 Likely, a water wall thinner than 6 inches is also not enough to act as a proper thermal mass that stores the heat during the day.• In the early Trombe wall design, there are vents on the walls to distribute the heat by natural convection (thermocirculation) from the exterior face of the wall, but only during the daytime and early evening.Solar radiation passing through the glass is absorbed by the wall heating its surface to temperature as high as 150 °F.