We are planning to use an "inverted roof" for our great room - sloping down from south to north, in Oregon.  Has anyone tried this design in a "true passive solar" house?  We will be using insulated curtains, but I'm not sure if the overhangs will be sufficient in spring and fall.

You'll find all the tools you need to design proper overhangs here: http://builditsolar.com/References/SunChartRS.htm
The sustainable by design calculator is easiest to use, but sketchup, if you have a year or more to play with it, is a phenomenally powerful tool. And free.

I saw a terrific solution for your design problem -- I wish I could tell you where to deliver the appropriate props. The designer divided the window wall into clerestory and main bank windows and installed the overhang between them. The designer then extended the overhang into the room a bit and spec'ed a bright paint on its upper surface. Voila! The main bank of windows is shaded when it should be, but the clerestory windows, bouncing light up onto a cathedral ceiling, provide super daylighting year round. With the right glass in the clerestory windows, you'd get little heat gain.

Thank you for the ideas - I will look at this solution with my designer.

As far as passive solar in Oregon goes - Oregon as a great climate for passive solar design.  Average winter temps rarely go below freezing, and our site has great southern exposure with shade in the west.  Spring and fall tend to be the problems, we can get pretty hot and sunny fall weather, and we'll need to find a way to keep sunlight out on those days, or we will cook!

 

Exterior solar shades or shutters solve the problem with overheating. While overhangs can provide much of the shading there are certain times of the year and day when they don't fully solve the problem. There are lots of good exterior shading systems that can solve the problem and give you better control than can be achieved with overhangs alone.

Tom Pittsley
[email protected]
www.eebt.org

Tom, do you have some links to exterior solar shades? thanks.

IF it is multistory on the south face, can you design it so the lowest windows are inset 2-3 feet  for the proper overhang?
My parents pasive solar house has the second floor cantileivered over the  first story on the south side.  In effect this creates a staggered overhang.  It works well.
Eric

I'm not Tom but...

http://www.coolaroousa.com/view-products.do?category_id=Window%20Shades

http://insolroll.com/products/oasis-exterior-window-shades

...there are others...

We're doing a shed roof (sloping downward from South to North) in Nebraska. Check it out: NE Passive Solar Home