Complex sentence: There exists other selective surfaces that are not normally used on solar thermal collector surfaces, such as low emissivity surfaces used in window glasses, which reflect thermal radiation and have high transmittance factors (being transparent) for visible sunlight.
Split into simpler sentences: There exists other selective surfaces that are not normally used on solar thermal collector surfaces. E.g. low emissivity surfaces used in window glasses, which reflect thermal radiation and has a high transmittance factor (e.g. is transparent) to visible sunlight.