said, many passive solar features amount to common sense — for example, plenty of insulation and south-facing windows. The windows will gather heat during the the fall and spring, even if they don't do much during the winter. Just be sure to include an active heating system.

   Finally, it should be noted that the decision to include PV is not really connected in any way with the decision to adopt passive solar features. Even if the sun rarely shines during the winter, a PV array can still make sense.

2. 
   Annette | Jul 23, 2009 02:28pm | #2

   Robert,
   I can appreciate your wanting to open up the house to the south-side. While researching for a similar type project, I am finding conflicts between 2009 IECC / Energy Star and National Green Building Standards. In our location in NC, the energy code would have U-factor and SHGC at 0.40. This insulates the window, but blocks most of the desired heat in months when the sun in low in the sky. Summer sun does not reach the glazing due to the use of solar overhangs and covered porches.
   Green Build encourages the use of "enhanced fenestration specifications". Our zone should aim for U-factor of 0.25 or 0.3 and SHGC of .5 or .6.
   All the window companies are providing windows to meet the Energy Star programs and tax incentives. NO ONE is making the type of window needed for passive solar design.
   Have you looked into this or resolved this?

3. GBA Editor
   Martin Holladay | Jul 24, 2009 04:11am | #3

   Annette,
   Check out Thermotech Windows, a Canadian company. The Thermotech people understand available glazing options better than American window companies. They will sell you high-SHGC glazing for the south side of your house, if that's what you want.

4. 
   Kori Fox | Oct 05, 2009 11:32am | #4

   You should also check out Serious Windows which are manufactured here in the US. We have recently become the distributor of this product. The 925 series has become the go to for Passive House builders. They have two glass packages one is designed for low solar heat gain and the other for high (used for the south facing elevation. Here are two examples: 1 - 925 casement with "seriousGlass 14" has a u-value of .15 and SHGC of .17 while the "SeriousGlass 9" has a u-value of .17 and SHGC of .33, 2 - 725 series casement with "SeriousGlass 9" has a u-value of .18 and SHGC of .27 while the "SeriousGlass 5" has a u-value of .22 and SHGC of .39. I am happy to answer any questions or forward on more technical data. The air and water infiltration numbers are impressive as well and make this window ideal for coastal applications.

5. GBA Editor
   Martin Holladay | Oct 05, 2009 01:12pm | #5

   Kori,
   I would advise against any of your glazing options for the south elevation of a cold-climate house. The listed SHGC numbers — 0.17, 0.33, 0.27. and 0.39 — are all low. Northern builders need south windows with SHGCs above 0.42. Thermotech sells triple-glazed casements with a U-factor of 0.19 and a SHGC of 0.42. Those who want more solar gain can choose casement windows with a U-factor of 0.29 and a SHGC of 0.47.

6. 
   Robert Riversong | Oct 05, 2009 04:35pm | #6

   Even in cloudy Vermont and elsewhere in New England, with a super-insulated envelope I've been able to achieve 40%-50% solar contribution with modest passive solar design strategies. Anywhere it's not perfectly dark in the winter is an appropriate venue for passive solar design. It costs nearly nothing and can significantly reduce a home's supplemental heat load.

   As several here have stated, the right windows are key. But even U-0.33 SHGC-0.41 double-glazed lowE windows will offer a net heat gain over the winter season if properly oriented and combined with modest direct-gain thermal mass.

7. 
   Steve Dearlove | Oct 06, 2009 05:12pm | #7

   You can also try contacting Inline FIbreglass Windows in Toronto (another Canadian company). Speak to Phil Warnell... he's a wealth of information on glass, U-values and SHGC's. 1-866-566-5656

8. 
   solarcraft | Oct 07, 2009 01:38am | #8

   Robert,
   In addition to Martin's suggesting Thermotech windows, I'd look at AccurateDorwin windows which is another Canadian window company . They can offer the right combo of very low U-value 0.19 and SHCG of 0.49 in a triple pane argon window and insulated fiberglass frame. Not a SHCG of 0.55 or 0.6 but a great window that will perform very well. Be prepared to spend some serious cash for them.

9. 
   Kori Fox | Oct 09, 2009 02:35pm | #9

   There are customizable glass options for specific needs through Serious.