Solar wall heater

[Eric D. Hart]

At 02:20 PM 5/8/97 -0700, Will Firstbrook  WCB of BC wrote:

>The idea is to use the sun to heat the exterior of the southern exposed
>cob walls. This could be accomplished by imbedding some glass on the
>southern exterior side of the structure and leaving a small air pocket
>between the glass and the cob. The cob would be painted/stained/dyed
>black for maximum heat absorption. This should transfer quite a bit of
>heat into the cob depending on how big this glass is and how much sun is
>available. If little sun is available the glass and air pocket provides
>a little insulation for the cob. In the summer if it gets very hot,
>shutters could be installed to minimize heat absorption; Or an overhang
>could be designed to allow winter sun to heat the window yet shade the
>window from the sun in the summer.
>
>A variation of this could be to build  a solar oven into a south wall
>near the kitchen with interior access.
>
>Does this seem feasible, or even worthwhile? I know this is essentially
>the passive solar way of heating the interior through the windows to
>heat an interior thermal mass wall. But at certain locations it may be
>desirable to not have a window to the interior.
   From what I understand of passive solar design, the idea is to let
sunlight into the house and heat mass *inside* the house, such as floors or
an interior wall, instead of an outside wall.  In theory anyway, the heat
spreads throughout the floor and radiates after the sun goes down.  Unless
you had a very narrow house with direct access to the south facing wall you
describe above, I doubt the south wall alone would be able to radiate enough
heat reach all corners of the house.  Besides I imagine you would like to
have a nice view out those south windows and some sunshine in your house.
You can calculate what sort of overhang you need to get optimal summer
shading and winter sunlight.  
        Methods like you describe above were used in the 1970's on the first
solar homes and some of them are spectacular failures.  One I looked at in
Minneapolis has the entire south face of this two storey home in glass with
*no* buffer between the glass and living space.  Needless to say, they had
to shade the glass during the summer and even then, it was routinely above
90 degrees F in the house.  I don't have the references of good solar design
books handy, but there are several and this sort of design has become almost
mainstream.  

Eric D. Hart			
Community Eco-design Network	
PO Box 6241  
Minneapolis, MN  55406-6241   USA		
(612) 306-2326 
erichart at mtn.org			
http://www.tc.umn.edu/nlhome/m037/kurtdand/cen