Greg Smith

Brian Knight wrote:There is some good research out there that suggests slanting the windows on the south side of a passive solar home has little to no measurable benefit. Cant remember where I read it but I think it was from a researcher at NREL.
Generally speaking, all windows will eventually leak water. Slanting them at an angle will emit more water sooner.

It can be tempting to buy used glass for your passive solar project. Be aware that most glass (glazing) currently available is Low E which typically translates to a low Solar Heat Gain Coefficient SHGC. This can have a serious negative impact to the design.

Most passive solar designers try to get a whole window SHGC of .5 or above. The best passive solar glass is Low E and High SHGC. This glass will let the sunlight in and allow the interior space to lose less heat through the reflective properties of the Low E coating.

The best glass currently available is Cardinal's Low E 180. http://www.cardinalcorp.com/products/coated-glass/loe-180-glass/

As you noted, the increase in passive solar gain from angling glass is minimal at best and while the potential for leakage increases when using slanted glass it's not generally well-known that angling dual pane glass also raises the U-value of the unit. The greater the angle from vertical, the more loss of insulating ability.

Cardinal has also recently introduced a new coating called I89 that has the highest SHGC of any coating used anywhere (glass-only SHGC .742 versus .771 for clear glass in a 3mm dual pane configuration) but still has a very respectable U-value as well.

Mike Sved wrote:"Arctic Glass" in Wisconsin used to sell these patio door panels. Their website is kissourglass.com but it seems to have not been tended to since 2011. Good luck.

Unfortunately, Arctic Glass has permanently closed their doors.