NOVELTY - The cell (20) has insulating spaces, and glass plates arranged on sides of a parallelepiped core provided in contact with O-rings, respectively, where the core comprises core halves molded from polypropylene. A set of elongated compression clips extends between shoulders and one of the plates and between the shoulders and the other plate to compress the plates against the corresponding O-rings, so as to enclose an interior volume filled with water, of the cell. The clips are made of extruded plastic material i.e. PVC, or pultruded composite plastic.    USE - Passive solar heating cell for use in a solar heating panel for an opening i.e. window, in an exterior wall in a building (all claimed) e.g. residential or commercial building, for heating an enclosed space in the building.    ADVANTAGE - The interior volume can be filled with hot water, or with water that is deacrated or degassed, so that formation of air bubbles on inner surfaces of the cell is reduced. The cell is configured such that any air bubbles formed from liquid mixture used to fill the interior volume of the cell rises, encounters inclined top surfaces, and moves along top surfaces towards and through a central gap into a compartment, thus permitting the bubbles to be removed from the interior volume so as to improve the aesthetic appearance of the cell. The cell can be removed from the panel, for replacement or repair regardless of its position, either from inside or outside the building, without necessary to disassemble the panel.    DETAILED DESCRIPTION - The insulating spaces contain insulating gas such as nitrogen, argon, krypton, mixture of argon and krypton. An INDEPENDENT CLAIM is also included for a solar heating panel comprising caulking strips made of rubber or resilient polymeric material, and extension members extruded from polymeric resin material.    DESCRIPTION OF DRAWING(S) - The drawing shows an elevational view of a solar heating panel.    Passive solar heating panel (10)    Solar heating cell (20)    External wall (22)    Molding (24)    Cruciform strips (106)