thick (e.g.) masonry wall designed to absorb the sun's energy during the day,
store it, and radiate heat evenly during the night or first overcast day in
Essentials | Advantages | Disadvantages | Related Sites
Solid masonry wall works well – storing about 200 calories per kg per degree
centigrade. The more massive the better. Also needs to be thermally conductive
so that the energy stored in one place moves uniformly across the wall for
re-radiation. If either eutectic or para-tetic salts were included in the
Trombe wall, this could add significantly to the stored energy – obtaining
up to 80,000 calories per kg stored as part of the phase change from solid to
Selective Solar Exposure
Collect in winter, reflect or conceal in Summer. Reflect with glaze on glass.
Conceal with eve that blocks summer sun but not winter sun. Location can be
either interior or exterior.
Painted on or natural pigment, to absorb the sun's energy.
Glass lets through the optical energy from the sun. The wall radiates in the
infrared, which does not pass through glass. Hence, the energy is trapped, and
infrared radiant energy is very pleasant to the human body. On an exterior
wall, install double-pane (or even triple in very cold regions). Glass plating
separation depends on the temperature gradients. Generally, in the US 2 cm (¾
inche works well).
Radiates in the infra red, which is more penetrating and pleasant than
traditional convective forced air heating systems.
No moving parts and essentially no maintenance.
Relatively easy to incorporate into building structure as an internal or
external wall. Materials (masonry, concrete) are relatively inexpensive.
Eutectic salt incorporation preferable where available.
Can reduce heating bills by large amounts; in our case,
we have no furnace.
Exterior walls become a heat loss source during extended overcast
days. Not a problem for interior Trombe wall.
a Better Trombe Wall - National Renewable Energy Laboratory
researchers improve passive solar technology. [Another
NREL page, with example links]
efficiency - discussing venting, insulation, btu gain.
"[External] Trombe walls are thermal disasters
during long strings of cloudy days. When the sun goes in for a week or two,
they lose their stored heat in less than a day, and then leak house heat
badly, dramatically raising backup heat or other solar thermal storage
requirements. A lot of people are apparently still willing to settle
for high-cost, low-performance passive solar house heating techniques, that
get them a 30% yearly savings in backup space heating costs over a 20 year
payback period, vs. warmstores, solar closets, sunspaces and transparent
siding, which really can save close to 100% of the space heating energy
needed for a house AND provide close to 100% of the hot water needed for a
house, as well, also, too, over the top, with a payback period of a year or
|Full and Half
Trombe Wall - blueprint
Return to David Allan's Solar Home
Page posted February 2, 2001
Last updated January 18, 2008