A Trombe wall is a thick wall that absorbs the sun's energy throughout the day and releases it during the cooler evening hours to maintain a consistent and comfortable temperature within your home. The concept was patented by Edward Morse in 1881 but is named after Félix Trombe, a French engineer who made it popular in the 1960s. Trombe walls are a common feature in passive building design, and represent a form of indirect solar gain when integrated on the south side of a structure in the Northern Hemisphere, or on north side for structures in the Southern Hemisphere.

Trombe walls may be constructed from dark-colored brick, stone, concrete or rammed earth and typically measure between 8 and 16 inches in depth. They feature a layer of glazing that is mounted a few inches from the exterior surface of the wall, encapsulating an air space. Heat transfers through Trombe walls at a rate of around one inch of penetration per hour.

In modern Trombe wall designs, vents are often integrated at the top and bottom of the wall so heat can transfer efficiently via convention to the interior. These vents operate in one direction to prevent heat loss at night, and they can be closed in the summer when heat gain is not desired. Other variations on Trombe walls include the integration of water or fish tanks, which serve as a thermal mass. Electric blowers may also be incorporated in Trombe wall designs to improve air quality and flow. It is possible to install windows for aesthetic purposes or to capture views, but they may decreases the wall's energy efficiency.