Visible light transmittance (VT, Tvis, or VLT) is an optical property that indicates the amount of visible light transmitted. Most VT values are between 0.3 and 0.8. The higher the VT, the more light is transmitted. A high VT is desirable to maximize daylight but must be balanced with consideration of possible glare problems. You can change the glass properties of a project by using the Design Alternatives feature or the Project Template feature.