Energy consumption can be reduced from room heating using coated architectural glass panes. With a system oxide/metal/oxide high transmittance in the visible as well as high reflectance in the thermal infrared can be achieved2-7. This heat mirrors can be deposited economically by diode- and high rate sputtering. Of most interest are heat mirrors based on Cu, Ag and Au coatings. In the visible Au and Cu show a remarkable amount of absorptance which leads to a clear decrease in visible light transmittance. Best results are obtained with Ag based coatings. Ag is still high reflective even at the near U-V region. This part of re-flected energy can be converted to transmittance by a properly designed optical interference stack of the type oxide/metal/oxide. For a single pane an average value of visible light transmittance between 380 nm and 780 nm of 81 % is possible without loss of infrared reflec-tance at 8 4m below 90 % which corresponds to a low-emittance of 0.1. For this high quality a smooth growth of the Ag layer is necessary. Experiments have shown that a bombardement of the Ag layer with high energetic ions must be avoided as far as possible.