FW: Solar wall heater

[John Schinnerer]

>Aloha,
>
>----------
>From: 	Will Firstbrook  WCB of BC[SMTP:wfirstbr at msmail.wcb.bc.ca]
>I was just thinking about low cost ways of heating a cob building and
>this idea came to mind. I would be interested in comments as I am not
>even sure if it is a problem in the first place.
>
>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.
>
>--------------
>
>Certainly seems feasible...one thing to consider is condensation within the
>space between the glass and cob.  Some ventilation or drain holes might be a
>start, but if there's not consistent airflow your cob will get damp and stay
>that way, which might not be good thing...you might find that you get enough
>warming of your mass without the need for this, but if not...
>
>...this could be a lot like what's called a Trombe wall (the "inventor's"
>name, I think - a passive solar heating technique) if you vent the bottom and
>top.  This can be used on any kind of structure, but if there is no thermal
>mass then a mass wall needs to be built as part of a "retrofit"...or if warm
>air is adequate, enough, no need for the thermal mass.  anyhow, cool air is
>drawn in the bottom and rises as it is warmed by solar gain, then flows into
>the house at the top of the collector - some heat comes in with the air and
>the rest still warms the wall.  Make the vents closable, and have some way to
>shade the collector when it's too sunny.  Run pipes through the upper part to
>heat water...set it up to divert the airflow for a solar food dryer...have
>the bottom fold out with extra panels to be a solar cooker...go crazy, man!
>:-)
>
>Best wishes,
>John Schinnerer
>