A Simple Trombe Wall


This simple scheme from Nick Pine allows a portion of an un-insulated masonry wall to be converted to a Trombe wall.   A Trombe wall is a south facing, high thermal mass, wall that is glazed on the south face.  The north face of the wall faces the living area.  During the day the sun heats the south face of the wall and warms it.  The heat works its way through the wall with some time delay to heat the inside of the space later in the day.  Here is a little more information on the traditional Trombe wall: http://www.nrel.gov/buildings/highperformance/trombe_walls.html

and NREL Trombe Wall Report (pdf)



The Trombe wall section can be seen toward the top of the photo.  It can be painted any dark color.  In this case it matches the building trim.



















Nick and the wall.





















Here is Nick's description:

This one is simple. It's been there 10 years. I painted the uninsulated
plastered masonry wall dark green (the building trim color), attached
a flat 1x3 frame with masonry screws and foam from a can, then added
1 layer of Dynaglas clear corrugated polycarbonate greenhouse glazing
with corrugated foam strips on the vertical edges, then screwed 1x3
cap strips over that and painted them green. (They could use more
paint now.)
There are no holes in the wall, but that's OK, since it's masonry with
no insulation. The glazing has the effect of making that part of the wall
very-well insulated on an average 30 F January day, when 900 Btu/ft^2
of sun (37.5 Btu/ft^2 per hour, averaged over 24 hours) falls on the wall.
The equivalent circuit looks like this:
     37.5     Tw
     ---      |   2.4 
|---|-->|-----*---www--- 70 F
     ---      |
         1    |
30 F ---www---
The glazing is R1, approximately, with 90% solar
transmission. The plastered stone wall is about
R2.4 (0.2 per inch.) With no glazing, the wall 
loses 24h(70-30)1ft^2/R2.4 = 400 Btu/day. The
glazing raises the equivalent wall temp to 
30+37.5xR1 = 67.5,  
         1    |   2.4 
67.5 ---www-------www--- 70 F
so the wall only loses 24h(70-67.5)1ft^2/R3.4 = 17.6 Btu/day,
equivalent to an 24(70-30)/17.6 = R54 wall :-)
It could do more than just keep itself warm if it had real
dark-colored  insulation outside (under the glazing) and
a fan or some ventilation holes that closed at night, but
it's hard to make holes in masonry walls, especially
with Ursinus facilities director Fred Klee watching. We
had already surprised Fred by installing a 1200 pound
solar closet test structure on the flat third floor roof
of the science building, without permission. Fred takes
care of 47 buildings and imagines he runs the place.  

Note how simple this is.  Basically, paint the wall a darker color, and add Polycarbonate glazing sheets over the dark part of the wall.   You could paint the whole wall dark, and then the Trombe section would hardly be visible.  The Polycarbonate glazing is about a $1 per square foot.


If you have a wall that is not massive (like metal siding) and not insulated, and you want a similar simple scheme, then take a look at the "Low Tech Garage/Barn Heater" that is part way down this page.