31. Such superwindows also have soft-coat low-emissivity coatings on all the glass surfaces. 32. The emissivity depends on the wavelength, \ varepsilon = \ varepsilon ( \ lambda ). 33. In response to thermal radiation, surface temperature depends on the thermal emissivity of the material. 34. The term emissivity is generally used to describe a simple, homogeneous surface such as silver. 35. A major consideration is the low emissivity of yttria, which limits background radiation upon heating. 36. The net emissivity may be low due to surface or atmospheric properties, including greenhouse effect. 37. This " naturally " low thermal emissivity is found in some formulations of borosilicate or Pyrex. 38. High emissivity roofs have much higher heat loss in cold climates for the same insulation values. 39. Its emissivity varies considerably with temperature. 40. The ability of a material to radiate energy is measured by the emissivity of the material.
