Abstract: A solar heat collector built about a new collector matrix formed from flexible sheet material, such as metallic foil. The matrix presented by the foil is folded into an accordion shape to form a series of linear channels to trap solar energy. The absorbed energy is transferred to air flowing through the channels. Proper support for the expended collector matrix is provided by taut lines stretched across a supporting frame and engaged with the folded flexible sheet. Inner and outer circulation channels are provided to permit air circulation by natural heating currents. The folded sheet and lines are constructed in kit form for expansion and support at the location of use. Transverse spacers might be included between pleats.