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Trombe Walls

Whatisit? A 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 the winter.

Page Contents:
Essentials | Advantages | Disadvantages | Related Sites



Thermal Mass
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 liquid.

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.

Dark Color
Painted on or natural pigment, to absorb the sun's energy.

Glass Interface
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 ( inche works well).



Comfortable Heat
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.

Simple Construction
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.



Extended Overcast
Exterior walls become a heat loss source during extended overcast days.  Not a problem for interior Trombe wall.


Related Sites

Building a Better Trombe Wall - National Renewable Energy Laboratory researchers improve passive solar technology. [Another NREL page, with example links]
Trombe wall 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 two."
Full and Half Trombe Wall - blueprint


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Page posted February 2, 2001
Last updated January 18, 2008



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